Android View的重绘ViewRootImpl的setView方法

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本篇文章来分析一下WindowManager的后续工作，也就是ViewRootImpl的setView函数的工作

/i**
     * We have one child
     */
    public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
        synchronized (this) {
            if (mView == null) {
                mView = view;
        //获取当前屏幕最新的状态，并且给当前DecorView注册屏幕监听，用来检测灭屏和亮屏
                mAttachInfo.mDisplayState = mDisplay.getState();
                mDisplayManager.registerDisplayListener(mDisplayListener, mHandler);

                mViewLayoutDirectionInitial = mView.getRawLayoutDirection();
                mFallbackEventHandler.setView(view);
                mWindowAttributes.copyFrom(attrs);
                if (mWindowAttributes.packageName == null) {
                    mWindowAttributes.packageName = mBasePackageName;
                }
                attrs = mWindowAttributes;
                // Keep track of the actual window flags supplied by the client.
                mClientWindowLayoutFlags = attrs.flags;
        //清除辅助功能的焦点
                setAccessibilityFocus(null, null);

                if (view instanceof RootViewSurfaceTaker) {
                    mSurfaceHolderCallback =
                            ((RootViewSurfaceTaker)view).willYouTakeTheSurface();
                    if (mSurfaceHolderCallback != null) {
                        mSurfaceHolder = new TakenSurfaceHolder();
                        mSurfaceHolder.setFormat(PixelFormat.UNKNOWN);
                    }
                }

                // Compute surface insets required to draw at specified Z value.
                // TODO: Use real shadow insets for a constant max Z.
                if (!attrs.hasManualSurfaceInsets) {
                    final int surfaceInset = (int) Math.ceil(view.getZ() * 2);
                    attrs.surfaceInsets.set(surfaceInset, surfaceInset, surfaceInset, surfaceInset);
                }
        //获取屏幕兼容模式,一般情况下不考虑 mTranslator是空的
                CompatibilityInfo compatibilityInfo = mDisplayAdjustments.getCompatibilityInfo();
                mTranslator = compatibilityInfo.getTranslator();

        //开启硬件加速功能
                if (mSurfaceHolder == null) {
                    enableHardwareAcceleration(attrs);
                }

                boolean restore = false;
        //Application不考虑兼容模式
                if (mTranslator != null) {
                    mSurface.setCompatibilityTranslator(mTranslator);
                    restore = true;
                    attrs.backup();
                    mTranslator.translateWindowLayout(attrs);
                }
                if (DEBUG_LAYOUT) Log.d(TAG, "WindowLayout in setView:" + attrs);
        //Application不考虑兼容模式
                if (!compatibilityInfo.supportsScreen()) {
                    attrs.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
                    mLastInCompatMode = true;
                }

                mSoftInputMode = attrs.softInputMode;
                mWindowAttributesChanged = true;
                mWindowAttributesChangesFlag = WindowManager.LayoutParams.EVERYTHING_CHANGED;
                mAttachInfo.mRootView = view;
                mAttachInfo.mScalingRequired = mTranslator != null;
                mAttachInfo.mApplicationScale =
                        mTranslator == null ? 1.0f : mTranslator.applicationScale;
                if (panelParentView != null) {
                    mAttachInfo.mPanelParentWindowToken
                            = panelParentView.getApplicationWindowToken();
                }
                mAdded = true;
                int res; /* = WindowManagerImpl.ADD_OKAY; */

        //在这里开始启用绘制线程，requestLayout会触发整个的绘制过程
                requestLayout();
                if ((mWindowAttributes.inputFeatures
                        & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
                    mInputChannel = new InputChannel();
                }
                try {
                    mOrigWindowType = mWindowAttributes.type;
                    mAttachInfo.mRecomputeGlobalAttributes = true;
                    collectViewAttributes();
            //mWindow是ViewRootImpl中的一个静态类，这个类可以用来和WindowSession交互，就等于间接在和WindowManagerService交互
            //是一个桥梁类
                    res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
                            getHostVisibility(), mDisplay.getDisplayId(),
                            mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
                            mAttachInfo.mOutsets, 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);
                } finally {
                    if (restore) {
                        attrs.restore();
                    }
                }

                if (mTranslator != null) {
                    mTranslator.translateRectInScreenToAppWindow(mAttachInfo.mContentInsets);
                }
                mPendingOverscanInsets.set(0, 0, 0, 0);
                mPendingContentInsets.set(mAttachInfo.mContentInsets);
                mPendingStableInsets.set(mAttachInfo.mStableInsets);
                mPendingVisibleInsets.set(0, 0, 0, 0);
                if (DEBUG_LAYOUT) Log.v(TAG, "Added window " + mWindow);
        //在这里处理WindowManagerServices的处理结果，在这里你能看到很多熟悉的异常
                if (res < WindowManagerGlobal.ADD_OKAY) {
                    mAttachInfo.mRootView = null;
                    mAdded = false;
                    mFallbackEventHandler.setView(null);
                    unscheduleTraversals();
                    setAccessibilityFocus(null, null);
                    switch (res) {
                        case WindowManagerGlobal.ADD_BAD_APP_TOKEN:
                        case WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN:
                            throw new WindowManager.BadTokenException(
                                    "Unable to add window -- token " + attrs.token
                                    + " is not valid; is your activity running?");
                        case WindowManagerGlobal.ADD_NOT_APP_TOKEN:
                            throw new WindowManager.BadTokenException(
                                    "Unable to add window -- token " + attrs.token
                                    + " is not for an application");
                        case WindowManagerGlobal.ADD_APP_EXITING:
                            throw new WindowManager.BadTokenException(
                                    "Unable to add window -- app for token " + attrs.token
                                    + " is exiting");
                        case WindowManagerGlobal.ADD_DUPLICATE_ADD:
                            throw new WindowManager.BadTokenException(
                                    "Unable to add window -- window " + mWindow
                                    + " has already been added");
                        case WindowManagerGlobal.ADD_STARTING_NOT_NEEDED:
                            // Silently ignore -- we would have just removed it
                            // right away, anyway.
                            return;
                        case WindowManagerGlobal.ADD_MULTIPLE_SINGLETON:
                            throw new WindowManager.BadTokenException(
                                    "Unable to add window " + mWindow +
                                    " -- another window of this type already exists");
                        case WindowManagerGlobal.ADD_PERMISSION_DENIED:
                            throw new WindowManager.BadTokenException(
                                    "Unable to add window " + mWindow +
                                    " -- permission denied for this window type");
                        case WindowManagerGlobal.ADD_INVALID_DISPLAY:
                            throw new WindowManager.InvalidDisplayException(
                                    "Unable to add window " + mWindow +
                                    " -- the specified display can not be found");
                        case WindowManagerGlobal.ADD_INVALID_TYPE:
                            throw new WindowManager.InvalidDisplayException(
                                    "Unable to add window " + mWindow
                                    + " -- the specified window type is not valid");
                    }
                    throw new RuntimeException(
                            "Unable to add window -- unknown error code " + res);
                }

                if (view instanceof RootViewSurfaceTaker) {
                    mInputQueueCallback =
                        ((RootViewSurfaceTaker)view).willYouTakeTheInputQueue();
                }
                if (mInputChannel != null) {
                    if (mInputQueueCallback != null) {
                        mInputQueue = new InputQueue();
                        mInputQueueCallback.onInputQueueCreated(mInputQueue);
                    }
                    mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,
                            Looper.myLooper());
                }
        //给DecorView绑定mParent参数
                view.assignParent(this);
                mAddedTouchMode = (res & WindowManagerGlobal.ADD_FLAG_IN_TOUCH_MODE) != 0;
                mAppVisible = (res & WindowManagerGlobal.ADD_FLAG_APP_VISIBLE) != 0;
        //判断辅助功能是否可用
                if (mAccessibilityManager.isEnabled()) {
                    mAccessibilityInteractionConnectionManager.ensureConnection();
                }

                if (view.getImportantForAccessibility() == View.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
                    view.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
                }

                // Set up the input pipeline.
                CharSequence counterSuffix = attrs.getTitle();
                mSyntheticInputStage = new SyntheticInputStage();
                InputStage viewPostImeStage = new ViewPostImeInputStage(mSyntheticInputStage);
                InputStage nativePostImeStage = new NativePostImeInputStage(viewPostImeStage,
                        "aq:native-post-ime:" + counterSuffix);
                InputStage earlyPostImeStage = new EarlyPostImeInputStage(nativePostImeStage);
                InputStage imeStage = new ImeInputStage(earlyPostImeStage,
                        "aq:ime:" + counterSuffix);
                InputStage viewPreImeStage = new ViewPreImeInputStage(imeStage);
                InputStage nativePreImeStage = new NativePreImeInputStage(viewPreImeStage,
                        "aq:native-pre-ime:" + counterSuffix);

                mFirstInputStage = nativePreImeStage;
                mFirstPostImeInputStage = earlyPostImeStage;
                mPendingInputEventQueueLengthCounterName = "aq:pending:" + counterSuffix;
            }
        }
    }

本篇内容很简单，仅仅是个大绘制流程的初始化工作，接下来会着重分析performTraversals函数，在这个函数中包含了View的onMeasure，onLayout，onDraw的调用
是View重绘过程中很重要的一个函数