requestLayout
當(dāng)前我們對(duì)View位置、大小進(jìn)行操作后會(huì)調(diào)用requestLayout通知窗口。
public void requestLayout() {
if (mMeasureCache != null) mMeasureCache.clear();
if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == null) {
// Only trigger request-during-layout logic if this is the view requesting it,
// not the views in its parent hierarchy
ViewRootImpl viewRoot = getViewRootImpl();
if (viewRoot != null && viewRoot.isInLayout()) { //viewRoot 已經(jīng)處于Layout過(guò)程則添加如等待隊(duì)列
if (!viewRoot.requestLayoutDuringLayout(this)) {
return;
}
}
mAttachInfo.mViewRequestingLayout = this;
}
//設(shè)置標(biāo)志位，需要布局及重繪
mPrivateFlags |= PFLAG_FORCE_LAYOUT;
mPrivateFlags |= PFLAG_INVALIDATED;
if (mParent != null && !mParent.isLayoutRequested()) {
mParent.requestLayout();//責(zé)任鏈模式，上報(bào)requestLayout
}
if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == this) {
mAttachInfo.mViewRequestingLayout = null;
}
}
從代碼中可以看出requestLayout通過(guò)責(zé)任鏈模式上報(bào)到可以處理的實(shí)現(xiàn)中去。這樣我門(mén)大概可以整理出大概執(zhí)行流程
View.requestLayout-
ViewRootImpl.requestLayout會(huì)判斷是否已經(jīng)在進(jìn)行l(wèi)ayout過(guò)程，已在進(jìn)行則忽視 ViewRootImpl.scheduleTraversals-
ViewRootImpl.doTraversalscheduleTraversals()通過(guò)Choreographer在下一幀調(diào)用方式回調(diào) ViewRootImpl.performTraversals
ViewRootImpl.performTraversals的分析就不再累述了，大概就是requestLayout使mLayoutRequested標(biāo)志位置為true，performTraversals將走完整套流程。稍微需要說(shuō)在requestLayout中對(duì)mHandlingLayoutInLayoutRequest標(biāo)志位的判斷原因。
boolean requestLayoutDuringLayout(final View view) {
if (view.mParent == null || view.mAttachInfo == null) {
return true;
}
if (!mLayoutRequesters.contains(view)) {
mLayoutRequesters.add(view);
}
if (!mHandlingLayoutInLayoutRequest) {
return true;
} else {
return false;
}
}
private void performLayout(WindowManager.LayoutParams lp, int desiredWindowWidth,
int desiredWindowHeight) {
....
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "layout");
try {
host.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight());
mInLayout = false;
int numViewsRequestingLayout = mLayoutRequesters.size();
if (numViewsRequestingLayout > 0) {//仍有requestLayout未處理
ArrayList<View> validLayoutRequesters = getValidLayoutRequesters(mLayoutRequesters,
false);
if (validLayoutRequesters != null) {
// 阻止二次傳遞，將新的requestLayout放到下一幀處理
mHandlingLayoutInLayoutRequest = true;
// 刷新 validLayoutRequesters 中的view，view.requestLayout()重新measure及l(fā)ayout
.....
mInLayout = true;
host.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight());
mHandlingLayoutInLayoutRequest = false;
// 仍未處理的requestLayout在下一幀處理
validLayoutRequesters = getValidLayoutRequesters(mLayoutRequesters, true);
if (validLayoutRequesters != null) {
final ArrayList<View> finalRequesters = validLayoutRequesters;
//通過(guò)getRunQueue.post，在下一幀繼續(xù)進(jìn)行requestLayout
.....
}
}
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
mInLayout = false;
}
可以看到如果ViewRootImpl已經(jīng)在處理layout過(guò)程了，這時(shí)View.requestLayout將會(huì)調(diào)用ViewRootImpl.requestLayoutDuringLayout讓ViewRootImpl在performLayout中處理這些View的請(qǐng)求。
而View.requestLayout設(shè)置的標(biāo)志位PFLAG_FORCE_LAYOUT、PFLAG_INVALIDATED將在measure、layout、draw流程中判斷時(shí)候執(zhí)行對(duì)應(yīng)流程。
public final void measure(int widthMeasureSpec, int heightMeasureSpec) {
...
//判斷是否需要強(qiáng)制布局，requestLayout時(shí)mPrivateFlags添加標(biāo)志位 PFLAG_FORCE_LAYOUT
final boolean forceLayout = (mPrivateFlags & PFLAG_FORCE_LAYOUT) == PFLAG_FORCE_LAYOUT;
....
if (forceLayout || needsLayout) {
// first clears the measured dimension flag
mPrivateFlags &= ~PFLAG_MEASURED_DIMENSION_SET;
...
if (cacheIndex < 0 || sIgnoreMeasureCache) {
// measure ourselves, this should set the measured dimension flag back
onMeasure(widthMeasureSpec, heightMeasureSpec);
mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT;
} else {
long value = mMeasureCache.valueAt(cacheIndex);
// Casting a long to int drops the high 32 bits, no mask needed
setMeasuredDimensionRaw((int) (value >> 32), (int) value);
mPrivateFlags3 |= PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT;
}
.....
mPrivateFlags |= PFLAG_LAYOUT_REQUIRED;//請(qǐng)求layout流程
}
....
}
public void layout(int l, int t, int r, int b) {
if ((mPrivateFlags3 & PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT) != 0) {
onMeasure(mOldWidthMeasureSpec, mOldHeightMeasureSpec);
mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT;
}
.....
//setFrame可能導(dǎo)致重繪
boolean changed = isLayoutModeOptical(mParent) ?
setOpticalFrame(l, t, r, b) : setFrame(l, t, r, b);
//measure完成后mPrivateFlags添加標(biāo)志位 PFLAG_LAYOUT_REQUIRED
if (changed || (mPrivateFlags & PFLAG_LAYOUT_REQUIRED) == PFLAG_LAYOUT_REQUIRED) {
onLayout(changed, l, t, r, b);
.....
//layout完成，取消layout標(biāo)志位
mPrivateFlags &= ~PFLAG_LAYOUT_REQUIRED;
.....
}
//measure、layout完成，取消requestLayout的forceLayout標(biāo)志位
mPrivateFlags &= ~PFLAG_FORCE_LAYOUT;
mPrivateFlags3 |= PFLAG3_IS_LAID_OUT;
if ((mPrivateFlags3 & PFLAG3_NOTIFY_AUTOFILL_ENTER_ON_LAYOUT) != 0) {
mPrivateFlags3 &= ~PFLAG3_NOTIFY_AUTOFILL_ENTER_ON_LAYOUT;
notifyEnterOrExitForAutoFillIfNeeded(true);
}
}
protected boolean setFrame(int left, int top, int right, int bottom) {
boolean changed = false;
if (mLeft != left || mRight != right || mTop != top || mBottom != bottom) {
....
// Invalidate our old position
invalidate(sizeChanged);
mLeft = left;
mTop = top;
mRight = right;
mBottom = bottom;
mRenderNode.setLeftTopRightBottom(mLeft, mTop, mRight, mBottom);
....
if ((mViewFlags & VISIBILITY_MASK) == VISIBLE || mGhostView != null) {
// If we are visible, force the DRAWN bit to on so that
// this invalidate will go through (at least to our parent).
// This is because someone may have invalidated this view
// before this call to setFrame came in, thereby clearing
// the DRAWN bit.
mPrivateFlags |= PFLAG_DRAWN;
invalidate(sizeChanged);
// parent display list may need to be recreated based on a change in the bounds
// of any child
invalidateParentCaches();
}
.....
}
return changed;
}
從源碼可以看出，requestLayout必然導(dǎo)致measure、layout過(guò)程(measure完成添加標(biāo)志位PFLAG_LAYOUT_REQUIRED)，是否發(fā)生重繪由setFrame中invalidate(sizeChanged)決定。
postInvalidate、Invalidate
postInvalidate通過(guò)ViewRootImpl.dispatchInvalidateDelayed發(fā)送MSG_INVALIDATE的Message,最后起調(diào)View.invalidate。而invalidate調(diào)用的invalidateInternal()。
因?yàn)閜ostInvalidate是通過(guò)Handler封裝的，所以可以在異步線(xiàn)程中調(diào)用。
invalidateInternal
//--------View.invalidateInternal(0, 0, mRight - mLeft, mBottom - mTop, true, true)
void invalidateInternal(int l, int t, int r, int b, boolean invalidateCache,
boolean fullInvalidate) {
.....
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; //設(shè)置標(biāo)志位PFLAG_DIRTY置1
if (invalidateCache) {//invalidate調(diào)用時(shí)為true
mPrivateFlags |= PFLAG_INVALIDATED; //標(biāo)志位PFLAG_INVALIDATED置1
mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;//標(biāo)志位PFLAG_DRAWING_CACHE_VALID置0
}
// 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); //將繪制區(qū)域傳遞給父布局
p.invalidateChild(this, damage); //轉(zhuǎn)遞給父布局
}
.......
}
}
invalidateInternal方法主要標(biāo)志PFLAG_DIRTY標(biāo)志位后，將重繪區(qū)域傳給parent處理，ViewGroup#invalidateChild處理接下來(lái)邏輯。
//-----------ViewGroup#invalidateChild
public final void invalidateChild(View child, final Rect dirty) {
final AttachInfo attachInfo = mAttachInfo;
......
ViewParent parent = this;
if (attachInfo != null) {
......
// 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;
}
//保存child左上角坐標(biāo)
final int[] location = attachInfo.mInvalidateChildLocation;
location[CHILD_LEFT_INDEX] = child.mLeft;
location[CHILD_TOP_INDEX] = child.mTop;
........
do {
View view = null;
if (parent instanceof View) {
view = (View) parent;
}
.......
// 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) {
//對(duì)當(dāng)前View的標(biāo)記位進(jìn)行設(shè)置
view.mPrivateFlags = (view.mPrivateFlags & ~PFLAG_DIRTY_MASK) | opaqueFlag;
}
}
//責(zé)任鏈模式上報(bào)，最終ViewRootImpl停止
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);
//更新dirty信息區(qū)域信息
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);
}
}
這里主要是先標(biāo)志子view位置，向上回溯父容器，然后求得父容器和子View需要重繪的區(qū)域的并集(dirty)，最后在ViewRootImpl#invalidateChildInParent中停止。
//----------ViewGroup#invalidateChildInParent
public ViewParent invalidateChildInParent(final int[] location, final Rect dirty) {
if ((mPrivateFlags & (PFLAG_DRAWN | PFLAG_DRAWING_CACHE_VALID)) != 0) {
// either DRAWN, or DRAWING_CACHE_VALID
if ((mGroupFlags & (FLAG_OPTIMIZE_INVALIDATE | FLAG_ANIMATION_DONE))
!= FLAG_OPTIMIZE_INVALIDATE) {
//將dirty中的坐標(biāo)轉(zhuǎn)化為父容器中的坐標(biāo)，考慮mScrollX和mScrollY的影響
dirty.offset(location[CHILD_LEFT_INDEX] - mScrollX,
location[CHILD_TOP_INDEX] - mScrollY);
if ((mGroupFlags & FLAG_CLIP_CHILDREN) == 0) {
//求并集，結(jié)果是把子視圖的dirty區(qū)域轉(zhuǎn)化為父容器的dirty區(qū)域
dirty.union(0, 0, mRight - mLeft, mBottom - mTop);
}
final int left = mLeft;
final int top = mTop;
if ((mGroupFlags & FLAG_CLIP_CHILDREN) == FLAG_CLIP_CHILDREN) {
if (!dirty.intersect(0, 0, mRight - left, mBottom - top)) {
dirty.setEmpty();
}
}
//記錄當(dāng)前視圖的mLeft和mTop值，在下一次循環(huán)中會(huì)把當(dāng)前值再向父容器的坐標(biāo)轉(zhuǎn)化
location[CHILD_LEFT_INDEX] = left;
location[CHILD_TOP_INDEX] = top;
} else {
if ((mGroupFlags & FLAG_CLIP_CHILDREN) == FLAG_CLIP_CHILDREN) {
dirty.set(0, 0, mRight - mLeft, mBottom - mTop);
} else {
// in case the dirty rect extends outside the bounds of this container
dirty.union(0, 0, mRight - mLeft, mBottom - mTop);
}
location[CHILD_LEFT_INDEX] = mLeft;
location[CHILD_TOP_INDEX] = mTop;
mPrivateFlags &= ~PFLAG_DRAWN;
}
//設(shè)置PFLAG_DRAWING_CACHE_VALID標(biāo)志位置0
mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
if (mLayerType != LAYER_TYPE_NONE) {//viewGroup需要重繪PFLAG_INVALIDATED標(biāo)志位置1
mPrivateFlags |= PFLAG_INVALIDATED;
}
return mParent;
}
return null;
}
//---------ViewRootImpl#invalidateChildInParent
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);
return null;
}
可以看到ViewGroup#invalidateChildInParent主要的作用為通過(guò)offset方法，把當(dāng)前dirty區(qū)域的坐標(biāo)轉(zhuǎn)化為父容器中的坐標(biāo)，接著調(diào)用union方法，把子dirty區(qū)域與父容器的區(qū)域求并集。即dirty區(qū)域轉(zhuǎn)化為父容器區(qū)域并返回當(dāng)前視圖的父容器，以便進(jìn)行下一次循環(huán)。
最后在ViewRootImpl#invalidateChildInParent所做工作與ViewGroup差不多，調(diào)整dirty區(qū)域并保存在mDirty中，最后調(diào)用了scheduleTraversals方法，觸發(fā)View的工作流程。因?yàn)闆](méi)有添加measure和layout的標(biāo)記位，因此對(duì)應(yīng)流程不會(huì)執(zhí)行，而是直接從draw流程開(kāi)始。
private void draw(boolean fullRedrawNeeded) {
.......
if (!dirty.isEmpty() || mIsAnimating || accessibilityFocusDirty) {
if (mAttachInfo.mThreadedRenderer != null && mAttachInfo.mThreadedRenderer.isEnabled()) {
......
mAttachInfo.mThreadedRenderer.draw(mView, mAttachInfo, this);
} else {
........
if (!drawSoftware(surface, mAttachInfo, xOffset, yOffset, scalingRequired, dirty)) {
return;
}
}
}
.........
}
在draw流程中，因?yàn)?code>!dirty.isEmpty()通過(guò)mAttachInfo.mThreadedRenderer.draw(mView, mAttachInfo, this);
最終會(huì)調(diào)用ThreadedRenderer#updateViewTreeDisplayList(View view),而此時(shí)的view為RootView。
private void updateViewTreeDisplayList(View view) {
view.mPrivateFlags |= View.PFLAG_DRAWN;
view.mRecreateDisplayList = (view.mPrivateFlags & View.PFLAG_INVALIDATED)
== View.PFLAG_INVALIDATED;
view.mPrivateFlags &= ~View.PFLAG_INVALIDATED;
view.updateDisplayListIfDirty();
view.mRecreateDisplayList = false;
}
通過(guò)View#updateDisplayListIfDirty()下發(fā)找到需要重繪的View。
因?yàn)樾枰猧nvalidate的View的標(biāo)志位PFLAG_DRAWING_CACHE_VALID 為0，PFLAG_INVALIDATED為1，而該view的父族ViewGroup的PFLAG_DRAWING_CACHE_VALID為0，PFLAG_INVALIDATED為0。所以只有需要重繪的view的mRecreateDisplayList==true，其父族mRecreateDisplayList==false。
最終下發(fā)找到需要重繪的view/viewgroup
public RenderNode updateDisplayListIfDirty() {
final RenderNode renderNode = mRenderNode;
.....
//與需要invalidate的view同族的ViewGreoup的標(biāo)志PFLAG_DRAWING_CACHE_VALID都為0
if ((mPrivateFlags & PFLAG_DRAWING_CACHE_VALID) == 0
|| !renderNode.isValid()
|| (mRecreateDisplayList)) {
// Don't need to recreate the display list, just need to tell our
// children to restore/recreate theirs
if (renderNode.isValid()
&& !mRecreateDisplayList) {
mPrivateFlags |= PFLAG_DRAWN | PFLAG_DRAWING_CACHE_VALID;
mPrivateFlags &= ~PFLAG_DIRTY_MASK;
dispatchGetDisplayList();//下發(fā)需要重繪的view
return renderNode; // no work needed
}
// If we got here, we're recreating it. Mark it as such to ensure that
// we copy in child display lists into ours in drawChild()
mRecreateDisplayList = true;
int width = mRight - mLeft;
int height = mBottom - mTop;
int layerType = getLayerType();
final DisplayListCanvas canvas = renderNode.start(width, height);
canvas.setHighContrastText(mAttachInfo.mHighContrastText);
try {
if (layerType == LAYER_TYPE_SOFTWARE) {
buildDrawingCache(true);
Bitmap cache = getDrawingCache(true);
if (cache != null) {
canvas.drawBitmap(cache, 0, 0, mLayerPaint);
}
} else {
computeScroll();
canvas.translate(-mScrollX, -mScrollY);
mPrivateFlags |= PFLAG_DRAWN | PFLAG_DRAWING_CACHE_VALID;
mPrivateFlags &= ~PFLAG_DIRTY_MASK;
// Fast path for layouts with no backgrounds
if ((mPrivateFlags & PFLAG_SKIP_DRAW) == PFLAG_SKIP_DRAW) {
dispatchDraw(canvas); //-------ViewGroup一般為PFLAG_SKIP_DRAW，直接下發(fā)
drawAutofilledHighlight(canvas);
if (mOverlay != null && !mOverlay.isEmpty()) {
mOverlay.getOverlayView().draw(canvas);
}
if (debugDraw()) {
debugDrawFocus(canvas);
}
} else {
draw(canvas); //-------view起調(diào)draw流程
}
}
} finally {
renderNode.end(canvas);
setDisplayListProperties(renderNode);
}
} else {
mPrivateFlags |= PFLAG_DRAWN | PFLAG_DRAWING_CACHE_VALID;
mPrivateFlags &= ~PFLAG_DIRTY_MASK;
}
return renderNode;
}
protected void dispatchGetDisplayList() {
final int count = mChildrenCount;
final View[] children = mChildren;
for (int i = 0; i < count; i++) {
final View child = children[i];
if (((child.mViewFlags & VISIBILITY_MASK) == VISIBLE || child.getAnimation() != null)) {
recreateChildDisplayList(child);//重置標(biāo)志位并下發(fā)
}
}
if (mOverlay != null) {
View overlayView = mOverlay.getOverlayView();
recreateChildDisplayList(overlayView);
}
if (mDisappearingChildren != null) {
final ArrayList<View> disappearingChildren = mDisappearingChildren;
final int disappearingCount = disappearingChildren.size();
for (int i = 0; i < disappearingCount; ++i) {
final View child = disappearingChildren.get(i);
recreateChildDisplayList(child);
}
}
}
private void recreateChildDisplayList(View child) {
child.mRecreateDisplayList = (child.mPrivateFlags & PFLAG_INVALIDATED) != 0;//需要重繪的view為true
child.mPrivateFlags &= ~PFLAG_INVALIDATED;
child.updateDisplayListIfDirty();
child.mRecreateDisplayList = false;
}
