剖析Android Activity側(cè)滑返回的實(shí)現(xiàn)原理
簡(jiǎn)介
使用側(cè)滑Activity返回很常見(jiàn),例如微信就用到了。那么它是怎么實(shí)現(xiàn)的呢。本文帶你剖析一下實(shí)現(xiàn)原理。我在github上找了一個(gè)star有2.6k的開(kāi)源,我們分析他是怎么實(shí)現(xiàn)的
//star 2.6k 'com.r0adkll:slidableactivity:2.0.5'
Slidr使用示例
它的使用很簡(jiǎn)單,首先要設(shè)置透明的窗口背景
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar"> <!-- Customize your theme here. --> <item name="android:textAllCaps">false</item> <item name="android:windowActionBar">false</item> <item name="windowActionBar">false</item> <item name="windowNoTitle">true</item> <item name="colorPrimary">@color/colorPrimary</item> <item name="colorPrimaryDark">@color/colorPrimaryDark</item> <item name="colorAccent">@color/colorAccent</item> <item name="android:windowIsTranslucent">true</item> <item name="android:windowBackground">@android:color/transparent</item> </style>
然后
//setContent(View view)后 Slidr.attach(this);
下面可以從三個(gè)步驟看其原理
步驟一 重新包裹界面
Slidr.class
public static SlidrInterface attach(final Activity activity, final int statusBarColor1, final int statusBarColor2){ //0 創(chuàng)建滑動(dòng)嵌套界面SliderPanel final SliderPanel panel = initSliderPanel(activity, null); //7 Set the panel slide listener for when it becomes closed or opened // 監(jiān)聽(tīng)回調(diào) panel.setOnPanelSlideListener(new SliderPanel.OnPanelSlideListener() { ... //open close等 }); // Return the lock interface return initInterface(panel); } private static SliderPanel initSliderPanel(final Activity activity, final SlidrConfig config) { //3 獲取decorview ViewGroup decorView = (ViewGroup)activity.getWindow().getDecorView(); //4 獲取我們布局的內(nèi)容并刪除 View oldScreen = decorView.getChildAt(0); decorView.removeViewAt(0); //5 Setup the slider panel and attach it to the decor // 建立滑動(dòng)嵌套視圖SliderPanel并且添加到DecorView中 SliderPanel panel = new SliderPanel(activity, oldScreen, config); panel.setId(R.id.slidable_panel); oldScreen.setId(R.id.slidable_content); //6 把我們的界面布局添加到SliderPanel,并且把SliderPanel添加到decorView中 panel.addView(oldScreen); decorView.addView(panel, 0); return panel; }
步驟二 使用ViewDragHelper.class
處理滑動(dòng)手勢(shì)
SliderPanel.class
private void init(){ ... //1 ViewDragHelper創(chuàng)建 mDragHelper = ViewDragHelper.create(this, mConfig.getSensitivity(), callback); mDragHelper.setMinVelocity(minVel); mDragHelper.setEdgeTrackingEnabled(mEdgePosition); //2 Setup the dimmer view 添加用于指示滑動(dòng)過(guò)程的View到底層 mDimView = new View(getContext()); mDimView.setBackgroundColor(mConfig.getScrimColor()); mDimView.setAlpha(mConfig.getScrimStartAlpha()); addView(mDimView); }
步驟三 在ViewDragHelper.Callback中處理我們的界面的拖動(dòng)
我們首先明確ViewDragHelper僅僅是處理ParentView與它子View的關(guān)系,不會(huì)一直遍歷到最頂層的View。ViewDragHelper的捕獲capture是這樣實(shí)現(xiàn)的
@Nullable public View findTopChildUnder(int x, int y) { final int childCount = mParentView.getChildCount(); for (int i = childCount - 1; i >= 0; i--) { final View child = mParentView.getChildAt(mCallback.getOrderedChildIndex(i)); if (x >= child.getLeft() && x < child.getRight() && y >= child.getTop() && y < child.getBottom()) { return child; } } return null; }
重點(diǎn)在SliderPanel.class的ViewDragHelper.Callback callback
的實(shí)現(xiàn),作者實(shí)現(xiàn)實(shí)現(xiàn)了很多個(gè)方向的滑動(dòng)處理mLeftCallback、mRightCallback、mTopCallback、mBottomCallback、mVerticalCallback、mHorizontalCallback, 我們?nèi)LeftCallback來(lái)分析
private ViewDragHelper.Callback mLeftCallback = new ViewDragHelper.Callback() { //捕獲View @Override public boolean tryCaptureView(View child, int pointerId) { boolean edgeCase = !mConfig.isEdgeOnly() || mDragHelper.isEdgeTouched(mEdgePosition, pointerId); //像前面說(shuō)的,我們的內(nèi)容是最上層子View,mDecorView這里指的是我們的contentView return child.getId() == mDecorView.getId() && edgeCase; } //拖動(dòng), 最終是通過(guò)view.offsetLeftAndRight(offset)實(shí)現(xiàn)移動(dòng) @Override public int clampViewPositionHorizontal(View child, int left, int dx) { return clamp(left, 0, mScreenWidth); } //滑動(dòng)范圍 @Override public int getViewHorizontalDragRange(View child) { return mScreenWidth; } //釋放處理,判斷是滾回屏幕 @Override public void onViewReleased(View releasedChild, float xvel, float yvel) { super.onViewReleased(releasedChild, xvel, yvel); int left = releasedChild.getLeft(); int settleLeft = 0; int leftThreshold = (int) (getWidth() * mConfig.getDistanceThreshold()); boolean isVerticalSwiping = Math.abs(yvel) > mConfig.getVelocityThreshold(); if(xvel > 0){ if(Math.abs(xvel) > mConfig.getVelocityThreshold() && !isVerticalSwiping){ settleLeft = mScreenWidth; }else if(left > leftThreshold){ settleLeft = mScreenWidth; } }else if(xvel == 0){ if(left > leftThreshold){ settleLeft = mScreenWidth; } } //滾動(dòng)到left=0(正常布局) 或者 滾動(dòng)到left=mScreenWidth(滾出屏幕)關(guān)閉Activity mDragHelper.settleCapturedViewAt(settleLeft, releasedChild.getTop()); invalidate(); } //轉(zhuǎn)換位置百分比,確定指示層的透明度 @Override public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) { super.onViewPositionChanged(changedView, left, top, dx, dy); float percent = 1f - ((float)left / (float)mScreenWidth); if(mListener != null) mListener.onSlideChange(percent); // Update the dimmer alpha applyScrim(percent); } //回調(diào)到Slidr處理Activity狀態(tài) @Override public void onViewDragStateChanged(int state) { super.onViewDragStateChanged(state); if(mListener != null) mListener.onStateChanged(state); switch (state){ case ViewDragHelper.STATE_IDLE: if(mDecorView.getLeft() == 0){ // State Open if(mListener != null) mListener.onOpened(); }else{ // State Closed 這里回調(diào)到Slidr處理activity.finish() if(mListener != null) mListener.onClosed(); } break; case ViewDragHelper.STATE_DRAGGING: break; case ViewDragHelper.STATE_SETTLING: break; } } };
對(duì)于mDragHelper.settleCapturedViewAt(settleLeft, releasedChild.getTop());
內(nèi)部是使用Scroller.class輔助滾動(dòng),所以要在SliderPanel
中重寫View.computeScroll()
@Override public void computeScroll() { super.computeScroll(); if(mDragHelper.continueSettling(true)){ ViewCompat.postInvalidateOnAnimation(this); } }
總結(jié)
整體方案如下圖所示
總體來(lái)看原理并不復(fù)雜, 就是通過(guò)ViewDragHelper對(duì)View進(jìn)行拖動(dòng)。
以上就是Android Activity側(cè)滑返回的實(shí)現(xiàn)原理的詳細(xì)內(nèi)容,更多關(guān)于Activity側(cè)滑返回的資料請(qǐng)關(guān)注腳本之家其它相關(guān)文章!
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