2019独角兽企业重金招聘Python工程师标准>>>
百度一下很多阻尼的ScrollView,但是阻尼效果看起来比较生硬,不够圆润,在体验ios的时候,发现那边做的拖动效果貌似还不错,所以就百度了一个阻尼的ScrollView的代码,再改了一下,效果感觉还可以,现在贴出来。
效果图:
代码:
import android.content.Context;
import android.graphics.Rect;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Interpolator;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;
/**
* Created by Admin on 2017/10/19.
*/
public class DampScrollView extends ScrollView {
// y方向上当前触摸点的前一次记录位置
private int previousY = 0;
// y方向上的触摸点的起始记录位置
private int startY = 0;
// y方向上的触摸点当前记录位置
private int currentY = 0;
// y方向上两次移动间移动的相对距离
private int deltaY = 0;
// 第一个子视图
private View childView;
// 用于记录childView的初始位置
private Rect topRect = new Rect();
//水平移动搞定距离
private float moveHeight;
public DampScrollView(Context context) {
super(context);
}
public DampScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public DampScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
@Override
protected void onFinishInflate() {
if (getChildCount() > 0) {
childView = getChildAt(0);
}
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
if (null == childView) {
return super.dispatchTouchEvent(event);
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
startY = (int) event.getY();
previousY = startY;
// 记录childView的初始位置
topRect.set(childView.getLeft(), childView.getTop(),
childView.getRight(), childView.getBottom());
moveHeight = 0;
break;
case MotionEvent.ACTION_MOVE:
currentY = (int) event.getY();
deltaY = currentY - previousY;
previousY = currentY;
//判定是否在顶部或者滑到了底部
if((!childView.canScrollVertically(-1)&&(currentY-startY)>0)||(!childView.canScrollVertically(1)&&(currentY-startY)<0)){
//计算阻尼
float distance = currentY - startY;
if (distance < 0) {
distance *= -1;
}
float damping = 0.5f;//阻尼值
float height = getHeight();
if (height != 0) {
if (distance > height) {
damping = 0;
} else {
damping = (height - distance) / height;
}
}
if (currentY - startY < 0) {
damping = 1 - damping;
}
//阻力值限制再0.3-0.5之间,平滑过度
damping *= 0.25;
damping += 0.25;
moveHeight = moveHeight + (deltaY * damping);
childView.layout(topRect.left, (int) (topRect.top + moveHeight), topRect.right,
(int) (topRect.bottom + moveHeight));
}
break;
case MotionEvent.ACTION_UP:
if (!topRect.isEmpty()) {
//开始回移动画
upDownMoveAnimation();
// 子控件回到初始位置
childView.layout(topRect.left, topRect.top, topRect.right,
topRect.bottom);
}
//重置一些参数
startY = 0;
currentY = 0;
topRect.setEmpty();
break;
}
return super.dispatchTouchEvent(event);
}
// 初始化上下回弹的动画效果
private void upDownMoveAnimation() {
TranslateAnimation animation = new TranslateAnimation(0.0f, 0.0f,
childView.getTop(), topRect.top);
animation.setDuration(600);
animation.setFillAfter(true);
//设置阻尼动画效果
animation.setInterpolator(new DampInterpolator());
childView.setAnimation(animation);
}
public class DampInterpolator implements Interpolator {
@Override
public float getInterpolation(float input) {
//没看过源码,猜测是input是时间(0-1),返回值应该是进度(0-1)
//先快后慢,为了更快更慢的效果,多乘了几次,现在这个效果比较满意
return 1 - (1 - input) * (1 - input) * (1 - input) * (1 - input) * (1 - input);
}
}