您无法在未连接的视图或片段上启动加载，其中getActivity（）返回空值
问题描述：
我正在使用FragmentStatePagerAdapter在活动中显示5个片段。在每个活动中，我显示的是从FirebaseListAdapter/FirebaseRecyclerAdapter。因为它是FragmentStagePagerAdapter相邻的视图/片段将被初始化，即使它们不可见。如果标签以快速方式滚动（向前/向后），应用程序崩溃与上述错误。我发现了一些类似的问题在互联网上，但没有能够解决此问题。我也越来越如果我开始一个新的活动（在活动中，我在网格视图中显示来自Firebase的图像）并立即关闭它（按下按钮），您无法为已销毁的活动启动加载错误后退按钮） 我正在使用以下代码。您无法在未连接的视图或片段上启动加载，其中getActivity（）返回空值
adapt= new FirebaseListAdapter<MyClassStudent>(getActivity(), MyClassStudent.class, R.layout.mychild_grid_template, myRef) {
@Override
protected void populateView(final View v, MyClassStudent model, int position) {
final TextView uname = (TextView) v.findViewById(R.id.mychild_uname);
final CircleImageView profileImage=(CircleImageView)v.findViewById(R.id.mychild_image);
studRef.child(model.getUsername()).addListenerForSingleValueEvent(new ValueEventListener() {
public void onDataChange(DataSnapshot dataSnapshot) {
Child child=dataSnapshot.getValue(Child.class);
uname.setText(child.getUsername());
Glide.with(getActivity()).load(child.getProfileImage()).into(profileImage);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
};
堆栈跟踪：
E/UncaughtException: java.lang.NullPointerException: You cannot start a load on a not yet attached View or a Fragment where getActivity() returns null (which usually occurs when getActivity() is called before the Fragment is attached or after the Fragment is destroyed).
at com.bumptech.glide.util.Preconditions.checkNotNull(Preconditions.java:27)
at com.bumptech.glide.Glide.getRetriever(Glide.java:509)
at com.bumptech.glide.Glide.with(Glide.java:563)
at com.mycompany.educareteacher.FragmentStudents$2$1.onDataChange(FragmentStudents.java:184)
at com.google.firebase.database.zzp.onDataChange(Unknown Source)
at com.google.android.gms.internal.tl.zza(Unknown Source)
at com.google.android.gms.internal.vg.zzHW(Unknown Source)
at com.google.android.gms.internal.vm.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5438)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:738)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:628)
D/FA: Logging event (FE): app_exception(_ae), Bundle[{firebase_event_origin(_o)=crash, firebase_screen_class(_sc)=ClassDetailActivity, firebase_screen_id(_si)=-4663411025690523798, timestamp=1500710706898, fatal=1}]
V/FA: Recording user engagement, ms: 3544
D/FA: Logging event (FE): user_engagement(_e), Bundle[{firebase_event_origin(_o)=auto, engagement_time_msec(_et)=3544, firebase_screen_class(_sc)=ClassDetailActivity, firebase_screen_id(_si)=-4663411025690523798}]
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.mycompany.com.educareteacher, PID: 5154
java.lang.NullPointerException: You cannot start a load on a not yet attached View or a Fragment where getActivity() returns null (which usually occurs when getActivity() is called before the Fragment is attached or after the Fragment is destroyed).
at com.bumptech.glide.util.Preconditions.checkNotNull(Preconditions.java:27)
at com.bumptech.glide.Glide.getRetriever(Glide.java:509)
at com.bumptech.glide.Glide.with(Glide.java:563)
at com.mycompany.educareteacher.FragmentStudents$2$1.onDataChange(FragmentStudents.java:184)
at com.google.firebase.database.zzp.onDataChange(Unknown Source)
at com.google.android.gms.internal.tl.zza(Unknown Source)
at com.google.android.gms.internal.vg.zzHW(Unknown Source)
at com.google.android.gms.internal.vm.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5438)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:738)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:628)
我怎样才能解决这个问题？
答
您的片段响应从火力点来之前分离，所以尽量使用
public void onDataChange(DataSnapshot dataSnapshot) {
if (getActivity() == null) {
return;
}
Child child = dataSnapshot.getValue(Child.class);
uname.setText(child.getUsername());
Glide.with(getActivity()).load(child.getProfileImage()).into(profileImage);
}
你可以这样做检查活动为空或不是在别的地方之前检查getActivity()空。
private Activity mActivity;
@Override
public void onAttach(Context context) {
super.onAttach(context);
mActivity = getActivity();
}
@Override
public void onDetach() {
super.onDetach();
mActivity = null;
}
private void doAction() {
if (mActivity == null) {
return;
}
adapt = new FirebaseListAdapter<MyClassStudent>(mActivity, MyClassStudent.class, R.layout.mychild_grid_template, myRef) {
@Override
protected void populateView(final View v, MyClassStudent model, int position) {
final TextView uname = (TextView) v.findViewById(R.id.mychild_uname);
final CircleImageView profileImage = (CircleImageView) v.findViewById(R.id.mychild_image);
studRef.child(model.getUsername()).addListenerForSingleValueEvent(new ValueEventListener() {
public void onDataChange(DataSnapshot dataSnapshot) {
if (mActivity == null) {
return;
}
Child child = dataSnapshot.getValue(Child.class);
uname.setText(child.getUsername());
Glide.with(mActivity).load(child.getProfileImage()).into(profileImage);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
};
}