Question

在我的应用中，用户从ListView中进行选择，并根据位置播放歌曲。当用户试图选择一首歌时，Galaxy SII \ SIII手机正在抛出NullPointerExceptions。我将活动设置为保持纵向方向，并具有一个主要布局（activity_main.xml）。

崩溃报告：

java.lang.NullPointerException
at com.soundboard.MainActivity.playSong(MainActivity.java:466)
at com.soundboard.MainActivity$10.onItemClick(MainActivity.java:286)
at android.widget.AdapterView.performItemClick(AdapterView.java:301)
at android.widget.AbsListView.performItemClick(AbsListView.java:1519)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3278)
at android.widget.AbsListView$1.run(AbsListView.java:4327)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5293)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
at dalvik.system.NativeStart.main(Native Method)

代码：

public void  playSong(int songIndex){
    Log.d(TAG, "Starting playSong(" + songIndex + ")");
    FlurryAgent.logEvent("Starting playSong("+songIndex+")");
    try {
        if(mp != null){
            mp.release();
        }
        try{
            mp = MediaPlayer.create(MainActivity.this, songManager.getSong(songIndex).getResId());
        } catch(Exception e){
            FlurryAgent.logEvent("playSong():mediaPlayer.create");
        }
        try{
            mp.prepare();
        } catch(Exception e){
            Log.e(TAG, "Caught error preparing: "+e.getMessage());
            FlurryAgent.logEvent("playSong():mediaPlayer.prepare");
            e.printStackTrace();
        }
        mp.start();//ERROR IS ON THIS LINE
        FlurryAgent.logEvent("mp.start()");
        // Displaying Song title
        String songTitle = songManager.getSong(songIndex).getName();
        songTitleLabel.setText(songTitle);

        // Changing Button Image to pause image
        btnPlay.setImageResource(R.drawable.btn_pause);

        // set Progress bar values
        songProgressBar.setProgress(0);
        songProgressBar.setMax(100);

        // Updating progress bar
        updateProgressBar();            
    } catch (IllegalArgumentException e) {
        Log.e(TAG, "Caught IllegalArgumentException: "+e.getMessage());
    } catch (IllegalStateException e) {
        Log.e(TAG, "Caught IllegalStateException: "+e.getMessage());
    }
}

    @Override
public void onPause(){
    super.onPause();
    if(mp != null){
        try{
        mp.stop();
        mp.release();
        } catch(Exception e){
            Log.e(TAG, "Error in onPause()\n ");
        }
    }
    mHandler.removeCallbacks(mUpdateTimeTask);
    songProgressBar.setProgress(0);
}

Answer 1

如果MediaPlayer.create失败，则mp可以为null。然后你会在它上面调用mp.prepare，这会崩溃。如果创建失败，您希望从此功能返回，而不是继续尝试播放歌曲。

Android NullPointerException仅适用于Galaxy SII / III手机

1 个答案: