java - MediaPlayer 使我的应用程序崩溃(编辑 : it was caused by an out of bound array)

Question

作为此问题的后续App Crashing when playing sounds in succession in MediaPlayer

我将 onCreate 中的代码复制到另一个方法(名为 buttonTapped)中。应用程序在 onCreate 期间正确播放声音，但在调用 buttonTapped 方法(通过点击按钮)时崩溃且不播放任何声音。错误信息是:

unfortunately the application has stopped.

这是代码，后面是堆栈跟踪

public class MainActivity extends Activity implements MediaPlayer.OnCompletionListener {

    int[] tracks = new int[3];
    int currentTrack = 0;
    private MediaPlayer mediaPlayer = null;    

    public void buttonTapped(View view){
        tracks[0] = R.raw.p46;
        tracks[1] = R.raw.p52;
        tracks[2] = R.raw.p55;
        mediaPlayer = MediaPlayer.create(getApplicationContext(), tracks[currentTrack]);
        mediaPlayer.setOnCompletionListener(this);
        mediaPlayer.start();

    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tracks[0] = R.raw.p46;
        tracks[1] = R.raw.p52;
        tracks[2] = R.raw.p55;
        mediaPlayer = MediaPlayer.create(getApplicationContext(), tracks[currentTrack]);
        mediaPlayer.setOnCompletionListener(this);
        mediaPlayer.start();    
    }

    public void onCompletion(MediaPlayer arg0) {
        arg0.release();
        currentTrack++;

        if (currentTrack < tracks.length) {
            arg0 = MediaPlayer.create(getApplicationContext(), tracks[currentTrack]);
            arg0.setOnCompletionListener(this);
            arg0.start();
        }
    }

  530-530/com.maxd.soundtesting E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.maxd.soundtesting, PID: 530
    java.lang.IllegalStateException: Could not execute method of the activity
            at android.view.View$1.onClick(View.java:4020)
            at android.view.View.performClick(View.java:4780)
            at android.view.View$PerformClick.run(View.java:19866)
            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:5257)
            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)
     Caused by: java.lang.reflect.InvocationTargetException
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at android.view.View$1.onClick(View.java:4015)
            at android.view.View.performClick(View.java:4780)
            at android.view.View$PerformClick.run(View.java:19866)
            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:5257)
            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)
     Caused by: java.lang.ArrayIndexOutOfBoundsException: length=3; index=3
            at com.maxd.soundtesting.MainActivity.buttonTapped(MainActivity.java:22)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at android.view.View$1.onClick(View.java:4015)
            at android.view.View.performClick(View.java:4780)
            at android.view.View$PerformClick.run(View.java:19866)
            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:5257)
            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)

Answer 1

在点击按钮时，您不会将 currentTrack 重置为 0。因此，在 onCreate 播放了 3 个声音后，currentTrack = 3，这是一个无效索引，因为当前轨道只能等于 0、1 或 2。