Question

我试图以固定的时间间隔更改活动的背景。这是我活动的代码

public class ExploreActivity extends Activity {

private int randNum = 0 ;
private int [] colorID = {R.color.AliceBlue,R.color.Beige,R.color.YellowGreen};
private Random rand = new Random();



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


     final Handler handler = new Handler(getMainLooper(), new Callback() {

        @Override
        public boolean handleMessage(Message msg) {
            // TODO Auto-generated method stub
            getWindow().setBackgroundDrawableResource(colorID[msg.arg1]);
            return true;
        }
    });

    final Message msg = new Message();


    Timer timer = new Timer();
    timer.schedule(new TimerTask() {


        @Override
        public void run() {
            // TODO Auto-generated method stub

            randNum = rand.nextInt(colorID.length);
            msg.arg1 = randNum;
            handler.sendMessageAtFrontOfQueue(msg);



        }
    }, 5000, 5000);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.explore, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // TODO Auto-generated method stub
    switch (item.getItemId()) {
    case R.id.action_logout:{
        SharedPreferences settings = getSharedPreferences("settings", MODE_PRIVATE);
        Editor editor = settings.edit();
        editor.putBoolean("login_state", false);
        editor.commit();
        finish();

    }
    default:
        return super.onOptionsItemSelected(item);

    }


}





 }

我收到此错误，颜色更改只发生一次，然后出现此错误

 07-01 08:03:28.364: E/AndroidRuntime(3104): FATAL EXCEPTION: main
 07-01 08:03:28.364: E/AndroidRuntime(3104): java.lang.IllegalStateException: The         specified message queue synchronization  barrier token has not been posted or has already been removed.
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.os.MessageQueue.removeSyncBarrier(MessageQueue.java:266)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.os.Looper.removeSyncBarrier(Looper.java:242)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:981)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.view.Choreographer.doCallbacks(Choreographer.java:562)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.view.Choreographer.doFrame(Choreographer.java:532)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.os.Handler.handleCallback(Handler.java:725)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.os.Handler.dispatchMessage(Handler.java:92)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.os.Looper.loop(Looper.java:137)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at android.app.ActivityThread.main(ActivityThread.java:5041)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at java.lang.reflect.Method.invokeNative(Native Method)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at java.lang.reflect.Method.invoke(Method.java:511)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
 07-01 08:03:28.364: E/AndroidRuntime(3104):    at dalvik.system.NativeStart.main(Native Method)

Plz帮助我采取适当的方式

Answer 1

您可以使用AnimationDrawable轻松实现所需内容。只需在AnimationDrawable xml文件中创建颜色列表即可。并在你的onCreate方法中，将drawable附加到背景并在屏幕获得焦点时启动动画。

示例darwable：

<?xml version="1.0" encoding="utf-8"?>
 <animation-list xmlns:android="http://schemas.android.com/apk/res/android" android:oneshot="false">
 <item android:drawable="@color/red" android:duration="600" />
 <item android:drawable="@color/blue" android:duration="600" />

</animation-list>

和活动：

    AnimationDrawable drawable;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    View parent = findViewById(R.id.parent);
    drawable = (AnimationDrawable) getResources().getDrawable(R.drawable.animation_drawable);
    parent.setBackgroundDrawable(drawable);
}
 @Override
public void onWindowFocusChanged(boolean gained){
  super.onWindowFocusChanged(gained);
  if(gained){
    drawable.start();
}
}

Answer 2

作为一项活动，您希望定期更改颜色，建议您在布局的父视图中添加 ID ，并使用findViewById(R.id.parentView)代替您的{{ 1}}。我相信错误就在那个地方。

Answer 3

您检查了文件[Link]吗？关于sendMessageAtFrontOfQueue：

此方法仅用于非常特殊的情况 - 它很容易使消息队列饿死，导致排序问题或出现其他意外的副作用。

您能否检查sendMessage而不是sendMessageAtFrontOfQueue是否解决了问题？

Answer 4

从developer.android.com上的示例中找出解决方案

 final Handler handler = new Handler(getMainLooper(), new Callback() {

        @Override
        public boolean handleMessage(Message msg) {
            // TODO Auto-generated method stub
            root.setBackgroundResource(imageID[msg.arg1]);
            return true;
        }
    });




    Timer timer = new Timer();
    timer.schedule(new TimerTask() {


        @Override
        public void run() {
            // TODO Auto-generated method stub
            randNum = rand.nextInt(imageID.length);
            Message msg = handler.obtainMessage(1, randNum, 0);
            msg.sendToTarget();
        }
    }, 5000, 8000);

以固定的时间间隔更改背景

4 个答案: