android TextView 走马灯效果

    <TextView android:layout_height="wrap_content"  
    android:layout_width="200dip" 

    android:text="I have a dream I have a dream I have a dream I have a dream"
    android:singleLine="true"     //表示单行显示

    android:ellipsize="marquee"  
    android:marqueeRepeatLimit="marquee_forever"  //表示循环滚动
    android:scrollHorizontally="true"     //表示水平显示
    android:focusableInTouchMode="true"  
    android:focusable="true">