轉(zhuǎn)載請標(biāo)明出處：http://www.reibang.com/p/705c2397a7f9
主要參考項目：https://github.com/ikew0ng/SwipeBackLayout
背景
首次通過向右滑動來返回的操作是在 IOS7系統(tǒng)上出現(xiàn)水泉，android系統(tǒng)特性上并不支持兩個activity間的滑動返回，但是android上有很多關(guān)于滑動的api窒盐，通過這些api也是可以實現(xiàn)視覺上的滑動返回效果草则。
效果圖
原理的簡單描述
首先設(shè)置activity的背景是透明的，然后讓每個頁面的DecorView下添加一個自定義的ViewGroup（SwipeBackLayout）蟹漓，讓原先的DecorView里的子view添加到SwipeBackLayout里炕横，通過滑動的api對SwipeBackLayout里的view進行滑動，當(dāng)滑動結(jié)束后就finish當(dāng)前的activity葡粒，為了實現(xiàn)聯(lián)動份殿，在滑動的過程中拿到下層的activity的SwipeBackLayout進行滑動操作即可。
布局圖
實現(xiàn)
主要有以下四個類：
SwipeBackActivity //滑動返回基類
SwipeBackLayout //滑動返回viewGroup
SwipeBackLayoutDragHelper //修改ViewDragHelper后助手類
TranslucentHelper //代碼中修改透明或者不透明的助手類
1. 設(shè)置activity為透明
這個看起來很簡單嗽交，其實在實際開發(fā)中遇到過一個比較麻煩的頁面切換動畫的問題卿嘲。在代碼中，和activity透明背景相關(guān)的地方有兩個：
- 第一個是在activity的主題style里設(shè)置
<item name="android:windowBackground">@color/transparent</item>
<item name="android:windowIsTranslucent">true</item>
但是問題來了夫壁，如果在某個activity的主題style中設(shè)置了android:windowIsTranslucent該屬性為true拾枣，那么該activity切換動畫變成了手機默認效果，不同手機有不同的效果，有些手機上完全不能看梅肤。于是需要自定義activity的切換動畫（windowAnimationStyle）司蔬，但是又發(fā)現(xiàn)以下幾個屬性是無效的
<!-- activity 新創(chuàng)建時進來的動畫-->
<item name="android:activityOpenEnterAnimation">@anim/activity_open_enter</item>
<!-- 上層activity返回后，下層activity重新出現(xiàn)的動畫-->
<item name="android:activityOpenExitAnimation">@anim/activity_open_exit</item>
<!-- 跳到新的activity后姨蝴，該activity被隱藏時的動畫-->
<item name="android:activityCloseEnterAnimation">@anim/activity_close_enter</item>
<!-- activity 銷毀時的動畫-->
<item name="android:activityCloseExitAnimation">@anim/activity_close_exit</item>
在網(wǎng)上搜了下俊啼，發(fā)現(xiàn)下面兩個屬性還是可以用的
<item name="windowEnterAnimation">@anim/***</item>
<item name="windowExitAnimation">@anim/***</item>
但是這個在一個真正的項目中明顯是不夠的，一個是窗口進來動畫似扔，一個是窗口退出動畫吨些，因此還需要在代碼中動態(tài)設(shè)置，也就有了TranslucentHelper 助手類炒辉。
- 第二個透明助手類（TranslucentHelper）里主要又有兩個方法豪墅，一個是讓activity變透明，一個是讓activity變不透明黔寇，這兩個都是通過反射來調(diào)用隱藏的系統(tǒng)api來實現(xiàn)的偶器。
public class TranslucentHelper {
public interface TranslucentListener {
void onTranslucent();
}
private static class MyInvocationHandler implements InvocationHandler {
private TranslucentListener listener;
MyInvocationHandler(TranslucentListener listener) {
this.listener = listener;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
boolean success = (boolean) args[0];
if (success && listener != null) {
listener.onTranslucent();
}
} catch (Exception ignored) {
}
return null;
}
}
public static boolean convertActivityFromTranslucent(Activity activity) {
try {
Method method = Activity.class.getDeclaredMethod("convertFromTranslucent");
method.setAccessible(true);
method.invoke(activity);
return true;
} catch (Throwable t) {
return false;
}
}
public static void convertActivityToTranslucent(Activity activity, final TranslucentListener listener) {
try {
Class<?>[] classes = Activity.class.getDeclaredClasses();
Class<?> translucentConversionListenerClazz = null;
for (Class clazz : classes) {
if (clazz.getSimpleName().contains("TranslucentConversionListener")) {
translucentConversionListenerClazz = clazz;
}
}
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);
} else {
Method method =
Activity.class.getDeclaredMethod("convertToTranslucent", translucentConversionListenerClazz);
method.setAccessible(true);
method.invoke(activity, obj);
}
} catch (Throwable t) {
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
if (listener != null) {
listener.onTranslucent();
}
}
}, 100);
}
}
}
讓activity變不透明的方法比較簡單就不多說了；讓activity變透明的方法參數(shù)里出入了一個listener 缝裤，這個后面再講屏轰，主要看調(diào)用invoke方法時，判斷了版本是否是大于等于5.0憋飞，如果是霎苗，需要再傳入一個ActivityOptions參數(shù)。
2. 讓BaseActivity繼承SwipeBackActivity
先直接看代碼榛做，比較少
public class SwipeBackActivity extends FragmentActivity {
/**
* 滑動返回ViewGroup
*/
private SwipeBackLayout mSwipeBackLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mSwipeBackLayout = new SwipeBackLayout(this);
getWindow().setBackgroundDrawableResource(R.color.transparent);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
mSwipeBackLayout.attachToActivity(this);
mSwipeBackLayout.setOnSwipeBackListener(new SwipeBackLayout.onSwipeBackListener() {
@Override
public void onStart() {
onSwipeBackStart();
}
@Override
public void onEnd() {
onSwipeBackEnd();
}
});
}
@Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
if (hasFocus) {
getSwipeBackLayout().recovery();
}
}
/**
* 滑動返回開始時的回調(diào)
*/
protected void onSwipeBackStart() {
}
/**
* 滑動返回結(jié)束時的回調(diào)
*/
protected void onSwipeBackEnd() {
}
@Override
public View findViewById(int id) {
View v = super.findViewById(id);
if (v == null && mSwipeBackLayout != null) {
return mSwipeBackLayout.findViewById(id);
}
return v;
}
/**
* 設(shè)置是否可以邊緣滑動返回唁盏，需要在onCreate方法調(diào)用
*/
public void setSwipeBackEnable(boolean enable) {
mSwipeBackLayout.setSwipeBackEnable(enable);
}
public SwipeBackLayout getSwipeBackLayout() {
return mSwipeBackLayout;
}
}
SwipeBackActivity中包含了一個SwipeBackLayout ，在onCreate方法中检眯，new了一個SwipeBackLayout 厘擂、設(shè)置了window的背景色為透明色、主題設(shè)置為不透明锰瘸。不要被這個透明搞暈了刽严，window的背景色相當(dāng)于在style中設(shè)置android:windowBackground為透明，這個也是activity透明的必要條件避凝，由于我所開發(fā)的這個項目已經(jīng)迭代了很多個版本舞萄，activity很多，而這些activity中android:windowBackground設(shè)置的顏色大部分是白色管削，少部分是灰色和透明的鹏氧，所以需要在代碼中設(shè)置統(tǒng)一設(shè)置一遍透明的，以達到最少修改代碼的目的佩谣，如果是一個新的項目把还，可以直接在style中寫死windowBackground為透明，這樣就不要再代碼中設(shè)置了。那么問題是在代碼中設(shè)置了window是透明的吊履，原來如果是灰色的視覺效果被影響到了怎么辦安皱？解決辦法是獲取原來的背景色賦值給原來DecorView的子view（也就是現(xiàn)在SwipeBackLayout的子view）就可以了。背景色賦值就是在onPostCreate方法的mSwipeBackLayout.attachToActivity(this);里做的艇炎。onPostCreate的執(zhí)行時機是在onStart和onResume之間的酌伊。attachToActivity就是將SwipeBackLayout插入到DecorView和其子view之間，可以先看下代碼：
/**
* 將View添加到Activity
*/
public void attachToActivity(Activity activity) {
mTopActivity = activity;
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);
}
}
代碼整體上都還是比較簡單的缀踪，應(yīng)該都能看懂居砖。前面是獲取window背景色，插入過程到decor.addView(this);為止驴娃，下面拿到backActivity 的引用是為了做到下層activity聯(lián)動時用到的奏候。
繼續(xù)來看SwipeBackActivity，onPostCreate還設(shè)置了開始滑動和滑動結(jié)束的回調(diào)唇敞，在某些場合下還是需要的蔗草，比如一些PopupWindow在滑動返回時不會被消除，這個時候可以在onSwipeBackStart()調(diào)用其dismiss()方法疆柔。在onWindowFocusChanged中如果是hasFocus == true咒精，就recovery()這個SwipeBackLayout，這個也是因為下層activity有聯(lián)動效果而移動了SwipeBackLayout旷档，所以需要recovery()下模叙，防止異常情況。最后再提下setSwipeBackEnable(…)鞋屈，某些不可以滑動返回的頁面比如MainActivity需要在其onCreate方法中調(diào)用下設(shè)置為false就可以了向楼。
3. SwipeBackLayout和SwipeBackLayoutDragHelper
@Override
protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
//繪制陰影
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);
}
@Override
public void computeScroll() {
mContentPercent = 1 - mScrollPercent;
if (mViewDragHelper.continueSettling(true)) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
/**
* 設(shè)置是否可以滑動返回
*/
public void setSwipeBackEnable(boolean enable) {
mIsSwipeBackEnable = enable;
}
public boolean isActivityTranslucent() {
return mIsActivityTranslucent;
}
/**
* 啟動進入動畫
*/
private void startEnterAnim() {
if (mContentView != null) {
ObjectAnimator anim = ObjectAnimator
.ofFloat(mContentView, "TranslationX", mContentView.getTranslationX(), 0f);
anim.setDuration((long) (125 * mContentPercent));
mEnterAnim = anim;
mEnterAnim.start();
}
}
protected View getContentView() {
return mContentView;
}
private void setContentView(ViewGroup decorChild) {
mContentView = decorChild;
}
private class ViewDragCallback extends SwipeBackLayoutDragHelper.Callback {
@Override
public boolean tryCaptureView(View child, int pointerId) {
if (mIsSwipeBackEnable && mViewDragHelper.isEdgeTouched(SwipeBackLayoutDragHelper.EDGE_LEFT, pointerId)) {
TranslucentHelper.convertActivityToTranslucent(mTopActivity,
new TranslucentHelper.TranslucentListener() {
@Override
public void onTranslucent() {
if (mListener != null) {
mListener.onStart();
}
mIsActivityTranslucent = true;
}
});
return true;
}
return false;
}
@Override
public int getViewHorizontalDragRange(View child) {
return mIsSwipeBackEnable ? SwipeBackLayoutDragHelper.EDGE_LEFT : 0;
}
@Override
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 = left;
//未執(zhí)行動畫就平移
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);
}
}
}
@Override
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();
}
}
} else {
mViewDragHelper.settleCapturedViewAt(0, 0);
}
if (mListener != null) {
mListener.onEnd();
}
invalidate();
}
@Override
public int clampViewPositionHorizontal(View child, int left, int dx) {
return Math.min(child.getWidth(), Math.max(left, 0));
}
@Override
public void onViewDragStateChanged(int state) {
super.onViewDragStateChanged(state);
if (state == SwipeBackLayoutDragHelper.STATE_IDLE && mScrollPercent < 1f) {
TranslucentHelper.convertActivityFromTranslucent(mTopActivity);
mIsActivityTranslucent = false;
}
}
@Override
public boolean isTranslucent() {
return SwipeBackLayout.this.isActivityTranslucent();
}
}
/**
* 背景Activity開始進入動畫
*/
private void startAnimOfBackActivity() {
if (mBackActivityWeakRf != null && ActivityUtils.activityIsAlive(mBackActivityWeakRf.get())) {
mIsEnterAnimRunning = true;
SwipeBackLayout swipeBackLayout = ((SwipeBackActivity) mBackActivityWeakRf.get()).getSwipeBackLayout();
swipeBackLayout.startEnterAnim();
}
}
/**
* 移動背景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));
}
}
}
/**
* 回復(fù)界面的平移到初始位置
*/
public void recovery() {
if (mEnterAnim != null && mEnterAnim.isRunning()) {
mEnterAnim.end();
} else {
mContentView.setTranslationX(0);
}
}
}
drawChild是來繪制了左側(cè)陰影的，獲取到原 子view 所在屏幕的矩形谐区，之后確定陰影所在的矩形，然后就直接繪制了逻卖。
child.getHitRect(mContentViewRect);
mShadowLeft.setBounds(mContentViewRect.left - mShadowLeft.getIntrinsicWidth(), mContentViewRect.top,
mContentViewRect.left, mContentViewRect.bottom);
mShadowLeft.draw(canvas);
代碼中滑動是用了ViewDragHelper宋列，如果不熟悉這個類需要先自行百度。只是這個官方封裝類有幾個地方不能滿足這個滑動返回的需求评也，于是就有了SwipeBackLayoutDragHelper炼杖，SwipeBackLayoutDragHelper主要是copy了ViewDragHelper源碼后再添加了一些代碼。
首先原生ViewDragHelper里面沒有setMaxVelocity方法盗迟，如果滑動過快坤邪，會導(dǎo)致下層聯(lián)動滑動跟不上，上層滑動結(jié)束后下層還沒移動好罚缕，這導(dǎo)致的結(jié)果就是下下層可以被看到艇纺，下下層也許就是手機桌面，影響了體驗，所以需要設(shè)置了最大速度黔衡。
我們知道ViewDragHelper需要通過shouldInterceptTouchEvent(event)和processTouchEvent(event)獲取該view的onInterceptTouchEvent和onTouchEvent事件蚓聘，之后設(shè)置一個回調(diào)ViewDragCallback里面寫幾個方法就基本上可以實現(xiàn)用手指拖拽了，回調(diào)中有許多的方法盟劫，其中isTranslucent()是自己添加進去的夜牡，接下來就講講重寫回調(diào)里的方法都做了什么。
@Override
public boolean tryCaptureView(View child, int pointerId) {
if (mIsSwipeBackEnable && mViewDragHelper.isEdgeTouched(SwipeBackLayoutDragHelper.EDGE_LEFT, pointerId)) {
TranslucentHelper.convertActivityToTranslucent(mTopActivity,
new TranslucentHelper.TranslucentListener() {
@Override
public void onTranslucent() {
if (mListener != null) {
mListener.onStart();
}
mIsActivityTranslucent = true;
}
});
return true;
}
return false;
}
** tryCaptureView**方法當(dāng)觸摸到SwipeBackLayout里的子View時觸發(fā)的侣签，當(dāng)返回true塘装，表示捕捉成功，否則失敗影所。判斷條件是如果支持滑動返回并且是左側(cè)邊距被觸摸時才可以蹦肴，我們知道這個時候的的背景色是不透明的，如果直接開始滑動則是黑色的型檀，所以需要在這里背景色改成透明的冗尤，如果直接調(diào)用 TranslucentHelper.convertActivityToTranslucent(mTopActivity)后直接返回true，會出現(xiàn)一個異常情況胀溺，就是滑動過快時會導(dǎo)致背景還來不及變成黑色就滑動出來了裂七，之后才變成透明的，從而導(dǎo)致了會從黑色到透明的一個閃爍現(xiàn)象仓坞，解決的辦法是在代碼中用了一個回調(diào)和標(biāo)記背零，當(dāng)變成透明后設(shè)置了mIsActivityTranslucent = true;通過mIsActivityTranslucent 這個變量來判斷是否進行移動的操作。由于修改activity變透明的方法是通過反射的无埃，不能簡單的設(shè)置一個接口后進行回調(diào)徙瓶，而是通過動態(tài)代理的方式來實現(xiàn)的（InvocationHandler），在convertToTranslucent方法的第一個參數(shù)剛好是一個判斷activity是否已經(jīng)變成透明的回調(diào)嫉称，看下面代碼中 if 語句里的注釋和回調(diào)侦镇，如果窗口已經(jīng)變成透明的話，就傳了一個drawComplete (true)织阅。
@SystemApi
public boolean convertToTranslucent(TranslucentConversionListener callback,
ActivityOptions options) {
boolean drawComplete;
try {
mTranslucentCallback = callback;
mChangeCanvasToTranslucent =
ActivityManagerNative.getDefault().convertToTranslucent(mToken, options);
WindowManagerGlobal.getInstance().changeCanvasOpacity(mToken, false);
drawComplete = true;
} catch (RemoteException e) {
// Make callback return as though it timed out.
mChangeCanvasToTranslucent = false;
drawComplete = false;
}
if (!mChangeCanvasToTranslucent && mTranslucentCallback != null) {
// Window is already translucent.
mTranslucentCallback.onTranslucentConversionComplete(drawComplete);
}
return mChangeCanvasToTranslucent;
}
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);
通過動態(tài)代理壳繁，將translucentConversionListenerClazz 執(zhí)行其方法onTranslucentConversionComplete的替換成myInvocationHandler中執(zhí)行invoke方法。
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
boolean success = (boolean) args[0];
if (success && listener.get() != null) {
listener.get().onTranslucent();
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
其中賦值給success的args[0]正是 drawComplete
mTranslucentCallback.onTranslucentConversionComplete(drawComplete);
isTranslucent是上面提到荔棉，在SwipeBackLayoutDragHelper中的Callback回調(diào)里闹炉，自己添加了一個方法，主要是返回activity是否是透明的
public boolean isTranslucent() {
return true;
}
默認為true润樱，在SwipeBackLayout重寫后將mIsActivityTranslucent返回SwipeBackLayoutDragHelper
@Override
public boolean isTranslucent() {
return SwipeBackLayout.this.isActivityTranslucent();
}
仔細看SwipeBackLayoutDragHelper方法的話渣触，會發(fā)現(xiàn)最后通過dragTo方法對view進行移動，因此在進行水平移動前判斷下是否是透明的壹若，只有透明了才能移動
private void dragTo(int left, int top, int dx, int dy) {
int clampedX = left;
int clampedY = top;
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 - oldLeft;
final int clampedDy = clampedY - oldTop;
if (mCallback.isTranslucent()) {
mCallback.onViewPositionChanged(mCapturedView, clampedX, clampedY,
clampedDx, clampedDy);
}
}
}
onViewPositionChanged view移動過程中會持續(xù)調(diào)用嗅钻，這里面的邏輯主要有這幾個：
實時計算滑動了多少距離皂冰，用于繪制左側(cè)陰影等
使下面的activity進行移動moveBackActivity();
當(dāng)view完全移出屏幕后，銷毀當(dāng)前的activity
@Override
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 = left;
//未執(zhí)行動畫就平移
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);
}
}
}
/**
* 移動背景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是手指釋放后觸發(fā)的一個方法
如果滑動速度大于最大速度或者滑動的距離大于設(shè)定的閾值距離啊犬，則直接移到屏幕外灼擂，同時觸發(fā)下層activity的復(fù)位動畫mViewDragHelper.settleCapturedViewAt(releasedChild.getWidth() + mShadowLeft.getIntrinsicWidth(), 0);
否則移會到原來位置 mViewDragHelper.settleCapturedViewAt(0, 0);
@Override
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();
}
}
} else {
mViewDragHelper.settleCapturedViewAt(0, 0);
}
if (mListener != null) {
mListener.onEnd();
}
invalidate();
}
/**
* 背景Activity開始進入動畫
*/
private void startAnimOfBackActivity() {
if (mBackActivityWeakRf != null && ActivityUtils.activityIsAlive(mBackActivityWeakRf.get())) {
mIsEnterAnimRunning = true;
SwipeBackLayout swipeBackLayout = ((SwipeBackActivity) mBackActivityWeakRf.get()).getSwipeBackLayout();
swipeBackLayout.startEnterAnim();
}
}
/**
* 啟動進入動畫
*/
private void startEnterAnim() {
if (mContentView != null) {
ObjectAnimator anim = ObjectAnimator
.ofFloat(mContentView, "TranslationX", mContentView.getTranslationX(), 0f);
anim.setDuration((long) (125 * mContentPercent));
mEnterAnim = anim;
mEnterAnim.start();
}
}
onViewDragStateChanged當(dāng)滑動的狀態(tài)發(fā)生改變時的回調(diào)
主要是停止滑動后，將背景改成不透明，這樣跳到別的頁面是動畫就是正常的。
@Override
public void onViewDragStateChanged(int state) {
super.onViewDragStateChanged(state);
if (state == SwipeBackLayoutDragHelper.STATE_IDLE && mScrollPercent < 1f) {
TranslucentHelper.convertActivityFromTranslucent(mTopActivity);
mIsActivityTranslucent = false;
}
}
clampViewPositionHorizontal 返回水平移動距離效斑，下面這樣寫可以防止滑出父 view
@Override
public int clampViewPositionHorizontal(View child, int left, int dx) {
return Math.min(child.getWidth(), Math.max(left, 0));
}
getViewHorizontalDragRange對于clickable=true的子view，需要返回大于0的數(shù)字才能正常捕獲峻贮。
@Override
public int getViewHorizontalDragRange(View child) {
return mIsSwipeBackEnable ? SwipeBackLayoutDragHelper.EDGE_LEFT : 0;
}
