采用Scroller实现任意布局的上下左右弹性效果

不知道Scroller是什么的同志先看下面：

Android Scroller类的详细分析

这里采用Scroller实现类似iphone的上下拖拉弹性效果，具体代码如下：

import android.content.Context;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.LinearLayout;
import android.widget.Scroller;

public class BouncyLinearLayout extends LinearLayout {

private static final String TAG = "BouncyLinearLayout";
private Scroller mScroller;
private GestureDetector mGestureDetector;

public BouncyLinearLayout(Context context) {
this(context, null);
}

public BouncyLinearLayout(Context context, AttributeSet attrs) {
super(context, attrs);
setClickable(true);
setLongClickable(true);
mScroller = new Scroller(context);
mGestureDetector = new GestureDetector(context, new BouncyGestureListener());
}

/**
* 滚动到目标位置
* @param fx
* @param fy
*/
protected void smoothScrollTo(int fx, int fy) {
int dx = fx - mScroller.getFinalX();
int dy = fy - mScroller.getFinalY();
smoothScrollBy(dx, dy);
}

/**
* 设置滚动的相对偏移
* @param dx
* @param dy
*/
protected void smoothScrollBy(int dx, int dy) {
//设置mScroller的滚动偏移量
mScroller.startScroll(mScroller.getFinalX(), mScroller.getFinalY(), dx, dy);
invalidate();//这里必须调用invalidate()才能保证computeScroll()会被调用，否则不一定会刷新界面，看不到滚动效果
}

@Override
public void computeScroll() {
//判断mScroller滚动是否完成
if (mScroller.computeScrollOffset()) {
//这里调用View的scrollTo()完成实际的滚动
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
//必须调用该方法，否则不一定能看到滚动效果
postInvalidate();
}
super.computeScroll();
}

@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_UP :
smoothScrollTo(0, 0);
break;
default:
return mGestureDetector.onTouchEvent(event);
}
return super.onTouchEvent(event);
}

class BouncyGestureListener implements GestureDetector.OnGestureListener {

@Override
public boolean onDown(MotionEvent e) {
// TODO Auto-generated method stub
return true;
}

@Override
public void onShowPress(MotionEvent e) {
// TODO Auto-generated method stub

}

@Override
public boolean onSingleTapUp(MotionEvent e) {
// TODO Auto-generated method stub
return false;
}

@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
int dis = (int)((distanceY-0.5)/2);
smoothScrollBy(0, dis);
return false;
}

@Override
public void onLongPress(MotionEvent e) {
// TODO Auto-generated method stub

}

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
// TODO Auto-generated method stub
return false;
}

}
}

以上代码只需要稍加改动就可以上下左右4个方向上的弹性效果了

看下面代码，只在BouncyGestureListener的onScroll方法中加了X方向的位移。

import android.content.Context;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.LinearLayout;
import android.widget.Scroller;

public class BouncyLinearLayout extends LinearLayout {

private static final String TAG = "BouncyLinearLayout";
private Scroller mScroller;
private GestureDetector mGestureDetector;

public BouncyLinearLayout(Context context) {
this(context, null);
}

public BouncyLinearLayout(Context context, AttributeSet attrs) {
super(context, attrs);
setClickable(true);
setLongClickable(true);
mScroller = new Scroller(context);
mGestureDetector = new GestureDetector(context, new BouncyGestureListener());
}

/**
* 滚动到目标位置
* @param fx
* @param fy
*/
protected void smoothScrollTo(int fx, int fy) {
int dx = fx - mScroller.getFinalX();
int dy = fy - mScroller.getFinalY();
smoothScrollBy(dx, dy);
}

/**
* 设置滚动的相对偏移
* @param dx
* @param dy
*/
protected void smoothScrollBy(int dx, int dy) {
//设置mScroller的滚动偏移量
mScroller.startScroll(mScroller.getFinalX(), mScroller.getFinalY(), dx, dy);
invalidate();//这里必须调用invalidate()才能保证computeScroll()会被调用，否则不一定会刷新界面，看不到滚动效果
}

@Override
public void computeScroll() {
//判断mScroller滚动是否完成
if (mScroller.computeScrollOffset()) {
//这里调用View的scrollTo()完成实际的滚动
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
//必须调用该方法，否则不一定能看到滚动效果
postInvalidate();
}
super.computeScroll();
}

@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_UP :
smoothScrollTo(0, 0);
break;
default:
return mGestureDetector.onTouchEvent(event);
}
return super.onTouchEvent(event);
}

class BouncyGestureListener implements GestureDetector.OnGestureListener {

@Override
public boolean onDown(MotionEvent e) {
// TODO Auto-generated method stub
return true;
}

@Override
public void onShowPress(MotionEvent e) {
// TODO Auto-generated method stub

}

@Override
public boolean onSingleTapUp(MotionEvent e) {
// TODO Auto-generated method stub
return false;
}

@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
int disX = (int)((distanceX-0.5)/2);
int disY = (int)((distanceY-0.5)/2);
smoothScrollBy(disX, disY);
return false;
}

@Override
public void onLongPress(MotionEvent e) {
// TODO Auto-generated method stub

}

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
// TODO Auto-generated method stub
return false;
}

}
}

一个iOS风格的边缘弹性效果，支持几乎所有滚动视图

http://www.jcodecraeer.com/a/opensource/2015/1205/3753.html