现在有很多App支持右滑返回，比如知乎，效果比较赞。
于是自己对Activity和Fragment进行了继承，派生出SwipeBackActivity和SwipeBackFragment，用于对这种效果的实现，也就是只要继承这两个类就可以了。
效果如下
Activity
Fragment
Frgament的效果实现比Activity稍微简单，因为Activity要考虑到dectorView。
支持滑动的控件SwipeLayout,核心思路就是把原有的控件添加到支持滑动的控件中，SwipeLayout要注意计算手势速度，源码如下：
package com.ui.jerry.swipebackdemo;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.Scroller;
import android.widget.Toast;
public class SwipeLayout extends LinearLayout {
public static final String TAG = "SwipeLayout";
private View mEmptyView;
private View mContentView;
private int mLeftEdge;
private int mWidth;
private int mMaxScrollX;
private Scroller mScroller;
private VelocityTracker mVelocityTracker = null;
private int mMaxFlingVelocity;
private int mLastX;
ViewGroup.LayoutParams childParams = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
private Context mContext;
public static final int DURATION = 1500; //满屏滑动时间
public static final int OPEN_ANIM_DURATION = 1000;
public static int SNAP_VELOCITY = 600; //最小的滑动速率
private OnFinishListener mOnFinishListener;
public SwipeLayout(Context context) {
this(context, null);
}
public SwipeLayout(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
init();
}
public void setOnFinishListener(OnFinishListener mOnFinishListener) {
this.mOnFinishListener = mOnFinishListener;
}
void init() {
mScroller = new Scroller(mContext);
mMaxFlingVelocity = ViewConfiguration.get(mContext).getScaledMaximumFlingVelocity();
mWidth = DisplayUtils.getScreenWidth(mContext) * 2;
mMaxScrollX = mWidth / 2;
mLeftEdge = mMaxScrollX - mMaxScrollX / 3;
setOrientation(LinearLayout.HORIZONTAL);
childParams.width = DisplayUtils.getScreenWidth(mContext);
mEmptyView = LayoutInflater.from(mContext).inflate(R.layout.view_translate, null);
addView(mEmptyView, childParams);
}
public void setContentView(View contentView) {
if (mContentView != null) {
removeView(mContentView);
}
mContentView = contentView;
addView(contentView, childParams);
postDelayed(new Runnable() {
@Override
public void run() {
openActivityAnimation();
}
}, 200);
}
private VelocityTracker getVelocityTracker() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
return mVelocityTracker;
}
private void recycleVelocityTracker() {
if (mVelocityTracker != null) {
mVelocityTracker.clear();
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
//1.获取速度追踪器
getVelocityTracker();
//2.将当前事件纳入到追踪器中
mVelocityTracker.addMovement(ev);
int pointId = -1;
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
//如果屏幕的动画还没结束，你就按下了，我们就结束上一次动画，即开始这次新ACTION_DOWN的动画
// clearScrollHis();
mLastX = (int) ev.getX();
pointId = ev.getPointerId(0);
break;
case MotionEvent.ACTION_MOVE:
int nextScrollX = (int) (mLastX - ev.getX() + getScrollX());
if (scrollTo(nextScrollX)) {
mLastX = (int) ev.getX();
}
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
//3.计算当前速度
mVelocityTracker.computeCurrentVelocity(1000, mMaxFlingVelocity);
//获取x y方向上的速度
float vX = mVelocityTracker.getXVelocity(pointId);
Log.i(TAG, "mVelocityX:" + vX);
//大于某个速率 直接滑动
if (vX > SNAP_VELOCITY) {
scrollToLeft();
} else if (vX < -SNAP_VELOCITY) {
scrollToRight();
} else {
snapToDestation();
}
//4.回收速度追踪器
recycleVelocityTracker();
break;
}
return true;
}
private void openActivityAnimation() {
clearScrollHis();
mScroller.startScroll(getScrollX(), 0, mMaxScrollX - getScrollX(), 0, OPEN_ANIM_DURATION);
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
}
public void closeActivityAnimation() {
clearScrollHis();
mScroller.startScroll(getScrollX(), 0, -getScrollX(), 0, OPEN_ANIM_DURATION);
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
}
private void clearScrollHis() {
if (mScroller != null) {
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
}
}
private void snapToDestation() {
int scrollX = getScrollX();
if (scrollX > 0 && scrollX <= mLeftEdge) {
smoothScrollTo(0);
} else if (scrollX > mLeftEdge) {
smoothScrollTo(mMaxScrollX);
}
}
public boolean scrollTo(int x) {
if (x < 0) {
scrollTo(0, 0);
} else if (x > mMaxScrollX) {
scrollTo(mMaxScrollX, 0);
} else {
scrollTo(x, 0);
}
return true;
}
public void scrollToRight() {
smoothScrollTo(mMaxScrollX);
}
public void scrollToLeft() {
smoothScrollTo(0);
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
Log.d(TAG, "left:" + l);
if (l == 0) {
Log.d(TAG, "OnFinish");
Toast.makeText(mContext, "Finished", Toast.LENGTH_SHORT).show();
if(mOnFinishListener!=null){
mOnFinishListener.onFinish();
}
}
}
public void smoothScrollTo(int fx) {
if (fx < 0) {
smoothScrollTo(0, 0);
} else if (fx > mMaxScrollX) {
smoothScrollTo(mMaxScrollX, 0);
} else {
smoothScrollTo(fx, 0);
}
}
// //调用此方法滚动到目标位置
public void smoothScrollTo(int fx, int fy) {
int dx = fx - getScrollX();
int dy = fy - getScrollY();
smoothScrollBy(dx, dy);
}
//调用此方法设置滚动的相对偏移
public void smoothScrollBy(int dx, int dy) {
//设置mScroller的滚动偏移量
mScroller.startScroll(getScrollX(), 0, dx, dy, Math.abs(dx * DURATION / mMaxScrollX));
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() {
//先判断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();
}
public interface OnFinishListener{
void onFinish();
}
}
