WMS you don't know

We finished the front Handler and Binder Learning from , It can be said that the foundation has been laid . If there are students who don't understand , Look at mine Framework Other articles in the column , The default here is that everyone has this foundation .

Let's think about a question first ：invalidate Will trigger other View Redrawn ？

The answer is obviously yes , But why ？ Many people may not be able to answer . Let's look at the system source code ！

Open my sublime Text, Search for invalidate(), A lot of things come out , Then right-click ,Goto definition.

（ remarks ：sublime Text Global search Find->Find Files）

We'll eventually find View The path of ：frameworks/base/core/java/android/view/View.java

Let's look at it first invalidate What do you mean by , At first, everyone may guess that this should mean refresh , But it actually means abandonment .

step1:

public void invalidate() {
        invalidate(true);
}

step2:

invalidateCache Set to true Indicates that the cache is completely discarded

public void invalidate(boolean invalidateCache) {
        invalidateInternal(0, 0, mRight - mLeft, 
mBottom - mTop, invalidateCache, true);
}

step3:

void invalidateInternal(int l, int t, int r, int b, boolean invalidateCache,
            boolean fullInvalidate) {
        if (mGhostView != null) {
            mGhostView.invalidate(true);
            return;
        }

        if (skipInvalidate()) {
            return;
        }

        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)) {
            if (fullInvalidate) {
                mLastIsOpaque = isOpaque();
                mPrivateFlags &= ~PFLAG_DRAWN;
            }

            mPrivateFlags |= PFLAG_DIRTY;

            if (invalidateCache) {
                mPrivateFlags |= PFLAG_INVALIDATED;
                mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
            }

            // 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);
            }

            // Damage the entire projection receiver, if necessary.
            if (mBackground != null && mBackground.isProjected()) {
                final View receiver = getProjectionReceiver();
                if (receiver != null) {
                    receiver.damageInParent();
                }
            }
        }
    }

Core code ：

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

This means that this area is handed over to the parent layout .

step4:

@Deprecated
    @Override
    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) {
            // If the child is drawing an animation, we want to copy this flag onto
            // ourselves and the parent to make sure the invalidate request goes
            // through
            final boolean drawAnimation = (child.mPrivateFlags & PFLAG_DRAW_ANIMATION) != 0;

            // Check whether the child that requests the invalidate is fully opaque
            // Views being animated or transformed are not considered opaque because we may
            // be invalidating their old position and need the parent to paint behind them.
            Matrix childMatrix = child.getMatrix();
            final boolean isOpaque = child.isOpaque() && !drawAnimation &&
                    child.getAnimation() == null && childMatrix.isIdentity();
            // Mark the child as dirty, using the appropriate flag
            // Make sure we do not set both flags at the same time
            int opaqueFlag = isOpaque ? PFLAG_DIRTY_OPAQUE : PFLAG_DIRTY;

            if (child.mLayerType != LAYER_TYPE_NONE) {
                mPrivateFlags |= PFLAG_INVALIDATED;
                mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
            }

            final int[] location = attachInfo.mInvalidateChildLocation;
            location[CHILD_LEFT_INDEX] = child.mLeft;
            location[CHILD_TOP_INDEX] = child.mTop;
            if (!childMatrix.isIdentity() ||
                    (mGroupFlags & ViewGroup.FLAG_SUPPORT_STATIC_TRANSFORMATIONS) != 0) {
                RectF boundingRect = attachInfo.mTmpTransformRect;
                boundingRect.set(dirty);
                Matrix transformMatrix;
                if ((mGroupFlags & ViewGroup.FLAG_SUPPORT_STATIC_TRANSFORMATIONS) != 0) {
                    Transformation t = attachInfo.mTmpTransformation;
                    boolean transformed = getChildStaticTransformation(child, t);
                    if (transformed) {
                        transformMatrix = attachInfo.mTmpMatrix;
                        transformMatrix.set(t.getMatrix());
                        if (!childMatrix.isIdentity()) {
                            transformMatrix.preConcat(childMatrix);
                        }
                    } else {
                        transformMatrix = childMatrix;
                    }
                } else {
                    transformMatrix = childMatrix;
                }
                transformMatrix.mapRect(boundingRect);
                dirty.set((int) Math.floor(boundingRect.left),
                        (int) Math.floor(boundingRect.top),
                        (int) Math.ceil(boundingRect.right),
                        (int) Math.ceil(boundingRect.bottom));
            }

            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);//1
                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);
        }

It's a cycle , If there is a parent layout , Will always call comments 1 This method . It will eventually arrive at decorView.

step5:

This method is the top ViewRootImpl Inside

 @Override
    public ViewParent invalidateChildInParent(int[] location, Rect dirty) {
        checkThread();
        if (DEBUG_DRAW) Log.v(mTag, "Invalidate child: " + dirty);

        if (dirty == null) {
            invalidate();
            return null;
        } else if (dirty.isEmpty() && !mIsAnimating) {
            return null;
        }

        if (mCurScrollY != 0 || mTranslator != null) {
            mTempRect.set(dirty);
            dirty = mTempRect;
            if (mCurScrollY != 0) {
                dirty.offset(0, -mCurScrollY);
            }
            if (mTranslator != null) {
                mTranslator.translateRectInAppWindowToScreen(dirty);
            }
            if (mAttachInfo.mScalingRequired) {
                dirty.inset(-1, -1);
            }
        }

        invalidateRectOnScreen(dirty);//1

        return null;
    }

step6:

private void invalidateRectOnScreen(Rect dirty) {
        final Rect localDirty = mDirty;
        if (!localDirty.isEmpty() && !localDirty.contains(dirty)) {
            mAttachInfo.mSetIgnoreDirtyState = true;
            mAttachInfo.mIgnoreDirtyState = true;
        }

        // Add the new dirty rect to the current one
        localDirty.union(dirty.left, dirty.top, dirty.right, dirty.bottom);
        // Intersect with the bounds of the window to skip
        // updates that lie outside of the visible region
        final float appScale = mAttachInfo.mApplicationScale;
        final boolean intersected = localDirty.intersect(0, 0,
                (int) (mWidth * appScale + 0.5f), (int) (mHeight * appScale + 0.5f));
        if (!intersected) {
            localDirty.setEmpty();
        }
        if (!mWillDrawSoon && (intersected || mIsAnimating)) {
            scheduleTraversals();//1
        }
    }

step7:

void scheduleTraversals() {
        if (!mTraversalScheduled) {
            mTraversalScheduled = true;
            mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
            mChoreographer.postCallback(
                    Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable//1, null);
            if (!mUnbufferedInputDispatch) {
                scheduleConsumeBatchedInput();
            }
            notifyRendererOfFramePending();
            pokeDrawLockIfNeeded();
        }
    }

Pay attention to the notes 1 It's about

step8:

final class TraversalRunnable implements Runnable {
        @Override
        public void run() {
            doTraversal();//1
        }
    }
    final TraversalRunnable mTraversalRunnable = new TraversalRunnable();

step9:

void doTraversal() {
        if (mTraversalScheduled) {
            mTraversalScheduled = false;
            mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);

            if (mProfile) {
                Debug.startMethodTracing("ViewAncestor");
            }

            performTraversals();//1

            if (mProfile) {
                Debug.stopMethodTracing();
                mProfile = false;
            }
        }
    }

step10:

private void performTraversals() {
       ···
                                    performMeasure(childWidthMeasureSpec,childHeightMeasureSpec);
···
                   performLayout(lp, mWidth, mHeight);
···
performDraw();
        
    }

This method code is very long , Is it deja vu ！

To sum up ： One of them View call invalidate Method , Call back up level by level until ViewRootimpl, Then go through the drawing process again .

I believe that the appetizer in front of me has been right View Of invalidate With some understanding , Then let's ask another question ：Activity How such window And view To carry out division of labor and cooperation ？

We know activity It's through window To manage view Of ,activity It is to manage the life cycle ,view Responsible for specific display .

To be continued ！