所有片段都在 activity 时加载
all fragments are loading at time of activity
我对 android 开发非常...非常陌生，我正在尝试重新创建一个我在 ionic 中构建的混合应用程序，但在实际 android 中进行。
我遇到无法弄清楚的布局或片段加载问题。
我想要的是类似于IG布局的东西，底部有一个导航栏，点击按钮会加载新页面。根据我的理解，实现该目标的最佳方法是使用主 activity，然后底部的每个选项卡都是片段。
所以我构建了它，但我希望顶部工具栏在第二个选项卡上消失，所以在第二个选项卡 "onCreateView" 方法中我添加了 toolbar.setVisibility(View.GONE);但是，一旦我加载应用程序，即使在第一个选项卡上，顶部的工具栏也消失了，这表明它正在加载应用程序加载时每个片段的视图。我认为这会严重影响大型应用程序的性能。我疯了吗？
这是我主要 activity...
的主要布局
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/main_layout">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:background="@color/colorPrimary"
android:elevation="6dp"
android:minHeight="?attr/actionBarSize"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
<android.support.v4.view.ViewPager
android:id="@+id/content"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/toolbar" />
<android.support.design.widget.TabLayout
android:id="@+id/tab_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMode="fixed"
android:gravity="center_horizontal"
android:layout_gravity="center_horizontal"
android:background="?attr/colorPrimary"
android:elevation="6dp"
app:tabSelectedTextColor="#FFFFFF"
app:tabTextColor="#D3D3D3"
app:tabIndicatorColor="#FF00FF"
android:minHeight="?attr/actionBarSize"
android:layout_alignParentBottom="true" />
</RelativeLayout>
然后我的HomeActivityclass..
public class HomeActivity extends BaseActivity implements OnFragmentTouched {
private TextView mTextMessage;
private static final String SELECTED_ITEM = "arg_selected_item";
private int mSelectedItem;
private BottomNavigationView mBottomNav;
private FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
@Override
protected void onSaveInstanceState(Bundle outState) {
outState.putInt(SELECTED_ITEM, mSelectedItem);
super.onSaveInstanceState(outState);
}
@Override
public void onBackPressed() {
MenuItem homeItem = mBottomNav.getMenu().getItem(0);
if (mSelectedItem != homeItem.getItemId()) {
// select home item
selectFragment(homeItem);
} else {
super.onBackPressed();
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
ViewPager pager = (ViewPager) findViewById(R.id.content);
PagerAdapter pagerAdapter = (PagerAdapter) new PagerAdapter(getSupportFragmentManager(), HomeActivity.this);
pager.setAdapter(pagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.setupWithViewPager(pager);
for(int i = 0; i < tabLayout.getTabCount(); i++) {
TabLayout.Tab tab = tabLayout.getTabAt(i);
tab.setCustomView(pagerAdapter.getTabView(i));
}
}
private void selectFragment(MenuItem item) {
Fragment frag = null;
switch(item.getItemId()) {
case R.id.navigation_home:
frag = new AllPostsFragment();
break;
case R.id.navigation_dashboard:
frag = ProfileFragment.newInstance(user.getUid());
break;
case R.id.navigation_notifications:
frag = new ChatListFragment();
break;
}
mSelectedItem = item.getItemId();
}
@VisibleForTesting
public ProgressDialog mProgressDialog;
public void showProgressDialog() {
if (mProgressDialog == null) {
mProgressDialog = new ProgressDialog(this);
mProgressDialog.setMessage(getString(R.string.loading));
mProgressDialog.setIndeterminate(true);
}
mProgressDialog.show();
}
public void hideProgressDialog() {
if (mProgressDialog != null && mProgressDialog.isShowing()) {
mProgressDialog.dismiss();
}
}
@Override
public void onStop() {
super.onStop();
hideProgressDialog();
}
@Override
public void onFragmentTouched(Fragment fragment, float x, float y) {
Log.d("FRAGMENT_TOUCHED", "The ChatListFragment touch happened");
if(fragment instanceof ChatFragment) {
final ChatFragment theFragment = (ChatFragment) fragment;
Animator unreveal = theFragment.prepareUnrevealAnimator(x, y);
unreveal.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
getSupportFragmentManager().beginTransaction().remove(theFragment).commit();
getSupportFragmentManager().executePendingTransactions();
}
@Override
public void onAnimationCancel(Animator animation) {}
@Override
public void onAnimationRepeat(Animator animation) {}
});
unreveal.start();
}
}
public String getUid() {
return FirebaseAuth.getInstance().getCurrentUser().getUid();
}
private class PagerAdapter extends FragmentPagerAdapter {
Context context;
String tabTitles[] = new String[] {"Home", "Profile", "Chat"};
public PagerAdapter(FragmentManager fm, Context context) {
super(fm);
this.context = context;
}
@Override
public Fragment getItem(int pos) {
switch(pos) {
case 0: return new AllPostsFragment();
case 1: return ProfileFragment.newInstance(user.getUid());
case 2: return new ChatListFragment();
default:
return new AllPostsFragment();
}
}
@Override
public int getCount() {
return tabTitles.length;
}
@Override
public CharSequence getPageTitle(int position) {
return tabTitles[position];
}
public View getTabView(int position) {
View tab = LayoutInflater.from(HomeActivity.this).inflate(R.layout.custom_tab, null);
TextView tv = (TextView) tab.findViewById(R.id.custom_text);
tv.setText(tabTitles[position]);
return tab;
}
}
}
所以，在 "ProfileFragment" 的 onCreateView 方法中，我有...
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_profile, container, false);
recyclerView = (RecyclerView) rootView.findViewById(R.id.userPostsRecycler);
RecyclerView.LayoutManager layoutManager = new GridLayoutManager(getContext(), 2);
recyclerView.setLayoutManager(layoutManager);
Toolbar toolbar = getActivity().findViewById(R.id.toolbar);
toolbar.setVisibility(View.GONE);
followingCountText = rootView.findViewById(R.id.following_count);
followersCountText = rootView.findViewById(R.id.followers_count);
titleLayout = rootView.findViewById(R.id.toolbar_layout);
titleLayout.setTitle(user.getDisplayName());
fab1Container = rootView.findViewById(R.id.fab_1);
fab2Container = rootView.findViewById(R.id.fab_2);
ImageView profilePhoto = (ImageView) rootView.findViewById(R.id.profile_photo);
Glide.with(this).load(user.getPhotoUrl()).into(profilePhoto);
fabContainer = (LinearLayout) rootView.findViewById(R.id.fabContainerLayout);
fab = (FloatingActionButton) rootView.findViewById(R.id.profile_fab);
instigatingFab = fab;
fabBaseX = fab.getX();
fabBaseY = fab.getY();
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
showBlurredDialog();
}
});
progressDialog = new ProgressDialog(getContext());
uploads = new ArrayList<>();
progressDialog.setMessage("Please wait...");
progressDialog.show();
DatabaseReference followersDB = FirebaseDatabase
.getInstance()
.getReference("followers")
.child(user.getUid())
.child("count");
followersDB.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
int followersCount = dataSnapshot.getValue(Integer.class);
followersCountText.setText(Integer.toString(followersCount));
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
DatabaseReference followingReference = FirebaseDatabase.getInstance().getReference("following").child(user.getUid()).child("users");
followingReference.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
DatabaseReference followingDB = FirebaseDatabase.getInstance().getReference("following").child(user.getUid()).child("count");
followingDB.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
int followingCount = dataSnapshot.getValue(Integer.class);
followingCountText.setText(Integer.toString(followingCount));
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
mDatabase = FirebaseDatabase.getInstance().getReference("/userPosts").child(user.getUid()).child("posts");
mDatabase.limitToFirst(25).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
progressDialog.dismiss();
for(DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
String postID = postSnapshot.getKey();
uploads.add(postID);
}
uploads.add("-KtvzkOL_75wiKA4CMsr");
adapter = new ProfileUserPostsViewHolder(getContext(), uploads);
recyclerView.setAdapter(adapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
progressDialog.dismiss();
}
});
return rootView;
}
如您所见，我将工具栏的可见性从 HomeActivity 设置为 View.GONE，但是，工具栏现在从所有片段中消失了。我只想要一个带有顶部工具栏的底部导航设置，该工具栏可以在某些片段加载时隐藏，但在其他片段中可见。这可能吗？谢谢。
您可以通过简单地使用此方法来控制在视图分页器中加载的片段数：
viewPager.setOffscreenPageLimit(1); // where n is the number of offscreen pages you want to load.
您可以根据需要增加或减少片段加载数量，但至少 1 个。
希望对您有所帮助。
我对 android 开发非常...非常陌生，我正在尝试重新创建一个我在 ionic 中构建的混合应用程序，但在实际 android 中进行。 我遇到无法弄清楚的布局或片段加载问题。 我想要的是类似于IG布局的东西，底部有一个导航栏，点击按钮会加载新页面。根据我的理解，实现该目标的最佳方法是使用主 activity，然后底部的每个选项卡都是片段。 所以我构建了它，但我希望顶部工具栏在第二个选项卡上消失，所以在第二个选项卡 "onCreateView" 方法中我添加了 toolbar.setVisibility(View.GONE);但是，一旦我加载应用程序，即使在第一个选项卡上，顶部的工具栏也消失了，这表明它正在加载应用程序加载时每个片段的视图。我认为这会严重影响大型应用程序的性能。我疯了吗？ 这是我主要 activity...
的主要布局<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/main_layout">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:background="@color/colorPrimary"
android:elevation="6dp"
android:minHeight="?attr/actionBarSize"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
<android.support.v4.view.ViewPager
android:id="@+id/content"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/toolbar" />
<android.support.design.widget.TabLayout
android:id="@+id/tab_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMode="fixed"
android:gravity="center_horizontal"
android:layout_gravity="center_horizontal"
android:background="?attr/colorPrimary"
android:elevation="6dp"
app:tabSelectedTextColor="#FFFFFF"
app:tabTextColor="#D3D3D3"
app:tabIndicatorColor="#FF00FF"
android:minHeight="?attr/actionBarSize"
android:layout_alignParentBottom="true" />
</RelativeLayout>
然后我的HomeActivityclass..
public class HomeActivity extends BaseActivity implements OnFragmentTouched {
private TextView mTextMessage;
private static final String SELECTED_ITEM = "arg_selected_item";
private int mSelectedItem;
private BottomNavigationView mBottomNav;
private FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
@Override
protected void onSaveInstanceState(Bundle outState) {
outState.putInt(SELECTED_ITEM, mSelectedItem);
super.onSaveInstanceState(outState);
}
@Override
public void onBackPressed() {
MenuItem homeItem = mBottomNav.getMenu().getItem(0);
if (mSelectedItem != homeItem.getItemId()) {
// select home item
selectFragment(homeItem);
} else {
super.onBackPressed();
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
ViewPager pager = (ViewPager) findViewById(R.id.content);
PagerAdapter pagerAdapter = (PagerAdapter) new PagerAdapter(getSupportFragmentManager(), HomeActivity.this);
pager.setAdapter(pagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.setupWithViewPager(pager);
for(int i = 0; i < tabLayout.getTabCount(); i++) {
TabLayout.Tab tab = tabLayout.getTabAt(i);
tab.setCustomView(pagerAdapter.getTabView(i));
}
}
private void selectFragment(MenuItem item) {
Fragment frag = null;
switch(item.getItemId()) {
case R.id.navigation_home:
frag = new AllPostsFragment();
break;
case R.id.navigation_dashboard:
frag = ProfileFragment.newInstance(user.getUid());
break;
case R.id.navigation_notifications:
frag = new ChatListFragment();
break;
}
mSelectedItem = item.getItemId();
}
@VisibleForTesting
public ProgressDialog mProgressDialog;
public void showProgressDialog() {
if (mProgressDialog == null) {
mProgressDialog = new ProgressDialog(this);
mProgressDialog.setMessage(getString(R.string.loading));
mProgressDialog.setIndeterminate(true);
}
mProgressDialog.show();
}
public void hideProgressDialog() {
if (mProgressDialog != null && mProgressDialog.isShowing()) {
mProgressDialog.dismiss();
}
}
@Override
public void onStop() {
super.onStop();
hideProgressDialog();
}
@Override
public void onFragmentTouched(Fragment fragment, float x, float y) {
Log.d("FRAGMENT_TOUCHED", "The ChatListFragment touch happened");
if(fragment instanceof ChatFragment) {
final ChatFragment theFragment = (ChatFragment) fragment;
Animator unreveal = theFragment.prepareUnrevealAnimator(x, y);
unreveal.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
getSupportFragmentManager().beginTransaction().remove(theFragment).commit();
getSupportFragmentManager().executePendingTransactions();
}
@Override
public void onAnimationCancel(Animator animation) {}
@Override
public void onAnimationRepeat(Animator animation) {}
});
unreveal.start();
}
}
public String getUid() {
return FirebaseAuth.getInstance().getCurrentUser().getUid();
}
private class PagerAdapter extends FragmentPagerAdapter {
Context context;
String tabTitles[] = new String[] {"Home", "Profile", "Chat"};
public PagerAdapter(FragmentManager fm, Context context) {
super(fm);
this.context = context;
}
@Override
public Fragment getItem(int pos) {
switch(pos) {
case 0: return new AllPostsFragment();
case 1: return ProfileFragment.newInstance(user.getUid());
case 2: return new ChatListFragment();
default:
return new AllPostsFragment();
}
}
@Override
public int getCount() {
return tabTitles.length;
}
@Override
public CharSequence getPageTitle(int position) {
return tabTitles[position];
}
public View getTabView(int position) {
View tab = LayoutInflater.from(HomeActivity.this).inflate(R.layout.custom_tab, null);
TextView tv = (TextView) tab.findViewById(R.id.custom_text);
tv.setText(tabTitles[position]);
return tab;
}
}
}
所以，在 "ProfileFragment" 的 onCreateView 方法中，我有...
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_profile, container, false);
recyclerView = (RecyclerView) rootView.findViewById(R.id.userPostsRecycler);
RecyclerView.LayoutManager layoutManager = new GridLayoutManager(getContext(), 2);
recyclerView.setLayoutManager(layoutManager);
Toolbar toolbar = getActivity().findViewById(R.id.toolbar);
toolbar.setVisibility(View.GONE);
followingCountText = rootView.findViewById(R.id.following_count);
followersCountText = rootView.findViewById(R.id.followers_count);
titleLayout = rootView.findViewById(R.id.toolbar_layout);
titleLayout.setTitle(user.getDisplayName());
fab1Container = rootView.findViewById(R.id.fab_1);
fab2Container = rootView.findViewById(R.id.fab_2);
ImageView profilePhoto = (ImageView) rootView.findViewById(R.id.profile_photo);
Glide.with(this).load(user.getPhotoUrl()).into(profilePhoto);
fabContainer = (LinearLayout) rootView.findViewById(R.id.fabContainerLayout);
fab = (FloatingActionButton) rootView.findViewById(R.id.profile_fab);
instigatingFab = fab;
fabBaseX = fab.getX();
fabBaseY = fab.getY();
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
showBlurredDialog();
}
});
progressDialog = new ProgressDialog(getContext());
uploads = new ArrayList<>();
progressDialog.setMessage("Please wait...");
progressDialog.show();
DatabaseReference followersDB = FirebaseDatabase
.getInstance()
.getReference("followers")
.child(user.getUid())
.child("count");
followersDB.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
int followersCount = dataSnapshot.getValue(Integer.class);
followersCountText.setText(Integer.toString(followersCount));
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
DatabaseReference followingReference = FirebaseDatabase.getInstance().getReference("following").child(user.getUid()).child("users");
followingReference.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
DatabaseReference followingDB = FirebaseDatabase.getInstance().getReference("following").child(user.getUid()).child("count");
followingDB.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
int followingCount = dataSnapshot.getValue(Integer.class);
followingCountText.setText(Integer.toString(followingCount));
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
mDatabase = FirebaseDatabase.getInstance().getReference("/userPosts").child(user.getUid()).child("posts");
mDatabase.limitToFirst(25).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
progressDialog.dismiss();
for(DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
String postID = postSnapshot.getKey();
uploads.add(postID);
}
uploads.add("-KtvzkOL_75wiKA4CMsr");
adapter = new ProfileUserPostsViewHolder(getContext(), uploads);
recyclerView.setAdapter(adapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
progressDialog.dismiss();
}
});
return rootView;
}
如您所见，我将工具栏的可见性从 HomeActivity 设置为 View.GONE，但是，工具栏现在从所有片段中消失了。我只想要一个带有顶部工具栏的底部导航设置，该工具栏可以在某些片段加载时隐藏，但在其他片段中可见。这可能吗？谢谢。
您可以通过简单地使用此方法来控制在视图分页器中加载的片段数：
viewPager.setOffscreenPageLimit(1); // where n is the number of offscreen pages you want to load.
您可以根据需要增加或减少片段加载数量，但至少 1 个。
希望对您有所帮助。