片段中的 Tablayout 包 - 空对象引用
Tablayout bundle in fragment - null object reference
我在这里使用本指南制作 activity：http://www.androidhive.info/2015/09/android-material-design-working-with-tabs
然后我添加了一个 AsyncTask。
我正在努力通过
Activity.java
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new ProfileFragment(), "Profile");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFrag(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
@Override
protected void onPostExecute(String JSON_STRING_GET_ID) {
try {
JSONObject jsonResponse = new JSONObject(JSON_STRING_GET_ID);
JSONArray jsonMainNode = jsonResponse.optJSONArray("server_response");
for (int i = 0; i < jsonMainNode.length(); i++) {
JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
get_nav_email = jsonChildNode.optString("email");
Bundle bundle = new Bundle();
bundle.putString("p_email", get_nav_email);
ProfileFragment fragToProfile = new ProfileFragment();
fragToProfile.setArguments(bundle);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
ProfileFragment.java:
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View myInflatedView = inflater.inflate(R.layout.fragment_profile, container,false);
String p_email = getArguments().getString("p_email");
TextView txtTitle = (TextView)myInflatedView.findViewById(R.id.tvUsername2);
txtTitle.setText(p_email);
// Inflate the layout for this fragment
return myInflatedView;
}
这是我得到的错误：
1779-1779/com.testing.dev.application E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.testing.dev.application, PID: 1779
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
at com.testing.dev.application.fragment.ProfileFragment.onCreateView(ProfileFragment.java:43)
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:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1177)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1025)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1545)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:664)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:731)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2615)
at android.view.View.measure(View.java:17547)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
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)
当 Bundle 为 null 时，您正在尝试从 Bundle 中获取 String。
尝试添加检查包是否为空：
String p_email = null;
if(getArguments() != null) {
p_email = getArguments().getString("p_email");
}
您应该使用 setArguments 方法将参数传递给 Fragment。通常推荐使用 newInstance 方法而不是默认构造函数来实例化片段。
参考this and this.
我有一个你可能想在这里考虑的方法！但是，当然，这取决于您。
创建您的 ViewPagerAdapter class 并在您的 addFrag() 方法中，您希望像这样传递电子邮件的值：
private String emailAddress;
public ViewPagerAdapter(FragmentManager manager, String email) {
super(manager);
emailAddress = email;
}
Thta 是您将在 Activity.
中创建的 ViewPagerAdapter 的构造函数
在同一个 ViewPagerAdapter class 中，您将拥有此方法 addFrag
public void addFrag(Fragment fragment, String title) {
Bundle bundle = new Bundle();
//important line here to note
bundle.putString("email", emailAddress);
fragment.setArguments(bundle);
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
现在您正在将电子邮件传递给片段，在片段的 onAttach 方法中，您可以将其提取并设置为 class 级变量。
@Override
public void onAttach(Context ctx){
super.onAttach(ctx);
String emailAddress = getArguments().getInt("email");
//do whatever you need here
}
但是，如果您想在用户不触摸选项卡的情况下更新片段，就像稍后在 AsyncTask 完成后一样，您可以考虑使用 Events.
您基本上是让要更新的片段从 AsyncTask 的 onPostExecute 方法订阅新事件。
我最喜欢的库正在使用 EventBus
您可以像这样简单地添加到您的 build.gradle 文件中：
compile 'org.greenrobot:eventbus:3.0.0'
希望这对您有所帮助，如果您需要任何进一步的帮助，请告诉我！
我在这里使用本指南制作 activity：http://www.androidhive.info/2015/09/android-material-design-working-with-tabs
然后我添加了一个 AsyncTask。
我正在努力通过
Activity.java
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new ProfileFragment(), "Profile");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFrag(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
@Override
protected void onPostExecute(String JSON_STRING_GET_ID) {
try {
JSONObject jsonResponse = new JSONObject(JSON_STRING_GET_ID);
JSONArray jsonMainNode = jsonResponse.optJSONArray("server_response");
for (int i = 0; i < jsonMainNode.length(); i++) {
JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
get_nav_email = jsonChildNode.optString("email");
Bundle bundle = new Bundle();
bundle.putString("p_email", get_nav_email);
ProfileFragment fragToProfile = new ProfileFragment();
fragToProfile.setArguments(bundle);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
ProfileFragment.java:
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View myInflatedView = inflater.inflate(R.layout.fragment_profile, container,false);
String p_email = getArguments().getString("p_email");
TextView txtTitle = (TextView)myInflatedView.findViewById(R.id.tvUsername2);
txtTitle.setText(p_email);
// Inflate the layout for this fragment
return myInflatedView;
}
这是我得到的错误：
1779-1779/com.testing.dev.application E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.testing.dev.application, PID: 1779
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
at com.testing.dev.application.fragment.ProfileFragment.onCreateView(ProfileFragment.java:43)
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:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1177)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1025)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1545)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:664)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:731)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2615)
at android.view.View.measure(View.java:17547)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
当 Bundle 为 null 时，您正在尝试从 Bundle 中获取 String。 尝试添加检查包是否为空：
String p_email = null;
if(getArguments() != null) {
p_email = getArguments().getString("p_email");
}
您应该使用 setArguments 方法将参数传递给 Fragment。通常推荐使用 newInstance 方法而不是默认构造函数来实例化片段。
参考this and this.
我有一个你可能想在这里考虑的方法！但是，当然，这取决于您。
创建您的 ViewPagerAdapter class 并在您的 addFrag() 方法中，您希望像这样传递电子邮件的值：
private String emailAddress;
public ViewPagerAdapter(FragmentManager manager, String email) {
super(manager);
emailAddress = email;
}
Thta 是您将在 Activity.
中创建的 ViewPagerAdapter 的构造函数在同一个 ViewPagerAdapter class 中，您将拥有此方法 addFrag
public void addFrag(Fragment fragment, String title) {
Bundle bundle = new Bundle();
//important line here to note
bundle.putString("email", emailAddress);
fragment.setArguments(bundle);
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
现在您正在将电子邮件传递给片段，在片段的 onAttach 方法中，您可以将其提取并设置为 class 级变量。
@Override
public void onAttach(Context ctx){
super.onAttach(ctx);
String emailAddress = getArguments().getInt("email");
//do whatever you need here
}
但是，如果您想在用户不触摸选项卡的情况下更新片段，就像稍后在 AsyncTask 完成后一样，您可以考虑使用 Events.
您基本上是让要更新的片段从 AsyncTask 的 onPostExecute 方法订阅新事件。
我最喜欢的库正在使用 EventBus
您可以像这样简单地添加到您的 build.gradle 文件中：
compile 'org.greenrobot:eventbus:3.0.0'
希望这对您有所帮助，如果您需要任何进一步的帮助，请告诉我！