android viewpager滑动卡顿

当SwipeRefreshLayout中放置了ViewPager控件,两者的滑动会相互冲突.具体表现为ViewPager的左右滑动不顺畅,容易被SwipeRefreshLayout拦截(即出现刷新的View). 问题原因:Vie

问题说明:当SwipeRefreshLayout中放置了ViewPager控件,两者的滑动会相互冲突.具体表现为ViewPager的左右滑动不顺畅,容易被SwipeRefreshLayout拦截(即出现刷新的View).

问题原因:ViewPager本身是处理了滚动事件的冲突,它在横向滑动时会调用requestDisallowInterceptTouchEvent()方法使父控件不拦截当前的Touch事件序列.但是SwipeRefreshLayout的requestDisallowInterceptTouchEvent()方法什么也没有做,所以仍然会拦截当前的Touch事件序列.

问题分析:为什么SwipeRefreshLayout的requestDisallowInterceptTouchEvent()方法什么都不做?

首先SwipeRefreshLayout继承自ViewGroup.

在requestDisallowInterceptTouchEvent()方法什么都不做的情况下,用户可以从底部下拉刷新一次拉出LoadingView. 如果方法调用ViewGroup的requestDisallowInterceptTouchEvent()方法, 可以解决ViewPager的兼容问题,但是用户在界面底部下拉至头部后,无法继续下拉,需要手指放开一次才能拉出LoadingView. 目标分析: 那么为了更加顺滑地滚动,想要的效果当然是一次性拉出LoadingView.既然ViewPager在左右滑动时才会调用requestDisallowInterceptTouchEvent()方法,那么SwipeRefreshLayout只应该在上下滑动时才拦截Touch事件.

具体逻辑如下:

记录是否调用了requestDisallowInterceptTouchEvent()方法,并且设置为true. 在SwipeRefreshLayout中判断是否是上下滑动. 如果同时满足1,2,则调用super.requestDisallowInterceptTouchEvent(true). 否则调用super.requestDisallowInterceptTouchEvent(false). 注意:因为ViewGroup的requestDisallowInterceptTouchEvent方法设置true后,Touch事件在dispatchTouchEvent()方法中就会被拦截,所以需要在dispatchTouchEvent()方法中判断是否为上下滑动.

实现代码(部分):

//非法按键
 private static final int INVALID_POINTER = -1; 
//dispatch方法记录第一次按下的x 
private float mInitialDisPatchDownX;
 //dispatch方法记录第一次按下的y 
private float mInitialDisPatchDownY; 
//dispatch方法记录的手指 
private int mActiveDispatchPointerId = INVALID_POINTER; 
//是否请求拦截 
private boolean hasRequestDisallowIntercept = false; 
@Override 
public void requestDisallowInterceptTouchEvent(boolean b) {
 hasRequestDisallowIntercept = b; // Nope. 
} 
@Override 
public boolean dispatchTouchEvent(MotionEvent ev) { 
switch (ev.getAction()) {
 case MotionEvent.ACTION_DOWN: 
mActiveDispatchPointerId = MotionEventCompat.getPointerId(ev, 0); 
final float initialDownX = getMotionEventX(ev, mActiveDispatchPointerId);
 if (initialDownX != INVALID_POINTER) { 
mInitialDisPatchDownX = initialDownX; 
} 
final float initialDownY = getMotionEventY(ev, mActiveDispatchPointerId); 
if (mInitialDisPatchDownY != INVALID_POINTER) { mInitialDisPatchDownY = initialDownY; 
} 
break;
case MotionEvent.ACTION_MOVE:
 if (hasRequestDisallowIntercept) { 
//解决viewPager滑动冲突问题
 final float x = getMotionEventX(ev, mActiveDispatchPointerId); 
final float y = getMotionEventY(ev, mActiveDispatchPointerId); 
if (mInitialDisPatchDownX != INVALID_POINTER && x != INVALID_POINTER && mInitialDisPatchDownY != INVALID_POINTER && y != INVALID_POINTER) { 
final float xDiff = Math.abs(x - mInitialDisPatchDownX);
final float yDiff = Math.abs(y - mInitialDisPatchDownY); 
if (xDiff > mTouchSlop && xDiff * 0.7f > yDiff) { 
//横向滚动不需要拦截
 super.requestDisallowInterceptTouchEvent(true); 
} else { 
super.requestDisallowInterceptTouchEvent(false);
 } 
} else {
 super.requestDisallowInterceptTouchEvent(false); 
} 
}
 break;
 case MotionEvent.ACTION_UP:
 case MotionEvent.ACTION_CANCEL: 
if (ev.getAction() == MotionEvent.ACTION_UP || ev.getAction() == MotionEvent.ACTION_CANCEL) { 
hasRequestDisallowIntercept = false;
 }
 break; 
}
 return super.dispatchTouchEvent(ev);
 }
 private float getMotionEventY(MotionEvent ev, int activePointerId) { final int index = MotionEventCompat.findPointerIndex(ev, activePointerId);
 if (index < 0) { return -1;
 }
 return MotionEventCompat.getY(ev, index);
 }
 private float getMotionEventX(MotionEvent ev, int activePointerId) { final int index = MotionEventCompat.findPointerIndex(ev, activePointerId);
 if (index < 0) { return -1;
 }
 return MotionEventCompat.getX(ev, index);
 }

大部分来自于：http://phpstudy.php.cn/b.php/103489.html