Android TextView跑马灯效果实现方法

public class MyTextView extends TextView{
  public MyTextView(Context context, AttributeSet attrs) {
    super(context, attrs);
    // TODO Auto-generated constructor stub
  }
  public MyTextView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    // TODO Auto-generated constructor stub
  }
  public MyTextView(Context context) {
    super(context);
    // TODO Auto-generated constructor stub
  }
  @Override
  public boolean isFocused() {
    // TODO Auto-generated method stub
    return true;   //must be return true;
  }
}

<packagename.MyTextView android:id="@+id/my_textview"
android:layout_width="400px" android:layout_height="35px" 
android:singleLine="true" android:ellipsize="marquee"
android:marqueeRepeatLimit="marquee_forever" android:textSize="22sp"/>