編輯:關於Android編程
一、WIndow和windowManager
Window是一個抽象類,它的具體實現是PhoneWindow,創建一個window很簡單,只需要創建一個windowManager即可,window具體實現在windowManagerService中,windowManager和windowManagerService的交互是一個IPC的過程。
下面是用windowManager的例子:
mFloatingButton = new Button(this); mFloatingButton.setText( "window"); mLayoutParams = new WindowManager.LayoutParams( LayoutParams. WRAP_CONTENT, LayoutParams.WRAP_CONTENT, 0, 0, PixelFormat. TRANSPARENT); mLayoutParams. flags = LayoutParams.FLAG_NOT_TOUCH_MODAL | LayoutParams. FLAG_NOT_FOCUSABLE | LayoutParams. FLAG_SHOW_WHEN_LOCKED; mLayoutParams. type = LayoutParams. TYPE_SYSTEM_ERROR; mLayoutParams. gravity = Gravity. LEFT | Gravity. TOP; mLayoutParams. x = 100; mLayoutParams. y = 300; mFloatingButton.setOnTouchListener( this); mWindowManager.addView( mFloatingButton, mLayoutParams);
flags和type兩個屬性很重要,下面對一些屬性進行介紹,首先是flags:
FLAG_NOT_TOUCH_MODAL表示不需要獲取焦點,也不需要接收各種輸入,最終事件直接傳遞給下層具有焦點的window。
FLAG_NOT_FOCUSABLE:在此window外的區域單擊事件傳遞到底層window中。當前的區域則自己處理,這個一般都要設置,很重要。
FLAG_SHOW_WHEN_LOCKED :開啟可以讓window顯示在鎖屏界面上。
再來看下type這個參數:
window有三種類型:應用window,子window,系統window。應用類對應一個Activity,子Window不能單獨存在,需要附屬在父Window上,比如常用的Dialog。系統Window是需要聲明權限再創建的window,如toast等。
window有z-ordered屬性,層級越大,越在頂層。應用window層級1-99,子window1000-1999,系統2000-2999。這此層級對應著windowManager的type參數。系統層級常用的有兩個TYPE_SYSTEM_OVERLAY或者TYPE_SYSTEM_ERROR。比如想用TYPE_SYSTEM_ERROR,只需
mLayoutParams.type = LayoutParams.TYPE_SYSTEM_ERROR。還要添加權限<uses-permission andorid:name="android.permission.SYSTEM_ALERT_WINDOW"/>。
有了對window的基本認識之後,我們來看下它底層如何實現加載View的。
二、window的創建
其實Window的創建跟之前我寫的一篇博客LayoutInflater源碼分析有點相似。Window的創建是在Activity創建的attach方法中,通過PolicyManager的makeNewWindow方法。Activity中實現了Window的Callback接口,因此當window狀態改變時就會回調Activity方法。如onAttachedToWindow等。PolicyManager的真正實現類是Policy,看下它的代碼:
public Window makeNewWindow(Context context) { return new PhoneWindow(context); }
到此Window創建完成。
下面分析view是如何附屬到window上的。看Activity的setContentView方法。
public void setContentView(int layoutResID) { getWindow().setContentView(layoutResID); initWindowDecorActionBar(); }
兩部分,設置內容和設置ActionBar。window的具體實現是PhoneWindow,看它的setContent。
public void setContentView(int layoutResID) { // Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window // decor, when theme attributes and the like are crystalized. Do not check the feature // before this happens. if (mContentParent == null) { installDecor(); } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) { mContentParent.removeAllViews(); } if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) { final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID, getContext()); transitionTo(newScene); } else { mLayoutInflater.inflate(layoutResID, mContentParent); } final Callback cb = getCallback(); if (cb != null && !isDestroyed()) { cb.onContentChanged(); } }
看到了吧,又是分析它。
這裡分三步執行:
1.如果沒有DecorView,在installDecor中的generateDecor()創建DecorView。之前就分析過,這次就不再分析它了。
2.將View添加到decorview中的mContentParent中。
3.回調Activity的onContentChanged接口。
經過以上操作,DecorView創建了,但還沒有正式添加到Window中。在ActivityResumeActivity中首先會調用Activity的onResume,再調用Activity的makeVisible,makeVisible中真正添加view ,代碼如下:
void makeVisible() { if (!mWindowAdded) { ViewManager wm = getWindowManager(); wm.addView(mDecor, getWindow().getAttributes()); mWindowAdded = true; } mDecor.setVisibility(View.VISIBLE); }
通過上面的addView方法將View添加到Window。
三、Window操作View內部機制
1.window的添加
一個window對應一個view和一個viewRootImpl,window和view通過ViewRootImpl來建立聯系,它並不存在,實體是view。只能通過 windowManager來操作它。
windowManager的實現類是windowManagerImpl。它並沒有直接實現三大操作,而是委托給WindowManagerGlobal。addView的實現分為以下幾步:
1).檢查參數是否合法。
if (view == null) { throw new IllegalArgumentException("view must not be null"); } if (display == null) { throw new IllegalArgumentException("display must not be null"); } if (!(params instanceof WindowManager.LayoutParams)) { throw new IllegalArgumentException("Params must be WindowManager.LayoutParams"); } final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams)params; if (parentWindow != null) { parentWindow.adjustLayoutParamsForSubWindow(wparams); } else { // If there's no parent and we're running on L or above (or in the // system context), assume we want hardware acceleration. final Context context = view.getContext(); if (context != null && context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.LOLLIPOP) { wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED; } }
2).創建ViewRootImpl並將View添加到列表中。
root = new ViewRootImpl(view.getContext(), display); view.setLayoutParams(wparams); mViews.add(view); mRoots.add(root); mParams.add(wparams);
3).通過ViewRootImpl來更新界面並完成window的添加過程 。
root.setView(view, wparams, panelParentView);
上面的root就是ViewRootImpl,setView中通過requestLayout()來完成異步刷新,看下requestLayout:
public void requestLayout() { if (!mHandlingLayoutInLayoutRequest) { checkThread(); mLayoutRequested = true; scheduleTraversals(); } }
接下來通過WindowSession來完成window添加過程,WindowSession是一個Binder對象,真正的實現類是 Session,window的添加是一次IPC調用。
try { mOrigWindowType = mWindowAttributes.type; mAttachInfo.mRecomputeGlobalAttributes = true; collectViewAttributes(); res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes, getHostVisibility(), mDisplay.getDisplayId(), mAttachInfo.mContentInsets, mAttachInfo.mStableInsets, mInputChannel); } catch (RemoteException e) { mAdded = false; mView = null; mAttachInfo.mRootView = null; mInputChannel = null; mFallbackEventHandler.setView(null); unscheduleTraversals(); setAccessibilityFocus(null, null); throw new RuntimeException("Adding window failed", e); }
在Session內部會通過WindowManagerService來實現Window的添加。
public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs, int viewVisibility, int displayId, Rect outContentInsets, Rect outStableInsets, InputChannel outInputChannel) { return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId, outContentInsets, outStableInsets, outInputChannel); }
在WindowManagerService內部會為每一個應用保留一個單獨的session。
2.window的刪除
看下WindowManagerGlobal的removeView:
public void removeView(View view, boolean immediate) { if (view == null) { throw new IllegalArgumentException("view must not be null"); } synchronized (mLock) { int index = findViewLocked(view, true); View curView = mRoots.get(index).getView(); removeViewLocked(index, immediate); if (curView == view) { return; } throw new IllegalStateException("Calling with view " + view + " but the ViewAncestor is attached to " + curView); } }
首先調用findViewLocked來查找刪除view的索引,這個過程就是建立數組遍歷。然後再調用removeViewLocked來做進一步的刪除。
private void removeViewLocked(int index, boolean immediate) { ViewRootImpl root = mRoots.get(index); View view = root.getView(); if (view != null) { InputMethodManager imm = InputMethodManager.getInstance(); if (imm != null) { imm.windowDismissed(mViews.get(index).getWindowToken()); } } boolean deferred = root.die(immediate); if (view != null) { view.assignParent(null); if (deferred) { mDyingViews.add(view); } } }
真正刪除操作是viewRootImpl來完成的。windowManager提供了兩種刪除接口,removeViewImmediate,removeView。它們分別表示異步刪除和同步刪除。具體的刪除操作由ViewRootImpl的die來完成。
boolean die(boolean immediate) { // Make sure we do execute immediately if we are in the middle of a traversal or the damage // done by dispatchDetachedFromWindow will cause havoc on return. if (immediate && !mIsInTraversal) { doDie(); return false; } if (!mIsDrawing) { destroyHardwareRenderer(); } else { Log.e(TAG, "Attempting to destroy the window while drawing!\n" + " window=" + this + ", title=" + mWindowAttributes.getTitle()); } mHandler.sendEmptyMessage(MSG_DIE); return true; }
由上可知如果是removeViewImmediate,立即調用doDie,如果是removeView,用handler發送消息,ViewRootImpl中的Handler會處理消息並調用doDie。重點看下doDie:
void doDie() { checkThread(); if (LOCAL_LOGV) Log.v(TAG, "DIE in " + this + " of " + mSurface); synchronized (this) { if (mRemoved) { return; } mRemoved = true; if (mAdded) { dispatchDetachedFromWindow(); } if (mAdded && !mFirst) { destroyHardwareRenderer(); if (mView != null) { int viewVisibility = mView.getVisibility(); boolean viewVisibilityChanged = mViewVisibility != viewVisibility; if (mWindowAttributesChanged || viewVisibilityChanged) { // If layout params have been changed, first give them // to the window manager to make sure it has the correct // animation info. try { if ((relayoutWindow(mWindowAttributes, viewVisibility, false) & WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) { mWindowSession.finishDrawing(mWindow); } } catch (RemoteException e) { } } mSurface.release(); } } mAdded = false; } WindowManagerGlobal.getInstance().doRemoveView(this); }
主要做四件事:
1.垃圾回收相關工作,比如清數據,回調等。
2.通過Session的remove方法刪除Window,最終調用WindowManagerService的removeWindow
3.調用dispathDetachedFromWindow,在內部會調用onDetachedFromWindow()和onDetachedFromWindowInternal()。當view移除時會調用onDetachedFromWindow,它用於作一些資源回收。
4.通過doRemoveView刷新數據,刪除相關數據,如在mRoot,mDyingViews中刪除對象等。
void doRemoveView(ViewRootImpl root) { synchronized (mLock) { final int index = mRoots.indexOf(root); if (index >= 0) { mRoots.remove(index); mParams.remove(index); final View view = mViews.remove(index); mDyingViews.remove(view); } } if (HardwareRenderer.sTrimForeground && HardwareRenderer.isAvailable()) { doTrimForeground(); } }
3.更新window
看下WindowManagerGlobal中的updateViewLayout。
public void updateViewLayout(View view, ViewGroup.LayoutParams params) { if (view == null) { throw new IllegalArgumentException("view must not be null"); } if (!(params instanceof WindowManager.LayoutParams)) { throw new IllegalArgumentException("Params must be WindowManager.LayoutParams"); } final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams)params; view.setLayoutParams(wparams); synchronized (mLock) { int index = findViewLocked(view, true); ViewRootImpl root = mRoots.get(index); mParams.remove(index); mParams.add(index, wparams); root.setLayoutParams(wparams, false); } }
通過viewRootImpl的setLayoutParams更新viewRootImpl的layoutParams,接著scheduleTraversals對view重新布局,包括測量,布局,重繪,此外它還會通過WindowSession來更新window。這個過程由WindowManagerService實現。這跟上面類似,就不再重復,到此Window底層源碼就分析完啦。
以上就是本文的全部內容,希望對大家的學習有所幫助。
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