Question

所以，在阅读了Android网站上有关DialogFragment的官方教程后，我决定自己使用它。代码如下：

    @Override
    public void feedItemSelected(Feed item) {
        if(isXHDPI == true){
            FragmentManager fm = getSupportFragmentManager();
            VideoFragment videoFragment = (VideoFragment) fm.findFragmentById(R.id.videoFragment);
            videoFragment.displayNewFeed(item);
        }else{
            //TODO add DialogFragment support
            VideoDialog v = new VideoDialog();
            v.show(getSupportFragmentManager(), "dialog");
            v.showNewVideo(item);
        }
    }

这段代码来自MainActivity。它实现了一个侦听器来从另一个Fragment获取事件并适当地响应它。对于平板电脑，它会在另一个片段中显示数据。对于小型手机，我需要显示DialogFragment用户可以看到视频的地方。

但是，我在小型手机中获得了NullPointerException。换句话说，DialogFragment永远不会显示。的为什么吗

VideoDialog：

import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.text.Html;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.MediaController;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.VideoView;

public class VideoDialog extends DialogFragment {

    MediaController controls = null;
    VideoView video = null;
    TextView title = null;
    TextView date = null;
    TextView description = null;
//------------------------------------------------------------------------------
        @Override
        public void onCreate(Bundle savedInstanceState){
            super.onCreate(savedInstanceState);
        }
//------------------------------------------------------------------------------
        @Override 
        public View onCreateView(LayoutInflater inflater, 
                ViewGroup container, 
                Bundle savedInstanceState){
            return inflater.inflate(
                    R.layout.video_fragment, 
                    container, 
                    false); // inflate the fragment layout
        }
//------------------------------------------------------------------------------
        @Override 
        public void onStart(){
            super.onStart();

            controls = new MediaController(getActivity());

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

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

        }
//------------------------------------------------------------------------------
        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()));
            video.start();

            Toast.makeText(getActivity(), "Video started", Toast.LENGTH_LONG).show();
        }
//------------------------------------------------------------------------------
}

<小时/> StackTrace：

08-03 11:22:35.944: E/AndroidRuntime(801): FATAL EXCEPTION: main
08-03 11:22:35.944: E/AndroidRuntime(801): java.lang.NullPointerException
08-03 11:22:35.944: E/AndroidRuntime(801):  at com.example.tqafragments.VideoDialog.showNewVideo(VideoDialog.java:55)
08-03 11:22:35.944: E/AndroidRuntime(801):  at com.example.tqafragments.MainActivity.feedItemSelected(MainActivity.java:36)
08-03 11:22:35.944: E/AndroidRuntime(801):  at com.example.tqafragments.FeedFragment$2.onItemClick(FeedFragment.java:73)
08-03 11:22:35.944: E/AndroidRuntime(801):  at android.widget.AdapterView.performItemClick(AdapterView.java:298)
08-03 11:22:35.944: E/AndroidRuntime(801):  at android.widget.AbsListView.performItemClick(AbsListView.java:1100)
08-03 11:22:35.944: E/AndroidRuntime(801):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:2749)
08-03 11:22:35.944: E/AndroidRuntime(801):  at android.widget.AbsListView$1.run(AbsListView.java:3423)
08-03 11:22:35.944: E/AndroidRuntime(801):  at android.os.Handler.handleCallback(Handler.java:725)
08-03 11:22:35.944: E/AndroidRuntime(801):  at android.os.Handler.dispatchMessage(Handler.java:92)
08-03 11:22:35.944: E/AndroidRuntime(801):  at android.os.Looper.loop(Looper.java:137)
08-03 11:22:35.944: E/AndroidRuntime(801):  at android.app.ActivityThread.main(ActivityThread.java:5041)
08-03 11:22:35.944: E/AndroidRuntime(801):  at java.lang.reflect.Method.invokeNative(Native Method)
08-03 11:22:35.944: E/AndroidRuntime(801):  at java.lang.reflect.Method.invoke(Method.java:511)
08-03 11:22:35.944: E/AndroidRuntime(801):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-03 11:22:35.944: E/AndroidRuntime(801):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-03 11:22:35.944: E/AndroidRuntime(801):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

DialogFragment创建类似

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

    View view = getActivity().getLayoutInflater().inflate(R.layout.video_fragment, null);
    builder.setView(view);
    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);
    return builder.create();
}

尝试显示DialogFragment时出现NullPointerException

1 个答案: