ScrollView和丢失滚动条

Question

我创建了我自己的类，它扩展了ScrollView，但滚动条消失了。当我滚动页面时如何显示滚动条。这是我的代码类：

package se.nindev.restaurant.views; 

import android.content.Context; 
import android.util.AttributeSet; 
import android.view.MotionEvent; 
import android.widget.ScrollView; 

public class ScrollViewer extends ScrollView { 
    private float mLastX; 
    private float mLastY; 
    private float mDiffX; 
    private float mDiffY; 

     public ScrollViewer(Context context) { 
      this(context, null); 
     } 

     public ScrollViewer(Context context, AttributeSet attrs) { 
      this(context, attrs, 0); 
     } 
     public ScrollViewer(Context context, AttributeSet attrs, int defStyle) { 
      super(context, attrs, defStyle); 
     } 

//  @Override 
//  public boolean dispatchTouchEvent(MotionEvent ev){ 
//   return super.dispatchTouchEvent(ev); 
//  } 
     @Override 
     public boolean onInterceptTouchEvent(MotionEvent ev) { 
      switch (ev.getAction()) { 
       case MotionEvent.ACTION_DOWN: 
        // reset difference values 
        mDiffX = 0; 
        mDiffY = 0; 

        mLastX = ev.getX(); 
        mLastY = ev.getY(); 
        break; 

       case MotionEvent.ACTION_MOVE: 
        final float curX = ev.getX(); 
        final float curY = ev.getY(); 
        mDiffX += Math.abs(curX - mLastX); 
        mDiffY += Math.abs(curY - mLastY); 
        mLastX = curX; 
        mLastY = curY; 

        // don't intercept event, when user tries to scroll horizontally 
        if (mDiffX > mDiffY) { 
         return false; 
        } 
      } 
     return super.onInterceptTouchEvent(ev); 
     } 
} 

更比别人当我在页面滚动型中间滚动元件disaper喜欢在页面的顶端底部GRAFIC的影响，但在我的课我没有说效果。我如何将正常滚动视图中的所有效果添加到我的课程中？

编辑：好，我添加滚动条：android:scrollbars="vertical"，但仍然不知道如何添加此GRAFIC效果

Answer 1

ScrollView scrollView = new ScrollView(getContext()); 
scrollView.setVerticalScrollBarEnabled(true); 
scrollView.setHorizontalScrollBarEnabled(true); 

Answer 2

android:background="@color/white" 
android:fadingEdge="vertical" 

我们需要改变在白色背景滚动视图和使用衰落边缘