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仿ios的滑动效果

package code.suibianchou.com.custormview2;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;

/**
* Created by Administrator on 2017/5/18 0018.
*/

public class BounceScrollView extends ScrollView {
private static final String TAG = "BounceScrollView";

private View inner;// 孩子View

private float y;// 点击时y坐标

private Rect normal = new Rect();// 矩形(这里只是个形式,只是用于判断是否需要动画.)

private boolean isCount = false;// 是否开始计算
private float lastX = 0;
private float lastY = 0;
private float currentX = 0;
private float currentY = 0;
private float distanceX = 0;
private float distanceY = 0;
private boolean upDownSlide = false; //判断上下滑动的flag

public BounceScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}

/***
* 根据 XML 生成视图工作完成.该函数在生成视图的最后调用,在所有子视图添加完之后. 即使子类覆盖了 onFinishInflate
* 方法,也应该调用父类的方法,使该方法得以执行.
*/
@SuppressLint("MissingSuperCall")
@Override
protected void onFinishInflate() {
if (getChildCount() > 0) {
inner = getChildAt(0);
View view;
}
}

@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
// TODO Auto-generated method stub

currentX = ev.getX();
currentY = ev.getY();
switch(ev.getAction()){
case MotionEvent.ACTION_DOWN:

break;
case MotionEvent.ACTION_MOVE:
distanceX = currentX - lastX;
distanceY = currentY - lastY;
if(Math.abs(distanceX)<Math.abs(distanceY) && Math.abs(distanceY)>12){

upDownSlide = true;
}
break;
case MotionEvent.ACTION_UP:

break;
default:
break;
}
lastX = currentX;
lastY = currentY;
if (upDownSlide && inner != null) commOnTouchEvent(ev);
return super.dispatchTouchEvent(ev);
}

@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
// TODO Auto-generated method stub
return super.onInterceptTouchEvent(ev);
}

/***
* 监听touch
*/
@Override
public boolean onTouchEvent(MotionEvent ev) {
return super.onTouchEvent(ev);
}


/***
* 触摸事件
*
* @param ev
*/
public void commOnTouchEvent(MotionEvent ev) {
int action = ev.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_UP:
// 手指松开.
if (isNeedAnimation()) {
animation();
isCount = false;
}
clear0();
break;
case MotionEvent.ACTION_MOVE:
final float preY = y;// 按下时的y坐标
float nowY = ev.getY();// 时时y坐标
int deltaY = (int) (preY - nowY);// 滑动距离
if (!isCount) {
deltaY = 0; // 在这里要归0.
}

y = nowY;
// 当滚动到最上或者最下时就不会再滚动,这时移动布局
if (isNeedMove()) {
// 初始化头部矩形
if (normal.isEmpty()) {
// 保存正常的布局位置
normal.set(inner.getLeft(), inner.getTop(),
inner.getRight(), inner.getBottom());
}
// 移动布局
inner.layout(inner.getLeft(), inner.getTop() - deltaY / 2,
inner.getRight(), inner.getBottom() - deltaY / 2);
}
isCount = true;
break;

default:
break;
}
}

/***
* 回缩动画
*/
public void animation() {
// 开启移动动画
TranslateAnimation ta = new TranslateAnimation(0, 0, inner.getTop(),
normal.top);
ta.setDuration(200);
inner.startAnimation(ta);
// 设置回到正常的布局位置
inner.layout(normal.left, normal.top, normal.right, normal.bottom);

normal.setEmpty();

}

// 是否需要开启动画
public boolean isNeedAnimation() {
return !normal.isEmpty();
}

/***
* 是否需要移动布局 inner.getMeasuredHeight():获取的是控件的总高度
*
* getHeight():获取的是屏幕的高度
*
* @return
*/
public boolean isNeedMove() {
int offset = inner.getMeasuredHeight() - getHeight();
int scrollY = getScrollY();
// 0是顶部,后面那个是底部
if (scrollY == 0 || scrollY == offset) {
return true;
}
return false;
}

private void clear0(){
lastX = 0;
lastY = 0;
distanceX = 0;
distanceY = 0;
upDownSlide = false;
}
}

仿ios的滑动效果