NullPointerException，但不明白為什么

Question

我有一個DialogFragment ，應該顯示一個VideoView和一些TextViews 。 但是，即使布局誇大了， VideoView以及其他控件也為null。

這是我檢索指向各種控件的指針的代碼：

@Override
public void onViewCreated (View view, Bundle savedInstanceState) {
    controls = new MediaController(getActivity());

    title = (TextView) view.findViewById(R.id.title);
    date = (TextView) view.findViewById(R.id.date);
    description = (TextView) view.findViewById(R.id.description);
    video = (VideoView) view.findViewById(R.id.video);

    controls.setAnchorView(video);
    video.setMediaController(controls);
}  

但是，調試器則相反：

為什么它們為空？ 我在定義它們的創建視圖中放大了布局。

堆棧跟蹤：

08-04 06:19:07.804: E/AndroidRuntime(1758): FATAL EXCEPTION: main
08-04 06:19:07.804: E/AndroidRuntime(1758): java.lang.NullPointerException
08-04 06:19:07.804: E/AndroidRuntime(1758):     at com.example.tqafragments.VideoDialog.showNewVideo(VideoDialog.java:61)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at com.example.tqafragments.MainActivity.feedItemSelected(MainActivity.java:36)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at com.example.tqafragments.FeedFragment$2.onItemClick(FeedFragment.java:73)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at android.widget.AdapterView.performItemClick(AdapterView.java:298)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at android.widget.AbsListView.performItemClick(AbsListView.java:1100)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at android.widget.AbsListView$PerformClick.run(AbsListView.java:2749)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at android.widget.AbsListView$1.run(AbsListView.java:3423)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at android.os.Handler.handleCallback(Handler.java:725)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at android.os.Handler.dispatchMessage(Handler.java:92)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at android.os.Looper.loop(Looper.java:137)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at android.app.ActivityThread.main(ActivityThread.java:5041)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at java.lang.reflect.Method.invokeNative(Native Method)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at java.lang.reflect.Method.invoke(Method.java:511)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-04 06:19:07.804: E/AndroidRuntime(1758):     at dalvik.system.NativeStart.main(Native Method)  

ShowNewVideo：

public void showNewVideo(Feed f){
                title.setText(f.getTitle());
                date.setText(f.getDate());
                description.setText(Html.fromHtml(f.getDescription()));
                video.setVideoURI(Uri.parse(f.getVideoURL())); // Line 61
                video.start();
        }

Answer 1

你需要一些改變

把你的代碼

title = (TextView) view.findViewById(R.id.title);
date = (TextView) view.findViewById(R.id.date);
description = (TextView) view.findViewById(R.id.description);
video = (VideoView) view.findViewById(R.id.video);

從onViewCreated（）到onCreateView（），然后在onViewCreated（）方法上綁定數據。