如何恢复已暂停的活动

Question

我一直在尝试恢复/重新启动活动。

预期结果： - 当用户打开App时，菜单活动会在启动屏幕及其背景音乐后打开。然后可以导航到其他活动。因此在移动到其他活动并使用手机的后退按钮返回菜单后菜单的背景音乐必须重新启动。

问题： - 重新调回音乐后不会重新启动，也不会按住home按钮并回到应用程序。

到目前为止我做了什么： - 我尝试使用onRestart（）和onResume（），但都给我致命错误。 代码菜单活动： -

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(); 
} 

的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 

它给了我IllegalStateException.How做我恢复媒体播放器为用户导航回菜单。 谢谢。 更新： - 现在我没有得到error.Error是由于mediaplayer返回null.But重新初始化mediaplayer它仍然不播放歌曲。

Answer 1

检查是否你的MediaPlayer返回null或返回到活动后的... ，如果返回null，那么你必须先初始化，然后开始......