一、postInvalidate和invalidate
其实postInvalidate最终也是调用的invalidate来实现。
public void postInvalidate() {
postInvalidateDelayed(0);
}
public void postInvalidateDelayed(long delayMilliseconds) {
// We try only with the AttachInfo because there's no point in invalidating
// if we are not attached to our window
final AttachInfo attachInfo = mAttachInfo;
if (attachInfo != null) {
attachInfo.mViewRootImpl.dispatchInvalidateDelayed(this, delayMilliseconds);
}
}
AttachInfo.mViewRootImpl其实就是ViewRootImpl对象
public void dispatchInvalidateDelayed(View view, long delayMilliseconds) {
Message msg = mHandler.obtainMessage(MSG_INVALIDATE, view);
mHandler.sendMessageDelayed(msg, delayMilliseconds);
}
这里的mHandler对象，其实是ViewRootImpl内部类ViewRootHandler对象，
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_INVALIDATE:
((View) msg.obj).invalidate();
break;
....
}
而这里的msg.obj其实就是View对象
二、invalidate源码分析
image.png
从网上拿来用的一张图，自己就不画了。
View.invalidate
public void invalidate() {
invalidate(true);
}
@UnsupportedAppUsage
public void invalidate(boolean invalidateCache) {
invalidateInternal(0, 0, mRight - mLeft, mBottom - mTop, invalidateCache, true);
}
View.invalidateInternal
void invalidateInternal(int l, int t, int r, int b, boolean invalidateCache,
boolean fullInvalidate) {
if (mGhostView != null) {
mGhostView.invalidate(true);
return;
}
if (skipInvalidate()) {
return;
}
// 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)) {
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);
// 调用了ViewParent的invalidateChild方法，而ViewGroup实现了ViewParent接口
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();
}
}
}
}
根据查找ViewParent接口实现我们可以知道，ViewGroup是ViewParent的实现类，所以这里是调用了ViewGroup.invalidateChild()
ViewGroup.invalidateChild()
@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) {
...
do {
...
parent = parent.invalidateChildInParent(location, dirty);
...
} while (parent != null);
}
}
因为parent是在invalidateChild中赋值的，其实就是ViewGroup本身，所以是调用的ViewGroup的invalidateChildInParent方法
ViewGroup.invalidateChildInParent()
@Deprecated
@Override
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) {
dirty.offset(location[CHILD_LEFT_INDEX] - mScrollX,
location[CHILD_TOP_INDEX] - mScrollY);
if ((mGroupFlags & FLAG_CLIP_CHILDREN) == 0) {
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();
}
}
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;
}
mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
if (mLayerType != LAYER_TYPE_NONE) {
mPrivateFlags |= PFLAG_INVALIDATED;
}
return mParent;
}
return null;
}
但是因为ViewGroup.invalidateChild方法中执行的是一个do-while循环，不断的循环返回View的mParent，而ViewGroup最终的mParent其实是DecorView，而DecorView.mParent其实就是ViewRootImpl，所以这里最终会调用到ViewRootImpl.invalidateChildInParent
ViewRootImpl.invalidateChildInParent()
@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);
return null;
}
ViewRootImpl.invalidateRectOnScreen()
private void invalidateRectOnScreen(Rect dirty) {
final Rect localDirty = mDirty;
// 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();
}
}
ViewGroup.scheduleTraversals()
@UnsupportedAppUsage
void scheduleTraversals() {
if (!mTraversalScheduled) {
mTraversalScheduled = true;
mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
mChoreographer.postCallback(
Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
if (!mUnbufferedInputDispatch) {
scheduleConsumeBatchedInput();
}
notifyRendererOfFramePending();
pokeDrawLockIfNeeded();
}
}
scheduleTraversals()方法内部通过调用Choreographer.postCallback方法，其内部就是通过Handler，然后在doFrame中调用doCallbacks，通过遍历CallbackRecord这个链表，执行保持在CallbackRecord中的action（即Runnable）的run方法。就是TraversalRunnable对象mTraversalRunnable
void doCallbacks(int callbackType, long frameTimeNanos) {
CallbackRecord callbacks;
synchronized (mLock) {
// We use "now" to determine when callbacks become due because it's possible
// for earlier processing phases in a frame to post callbacks that should run
// in a following phase, such as an input event that causes an animation to start.
// 确认回调的时机
final long now = System.nanoTime();
callbacks = mCallbackQueues[callbackType].extractDueCallbacksLocked(
now / TimeUtils.NANOS_PER_MS);
if (callbacks == null) {
return;
}
...
try {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, CALLBACK_TRACE_TITLES[callbackType]);
for (CallbackRecord c = callbacks; c != null; c = c.next) {
if (DEBUG_FRAMES) {
Log.d(TAG, "RunCallback: type=" + callbackType
+ ", action=" + c.action + ", token=" + c.token
+ ", latencyMillis=" + (SystemClock.uptimeMillis() - c.dueTime));
}
c.run(frameTimeNanos);
}
} finally {
synchronized (mLock) {
mCallbacksRunning = false;
do {
final CallbackRecord next = callbacks.next;
recycleCallbackLocked(callbacks);
callbacks = next;
} while (callbacks != null);
}
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
}
CallbackRecord是一个链表结构，在这里最终就会判断是否是帧callback token，如果不是，则调用action.run()，这里的action其实就是TraversalRunnable
private static final class CallbackRecord {
public CallbackRecord next;
public long dueTime;
public Object action; // Runnable or FrameCallback
public Object token;
@UnsupportedAppUsage
public void run(long frameTimeNanos) {
if (token == FRAME_CALLBACK_TOKEN) {
((FrameCallback)action).doFrame(frameTimeNanos);
} else {
((Runnable)action).run();
}
}
}
执行到TraversalRunnable的run()
ViewRootImpl.TraversalRunnable内部类
final class TraversalRunnable implements Runnable {
@Override
public void run() {
doTraversal();
}
}
调用了ViewRootImpl.doTraversal()
ViewRootImpl.doTraversal()
void doTraversal() {
if (mTraversalScheduled) {
mTraversalScheduled = false;
mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);
if (mProfile) {
Debug.startMethodTracing("ViewAncestor");
}
performTraversals();
if (mProfile) {
Debug.stopMethodTracing();
mProfile = false;
}
}
}
在这里会调用performTraversals()
ViewRootImpl.performTraversals()
performTraversals方法比较长，所以看一部分
private void performTraversals() {
...
boolean cancelDraw = mAttachInfo.mTreeObserver.dispatchOnPreDraw() || !isViewVisible;
if (!cancelDraw) {
if (mPendingTransitions != null && mPendingTransitions.size() > 0) {
for (int i = 0; i < mPendingTransitions.size(); ++i) {
mPendingTransitions.get(i).startChangingAnimations();
}
mPendingTransitions.clear();
}
performDraw();
} else {
if (isViewVisible) {
// Try again
scheduleTraversals();
} else if (mPendingTransitions != null && mPendingTransitions.size() > 0) {
for (int i = 0; i < mPendingTransitions.size(); ++i) {
mPendingTransitions.get(i).endChangingAnimations();
}
mPendingTransitions.clear();
}
}
}
这个方法主要是做了三个操作，即调用performMeasure、performLayout、performDraw，而invalidate流程是否会触发performMeasure和performLayout姑且不论，因为这里需要经过繁琐的标志位的判断，但是会执行performDraw。而performMeasure和performLayout分别是measure过程和layout过程，是由View.requestLayout()或者WindowManagerImpl.addView调用WindowManagerGlobal.addView这个两种情况最终调用了ViewRootImpl.requestLayout来触发调用performMeasure和performLayout。
private void performDraw() {
...
try {
boolean canUseAsync = draw(fullRedrawNeeded);
if (usingAsyncReport && !canUseAsync) {
mAttachInfo.mThreadedRenderer.setFrameCompleteCallback(null);
usingAsyncReport = false;
}
} finally {
mIsDrawing = false;
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
...
}
在这里调用了ViewRootImpl.draw()
ViewRootImpl.draw()
private boolean draw(boolean fullRedrawNeeded) {
Surface surface = mSurface;
if (!surface.isValid()) {
return false;
}
if (DEBUG_FPS) {
trackFPS();
}
if (!sFirstDrawComplete) {
synchronized (sFirstDrawHandlers) {
sFirstDrawComplete = true;
final int count = sFirstDrawHandlers.size();
for (int i = 0; i< count; i++) {
mHandler.post(sFirstDrawHandlers.get(i));
}
}
}
scrollToRectOrFocus(null, false);
if (mAttachInfo.mViewScrollChanged) {
mAttachInfo.mViewScrollChanged = false;
mAttachInfo.mTreeObserver.dispatchOnScrollChanged();
}
boolean animating = mScroller != null && mScroller.computeScrollOffset();
final int curScrollY;
if (animating) {
curScrollY = mScroller.getCurrY();
} else {
curScrollY = mScrollY;
}
if (mCurScrollY != curScrollY) {
mCurScrollY = curScrollY;
fullRedrawNeeded = true;
if (mView instanceof RootViewSurfaceTaker) {
((RootViewSurfaceTaker) mView).onRootViewScrollYChanged(mCurScrollY);
}
}
final float appScale = mAttachInfo.mApplicationScale;
final boolean scalingRequired = mAttachInfo.mScalingRequired;
final Rect dirty = mDirty;
if (mSurfaceHolder != null) {
// The app owns the surface, we won't draw.
dirty.setEmpty();
if (animating && mScroller != null) {
mScroller.abortAnimation();
}
return false;
}
if (fullRedrawNeeded) {
dirty.set(0, 0, (int) (mWidth * appScale + 0.5f), (int) (mHeight * appScale + 0.5f));
}
if (DEBUG_ORIENTATION || DEBUG_DRAW) {
Log.v(mTag, "Draw " + mView + "/"
+ mWindowAttributes.getTitle()
+ ": dirty={" + dirty.left + "," + dirty.top
+ "," + dirty.right + "," + dirty.bottom + "} surface="
+ surface + " surface.isValid()=" + surface.isValid() + ", appScale:" +
appScale + ", width=" + mWidth + ", height=" + mHeight);
}
mAttachInfo.mTreeObserver.dispatchOnDraw();
int xOffset = -mCanvasOffsetX;
int yOffset = -mCanvasOffsetY + curScrollY;
final WindowManager.LayoutParams params = mWindowAttributes;
final Rect surfaceInsets = params != null ? params.surfaceInsets : null;
if (surfaceInsets != null) {
xOffset -= surfaceInsets.left;
yOffset -= surfaceInsets.top;
// Offset dirty rect for surface insets.
dirty.offset(surfaceInsets.left, surfaceInsets.right);
}
boolean accessibilityFocusDirty = false;
final Drawable drawable = mAttachInfo.mAccessibilityFocusDrawable;
if (drawable != null) {
final Rect bounds = mAttachInfo.mTmpInvalRect;
final boolean hasFocus = getAccessibilityFocusedRect(bounds);
if (!hasFocus) {
bounds.setEmpty();
}
if (!bounds.equals(drawable.getBounds())) {
accessibilityFocusDirty = true;
}
}
mAttachInfo.mDrawingTime =
mChoreographer.getFrameTimeNanos() / TimeUtils.NANOS_PER_MS;
boolean useAsyncReport = false;
if (!dirty.isEmpty() || mIsAnimating || accessibilityFocusDirty) {
if (mAttachInfo.mThreadedRenderer != null && mAttachInfo.mThreadedRenderer.isEnabled()) {
...
} else {
...
if (!drawSoftware(surface, mAttachInfo, xOffset, yOffset,
scalingRequired, dirty, surfaceInsets)) {
return false;
}
}
}
if (animating) {
mFullRedrawNeeded = true;
scheduleTraversals();
}
return useAsyncReport;
}
ViewRootImpl.drawSoftWare()
private boolean drawSoftware(Surface surface, AttachInfo attachInfo, int xoff, int yoff,
boolean scalingRequired, Rect dirty, Rect surfaceInsets) {
...
try {
...
mView.draw(canvas);
drawAccessibilityFocusedDrawableIfNeeded(canvas);
} finally {
...
}
return true;
}
从这里可以看出，最终是调用了View.draw()方法。
其实invalidate()方法的使用，就是重新触发一次draw流程，进行绘制。通过View.invalidate()方法在ViewGroup的invalidateChild()方法中执行一个do-while循环，最终调用了ViewRootImpl.invalidateChildInParent()，而在ViewRootImpl.invalidateChildInParent()方法中最终触发调用了ViewRootImpl.scheduleTraversals()，又一次执行了与measure过程和layout过程一致的流程，因为scheduleTraversals()方法会通过一系列的调用最终调用TraversalRunnable.run()方法，在TraversalRunnable.run()方法中会调用performTraversals()，这个方法其实就是做了三件事：measure、layout和draw
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