《Try and Catch》在Android上的问题

Question

一旦我执行下面的代码，媒体播放了60秒，我的应用程序关闭了一个错误"不幸的是，你的应用程序已经停止。"． 如果我在最后一个块上删除"bv.setImageResource(R.drawable.play);"，应用程序就会完美运行。

bv.setImageResource(R.drawable.play)最后块的问题是什么?

这是我的代码

bv = (ImageButton) findViewById(R.id.imageButton1);
private void mpsleep() {
    mp.start();
    Thread timer= new Thread(){
        public void run(){
            try{
                for (i =1;i<60;i++){
                    sleep(1000);//1 second pause
                }
            }catch(Exception e){
                e.printStackTrace();
            }finally{
                mp.pause();
                mp.seekTo(0);
                bv.setImageResource(R.drawable.play);
            }
        }
    };
    timer.start();
}

LogCat

03-06 11:03:39.743: V/MediaPlayer(31802): message received msg=4, ext1=0, ext2=0
03-06 11:03:39.743: V/MediaPlayer(31802): Received seek complete
03-06 11:03:39.743: V/MediaPlayer(31802): All seeks complete - return to regularly scheduled program
03-06 11:03:39.743: V/MediaPlayer(31802): callback application
03-06 11:03:39.743: V/MediaPlayer(31802): back from callback
03-06 11:03:39.743: E/MediaPlayer(31802): mOnSeekCompleteListener is null. Failed to send MEDIA_SEEK_COMPLETE message.
03-06 11:03:40.918: V/MediaPlayer(31802): isPlaying: 1
03-06 11:03:40.918: V/MediaPlayer-JNI(31802): isPlaying: 1
03-06 11:03:40.918: V/MediaPlayer-JNI(31802): pause
03-06 11:03:40.918: V/MediaPlayer(31802): pause
03-06 11:03:40.923: V/MediaPlayer-JNI(31802): seekTo: 0(msec)
03-06 11:03:40.923: V/MediaPlayer(31802): seekTo 0
03-06 11:03:40.923: V/MediaPlayer(31802): getDuration
03-06 11:03:40.923: V/MediaPlayer(31802): message received msg=4, ext1=0, ext2=0
03-06 11:03:40.923: W/dalvikvm(31802): threadid=11: thread exiting with uncaught exception (group=0x40c541f8)
03-06 11:03:40.923: V/MediaPlayer(31802): Received seek complete
03-06 11:03:40.923: V/MediaPlayer(31802): All seeks complete - return to regularly scheduled program
03-06 11:03:40.923: V/MediaPlayer(31802): callback application
03-06 11:03:40.923: V/MediaPlayer(31802): back from callback
03-06 11:03:40.928: E/MediaPlayer(31802): mOnSeekCompleteListener is null. Failed to send MEDIA_SEEK_COMPLETE message.
03-06 11:03:40.953: E/AndroidRuntime(31802): FATAL EXCEPTION: Thread-20100
03-06 11:03:40.953: E/AndroidRuntime(31802): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4286)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:885)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.view.View.requestLayout(View.java:12881)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.view.View.requestLayout(View.java:12881)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.view.View.requestLayout(View.java:12881)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.view.View.requestLayout(View.java:12881)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:268)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.view.View.requestLayout(View.java:12881)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:268)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.view.View.requestLayout(View.java:12881)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at android.widget.ImageView.setImageResource(ImageView.java:316)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at com.hello.YourApp.MainActivity.stopsound(MainActivity.java:118)
03-06 11:03:40.953: E/AndroidRuntime(31802):    at com.hello.YourApp.MainActivity$6.run(MainActivity.java:143)
03-06 11:03:46.068: D/OpenGLRenderer(31802): Flushing caches (mode 0)

Answer 1

异常信息说明得很清楚:

android.view。ViewRootImpl$ callledfromwrongthreadeexception:只有创建视图层次结构的原始线程可以触摸它的视图。

你不能从单独的线程访问UI元素。删除

setImageResource(R.drawable.play) 

from run() .

如果有一小段代码(Activity类内部)需要在UI线程上运行，你可以在Activity中使用这个方法:

runOnUiThread(new Runnable(){
  @override
  public void run(){
    //-- put code here--
  }
});

Answer 2

按照下面的代码使用UI线程

    bv = (ImageButton) findViewById(R.id.imageButton1);
private void mpsleep() {
    mp.start();
    Thread timer= new Thread(){
        public void run(){
            try{
                for (i =1;i<60;i++){
                    sleep(1000);//5 second pause
                }
            }catch(Exception e){
                e.printStackTrace();
            }finally{
                mp.pause();
                mp.seekTo(0);
        runOnUiThread(new Runnable() {
        @Override
        public void run() {
                bv.setImageResource(R.drawable.play);
        }
    });
            }
        }
    };
    timer.start();
}

解释:

->您可能在Main thread(UI thread)上运行的onCreate或onResume方法中编写了bv = (ImageButton) findViewById(R.id.imageButton1);。

->你已经创建了一个新的线程Thread timer= new Thread()，并试图操纵组件bv，但bv绑定到Main Thread(UI thread)，所以你有麻烦。使用runOnUiThread(new Runnable)方法即可解决。

希望对大家有帮助!

Answer 3

使用处理程序来运行代码bv.setImageResource (R.drawable.play);