解决AnimationDrawable动画不运行的问题

在Activity的onCreate()或者onStart() ,调用AnimationDrawable.start()方法，动画是不会运行的
解决办法:
private Handler handler = new Handler();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.loading);
ImageView line = (ImageView) findViewById(R.id.loading_line);
  handler.postDelayed(new Runnable() {
public void run() {
AnimationDrawable frameAnimation = (AnimationDrawable) line.getBackground();
frameAnimation.start();
}
}, 50);
}
}