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);

}

}