android 全局页面滑动返回联动效果的实现 - 简书
android 全局页面滑动返回联动效果的实现
转载请标明出处：主要参考项目：
首次通过向右滑动来返回的操作是在 IOS7系统上出现，android系统特性上并不支持两个activity间的滑动返回，但是android上有很多关于滑动的api，通过这些api也是可以实现视觉上的滑动返回效果。
下层联动滑动返回
原理的简单描述
首先设置activity的背景是透明的，然后让每个页面的DecorView下添加一个自定义的ViewGroup（SwipeBackLayout），让原先的DecorView里的子view添加到SwipeBackLayout里，通过滑动的api对SwipeBackLayout里的view进行滑动，当滑动结束后就finish当前的activity，为了实现联动，在滑动的过程中拿到下层的activity的SwipeBackLayout进行滑动操作即可。
Hierarchy View
主要有以下四个类：SwipeBackActivity //滑动返回基类SwipeBackLayout //滑动返回viewGroupSwipeBackLayoutDragHelper
//修改ViewDragHelper后助手类TranslucentHelper //代码中修改透明或者不透明的助手类
1. 设置activity为透明
这个看起来很简单，其实在实际开发中遇到过一个比较麻烦的页面切换动画的问题。在代码中，和activity透明背景相关的地方有两个：
第一个是在activity的主题style里设置 &item name="android:windowBackground"&@color/transparent&/item&
&item name="android:windowIsTranslucent"&true&/item&
但是问题来了，如果在某个activity的主题style中设置了android:windowIsTranslucent该属性为true，那么该activity切换动画变成了手机默认效果，不同手机有不同的效果，有些手机上完全不能看。于是需要自定义activity的切换动画（windowAnimationStyle），但是又发现以下几个属性是无效的&!-- activity 新创建时进来的动画--&
&item name="android:activityOpenEnterAnimation"&@anim/activity_open_enter&/item&
&!-- 上层activity返回后，下层activity重新出现的动画--&
&item name="android:activityOpenExitAnimation"&@anim/activity_open_exit&/item&
&!-- 跳到新的activity后，该activity被隐藏时的动画--&
&item name="android:activityCloseEnterAnimation"&@anim/activity_close_enter&/item&
&!-- activity 销毁时的动画--&
&item name="android:activityCloseExitAnimation"&@anim/activity_close_exit&/item&
在网上搜了下，发现下面两个属性还是可以用的&item name="windowEnterAnimation"&@anim/***&/item&
&item name="windowExitAnimation"&@anim/***&/item&
但是这个在一个真正的项目中明显是不够的，一个是窗口进来动画，一个是窗口退出动画，因此还需要在代码中动态设置，也就有了TranslucentHelper 助手类。
第二个透明助手类（TranslucentHelper）里主要又有两个方法，一个是让activity变透明，一个是让activity变不透明，这两个都是通过反射来调用隐藏的系统api来实现的。
public class TranslucentHelper {
public interface TranslucentListener {
void onTranslucent();
private static class MyInvocationHandler implements InvocationHandler {
private TranslucentL
MyInvocationHandler(TranslucentListener listener) {
this.listener =
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
boolean success = (boolean) args[0];
if (success && listener != null) {
listener.onTranslucent();
} catch (Exception ignored) {
public static boolean convertActivityFromTranslucent(Activity activity) {
Method method = Activity.class.getDeclaredMethod("convertFromTranslucent");
method.setAccessible(true);
method.invoke(activity);
} catch (Throwable t) {
public static void convertActivityToTranslucent(Activity activity, final TranslucentListener listener) {
Class&?&[] classes = Activity.class.getDeclaredClasses();
Class&?& translucentConversionListenerClazz =
for (Class clazz : classes) {
if (clazz.getSimpleName().contains("TranslucentConversionListener")) {
translucentConversionListenerClazz =
MyInvocationHandler myInvocationHandler = new MyInvocationHandler(listener);
Object obj = Proxy.newProxyInstance(Activity.class.getClassLoader(),
new Class[] { translucentConversionListenerClazz }, myInvocationHandler);
if (Build.VERSION.SDK_INT &= Build.VERSION_CODES.LOLLIPOP) {
Method getActivityOptions = Activity.class.getDeclaredMethod("getActivityOptions");
getActivityOptions.setAccessible(true);
Object options = getActivityOptions.invoke(activity);
Method method = Activity.class.getDeclaredMethod("convertToTranslucent",
translucentConversionListenerClazz, ActivityOptions.class);
method.setAccessible(true);
method.invoke(activity, obj, options);
Method method =
Activity.class.getDeclaredMethod("convertToTranslucent", translucentConversionListenerClazz);
method.setAccessible(true);
method.invoke(activity, obj);
} catch (Throwable t) {
new Handler().postDelayed(new Runnable() {
public void run() {
if (listener != null) {
listener.onTranslucent();
让activity变不透明的方法比较简单就不多说了；让activity变透明的方法参数里出入了一个listener ，这个后面再讲，主要看调用invoke方法时，判断了版本是否是大于等于5.0，如果是，需要再传入一个ActivityOptions参数。
2. 让BaseActivity继承SwipeBackActivity
先直接看代码，比较少
public class SwipeBackActivity extends FragmentActivity {
* 滑动返回ViewGroup
private SwipeBackLayout mSwipeBackL
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mSwipeBackLayout = new SwipeBackLayout(this);
getWindow().setBackgroundDrawableResource(R.color.transparent);
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
mSwipeBackLayout.attachToActivity(this);
mSwipeBackLayout.setOnSwipeBackListener(new SwipeBackLayout.onSwipeBackListener() {
public void onStart() {
onSwipeBackStart();
public void onEnd() {
onSwipeBackEnd();
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
if (hasFocus) {
getSwipeBackLayout().recovery();
* 滑动返回开始时的回调
protected void onSwipeBackStart() {
* 滑动返回结束时的回调
protected void onSwipeBackEnd() {
public View findViewById(int id) {
View v = super.findViewById(id);
if (v == null && mSwipeBackLayout != null) {
return mSwipeBackLayout.findViewById(id);
* 设置是否可以边缘滑动返回，需要在onCreate方法调用
public void setSwipeBackEnable(boolean enable) {
mSwipeBackLayout.setSwipeBackEnable(enable);
public SwipeBackLayout getSwipeBackLayout() {
return mSwipeBackL
SwipeBackActivity中包含了一个SwipeBackLayout ，在onCreate方法中，new了一个SwipeBackLayout 、设置了window的背景色为透明色、主题设置为不透明。不要被这个透明搞晕了，window的背景色相当于在style中设置android:windowBackground为透明，这个也是activity透明的必要条件，由于我所开发的这个项目已经迭代了很多个版本，activity很多，而这些activity中android:windowBackground设置的颜色大部分是白色，少部分是灰色和透明的，所以需要在代码中设置统一设置一遍透明的，以达到最少修改代码的目的，如果是一个新的项目，可以直接在style中写死windowBackground为透明，这样就不要再代码中设置了。那么问题是在代码中设置了window是透明的，原来如果是灰色的视觉效果被影响到了怎么办？解决办法是获取原来的背景色赋值给原来DecorView的子view（也就是现在SwipeBackLayout的子view）就可以了。背景色赋值就是在onPostCreate方法的mSwipeBackLayout.attachToActivity(this);里做的。onPostCreate的执行时机是在onStart和onResume之间的。attachToActivity就是将SwipeBackLayout插入到DecorView和其子view之间，可以先看下代码：
* 将View添加到Activity
public void attachToActivity(Activity activity) {
mTopActivity =
TypedArray a = activity.getTheme().obtainStyledAttributes(new int[] {
android.R.attr.windowBackground
int background = a.getResourceId(0, 0);
a.recycle();
ViewGroup decor = (ViewGroup) activity.getWindow().getDecorView();
ViewGroup decorChild = (ViewGroup) decor.getChildAt(0);
decorChild.setBackgroundResource(background);
decor.removeView(decorChild);
addView(decorChild);
setContentView(decorChild);
decor.addView(this);
Activity backActivity = ActivityUtils.getSecondTopActivity();
if (backActivity != null && backActivity instanceof SwipeBackActivity) {
mBackActivityWeakRf = new WeakReference&&(backActivity);
代码整体上都还是比较简单的，应该都能看懂。前面是获取window背景色，插入过程到decor.addView(this);为止，下面拿到backActivity 的引用是为了做到下层activity联动时用到的。
继续来看SwipeBackActivity，onPostCreate还设置了开始滑动和滑动结束的回调，在某些场合下还是需要的，比如一些PopupWindow在滑动返回时不会被消除，这个时候可以在onSwipeBackStart()调用其dismiss()方法。在onWindowFocusChanged中如果是hasFocus == true，就recovery()这个SwipeBackLayout，这个也是因为下层activity有联动效果而移动了SwipeBackLayout，所以需要recovery()下，防止异常情况。最后再提下setSwipeBackEnable(…)，某些不可以滑动返回的页面比如MainActivity需要在其onCreate方法中调用下设置为false就可以了。
3. SwipeBackLayout和SwipeBackLayoutDragHelper
protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
//绘制阴影
if (mContentPercent & 0
&& child == mContentView
&& mViewDragHelper.getViewDragState() != SwipeBackLayoutDragHelper.STATE_IDLE) {
child.getHitRect(mContentViewRect);
mShadowLeft.setBounds(mContentViewRect.left - mShadowLeft.getIntrinsicWidth(), mContentViewRect.top,
mContentViewRect.left, mContentViewRect.bottom);
//mShadowLeft.setAlpha((int) (mContentPercent * FULL_ALPHA));
mShadowLeft.draw(canvas);
return super.drawChild(canvas, child, drawingTime);
public void computeScroll() {
mContentPercent = 1 - mScrollP
if (mViewDragHelper.continueSettling(true)) {
ViewCompat.postInvalidateOnAnimation(this);
* 设置是否可以滑动返回
public void setSwipeBackEnable(boolean enable) {
mIsSwipeBackEnable =
public boolean isActivityTranslucent() {
return mIsActivityT
* 启动进入动画
private void startEnterAnim() {
if (mContentView != null) {
ObjectAnimator anim = ObjectAnimator
.ofFloat(mContentView, "TranslationX", mContentView.getTranslationX(), 0f);
anim.setDuration((long) (125 * mContentPercent));
mEnterAnim =
mEnterAnim.start();
protected View getContentView() {
return mContentV
private void setContentView(ViewGroup decorChild) {
mContentView = decorC
private class ViewDragCallback extends SwipeBackLayoutDragHelper.Callback {
public boolean tryCaptureView(View child, int pointerId) {
if (mIsSwipeBackEnable && mViewDragHelper.isEdgeTouched(SwipeBackLayoutDragHelper.EDGE_LEFT, pointerId)) {
TranslucentHelper.convertActivityToTranslucent(mTopActivity,
new TranslucentHelper.TranslucentListener() {
public void onTranslucent() {
if (mListener != null) {
mListener.onStart();
mIsActivityTranslucent =
public int getViewHorizontalDragRange(View child) {
return mIsSwipeBackEnable ? SwipeBackLayoutDragHelper.EDGE_LEFT : 0;
public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
super.onViewPositionChanged(changedView, left, top, dx, dy);
if (changedView == mContentView) {
mScrollPercent = Math.abs((float) left / mContentView.getWidth());
mContentLeft =
//未执行动画就平移
if (!mIsEnterAnimRunning) {
moveBackActivity();
invalidate();
if (mScrollPercent &= 1 && !mTopActivity.isFinishing()) {
if (mBackActivityWeakRf != null && ActivityUtils.activityIsAlive(mBackActivityWeakRf.get())) {
((SwipeBackActivity) mBackActivityWeakRf.get()).getSwipeBackLayout().invalidate();
mTopActivity.finish();
mTopActivity.overridePendingTransition(0, 0);
public void onViewReleased(View releasedChild, float xvel, float yvel) {
if (xvel & DEFAULT_VELOCITY_THRESHOLD || mScrollPercent & DEFAULT_SCROLL_THRESHOLD){
if (mIsActivityTranslucent) {
mViewDragHelper.settleCapturedViewAt(releasedChild.getWidth() + mShadowLeft.getIntrinsicWidth(), 0);
if (mContentPercent & 0.85f) {
startAnimOfBackActivity();
mViewDragHelper.settleCapturedViewAt(0, 0);
if (mListener != null) {
mListener.onEnd();
invalidate();
public int clampViewPositionHorizontal(View child, int left, int dx) {
return Math.min(child.getWidth(), Math.max(left, 0));
public void onViewDragStateChanged(int state) {
super.onViewDragStateChanged(state);
if (state == SwipeBackLayoutDragHelper.STATE_IDLE && mScrollPercent & 1f) {
TranslucentHelper.convertActivityFromTranslucent(mTopActivity);
mIsActivityTranslucent =
public boolean isTranslucent() {
return SwipeBackLayout.this.isActivityTranslucent();
* 背景Activity开始进入动画
private void startAnimOfBackActivity() {
if (mBackActivityWeakRf != null && ActivityUtils.activityIsAlive(mBackActivityWeakRf.get())) {
mIsEnterAnimRunning =
SwipeBackLayout swipeBackLayout = ((SwipeBackActivity) mBackActivityWeakRf.get()).getSwipeBackLayout();
swipeBackLayout.startEnterAnim();
* 移动背景Activity
private void moveBackActivity() {
if (mBackActivityWeakRf != null && ActivityUtils.activityIsAlive(mBackActivityWeakRf.get())) {
View view = ((SwipeBackActivity) mBackActivityWeakRf.get()).getSwipeBackLayout().getContentView();
if (view != null) {
int width = view.getWidth();
view.setTranslationX(-width * 0.3f * Math.max(0f, mContentPercent - 0.15f));
* 回复界面的平移到初始位置
public void recovery() {
if (mEnterAnim != null && mEnterAnim.isRunning()) {
mEnterAnim.end();
mContentView.setTranslationX(0);
drawChild是来绘制了左侧阴影的，获取到原 子view 所在屏幕的矩形，之后确定阴影所在的矩形，然后就直接绘制了。
child.getHitRect(mContentViewRect);
mShadowLeft.setBounds(mContentViewRect.left - mShadowLeft.getIntrinsicWidth(), mContentViewRect.top,
mContentViewRect.left, mContentViewRect.bottom);
mShadowLeft.draw(canvas);
代码中滑动是用了ViewDragHelper，如果不熟悉这个类需要先自行百度。只是这个官方封装类有几个地方不能满足这个滑动返回的需求，于是就有了SwipeBackLayoutDragHelper，SwipeBackLayoutDragHelper主要是copy了ViewDragHelper源码后再添加了一些代码。
首先原生ViewDragHelper里面没有setMaxVelocity方法，如果滑动过快，会导致下层联动滑动跟不上，上层滑动结束后下层还没移动好，这导致的结果就是下下层可以被看到，下下层也许就是手机桌面，影响了体验，所以需要设置了最大速度。
我们知道ViewDragHelper需要通过shouldInterceptTouchEvent(event)和processTouchEvent(event)获取该view的onInterceptTouchEvent和onTouchEvent事件，之后设置一个回调ViewDragCallback里面写几个方法就基本上可以实现用手指拖拽了，回调中有许多的方法，其中isTranslucent()是自己添加进去的，接下来就讲讲重写回调里的方法都做了什么。
public boolean tryCaptureView(View child, int pointerId) {
if (mIsSwipeBackEnable && mViewDragHelper.isEdgeTouched(SwipeBackLayoutDragHelper.EDGE_LEFT, pointerId)) {
TranslucentHelper.convertActivityToTranslucent(mTopActivity,
new TranslucentHelper.TranslucentListener() {
public void onTranslucent() {
if (mListener != null) {
mListener.onStart();
mIsActivityTranslucent =
tryCaptureView方法当触摸到SwipeBackLayout里的子View时触发的，当返回true，表示捕捉成功，否则失败。判断条件是如果支持滑动返回并且是左侧边距被触摸时才可以，我们知道这个时候的的背景色是不透明的，如果直接开始滑动则是黑色的，所以需要在这里背景色改成透明的，如果直接调用 TranslucentHelper.convertActivityToTranslucent(mTopActivity)后直接返回true，会出现一个异常情况，就是滑动过快时会导致背景还来不及变成黑色就滑动出来了，之后才变成透明的，从而导致了会从黑色到透明的一个闪烁现象，解决的办法是在代码中用了一个回调和标记，当变成透明后设置了mIsActivityTranslucent =通过mIsActivityTranslucent 这个变量来判断是否进行移动的操作。由于修改activity变透明的方法是通过反射的，不能简单的设置一个接口后进行回调，而是通过动态代理的方式来实现的（InvocationHandler），在convertToTranslucent方法的第一个参数刚好是一个判断activity是否已经变成透明的回调，看下面代码中 if 语句里的注释和回调，如果窗口已经变成透明的话，就传了一个drawComplete (true)。
@SystemApi
public boolean convertToTranslucent(TranslucentConversionListener callback,
ActivityOptions options) {
boolean drawC
mTranslucentCallback =
mChangeCanvasToTranslucent =
ActivityManagerNative.getDefault().convertToTranslucent(mToken, options);
WindowManagerGlobal.getInstance().changeCanvasOpacity(mToken, false);
drawComplete =
} catch (RemoteException e) {
// Make callback return as though it timed out.
mChangeCanvasToTranslucent =
drawComplete =
if (!mChangeCanvasToTranslucent && mTranslucentCallback != null) {
// Window is already translucent.
mTranslucentCallback.onTranslucentConversionComplete(drawComplete);
return mChangeCanvasToT
在TranslucentHelper的convertActivityToTranslucent(…)方法中
MyInvocationHandler myInvocationHandler =
new MyInvocationHandler(new WeakReference&&(listener));
Object obj = Proxy.newProxyInstance(Activity.class.getClassLoader(),
new Class[] { translucentConversionListenerClazz }, myInvocationHandler);
通过动态代理，将translucentConversionListenerClazz 执行其方法onTranslucentConversionComplete的替换成myInvocationHandler中执行invoke方法。
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
boolean success = (boolean) args[0];
if (success && listener.get() != null) {
listener.get().onTranslucent();
} catch (Exception e) {
e.printStackTrace();
其中赋值给success的args[0]正是 drawCompletemTranslucentCallback.onTranslucentConversionComplete(drawComplete);
isTranslucent是上面提到，在SwipeBackLayoutDragHelper中的Callback回调里，自己添加了一个方法，主要是返回activity是否是透明的
public boolean isTranslucent() {
默认为true，在SwipeBackLayout重写后将mIsActivityTranslucent返回SwipeBackLayoutDragHelper
public boolean isTranslucent() {
return SwipeBackLayout.this.isActivityTranslucent();
仔细看SwipeBackLayoutDragHelper方法的话，会发现最后通过dragTo方法对view进行移动，因此在进行水平移动前判断下是否是透明的，只有透明了才能移动
private void dragTo(int left, int top, int dx, int dy) {
int clampedX =
int clampedY =
final int oldLeft = mCapturedView.getLeft();
final int oldTop = mCapturedView.getTop();
if (dx != 0) {
clampedX = mCallback.clampViewPositionHorizontal(mCapturedView, left, dx);
if (mCallback.isTranslucent()) {
ViewCompat.offsetLeftAndRight(mCapturedView, clampedX - oldLeft);
if (dy != 0) {
clampedY = mCallback.clampViewPositionVertical(mCapturedView, top, dy);
ViewCompat.offsetTopAndBottom(mCapturedView, clampedY - oldTop);
if (dx != 0 || dy != 0) {
final int clampedDx = clampedX - oldL
final int clampedDy = clampedY - oldT
if (mCallback.isTranslucent()) {
mCallback.onViewPositionChanged(mCapturedView, clampedX, clampedY,
clampedDx, clampedDy);
onViewPositionChanged
view移动过程中会持续调用，这里面的逻辑主要有这几个：实时计算滑动了多少距离，用于绘制左侧阴影等使下面的activity进行移动moveBackActivity();当view完全移出屏幕后，销毁当前的activity
public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
super.onViewPositionChanged(changedView, left, top, dx, dy);
if (changedView == mContentView) {
mScrollPercent = Math.abs((float) left / mContentView.getWidth());
mContentLeft =
//未执行动画就平移
if (!mIsEnterAnimRunning) {
moveBackActivity();
invalidate();
if (mScrollPercent &= 1 && !mTopActivity.isFinishing()) {
if (mBackActivityWeakRf != null && ActivityUtils.activityIsAlive(mBackActivityWeakRf.get())) {
((SwipeBackActivity) mBackActivityWeakRf.get()).getSwipeBackLayout().invalidate();
mTopActivity.finish();
mTopActivity.overridePendingTransition(0, 0);
* 移动背景Activity
private void moveBackActivity() {
if (mBackActivityWeakRf != null && ActivityUtils.activityIsAlive(mBackActivityWeakRf.get())) {
View view = ((SwipeBackActivity) mBackActivityWeakRf.get()).getSwipeBackLayout().getContentView();
if (view != null) {
int width = view.getWidth();
view.setTranslationX(-width * 0.3f * Math.max(0f, mContentPercent - 0.15f));
onViewReleased是手指释放后触发的一个方法如果滑动速度大于最大速度或者滑动的距离大于设定的阈值距离，则直接移到屏幕外，同时触发下层activity的复位动画mViewDragHelper.settleCapturedViewAt(releasedChild.getWidth() + mShadowLeft.getIntrinsicWidth(), 0);否则移会到原来位置 mViewDragHelper.settleCapturedViewAt(0, 0);
public void onViewReleased(View releasedChild, float xvel, float yvel) {
if (xvel & DEFAULT_VELOCITY_THRESHOLD || mScrollPercent & DEFAULT_SCROLL_THRESHOLD){
if (mIsActivityTranslucent) {
mViewDragHelper.settleCapturedViewAt(releasedChild.getWidth() + mShadowLeft.getIntrinsicWidth(), 0);
if (mContentPercent & 0.85f) {
startAnimOfBackActivity();
mViewDragHelper.settleCapturedViewAt(0, 0);
if (mListener != null) {
mListener.onEnd();
invalidate();
* 背景Activity开始进入动画
private void startAnimOfBackActivity() {
if (mBackActivityWeakRf != null && ActivityUtils.activityIsAlive(mBackActivityWeakRf.get())) {
mIsEnterAnimRunning =
SwipeBackLayout swipeBackLayout = ((SwipeBackActivity) mBackActivityWeakRf.get()).getSwipeBackLayout();
swipeBackLayout.startEnterAnim();
* 启动进入动画
private void startEnterAnim() {
if (mContentView != null) {
ObjectAnimator anim = ObjectAnimator
.ofFloat(mContentView, "TranslationX", mContentView.getTranslationX(), 0f);
anim.setDuration((long) (125 * mContentPercent));
mEnterAnim =
mEnterAnim.start();
onViewDragStateChanged当滑动的状态发生改变时的回调主要是停止滑动后，将背景改成不透明，这样跳到别的页面是动画就是正常的。
public void onViewDragStateChanged(int state) {
super.onViewDragStateChanged(state);
if (state == SwipeBackLayoutDragHelper.STATE_IDLE && mScrollPercent & 1f) {
TranslucentHelper.convertActivityFromTranslucent(mTopActivity);
mIsActivityTranslucent =
clampViewPositionHorizontal 返回水平移动距离，下面这样写可以防止滑出父 view
public int clampViewPositionHorizontal(View child, int left, int dx) {
return Math.min(child.getWidth(), Math.max(left, 0));
getViewHorizontalDragRange对于clickable=true的子view，需要返回大于0的数字才能正常捕获。
public int getViewHorizontalDragRange(View child) {
return mIsSwipeBackEnable ? SwipeBackLayoutDragHelper.EDGE_LEFT : 0;
总要做点没有意义的事，才能让人生更有意义。