[TOC] 備註：本文基於sdk28， **ViewActivity頁面禁用了硬體加速(AndroidManifest.xml中添加了android:hardwareAccelerated="false")**。 # 1、異常出處 ViewActivity程式碼連結：https://gitee.com/2820174512/application/blob/master/app/src/main/java/com/example/myapplication/threadcheck/ViewActivity.java 點選Hello，World！後報如下異常：  從圖片中可以看出異常在ViewRootImpl類的**invalidateChildInParent**方法中進行檢查的，判斷當前執行緒是否是建立執行緒（View類一般是在主執行緒建立的），部分程式碼如下, 可以看出就是在checkThread方法中丟擲的異常。 ``` @Override public ViewParent invalidateChildInParent(int[] location, Rect dirty) { checkThread(); if (DEBUG_DRAW) Log.v(mTag, "Invalidate child: " + dirty); ... return null; } void checkThread() { if (mThread != Thread.currentThread()) { throw new CalledFromWrongThreadException( "Only the original thread that created a view hierarchy can touch its views."); } } ``` # 2、從View.invalidate()方法開始分析 先看下TextView.invalidate()方法（View的invalidate()方法） ``` public void invalidate() { invalidate(true); } public void invalidate(boolean invalidateCache) { invalidateInternal(0, 0, mRight - mLeft, mBottom - mTop, invalidateCache, true); } void invalidateInternal(int l, int t, int r, int b, boolean invalidateCache, boolean fullInvalidate) { ... // Reset content capture caches mCachedContentCaptureSession = null; if ((mPrivateFlags & (PFLAG_DRAWN | PFLAG_HAS_BOUNDS)) == (PFLAG_DRAWN | PFLAG_HAS_BOUNDS) || (invalidateCache && (mPrivateFlags & PFLAG_DRAWING_CACHE_VALID) == PFLAG_DRAWING_CACHE_VALID) || (mPrivateFlags & PFLAG_INVALIDATED) != PFLAG_INVALIDATED || (fullInvalidate && isOpaque() != mLastIsOpaque)) { ... // Propagate the damage rectangle to the parent view. final AttachInfo ai = mAttachInfo; final ViewParent p = mParent; if (p != null && ai != null && l < r && t < b) { final Rect damage = ai.mTmpInvalRect; damage.set(l, t, r, b); p.invalidateChild(this, damage); } ... } } ``` 主要執行邏輯：向上請求父View執行invalidateChild()方法， 該方法為ViewParent介面的方法，ViewGroup類實現了該介面的invalidateChild方法 ``` public final void invalidateChild(View child, final Rect dirty) { final AttachInfo attachInfo = mAttachInfo; if (attachInfo != null && attachInfo.mHardwareAccelerated) { // HW accelerated fast path onDescendantInvalidated(child, child); return; } ViewParent parent = this; if (attachInfo != null) { ... do { View view = null; if (parent instanceof View) { view = (View) parent; } if (drawAnimation) { if (view != null) { view.mPrivateFlags |= PFLAG_DRAW_ANIMATION; } else if (parent instanceof ViewRootImpl) { ((ViewRootImpl) parent).mIsAnimating = true; } } ... parent = parent.invalidateChildInParent(location, dirty); if (view != null) { // Account for transform on current parent Matrix m = view.getMatrix(); if (!m.isIdentity()) { RectF boundingRect = attachInfo.mTmpTransformRect; boundingRect.set(dirty); m.mapRect(boundingRect); dirty.set((int) Math.floor(boundingRect.left), (int) Math.floor(boundingRect.top), (int) Math.ceil(boundingRect.right), (int) Math.ceil(boundingRect.bottom)); } } } while (parent != null); } } public ViewParent invalidateChildInParent(final int[] location, final Rect dirty) { if ((mPrivateFlags & (PFLAG_DRAWN | PFLAG_DRAWING_CACHE_VALID)) != 0) { ... return mParent; } return null; } ``` do while迴圈一層層向上請求重繪，最終應該是到ViewRootImpl類的**invalidateChildInParent**方法 # 3、ViewRootImpl如何與View進行關聯：從Activity的setContentView開始分析 ## 3.1 最頂層的View——DecorView 要將View顯示到介面上，需要在Activity中執行setContentView，這裡主要分析setContentView(View)方法 ``` public void setContentView(View view) { getWindow().setContentView(view); initWindowDecorActionBar(); } public Window getWindow() { return mWindow; } final void attach(Context context, ActivityThread aThread, Instrumentation instr, IBinder token, int ident, Application application, Intent intent, ActivityInfo info, CharSequence title, Activity parent, String id, NonConfigurationInstances lastNonConfigurationInstances, Configuration config, String referrer, IVoiceInteractor voiceInteractor, Window window, ActivityConfigCallback activityConfigCallback) { attachBaseContext(context); mFragments.attachHost(null /*parent*/); mWindow = new PhoneWindow(this, window, activityConfigCallback); ... } ``` mWindow屬性在android.app.Activity#attach方法中進行賦值， 實現類為PhoneWindow，而PhoneWindow的setContentView實現如下： ``` // This is the top-level view of the window, containing the window decor. private DecorView mDecor; @Override public void setContentView(View view) { setContentView(view, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT)); } @Override public void setContentView(View view, ViewGroup.LayoutParams params) { // 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)) { view.setLayoutParams(params); final Scene newScene = new Scene(mContentParent, view); transitionTo(newScene); } else { mContentParent.addView(view, params); } mContentParent.requestApplyInsets(); final Callback cb = getCallback(); if (cb != null && !isDestroyed()) { cb.onContentChanged(); } mContentParentExplicitlySet = true; } private void installDecor() { mForceDecorInstall = false; if (mDecor == null) { mDecor = generateDecor(-1); mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS); mDecor.setIsRootNamespace(true); if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) { mDecor.postOnAnimation(mInvalidatePanelMenuRunnable); } } else { mDecor.setWindow(this); } ... } protected DecorView generateDecor(int featureId) { // System process doesn't have application context and in that case we need to directly use // the context we have. Otherwise we want the application context, so we don't cling to the // activity. Context context; if (mUseDecorContext) { Context applicationContext = getContext().getApplicationContext(); if (applicationContext == null) { context = getContext(); } else { context = new DecorContext(applicationContext, getContext()); if (mTheme != -1) { context.setTheme(mTheme); } } } else { context = getContext(); } return new DecorView(context, featureId, this, getAttributes()); } ``` 可以看出mDecor為View樹中最頂層的View，是DecorView類的一個例項。 ## 3.2 DecorView與ViewRootImpl進行關聯 這裡我是通過搜尋“DecorView如何與ViewRootImpl進行關聯”才知道具體關聯程式碼，見連結https://www.cnblogs.com/huansky/p/11911549.html 主要在ActivityThread類的handleResumeActivity方法中 ``` @Override public void handleResumeActivity(IBinder token, boolean finalStateRequest, boolean isForward, String reason) { // If we are getting ready to gc after going to the background, well // we are back active so skip it. unscheduleGcIdler(); mSomeActivitiesChanged = true; // TODO Push resumeArgs into the activity for consideration final ActivityClientRecord r = performResumeActivity(token, finalStateRequest, reason); if (r == null) { // We didn't actually resume the activity, so skipping any follow-up actions. return; } final Activity a = r.activity; if (localLOGV) { Slog.v(TAG, "Resume " + r + " started activity: " + a.mStartedActivity + ", hideForNow: " + r.hideForNow + ", finished: " + a.mFinished); } final int forwardBit = isForward ? WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION : 0; // If the window hasn't yet been added to the window manager, // and this guy didn't finish itself or start another activity, // then go ahead and add the window. boolean willBeVisible = !a.mStartedActivity; if (!willBeVisible) { try { willBeVisible = ActivityManager.getService().willActivityBeVisible( a.getActivityToken()); } catch (RemoteException e) { throw e.rethrowFromSystemServer(); } } if (r.window == null && !a.mFinished && willBeVisible) { r.window = r.activity.getWindow(); View decor = r.window.getDecorView(); decor.setVisibility(View.INVISIBLE); ViewManager wm = a.getWindowManager(); WindowManager.LayoutParams l = r.window.getAttributes(); a.mDecor = decor; l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION; l.softInputMode |= forwardBit; if (r.mPreserveWindow) { a.mWindowAdded = true; r.mPreserveWindow = false; // Normally the ViewRoot sets up callbacks with the Activity // in addView->ViewRootImpl#setView. If we are instead reusing // the decor view we have to notify the view root that the // callbacks may have changed. ViewRootImpl impl = decor.getViewRootImpl(); if (impl != null) { impl.notifyChildRebuilt(); } } if (a.mVisibleFromClient) { if (!a.mWindowAdded) { a.mWindowAdded = true; wm.addView(decor, l); } else { // The activity will get a callback for this {@link LayoutParams} change // earlier. However, at that time the decor will not be set (this is set // in this method), so no action will be taken. This call ensures the // callback occurs with the decor set. a.onWindowAttributesChanged(l); } } // If the window has already been added, but during resume // we started another activity, then don't yet make the // window visible. } else if (!willBeVisible) { if (localLOGV) Slog.v(TAG, "Launch " + r + " mStartedActivity set"); r.hideForNow = true; } ... } ``` 一般執行流程： 獲取Activity例項a對應的WindowManager例項wm，然後addView。 Activity的attach方法中對mWindowManager物件賦值，mWindowManager物件從mWindow物件中獲得 ``` final void attach(Context context, ActivityThread aThread, Instrumentation instr, IBinder token, int ident, Application application, Intent intent, ActivityInfo info, CharSequence title, Activity parent, String id, NonConfigurationInstances lastNonConfigurationInstances, Configuration config, String referrer, IVoiceInteractor voiceInteractor, Window window, ActivityConfigCallback activityConfigCallback) { attachBaseContext(context); mFragments.attachHost(null /*parent*/); mWindow = new PhoneWindow(this, window, activityConfigCallback); ... mWindowManager = mWindow.getWindowManager(); ... } ``` mWindow物件為Window類，getWindowManager實現如下，則ActivityThread類中handleResumeActivity獲取的wm物件實現類為WindowManagerImpl類 ``` public WindowManager getWindowManager() { return mWindowManager; } public void setWindowManager(WindowManager wm, IBinder appToken, String appName, boolean hardwareAccelerated) { mAppToken = appToken; mAppName = appName; mHardwareAccelerated = hardwareAccelerated || SystemProperties.getBoolean(PROPERTY_HARDWARE_UI, false); if (wm == null) { wm = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE); } mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this); } ``` WindowManagerImpl類addView(View, ViewGroup.LayoutParams)實現如下 ``` @Override public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) { applyDefaultToken(params); mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow); } ``` 委託給WindowManagerGlobal類的addView(View, ViewGroup.LayoutParams, Display, Window)實現，最終呼叫ViewRootImpl的setView方法關聯DecorView與ViewRootImpl ``` public void addView(View view, ViewGroup.LayoutParams params, Display display, Window parentWindow) { ... ViewRootImpl root; View panelParentView = null; synchronized (mLock) { ... root = new ViewRootImpl(view.getContext(), display); view.setLayoutParams(wparams); mViews.add(view); mRoots.add(root); mParams.add(wparams); // do this last because it fires off messages to start doing things try { root.setView(view, wparams, panelParentView); } catch (RuntimeException e) { // BadTokenException or InvalidDisplayException, clean up. if (index >= 0) { removeViewLocked(index, true); } throw e; } } } ``` # 4、其他 ## 4.1 獲取DecorView與ViewRootImpl的直接方法 在View中mParent只有一處賦值，就是在void assignParent(ViewParent parent)方法中，可以在這裡新增一個條件斷點 parent instanceof ViewRootImpl， 就可以獲取對應的呼叫資訊  ## 4.2 硬體加速相關以及invalidate()流程圖 ViewGroup類的invalidateChild部分程式碼如下， ``` public final void invalidateChild(View child, final Rect dirty) { final AttachInfo attachInfo = mAttachInfo; if (attachInfo != null && attachInfo.mHardwareAccelerated) { // HW accelerated fast path onDescendantInvalidated(child, child); return; } ... do { View view = null; if (parent instanceof View) { view = (View) parent; } if (drawAnimation) { if (view != null) { view.mPrivateFlags |= PFLAG_DRAW_ANIMATION; } else if (parent instanceof ViewRootImpl) { ((ViewRootImpl) parent).mIsAnimating = true; } } // If the parent is dirty opaque or not dirty, mark it dirty with the opaque // flag coming from the child that initiated the invalidate if (view != null) { if ((view.mViewFlags & FADING_EDGE_MASK) != 0 && view.getSolidColor() == 0) { opaqueFlag = PFLAG_DIRTY; } if ((view.mPrivateFlags & PFLAG_DIRTY_MASK) != PFLAG_DIRTY) { view.mPrivateFlags = (view.mPrivateFlags & ~PFLAG_DIRTY_MASK) | opaqueFlag; } } parent = parent.invalidateChildInParent(location, dirty); if (view != null) { // Account for transform on current parent Matrix m = view.getMatrix(); if (!m.isIdentity()) { RectF boundingRect = attachInfo.mTmpTransformRect; boundingRect.set(dirty); m.mapRect(boundingRect); dirty.set((int) Math.floor(boundingRect.left), (int) Math.floor(boundingRect.top), (int) Math.ceil(boundingRect.right), (int) Math.ceil(boundingRect.bottom)); } } } while (parent != null); } ``` 其中attachInfo.mHardwareAccelerated表示啟用硬體加速，如果啟用硬體加速，子執行緒invalidate()不會產生異常（genymotion9.0模擬器中未產生異常，genymotion6.0模擬器中會產生異常）。 本文開始在activity中禁用硬體加速就是因為這個原因，而像子執行緒中requestLayout、addView等硬體沒有加速問題，一定會報異常。 invalidate()執行後方法呼叫流程圖如下：  ## 4.3 View載入執行緒問題 只要View沒有新增到Window中View就可以在子執行緒中操作，不過會有執行緒安全