Android 片段内的 TabLayout
Android TabLayout inside Fragment
我正在使用 Navigation Drawer
在它们都使用 MainActivity 工具栏的片段之间导航,但每个片段都有自己的 TabLayout
和 3 个选项卡,在每个选项卡中我使用 RecyclerView
来显示不同的文字和图片。
我上次是使用 actvities 而不是 fragments 做的,但现在使用抽屉,最好使用 fragments。
我已经到了可以使用选项卡的地步,但是只要我将 ViewPager
放入并将适配器连接到选项卡,然后从抽屉中打开新片段,我就会得到一个空指针可能是这里的问题?
MainActivity.java
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
return id == R.id.action_settings || super.onOptionsItemSelected(item);
}
@Override
public boolean onNavigationItemSelected(MenuItem item) {
int id = item.getItemId();
Fragment fragment;
if (id == R.id.fragment_one) {
fragment = new NewFragment();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.container, fragment);
ft.commit();
} else if (id == R.id.fragment_two) {
fragment = new NewFragment();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.container, fragment);
ft.commit();
} else if (id == R.id.fragment_three) {
fragment = new NewFragment();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.container, fragment);
ft.commit();
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
activity_main.xml
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:openDrawer="start">
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.xcandy.guideforfifa17.MainActivity">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="@style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<include layout="@layout/content_main" />
</android.support.design.widget.CoordinatorLayout>
<android.support.design.widget.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="@layout/nav_header_main"
app:menu="@menu/activity_main_drawer" />
</android.support.v4.widget.DrawerLayout>
NewFragment.java
public class NewFragment extends Fragment {
private RecyclerView mRecyclerView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_fragment_one, container, false);
TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tabs);
tabLayout.addTab(tabLayout.newTab().setText("A"));
tabLayout.addTab(tabLayout.newTab().setText("B"));
tabLayout.addTab(tabLayout.newTab().setText("C"));
final ViewPager viewPager = (ViewPager) view.findViewById(R.id.viewpager);
mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(mLayoutManager);
viewPager.setAdapter(new PagerAdapter
(getFragmentManager(), tabLayout.getTabCount()));
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
return view;
}
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
RecyclerView.Adapter mAdapter = new AdapterOne();
mRecyclerView.setAdapter(mAdapter);
case 1:
mAdapter = new AdapterTwo();
mRecyclerView.setAdapter(mAdapter);
case 2:
mAdapter = new AdapterThree();
mRecyclerView.setAdapter(mAdapter);
default:
return null;
}
}
@Override
public int getCount() {
return mNumOfTabs;
}
}
}
activity_fragment.xml
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".NewFragment">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMode="fixed"
app:tabGravity="fill"/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:color/white"/>
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</android.support.design.widget.CoordinatorLayout>
错误日志
--------- beginning of crash
06-23 11:19:56.985 2466-2466/com.candyx.sims E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.candyx.sims, PID: 2466
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.candyx.sims.BlankFragment.onCreateView(BlankFragment.java:38)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
06-23 11:23:14.912 5839-5873/com.candyx.sims D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
[ 06-23 11:23:14.920 5839: 5839 D/ ]
HostConnection::get() New Host Connection established 0xb4125190, tid 5839
06-23 11:23:14.927 5839-5839/com.candyx.sims D/Atlas: Validating map...
06-23 11:23:15.011 5839-5873/com.candyx.sims I/OpenGLRenderer: Initialized EGL, version 1.4
06-23 11:23:15.027 5839-5873/com.candyx.sims D/OpenGLRenderer: Enabling debug mode 0
06-23 11:23:15.039 5839-5873/com.candyx.sims W/EGL_emulation: eglSurfaceAttrib not implemented
06-23 11:23:15.039 5839-5873/com.candyx.sims W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xae838600, error=EGL_SUCCESS
06-23 11:23:16.444 5839-5839/com.candyx.sims W/PathParser: Points are too far apart 4.000000596046461
06-23 11:23:17.342 5839-5839/com.candyx.sims W/PathParser: Points are too far apart 4.000000596046461
06-23 11:23:17.350 5839-5839/com.candyx.sims I/AppCompatViewInflater: app:theme is now deprecated. Please move to using android:theme instead.
06-23 11:23:17.369 5839-5839/com.candyx.sims D/AndroidRuntime: Shutting down VM
06-23 11:23:17.369 5839-5839/com.candyx.sims E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.candyx.sims, PID: 5839
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.candyx.sims.NewFragment.onCreateView(NewFragment.java:38)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
06-23 11:25:16.961 7518-7518/com.candyx.sims W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
06-23 11:25:17.078 7518-7548/com.candyx.sims D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
[ 06-23 11:25:17.081 7518: 7518 D/ ]
HostConnection::get() New Host Connection established 0xb412a1f0, tid 7518
06-23 11:25:17.082 7518-7518/com.candyx.sims D/Atlas: Validating map...
06-23 11:25:17.109 7518-7548/com.candyx.sims I/OpenGLRenderer: Initialized EGL, version 1.4
06-23 11:25:17.126 7518-7548/com.candyx.sims D/OpenGLRenderer: Enabling debug mode 0
06-23 11:25:17.134 7518-7548/com.candyx.sims W/EGL_emulation: eglSurfaceAttrib not implemented
06-23 11:25:17.134 7518-7548/com.candyx.sims W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xb41234c0, error=EGL_SUCCESS
06-23 11:25:31.030 7518-7518/com.candyx.sims W/PathParser: Points are too far apart 4.000000596046461
06-23 11:25:32.174 7518-7518/com.candyx.sims W/PathParser: Points are too far apart 4.000000596046461
06-23 11:25:32.187 7518-7518/com.candyx.sims I/AppCompatViewInflater: app:theme is now deprecated. Please move to using android:theme instead.
06-23 11:25:32.207 7518-7518/com.candyx.sims D/AndroidRuntime: Shutting down VM
06-23 11:25:32.207 7518-7518/com.candyx.sims E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.candyx.sims, PID: 7518
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.candyx.sims.NewFragment.onCreateView(NewFragment.java:38)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
这个方法getItem
在PagerAdapter
错了,它returnFragment
init
你应该 return Fragment
。在片段中,你 setView
recyclerView
到它
如果没有错误日志,很难说出您在哪里以及为什么得到 NullPointerException
。
引起我注意的第一件事是你没有 link 你的 TabLayout
和 ViewPager
。在为 ViewPager
设置适配器后使用以下代码:
// setUpWithViewPager doesn't work without using a Runnable interface.
// Support library bug, maybe?
tabLayout.post(new Runnable() {
@Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
}
});
我不确定这是否是问题所在,但试一试:)
我建议在
中使用getChildFragmentManager
而不是getFragmentManager
viewPager.setAdapter(new PagerAdapter
(getFragmentManager(), tabLayout.getTabCount()));
查看您的代码后,我发现您忘记了 return 您从 FragmentStatePagerAdapter 覆盖的 PagerAdapter 的 getItem 方法中的一个片段,并且没有中断每种情况下的语句,由于每次空值都是 returned.
为此,您需要为 ViewPager 中的每个页面创建另一个新片段,或者您可以创建一个可在 ViewPager 的所有页面中使用的新片段。
您不能在父片段中定义的视图寻呼机选项卡中使用相同的 recyclerview。
activity_fragment_one.xml
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".NewFragment">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
app:tabTextAppearance="?android:attr/textAppearanceMedium"
app:tabTextColor="#ffffff"
android:layout_height="?android:actionBarSize"
app:tabMode="fixed"
app:tabGravity="fill"/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
android:background="@android:color/white"/>
</android.support.design.widget.CoordinatorLayout>
我已经修复了您的片段并创建了一个您可以在 ViewPager Pages 中使用的新片段。
public class NewFragment extends Fragment {
private RecyclerView mRecyclerView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_fragment_one, container, false);
TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tabs);
tabLayout.addTab(tabLayout.newTab().setText("A"));
tabLayout.addTab(tabLayout.newTab().setText("B"));
tabLayout.addTab(tabLayout.newTab().setText("C"));
final ViewPager viewPager = (ViewPager) view.findViewById(R.id.viewpager);
// mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
LinearLayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
//mRecyclerView.setLayoutManager(mLayoutManager);
viewPager.setAdapter(new PagerAdapter(getFragmentManager(), tabLayout.getTabCount()));
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setupWithViewPager(viewPager);
tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
return view;
}
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new FragmentTab();
case 1:
return new FragmentTab();
case 2:
return new FragmentTab();
default:
return null;
}
}
@Override
public int getCount() {
return mNumOfTabs;
}
}
}
View Pager 中每个页面的 FragmentTab(或者您可以根据需要为每个页面创建不同的片段)。
public class FragmentTab extends Fragment {
RecyclerView mRecyclerView;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_tab, container, false);
mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
LinearLayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
mRecyclerView.setLayoutManager(mLayoutManager);
RecyclerView.Adapter mAdapter = new AdapterOne();
mRecyclerView.setAdapter(mAdapter);
return view;
}
}
fragment_tab.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
好吧,前段时间我实现了完全相同的应用程序设计。我有一个片段,旨在容纳 Tabs 和 ViewPager。这是一项棘手的任务,我记得我遇到过与您类似的问题。这是我解决它的方法:
布局顺序为:
Activity -> Fragment -> Tab Layout + ViewPager -> FragmentStatePagerAdapter -> Fragment -> RecyclerView
您与 Main Activity 没有任何关系。所有的东西都是碎片。因此,在您的 activity_main.xml
中摆脱 TabLayout。
您将不得不处理分页器中的嵌套片段。所有页面内容都必须存在,并且 TabLayout 必须与 ViewPager 所在的布局相同。
我的项目有点旧,我用了android.support.v4.app.Fragment
以防万一。我从您不需要的数据中删除了来源,因此您可能会看到一些孤立的方法。
任务是显示带有类别的价目表,并在其自己的页面上呈现每个类别的产品,以便水平滑动可以切换类别和垂直滑动 - 列出产品。
带有 ViewPager 和 TabLayout 的每个片段都具有以下 subfragment_price_list_pager.xml
布局:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/icons"
app:cardCornerRadius="4dp"
app:cardElevation="4dp"
app:cardPreventCornerOverlap="true">
<android.support.v7.widget.Toolbar
android:id="@+id/priceListToolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:elevation="4dp"
android:theme="@style/AppTheme.Toolbar.TabLayout"
app:navigationIcon="@drawable/ic_tag_multiple_grey600_24dp"
tools:ignore="UnusedAttribute">
<android.support.design.widget.TabLayout
android:id="@+id/tabBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
</android.support.v7.widget.Toolbar>
<android.support.v4.view.ViewPager
android:id="@+id/priceList"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="58dp"
android:padding="5dp"
android:scrollbars="horizontal" />
</android.support.v7.widget.CardView>
这里是 PriceListPagerFragment.class
:
public class PriceListPagerFragment extends Fragment {
private static final String TAG = "PriceListPagerFragment";
private PriceList mPriceList;
private ViewPager mCategoriesViewPager;
private TabLayout tabLayout;
private Loader<PriceList> priceListLoader;
private EditText scanerBarcodeText;
private OnCartActionListener mListener;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.subfragment_price_list_pager, container, false);
// Pager that would be inflated with page fragments.
mCategoriesViewPager = (ViewPager) rootView.findViewById(R.id.priceList);
tabLayout = (TabLayout) rootView.findViewById(R.id.tabBar);
tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);
// Do all the stuff with pager here:
updatePriceListPages();
return rootView;
}
private void updatePriceListPages() {
if (mCategoriesViewPager != null && mPriceList != null) {
Log.d(TAG, this + "updatePriceListPages");
if (mCategoriesViewPager.getAdapter() == null) {
PriceListCategoriesAdapter adapter = new PriceListCategoriesAdapter(
getFragmentManager(),
tabLayout
);
mCategoriesViewPager.setAdapter(
adapter
);
// Each page is a content of a single category of one-level catalog
// We did not supply catalog to adapter before it is bound to ViewPager for some serious reason which I can't recall now
adapter.setPriceList(mPriceList);
tabLayout.setupWithViewPager(mCategoriesViewPager);
} else {
((PriceListCategoriesAdapter) mCategoriesViewPager.getAdapter()).setPriceList(mPriceList);
}
}
}
}
自定义 FragmentStatePagerAdapter
实现,PriceListCategoriesAdapter.class
:
public class PriceListCategoriesAdapter extends FragmentStatePagerAdapter {
private static final String TAG = "PriceListCategoriesAd";
private final TabLayout mTabLayout;
private FragmentManager mFm;
private Vector<PriceListFragment> recyclerViewList;
private Vector<String> titles;
public PriceListCategoriesAdapter(FragmentManager fm, TabLayout tabLayout) {
super(fm);
mFm = fm;
mTabLayout = tabLayout;
recyclerViewList = new Vector<>();
titles = new Vector<>();
}
// All the magic with nested page fragments is done here
public void setPriceList(PriceList priceList) {
boolean updateTabs = false;
Vector<String> newTitles = new Vector<>();
int position = 0;
for (CatalogItem catalogItem : priceList.getCatalogs()) {
if (catalogItem.getProducts() == null)
continue;
boolean newFragment;
PriceListFragment fragment;
try {
fragment = recyclerViewList.get(position);
newFragment = false;
} catch (ArrayIndexOutOfBoundsException e) {
fragment = new PriceListFragment();
newFragment = true;
}
fragment.setCatalogItem(catalogItem);
newTitles.add(catalogItem.getName());
if (newFragment) {
recyclerViewList.add(fragment);
}
position++;
}
if (titles.size() != newTitles.size()) {
updateTabs = true;
} else {
for (int position = 0; position < titles.size(); position++) {
if (!titles.get(position).equals(newTitles.get(position))) {
updateTabs = true;
break;
}
}
}
titles = newTitles;
notifyDataSetChanged();
if (updateTabs)
mTabLayout.setTabsFromPagerAdapter(this);
}
@Override
public Fragment getItem(int position) {
return recyclerViewList.get(position);
}
@Override
public int getItemPosition(Object object) {
PriceListFragment fragment = (PriceListFragment) object;
String title = (String) fragment.getTitle();
int position = titles.indexOf(title);
if (position >= 0) {
return position;
} else {
return POSITION_NONE;
}
}
@Override
public int getCount() {
return titles.size();
}
@Override
public CharSequence getPageTitle(int position) {
return recyclerViewList.get(position).getTitle();
}
// We don't keep states
@Override
public Parcelable saveState() {
return null;
}
// We don't keep states
@Override
public void restoreState(Parcelable state, ClassLoader loader) {
}
}
最后 PriceListFragment
布局:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView android:id="@+id/categoryList"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical" />
PriceListFragment.class
本身并没有什么特别之处。只需使用适当的数据实例化它的 RecyclerView 即可。
使用getChildFragmentManager()
代替getSupportFragmentManager()
我正在使用 Navigation Drawer
在它们都使用 MainActivity 工具栏的片段之间导航,但每个片段都有自己的 TabLayout
和 3 个选项卡,在每个选项卡中我使用 RecyclerView
来显示不同的文字和图片。
我上次是使用 actvities 而不是 fragments 做的,但现在使用抽屉,最好使用 fragments。
我已经到了可以使用选项卡的地步,但是只要我将 ViewPager
放入并将适配器连接到选项卡,然后从抽屉中打开新片段,我就会得到一个空指针可能是这里的问题?
MainActivity.java
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
return id == R.id.action_settings || super.onOptionsItemSelected(item);
}
@Override
public boolean onNavigationItemSelected(MenuItem item) {
int id = item.getItemId();
Fragment fragment;
if (id == R.id.fragment_one) {
fragment = new NewFragment();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.container, fragment);
ft.commit();
} else if (id == R.id.fragment_two) {
fragment = new NewFragment();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.container, fragment);
ft.commit();
} else if (id == R.id.fragment_three) {
fragment = new NewFragment();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.container, fragment);
ft.commit();
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
activity_main.xml
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:openDrawer="start">
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.xcandy.guideforfifa17.MainActivity">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="@style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<include layout="@layout/content_main" />
</android.support.design.widget.CoordinatorLayout>
<android.support.design.widget.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="@layout/nav_header_main"
app:menu="@menu/activity_main_drawer" />
</android.support.v4.widget.DrawerLayout>
NewFragment.java
public class NewFragment extends Fragment {
private RecyclerView mRecyclerView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_fragment_one, container, false);
TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tabs);
tabLayout.addTab(tabLayout.newTab().setText("A"));
tabLayout.addTab(tabLayout.newTab().setText("B"));
tabLayout.addTab(tabLayout.newTab().setText("C"));
final ViewPager viewPager = (ViewPager) view.findViewById(R.id.viewpager);
mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(mLayoutManager);
viewPager.setAdapter(new PagerAdapter
(getFragmentManager(), tabLayout.getTabCount()));
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
return view;
}
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
RecyclerView.Adapter mAdapter = new AdapterOne();
mRecyclerView.setAdapter(mAdapter);
case 1:
mAdapter = new AdapterTwo();
mRecyclerView.setAdapter(mAdapter);
case 2:
mAdapter = new AdapterThree();
mRecyclerView.setAdapter(mAdapter);
default:
return null;
}
}
@Override
public int getCount() {
return mNumOfTabs;
}
}
}
activity_fragment.xml
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".NewFragment">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMode="fixed"
app:tabGravity="fill"/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:color/white"/>
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</android.support.design.widget.CoordinatorLayout>
错误日志
--------- beginning of crash
06-23 11:19:56.985 2466-2466/com.candyx.sims E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.candyx.sims, PID: 2466
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.candyx.sims.BlankFragment.onCreateView(BlankFragment.java:38)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
06-23 11:23:14.912 5839-5873/com.candyx.sims D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
[ 06-23 11:23:14.920 5839: 5839 D/ ]
HostConnection::get() New Host Connection established 0xb4125190, tid 5839
06-23 11:23:14.927 5839-5839/com.candyx.sims D/Atlas: Validating map...
06-23 11:23:15.011 5839-5873/com.candyx.sims I/OpenGLRenderer: Initialized EGL, version 1.4
06-23 11:23:15.027 5839-5873/com.candyx.sims D/OpenGLRenderer: Enabling debug mode 0
06-23 11:23:15.039 5839-5873/com.candyx.sims W/EGL_emulation: eglSurfaceAttrib not implemented
06-23 11:23:15.039 5839-5873/com.candyx.sims W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xae838600, error=EGL_SUCCESS
06-23 11:23:16.444 5839-5839/com.candyx.sims W/PathParser: Points are too far apart 4.000000596046461
06-23 11:23:17.342 5839-5839/com.candyx.sims W/PathParser: Points are too far apart 4.000000596046461
06-23 11:23:17.350 5839-5839/com.candyx.sims I/AppCompatViewInflater: app:theme is now deprecated. Please move to using android:theme instead.
06-23 11:23:17.369 5839-5839/com.candyx.sims D/AndroidRuntime: Shutting down VM
06-23 11:23:17.369 5839-5839/com.candyx.sims E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.candyx.sims, PID: 5839
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.candyx.sims.NewFragment.onCreateView(NewFragment.java:38)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
06-23 11:25:16.961 7518-7518/com.candyx.sims W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
06-23 11:25:17.078 7518-7548/com.candyx.sims D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
[ 06-23 11:25:17.081 7518: 7518 D/ ]
HostConnection::get() New Host Connection established 0xb412a1f0, tid 7518
06-23 11:25:17.082 7518-7518/com.candyx.sims D/Atlas: Validating map...
06-23 11:25:17.109 7518-7548/com.candyx.sims I/OpenGLRenderer: Initialized EGL, version 1.4
06-23 11:25:17.126 7518-7548/com.candyx.sims D/OpenGLRenderer: Enabling debug mode 0
06-23 11:25:17.134 7518-7548/com.candyx.sims W/EGL_emulation: eglSurfaceAttrib not implemented
06-23 11:25:17.134 7518-7548/com.candyx.sims W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xb41234c0, error=EGL_SUCCESS
06-23 11:25:31.030 7518-7518/com.candyx.sims W/PathParser: Points are too far apart 4.000000596046461
06-23 11:25:32.174 7518-7518/com.candyx.sims W/PathParser: Points are too far apart 4.000000596046461
06-23 11:25:32.187 7518-7518/com.candyx.sims I/AppCompatViewInflater: app:theme is now deprecated. Please move to using android:theme instead.
06-23 11:25:32.207 7518-7518/com.candyx.sims D/AndroidRuntime: Shutting down VM
06-23 11:25:32.207 7518-7518/com.candyx.sims E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.candyx.sims, PID: 7518
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.candyx.sims.NewFragment.onCreateView(NewFragment.java:38)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
这个方法getItem
在PagerAdapter
错了,它returnFragment
init
你应该 return Fragment
。在片段中,你 setView
recyclerView
到它
如果没有错误日志,很难说出您在哪里以及为什么得到 NullPointerException
。
引起我注意的第一件事是你没有 link 你的 TabLayout
和 ViewPager
。在为 ViewPager
设置适配器后使用以下代码:
// setUpWithViewPager doesn't work without using a Runnable interface.
// Support library bug, maybe?
tabLayout.post(new Runnable() {
@Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
}
});
我不确定这是否是问题所在,但试一试:)
我建议在
中使用getChildFragmentManager
而不是getFragmentManager
viewPager.setAdapter(new PagerAdapter
(getFragmentManager(), tabLayout.getTabCount()));
查看您的代码后,我发现您忘记了 return 您从 FragmentStatePagerAdapter 覆盖的 PagerAdapter 的 getItem 方法中的一个片段,并且没有中断每种情况下的语句,由于每次空值都是 returned.
为此,您需要为 ViewPager 中的每个页面创建另一个新片段,或者您可以创建一个可在 ViewPager 的所有页面中使用的新片段。
您不能在父片段中定义的视图寻呼机选项卡中使用相同的 recyclerview。
activity_fragment_one.xml
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".NewFragment">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
app:tabTextAppearance="?android:attr/textAppearanceMedium"
app:tabTextColor="#ffffff"
android:layout_height="?android:actionBarSize"
app:tabMode="fixed"
app:tabGravity="fill"/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
android:background="@android:color/white"/>
</android.support.design.widget.CoordinatorLayout>
我已经修复了您的片段并创建了一个您可以在 ViewPager Pages 中使用的新片段。
public class NewFragment extends Fragment {
private RecyclerView mRecyclerView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_fragment_one, container, false);
TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tabs);
tabLayout.addTab(tabLayout.newTab().setText("A"));
tabLayout.addTab(tabLayout.newTab().setText("B"));
tabLayout.addTab(tabLayout.newTab().setText("C"));
final ViewPager viewPager = (ViewPager) view.findViewById(R.id.viewpager);
// mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
LinearLayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
//mRecyclerView.setLayoutManager(mLayoutManager);
viewPager.setAdapter(new PagerAdapter(getFragmentManager(), tabLayout.getTabCount()));
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setupWithViewPager(viewPager);
tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
return view;
}
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new FragmentTab();
case 1:
return new FragmentTab();
case 2:
return new FragmentTab();
default:
return null;
}
}
@Override
public int getCount() {
return mNumOfTabs;
}
}
}
View Pager 中每个页面的 FragmentTab(或者您可以根据需要为每个页面创建不同的片段)。
public class FragmentTab extends Fragment {
RecyclerView mRecyclerView;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_tab, container, false);
mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
LinearLayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
mRecyclerView.setLayoutManager(mLayoutManager);
RecyclerView.Adapter mAdapter = new AdapterOne();
mRecyclerView.setAdapter(mAdapter);
return view;
}
}
fragment_tab.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
好吧,前段时间我实现了完全相同的应用程序设计。我有一个片段,旨在容纳 Tabs 和 ViewPager。这是一项棘手的任务,我记得我遇到过与您类似的问题。这是我解决它的方法:
布局顺序为:
Activity -> Fragment -> Tab Layout + ViewPager -> FragmentStatePagerAdapter -> Fragment -> RecyclerView
您与 Main Activity 没有任何关系。所有的东西都是碎片。因此,在您的 activity_main.xml
中摆脱 TabLayout。
您将不得不处理分页器中的嵌套片段。所有页面内容都必须存在,并且 TabLayout 必须与 ViewPager 所在的布局相同。
我的项目有点旧,我用了android.support.v4.app.Fragment
以防万一。我从您不需要的数据中删除了来源,因此您可能会看到一些孤立的方法。
任务是显示带有类别的价目表,并在其自己的页面上呈现每个类别的产品,以便水平滑动可以切换类别和垂直滑动 - 列出产品。
带有 ViewPager 和 TabLayout 的每个片段都具有以下 subfragment_price_list_pager.xml
布局:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/icons"
app:cardCornerRadius="4dp"
app:cardElevation="4dp"
app:cardPreventCornerOverlap="true">
<android.support.v7.widget.Toolbar
android:id="@+id/priceListToolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:elevation="4dp"
android:theme="@style/AppTheme.Toolbar.TabLayout"
app:navigationIcon="@drawable/ic_tag_multiple_grey600_24dp"
tools:ignore="UnusedAttribute">
<android.support.design.widget.TabLayout
android:id="@+id/tabBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
</android.support.v7.widget.Toolbar>
<android.support.v4.view.ViewPager
android:id="@+id/priceList"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="58dp"
android:padding="5dp"
android:scrollbars="horizontal" />
</android.support.v7.widget.CardView>
这里是 PriceListPagerFragment.class
:
public class PriceListPagerFragment extends Fragment {
private static final String TAG = "PriceListPagerFragment";
private PriceList mPriceList;
private ViewPager mCategoriesViewPager;
private TabLayout tabLayout;
private Loader<PriceList> priceListLoader;
private EditText scanerBarcodeText;
private OnCartActionListener mListener;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.subfragment_price_list_pager, container, false);
// Pager that would be inflated with page fragments.
mCategoriesViewPager = (ViewPager) rootView.findViewById(R.id.priceList);
tabLayout = (TabLayout) rootView.findViewById(R.id.tabBar);
tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);
// Do all the stuff with pager here:
updatePriceListPages();
return rootView;
}
private void updatePriceListPages() {
if (mCategoriesViewPager != null && mPriceList != null) {
Log.d(TAG, this + "updatePriceListPages");
if (mCategoriesViewPager.getAdapter() == null) {
PriceListCategoriesAdapter adapter = new PriceListCategoriesAdapter(
getFragmentManager(),
tabLayout
);
mCategoriesViewPager.setAdapter(
adapter
);
// Each page is a content of a single category of one-level catalog
// We did not supply catalog to adapter before it is bound to ViewPager for some serious reason which I can't recall now
adapter.setPriceList(mPriceList);
tabLayout.setupWithViewPager(mCategoriesViewPager);
} else {
((PriceListCategoriesAdapter) mCategoriesViewPager.getAdapter()).setPriceList(mPriceList);
}
}
}
}
自定义 FragmentStatePagerAdapter
实现,PriceListCategoriesAdapter.class
:
public class PriceListCategoriesAdapter extends FragmentStatePagerAdapter {
private static final String TAG = "PriceListCategoriesAd";
private final TabLayout mTabLayout;
private FragmentManager mFm;
private Vector<PriceListFragment> recyclerViewList;
private Vector<String> titles;
public PriceListCategoriesAdapter(FragmentManager fm, TabLayout tabLayout) {
super(fm);
mFm = fm;
mTabLayout = tabLayout;
recyclerViewList = new Vector<>();
titles = new Vector<>();
}
// All the magic with nested page fragments is done here
public void setPriceList(PriceList priceList) {
boolean updateTabs = false;
Vector<String> newTitles = new Vector<>();
int position = 0;
for (CatalogItem catalogItem : priceList.getCatalogs()) {
if (catalogItem.getProducts() == null)
continue;
boolean newFragment;
PriceListFragment fragment;
try {
fragment = recyclerViewList.get(position);
newFragment = false;
} catch (ArrayIndexOutOfBoundsException e) {
fragment = new PriceListFragment();
newFragment = true;
}
fragment.setCatalogItem(catalogItem);
newTitles.add(catalogItem.getName());
if (newFragment) {
recyclerViewList.add(fragment);
}
position++;
}
if (titles.size() != newTitles.size()) {
updateTabs = true;
} else {
for (int position = 0; position < titles.size(); position++) {
if (!titles.get(position).equals(newTitles.get(position))) {
updateTabs = true;
break;
}
}
}
titles = newTitles;
notifyDataSetChanged();
if (updateTabs)
mTabLayout.setTabsFromPagerAdapter(this);
}
@Override
public Fragment getItem(int position) {
return recyclerViewList.get(position);
}
@Override
public int getItemPosition(Object object) {
PriceListFragment fragment = (PriceListFragment) object;
String title = (String) fragment.getTitle();
int position = titles.indexOf(title);
if (position >= 0) {
return position;
} else {
return POSITION_NONE;
}
}
@Override
public int getCount() {
return titles.size();
}
@Override
public CharSequence getPageTitle(int position) {
return recyclerViewList.get(position).getTitle();
}
// We don't keep states
@Override
public Parcelable saveState() {
return null;
}
// We don't keep states
@Override
public void restoreState(Parcelable state, ClassLoader loader) {
}
}
最后 PriceListFragment
布局:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView android:id="@+id/categoryList"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical" />
PriceListFragment.class
本身并没有什么特别之处。只需使用适当的数据实例化它的 RecyclerView 即可。
使用getChildFragmentManager()
代替getSupportFragmentManager()