ListView 实现阻尼回弹效果并去除边缘阴影

灰太狼 2022-08-06 11:05 213阅读 0赞

我们使用ListView将位置拖到顶部和底部默认是没有回弹效果的，为了增加这个效果，方法如下：

1、开启overScrollMode为always  
在布局中  
android:overScrollMode="always"  
或在代码中  
setOverScrollMode(View.OVER\_SCROLL\_ALWAYS);

2、继承listview 覆盖overScrollBy方法，并且利用反射机制修改阴影效果为透明

public class BounceListView extends ListView {
        private static final int MAX_Y_OVERSCROLL_DISTANCE = 100;
     
        private Context mContext;
        private int mMaxYOverscrollDistance;
     
        public BounceListView(Context context) {
            super(context);
            mContext = context;
            initBounceListView();
        }
     
        public BounceListView(Context context, AttributeSet attrs) {
            super(context, attrs);
            mContext = context;
            initBounceListView();
        }
     
        public BounceListView(Context context, AttributeSet attrs, int defStyle) {
            super(context, attrs, defStyle);
            mContext = context;
            initBounceListView();
        }
     
        private void initBounceListView() {
            // get the density of the screen and do some maths with it on the max
            // overscroll distance
            // variable so that you get similar behaviors no matter what the screen
            // size
     
            final DisplayMetrics metrics = mContext.getResources()
                    .getDisplayMetrics();
            final float density = metrics.density;
            mMaxYOverscrollDistance = (int) (density * MAX_Y_OVERSCROLL_DISTANCE);
             
    //      this.setOverScrollMode(View.OVER_SCROLL_ALWAYS);
             
            try {
                Class<?> c = (Class<?>) Class.forName(AbsListView.class.getName());
                Field egtField = c.getDeclaredField("mEdgeGlowTop");
                Field egbBottom = c.getDeclaredField("mEdgeGlowBottom");
                egtField.setAccessible(true);
                egbBottom.setAccessible(true);
                Object egtObject = egtField.get(this); // this 指的是ListiVew实例
                Object egbObject = egbBottom.get(this);
     
                // egtObject.getClass() 实际上是一个 EdgeEffect 其中有两个重要属性 mGlow mEdge
                // 并且这两个属性都是Drawable类型
                Class<?> cc = (Class<?>) Class.forName(egtObject.getClass()
                        .getName());
                Field mGlow = cc.getDeclaredField("mGlow");
                mGlow.setAccessible(true);
                mGlow.set(egtObject, new ColorDrawable(Color.TRANSPARENT));
                mGlow.set(egbObject, new ColorDrawable(Color.TRANSPARENT));
     
                Field mEdge = cc.getDeclaredField("mEdge");
                mEdge.setAccessible(true);
                mEdge.set(egtObject, new ColorDrawable(Color.TRANSPARENT));
                mEdge.set(egbObject, new ColorDrawable(Color.TRANSPARENT));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
     
        @SuppressLint("NewApi")
        @Override
        protected boolean overScrollBy(int deltaX, int deltaY, int scrollX,
                int scrollY, int scrollRangeX, int scrollRangeY,
                int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {
            // This is where the magic happens, we have replaced the incoming
            // maxOverScrollY with our own custom variable mMaxYOverscrollDistance;
            return super.overScrollBy(deltaX, deltaY, scrollX, scrollY,
                    scrollRangeX, scrollRangeY, maxOverScrollX,
                    mMaxYOverscrollDistance, isTouchEvent);
        }
    }

转载：

http://www.apkbus.com/android-208825-1-1.html

http://bbs.csdn.net/topics/390350587?page=1\#post-393524028