Android基于TextView不获取焦点实现跑马灯效果

package com.example.tt;
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.widget.TextView;
public class ScrollingTextView extends TextView {
  public ScrollingTextView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }
  public ScrollingTextView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }
  public ScrollingTextView(Context context) {
    super(context);
  }
  @Override
  protected void onFocusChanged(boolean focused, int direction, Rect previouslyFocusedRect) {
    if(focused)
      super.onFocusChanged(focused, direction, previouslyFocusedRect);
  }
  @Override
  public void onWindowFocusChanged(boolean focused) {
    if(focused)
      super.onWindowFocusChanged(focused);
  }
  @Override
  public boolean isFocused() {
    return true;
  }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >
<com.example.tt.ScrollingTextView
   android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="80dip"
    android:layout_marginBottom="25dip"
    android:textSize="25sp"
    android:singleLine="true"
    android:textColor="@android:color/black"
    android:ellipsize="marquee"
    android:focusable="true"
    android:marqueeRepeatLimit="marquee_forever"
    android:focusableInTouchMode="true"
    android:scrollHorizontally="true"
    android:text="这才是真正的文字跑马灯效果,文字移动速度，文字移动方向，文字移动的样式，动画等等……"
    android:background="#2FFFFFFF" />
<Button
  android:id="@+id/button1"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="Button" />
</LinearLayout>

package com.example.tt;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class MainActivity extends Activity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  }
}