完美关闭Android中的应用当按HOME或BACK时

Question

我有一个播放声音的android应用，但是当按HOME/BACK时，我希望声音停止并关闭应用，并且当用户返回到应用程序，我想再次启动该活动，而不是恢复。

我的onPause（）代码：

@Override 
protected void onPause() 
{ 
    super.onPause(); 
    if (pS.isPlaying()) { 
     pS.pause(); //stop the sound 
     finish(); 
    } 
    else 
     finish(); 
} 

当播放声音时，我打HOME或后面我的应用程序FC和我张贴下面的日志：

04-02 13:06:40.563: E/AndroidRuntime(925): FATAL EXCEPTION: main 
04-02 13:06:40.563: E/AndroidRuntime(925): java.lang.RuntimeException: Unable to pause activity {com.testcom.myapp/com.testcom.myapp.MyappActivity}: java.lang.NullPointerException 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2354) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2311) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:2291) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.ActivityThread.access$1700(ActivityThread.java:117) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:938) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.os.Handler.dispatchMessage(Handler.java:99) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.os.Looper.loop(Looper.java:123) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.ActivityThread.main(ActivityThread.java:3683) 
04-02 13:06:40.563: E/AndroidRuntime(925): at java.lang.reflect.Method.invokeNative(Native Method) 
04-02 13:06:40.563: E/AndroidRuntime(925): at java.lang.reflect.Method.invoke(Method.java:507) 
04-02 13:06:40.563: E/AndroidRuntime(925): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
04-02 13:06:40.563: E/AndroidRuntime(925): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
04-02 13:06:40.563: E/AndroidRuntime(925): at dalvik.system.NativeStart.main(Native Method) 
04-02 13:06:40.563: E/AndroidRuntime(925): Caused by: java.lang.NullPointerException 
04-02 13:06:40.563: E/AndroidRuntime(925): at com.testcom.myapp.MyappActivity.onPause(MyappActivity.java:119) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.Activity.performPause(Activity.java:3851) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.Instrumentation.callActivityOnPause(Instrumentation.java:1191) 
04-02 13:06:40.563: E/AndroidRuntime(925): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2341) 
04-02 13:06:40.563: E/AndroidRuntime(925): ... 12 more 

注意：如果正在播放声音并且按HOME/BACK，但在按HOME/BACK时没有声音播放应用FC，则该应用会关闭。我该如何解决这个问题？

Answer 1

尝试：

@Override 
protected void onPause() 
{ 
    super.onPause(); 
    if (pS!= null && pS.isPlaying()) { 
     pS.pause(); //stop the sound 
     finish(); 
    } 
    else 
     finish(); 
} 

我猜测，最有可能在没有播放声音时您pS变量为空，因此您在使用时，它得到一个NPE。

Answer 2

没有必要等待在活动周期的onPause（）达之前ü可以完成（）的活动

@Override 
public boolean onKeyDown(int keyCode, KeyEvent event) 
{  

if(keyCode == KeyEvent.KEYCODE_HOME||keyCode == KeyEvent.KEYCODE_BACK) 
{ 
    if (ps!=null) { 
    pS.pause(); //stop the sound 
    finish(); 
} 
else 
    finish(); 
} 
});