レイヤーをクロスフェードさせて画像を入れ替えます。
動的に実行する場合はコンストラクターに配列で渡します。

TransitionDrawable(Drawable[] layers)

main.xml

<?xml version="1.0" encoding="utf-8"?>
<transition xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/image1"  />
    <item android:drawable="@drawable/image2"  />
</transition>

public classSampleActivity extends Activity {
  TransitionDrawable mTransitionDrawable;

  private static final int TRANSITION_DURATION = 1000;

  @Override public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    ImageView imageView = (ImageView)findViewById(R.id.imageview);
    mTransitionDrawable = (TransitionDrawable)imageView.getDrawable();
    mTransitionDrawable.setCrossFadeEnabled(false);
  }

  public void Reset() {
    mTransitionDrawable.resetTransition();
  }

  public void Transition() {
    mTransitionDrawable.startTransition(TRANSITION_DURATION);
  }

  public void Reverse() {
    mTransitionDrawable.reverseTransition(TRANSITION_DURATION);
  }

}

参考URL:http://y-anz-m.blogspot.jp/2011/08/androidtransitiondrawable.html