ScrollviewWithToolbar.gif
最近遇到这样的需求，一开始自己写出来，总是会有跳顿感，不是那么流畅，去网上查了下，在加上自己修改了下，便成了现在的样子。（滑动过程中上面的图片是缩放的，里面的一个小icon是缩小放大透明度渐变的，真机加Vysor，看的效果特别模糊的，没入Vysor pro，这画质将就看吧）
当然应该还可以继续优化吧，不过最近比较忙，暂时先这样吧。
为了以后方便自己整理学习，先写到简书吧。
首先初始化一些基本的参数
private void initDistance() {
//这是顶部标题栏的初始高度；
OrignHight = layout.getLayoutParams().height;
//给它设定个上拉的最小高度；
minHight = px2dp(100);
//需要滑动的距离；
Distance = OrignHight - minHight;
}
判断ListView是否滑动到顶部；
public boolean isListViewReachTopEdge(ListView listView){
boolean result = false;
if(listView.getFirstVisiblePosition() == 0){
View childAt = listView.getChildAt(0);
result = childAt.getTop()==0;
}
return result;
}
下面的是对touchevent的处理
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
//如果ListView是在顶部，进行处理，不在顶部，不执行
if(isListViewReachTopEdge(listView)){
int y = (int) ev.getY();
int distanceY = 0;
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
pointY = y;
afterup = false;
return super.dispatchTouchEvent(ev);
case MotionEvent.ACTION_MOVE:
y = (int) ev.getY();
if (currentDistance >= Distance && distanceY > 0) {
return super.dispatchTouchEvent(ev);
}
if (currentDistance <= 0 && distanceY < 0) {
return super.dispatchTouchEvent(ev);
}
distanceY = pointY - y;
if (rate == 1) {
if (distanceY > 0) {
return super.dispatchTouchEvent(ev);
}
}
moveLayout(distanceY);
pointY = y;
break;
case MotionEvent.ACTION_UP:
afterup = true;
elasticityHeight();
return super.dispatchTouchEvent(ev);
}
}else {
return super.dispatchTouchEvent(ev);
}
return false;
}```
接下来就是里面用的各种方法
```java
//滑动过程中的处理
private void moveLayout(int distanceY) {
ViewGroup.LayoutParams layoutParams = layout.getLayoutParams();
layoutParams.height = layoutParams.height - distanceY;
layout.setLayoutParams(layoutParams);
elasticityHeight();
layout.requestLayout();
currentDistance = OrignHight - layout.getLayoutParams().height;
rate = (float) (currentDistance * 1.0 / Distance);
moveViewByrate(rate);}
//抬手后进行的处理
private void elasticityHeight() {
ViewGroup.LayoutParams layoutParams = layout.getLayoutParams();
if (layoutParams.height < minHight) {
layoutParams.height = minHight;
layout.setLayoutParams(layoutParams);
layout.requestLayout();
}
if (layoutParams.height > OrignHight) {
layoutParams.height = OrignHight;
layout.setLayoutParams(layoutParams);
layout.requestLayout();
}
if (afterup) {
if (layoutParams.height < OrignHight / 1.8) {
layoutParams.height = minHight;
layout.setLayoutParams(layoutParams);
imageView.setVisibility(View.GONE);
layout.requestLayout();
}
if (layoutParams.height >= OrignHight / 1.8) {
layoutParams.height = OrignHight;
layout.setLayoutParams(layoutParams);
imageView.setVisibility(View.VISIBLE);
imageView.setAlpha((float) 1.0 - 0);
imageView.setScaleX(1);
imageView.setScaleY(1);
layout.requestLayout();
}
}
}
//滑动过程中，控件的大小，透明度的变化
private void moveViewByrate(float rate) {
if (rate >= 1) {
imageView.setVisibility(View.GONE);
} else {
imageView.setVisibility(View.VISIBLE);
imageView.setAlpha(1 - rate);
imageView.setScaleX(1 - rate);
imageView.setScaleY(1 - rate);
}
}
文章中有部分是转载自网络，在这里说声抱歉。
因为时间仓促，里面可能有些错误，希望指正。
