Animating custom View class

when i try to animate custom View (created in java code), there is no effect, animation doesn't start. This is how i do that:

    final Animation animation = AnimationUtils.loadAnimation(this, R.anim.animation);
    final CustomView background = new CustomView(this);
    background.setBackgroundResource(R.drawable.bg);
    background.startAnimation(animation);

CustomView extends ImageView.

This code doesn't start animation, i tried also with ImageView, and also doesn't work.

Animation works only when i am getting View from findViewById(id).

Here is animation code:

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"开发者_StackOverflow
    android:shareInterpolator="false"
    >
    <alpha
        android:fromAlpha="0.0"
        android:toAlpha="1.0"
        android:duration="1000"
        />
    <alpha
        android:fromAlpha="1.0"
        android:toAlpha="1.0"
        android:startOffset="1000"
        android:duration="6000"
        />
    <alpha
        android:fromAlpha="1.0"
        android:toAlpha="0.0"
        android:startOffset="7000"
        android:duration="1000"
        />
</set>

Problem solved. I found that animation in fact was executing, but real problem was in my custom View class, where i forget to call super in onAnimationStart and onAnimationEnd.