如何恢复暂停 activity

Question

我一直在尝试 resume/restart activity。

预期结果：-当用户打开应用程序时，菜单 Activity 在初始屏幕及其背景 music.And 之后打开，然后在移动到其他 activities.So 之后可以导航到其他 activities.So 31=] 并使用 phone 的后退按钮返回菜单，菜单的背景音乐必须重新启动。

问题：-重新调回后音乐不会重新启动，按下主页按钮并返回应用程序时也不会重新启动。

到目前为止我做了什么：-我尝试使用 onRestart() 和 onResume()，但两者都给我致命错误。菜单代码Activity:-

 public class Menu  extends ListActivity {
 MediaPlayer song;

String classes[] = { "MainActivity", "Text", "Email", "Sample", "About",
        "AboutMe", "example6"};

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setListAdapter(new ArrayAdapter<String>(Menu.this, android.R.layout.simple_expandable_list_item_1, classes));
    song = MediaPlayer.create(Menu.this, R.raw.backmusic);
    song.start();
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    // TODO Auto-generated method stub
    super.onListItemClick(l, v, position, id);
    String cheese = classes[position];
    try{
    Class ourClass = Class.forName("com.stenstudios.secondapp." + cheese);
    Intent ourIntent = new Intent(Menu.this, ourClass);
    startActivity(ourIntent);
}catch(ClassNotFoundException e){
    e.printStackTrace();
}


}
@Override
protected void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
    song.release(); 
}

@Override
protected void onRestart() {
    // TODO Auto-generated method stub
    super.onRestart();
    song.start();
}

LogCat:-`

  04-07 15:44:29.500: E/AndroidRuntime(18816): FATAL EXCEPTION: main
  04-07 15:44:29.500: E/AndroidRuntime(18816):Process:com.stenstudios.secondapp, PID: 18816
  04-07 15:44:29.500: E/AndroidRuntime(18816): java.lang.RuntimeException: Unable to resume activity {com.stenstudios.secondapp/com.stenstudios.secondapp.Menu}: java.lang.IllegalStateException
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2812)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2841)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.os.Handler.dispatchMessage(Handler.java:102)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.os.Looper.loop(Looper.java:136)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.app.ActivityThread.main(ActivityThread.java:5146)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at java.lang.reflect.Method.invokeNative(Native Method)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at java.lang.reflect.Method.invoke(Method.java:515)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at dalvik.system.NativeStart.main(Native Method)
  04-07 15:44:29.500: E/AndroidRuntime(18816): Caused by: java.lang.IllegalStateException
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.media.MediaPlayer._start(Native Method)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.media.MediaPlayer.start(MediaPlayer.java:1064)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at com.stenstudios.secondapp.Menu.onRestart(Menu.java:53)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.app.Instrumentation.callActivityOnRestart(Instrumentation.java:1181)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.app.Activity.performRestart(Activity.java:5291)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.app.Activity.performResume(Activity.java:5302)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2802)
  04-07 15:44:29.500: E/AndroidRuntime(18816):  ... 10 more
  04-07 15:44:30.992: I/Process(18816): Sending signal. PID: 18816 SIG: 9

它让我 IllegalStateException.How 当用户导航回菜单时我是否恢复媒体播放器。谢谢。更新：- 现在我不明白 error.Error 是因为 mediaplayer 在重新初始化 mediaplayer 后返回 null.But 它仍然没有播放歌曲。

Answer 1

检查您的 MediaPlayer return 是否为 null 或 returning 到 activity 之后的内容... 如果它 return 为 null 那么你必须先初始化它然后开始...

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