Question

我有3个按钮，当按下按钮时会播放声音。但由于某种原因，我现在开始得到这个错误，在我实现了所有3个按钮之后。当我只做一个按钮时，它播放的声音没有错误。在我实施了2个之后，应用程序开始崩溃这是我的.xml

按钮的代码

 <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Play!"
        android:id="@+id/play1"
        android:layout_below="@+id/imageView"
        android:layout_toLeftOf="@+id/play3"
        android:layout_toStartOf="@+id/play3" />

这是mainactivity.java

中的代码

//    final MediaPlayer mp = MediaPlayer.create(this, R.raw.sounds1);
//    final MediaPlayer mp2 = MediaPlayer.create(this, R.raw.sounds2);
//    final MediaPlayer mp3 = MediaPlayer.create(this, R.raw.sounds3);

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

//        Button play_button = (Button)this.findViewById(R.id.play1);
////        Button play_button2 = (Button)this.findViewById(R.id.play2);
////        Button play_button3 = (Button)this.findViewById(R.id.play3);
//
//        play_button.setOnClickListener(new View.OnClickListener() {
//            public void onClick(View v) {
//
//
//                mp.start();
//            }
//        });
//
//        play_button2.setOnClickListener(new View.OnClickListener() {
//            public void onClick(View v) {
//
//
//                mp2.start();
//            }
//        });
//
//        play_button3.setOnClickListener(new View.OnClickListener() {
//            public void onClick(View v) {
//
//
//                mp3.start();
//            }
//        });
    }

这也是日志！

  java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.sounds.apps.sounds/com.sounds.apps.sounds.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
            at android.content.ContextWrapper.getResources(ContextWrapper.java:85)
            at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:74)
            at android.media.MediaPlayer.create(MediaPlayer.java:919)
            at android.media.MediaPlayer.create(MediaPlayer.java:902)
            at com.sounds.apps.sounds.MainActivity.<init>(MainActivity.java:14)
            at java.lang.reflect.Constructor.newInstance(Native Method)
            at java.lang.Class.newInstance(Class.java:1572)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer 1

       @Override
       protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
      final MediaPlayer mp = MediaPlayer.create(this, R.raw.sounds1);
     final MediaPlayer mp2 = MediaPlayer.create(this, R.raw.sounds2);
    final MediaPlayer mp3 = MediaPlayer.create(this, R.raw.sounds3);
   Button play_button = (Button)this.findViewById(R.id.play1);
    Button play_button2 = (Button)this.findViewById(R.id.play2);
    Button play_button3 = (Button)this.findViewById(R.id.play3);

    play_button.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {


           mp.start();
       }
    });

    play_button2.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {


            mp2.start();
        }
   });

    play_button3.setOnClickListener(new View.OnClickListener() {
       public void onClick(View v) {


            mp3.start();
       }
    });
}

通过按钮崩溃播放声音（Android）

1 个答案: