• 你所不知道的WMS

    前面我们完成了Handler和Binder的学习，可以说基础已经打好了。如果有不理解的同学，可以看看我的Framework专栏的其他文章，这里默认大家都是有这方面基础的了。

    我们先来思考一个问题：invalidate会触发其他View的重绘吗？

    答案很明显是会，但是为什么会呢？可能很多人就回答不上来了。还是来看系统源码吧！

    打开我的sublime Text，搜索invalidate()，出来很多东西，然后右击，Goto definition。

    （备注：sublime Text全局搜索 Find->Find Files）

    我们最终会找到View的路径：frameworks/base/core/java/android/view/View.java

    首先我们来看一下invalidate的英文是什么意思，一开始可能大家都会去猜这应该是刷新的意思，但是实际却是废弃的意思。

    step1:

    1. public void invalidate() {
    2.         invalidate(true);
    3. }

    step2:

    invalidateCache设置为true表示完全废弃缓存

    1. public void invalidate(boolean invalidateCache) {
    2.         invalidateInternal(0, 0, mRight - mLeft, 
    3. mBottom - mTop, invalidateCache, true);
    4. }

    step3:

    1. void invalidateInternal(int l, int t, int r, int b, boolean invalidateCache,
    2.             boolean fullInvalidate) {
    3.         if (mGhostView != null) {
    4.             mGhostView.invalidate(true);
    5.             return;
    6.         }
    7.  
    8.         if (skipInvalidate()) {
    9.             return;
    10.         }
    11.  
    12.         if ((mPrivateFlags & (PFLAG_DRAWN | PFLAG_HAS_BOUNDS)) == (PFLAG_DRAWN | PFLAG_HAS_BOUNDS)
    13.                 || (invalidateCache && (mPrivateFlags & PFLAG_DRAWING_CACHE_VALID) == PFLAG_DRAWING_CACHE_VALID)
    14.                 || (mPrivateFlags & PFLAG_INVALIDATED) != PFLAG_INVALIDATED
    15.                 || (fullInvalidate && isOpaque() != mLastIsOpaque)) {
    16.             if (fullInvalidate) {
    17.                 mLastIsOpaque = isOpaque();
    18.                 mPrivateFlags &= ~PFLAG_DRAWN;
    19.             }
    20.  
    21.             mPrivateFlags |= PFLAG_DIRTY;
    22.  
    23.             if (invalidateCache) {
    24.                 mPrivateFlags |= PFLAG_INVALIDATED;
    25.                 mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
    26.             }
    27.  
    28.             // Propagate the damage rectangle to the parent view.
    29.             final AttachInfo ai = mAttachInfo;
    30.             final ViewParent p = mParent;
    31.             if (p != null && ai != null && l < r && t < b) {
    32.                 final Rect damage = ai.mTmpInvalRect;
    33.                 damage.set(l, t, r, b);
    34.                 p.invalidateChild(this, damage);
    35.             }
    36.  
    37.             // Damage the entire projection receiver, if necessary.
    38.             if (mBackground != null && mBackground.isProjected()) {
    39.                 final View receiver = getProjectionReceiver();
    40.                 if (receiver != null) {
    41.                     receiver.damageInParent();
    42.                 }
    43.             }
    44.         }
    45.     }

    核心代码：

    1. damage.set(l, t, r, b);
    2. p.invalidateChild(this, damage);

    意思就是把这块区域交给父布局去处理。

    step4:

    1. @Deprecated
    2.     @Override
    3.     public final void invalidateChild(View child, final Rect dirty) {
    4.         final AttachInfo attachInfo = mAttachInfo;
    5.         if (attachInfo != null && attachInfo.mHardwareAccelerated) {
    6.             // HW accelerated fast path
    7.             onDescendantInvalidated(child, child);
    8.             return;
    9.         }
    10.  
    11.         ViewParent parent = this;
    12.         if (attachInfo != null) {
    13.             // If the child is drawing an animation, we want to copy this flag onto
    14.             // ourselves and the parent to make sure the invalidate request goes
    15.             // through
    16.             final boolean drawAnimation = (child.mPrivateFlags & PFLAG_DRAW_ANIMATION) != 0;
    17.  
    18.             // Check whether the child that requests the invalidate is fully opaque
    19.             // Views being animated or transformed are not considered opaque because we may
    20.             // be invalidating their old position and need the parent to paint behind them.
    21.             Matrix childMatrix = child.getMatrix();
    22.             final boolean isOpaque = child.isOpaque() && !drawAnimation &&
    23.                     child.getAnimation() == null && childMatrix.isIdentity();
    24.             // Mark the child as dirty, using the appropriate flag
    25.             // Make sure we do not set both flags at the same time
    26.             int opaqueFlag = isOpaque ? PFLAG_DIRTY_OPAQUE : PFLAG_DIRTY;
    27.  
    28.             if (child.mLayerType != LAYER_TYPE_NONE) {
    29.                 mPrivateFlags |= PFLAG_INVALIDATED;
    30.                 mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
    31.             }
    32.  
    33.             final int[] location = attachInfo.mInvalidateChildLocation;
    34.             location[CHILD_LEFT_INDEX] = child.mLeft;
    35.             location[CHILD_TOP_INDEX] = child.mTop;
    36.             if (!childMatrix.isIdentity() ||
    37.                     (mGroupFlags & ViewGroup.FLAG_SUPPORT_STATIC_TRANSFORMATIONS) != 0) {
    38.                 RectF boundingRect = attachInfo.mTmpTransformRect;
    39.                 boundingRect.set(dirty);
    40.                 Matrix transformMatrix;
    41.                 if ((mGroupFlags & ViewGroup.FLAG_SUPPORT_STATIC_TRANSFORMATIONS) != 0) {
    42.                     Transformation t = attachInfo.mTmpTransformation;
    43.                     boolean transformed = getChildStaticTransformation(child, t);
    44.                     if (transformed) {
    45.                         transformMatrix = attachInfo.mTmpMatrix;
    46.                         transformMatrix.set(t.getMatrix());
    47.                         if (!childMatrix.isIdentity()) {
    48.                             transformMatrix.preConcat(childMatrix);
    49.                         }
    50.                     } else {
    51.                         transformMatrix = childMatrix;
    52.                     }
    53.                 } else {
    54.                     transformMatrix = childMatrix;
    55.                 }
    56.                 transformMatrix.mapRect(boundingRect);
    57.                 dirty.set((int) Math.floor(boundingRect.left),
    58.                         (int) Math.floor(boundingRect.top),
    59.                         (int) Math.ceil(boundingRect.right),
    60.                         (int) Math.ceil(boundingRect.bottom));
    61.             }
    62.  
    63.             do {
    64.                 View view = null;
    65.                 if (parent instanceof View) {
    66.                     view = (View) parent;
    67.                 }
    68.  
    69.                 if (drawAnimation) {
    70.                     if (view != null) {
    71.                         view.mPrivateFlags |= PFLAG_DRAW_ANIMATION;
    72.                     } else if (parent instanceof ViewRootImpl) {
    73.                         ((ViewRootImpl) parent).mIsAnimating = true;
    74.                     }
    75.                 }
    76.  
    77.                 // If the parent is dirty opaque or not dirty, mark it dirty with the opaque
    78.                 // flag coming from the child that initiated the invalidate
    79.                 if (view != null) {
    80.                     if ((view.mViewFlags & FADING_EDGE_MASK) != 0 &&
    81.                             view.getSolidColor() == 0) {
    82.                         opaqueFlag = PFLAG_DIRTY;
    83.                     }
    84.                     if ((view.mPrivateFlags & PFLAG_DIRTY_MASK) != PFLAG_DIRTY) {
    85.                         view.mPrivateFlags = (view.mPrivateFlags & ~PFLAG_DIRTY_MASK) | opaqueFlag;
    86.                     }
    87.                 }
    88.  
    89.                 parent = parent.invalidateChildInParent(location, dirty);//1
    90.                 if (view != null) {
    91.                     // Account for transform on current parent
    92.                     Matrix m = view.getMatrix();
    93.                     if (!m.isIdentity()) {
    94.                         RectF boundingRect = attachInfo.mTmpTransformRect;
    95.                         boundingRect.set(dirty);
    96.                         m.mapRect(boundingRect);
    97.                         dirty.set((int) Math.floor(boundingRect.left),
    98.                                 (int) Math.floor(boundingRect.top),
    99.                                 (int) Math.ceil(boundingRect.right),
    100.                                 (int) Math.ceil(boundingRect.bottom));
    101.                     }
    102.                 }
    103.             } while (parent != null);
    104.         }

    这里面是一个循环，就是如果还有父布局，就一直会调用注释1这个方法。最终会走到decorView。

    step5:

    这个方法是最上层ViewRootImpl里面的

    1.  @Override
    2.     public ViewParent invalidateChildInParent(int[] location, Rect dirty) {
    3.         checkThread();
    4.         if (DEBUG_DRAW) Log.v(mTag, "Invalidate child: " + dirty);
    5.  
    6.         if (dirty == null) {
    7.             invalidate();
    8.             return null;
    9.         } else if (dirty.isEmpty() && !mIsAnimating) {
    10.             return null;
    11.         }
    12.  
    13.         if (mCurScrollY != 0 || mTranslator != null) {
    14.             mTempRect.set(dirty);
    15.             dirty = mTempRect;
    16.             if (mCurScrollY != 0) {
    17.                 dirty.offset(0, -mCurScrollY);
    18.             }
    19.             if (mTranslator != null) {
    20.                 mTranslator.translateRectInAppWindowToScreen(dirty);
    21.             }
    22.             if (mAttachInfo.mScalingRequired) {
    23.                 dirty.inset(-1, -1);
    24.             }
    25.         }
    26.  
    27.         invalidateRectOnScreen(dirty);//1
    28.  
    29.         return null;
    30.     }

    step6:

    1. private void invalidateRectOnScreen(Rect dirty) {
    2.         final Rect localDirty = mDirty;
    3.         if (!localDirty.isEmpty() && !localDirty.contains(dirty)) {
    4.             mAttachInfo.mSetIgnoreDirtyState = true;
    5.             mAttachInfo.mIgnoreDirtyState = true;
    6.         }
    7.  
    8.         // Add the new dirty rect to the current one
    9.         localDirty.union(dirty.left, dirty.top, dirty.right, dirty.bottom);
    10.         // Intersect with the bounds of the window to skip
    11.         // updates that lie outside of the visible region
    12.         final float appScale = mAttachInfo.mApplicationScale;
    13.         final boolean intersected = localDirty.intersect(0, 0,
    14.                 (int) (mWidth * appScale + 0.5f), (int) (mHeight * appScale + 0.5f));
    15.         if (!intersected) {
    16.             localDirty.setEmpty();
    17.         }
    18.         if (!mWillDrawSoon && (intersected || mIsAnimating)) {
    19.             scheduleTraversals();//1
    20.         }
    21.     }

    step7:

    1. void scheduleTraversals() {
    2.         if (!mTraversalScheduled) {
    3.             mTraversalScheduled = true;
    4.             mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
    5.             mChoreographer.postCallback(
    6.                     Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable//1, null);
    7.             if (!mUnbufferedInputDispatch) {
    8.                 scheduleConsumeBatchedInput();
    9.             }
    10.             notifyRendererOfFramePending();
    11.             pokeDrawLockIfNeeded();
    12.         }
    13.     }

    注意注释1处

    step8:

    1. final class TraversalRunnable implements Runnable {
    2.         @Override
    3.         public void run() {
    4.             doTraversal();//1
    5.         }
    6.     }
    7.     final TraversalRunnable mTraversalRunnable = new TraversalRunnable();

    step9:

    1. void doTraversal() {
    2.         if (mTraversalScheduled) {
    3.             mTraversalScheduled = false;
    4.             mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);
    5.  
    6.             if (mProfile) {
    7.                 Debug.startMethodTracing("ViewAncestor");
    8.             }
    9.  
    10.             performTraversals();//1
    11.  
    12.             if (mProfile) {
    13.                 Debug.stopMethodTracing();
    14.                 mProfile = false;
    15.             }
    16.         }
    17.     }

    step10:

    1. private void performTraversals() {
    2.        ···
    3.                                     performMeasure(childWidthMeasureSpec,childHeightMeasureSpec);
    4. ···
    5.                    performLayout(lp, mWidth, mHeight);
    6. ···
    7. performDraw();
    8.         
    9.     }

    这个方法代码非常长，是不是似曾相识了！

    总结一下：某一个View调用invalidate方法，回逐级向上调用直到ViewRootimpl，然后重新走绘制流程。

    相信通过前面的开胃菜已经对View的invalidate有了一定的理解，那么我们再抛出一个问题：Activity如何如window与view进行分工合作的？

    我们知道activity是通过window来管理view的，activity是管理生命周期的，view负责具体显示。

    未完待续！

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  • 原文地址：https://blog.csdn.net/qq_36428821/article/details/126003744