View.post特殊的地方

view.post

public boolean post(Runnable action) {
        final AttachInfo attachInfo = mAttachInfo;
        if (attachInfo != null) {
            return attachInfo.mHandler.post(action);
        }

        // Postpone the runnable until we know on which thread it needs to run.
        // Assume that the runnable will be successfully placed after attach.
        getRunQueue().post(action);
        return true;
    }

getHandler().post

public Handler getHandler() {
        final AttachInfo attachInfo = mAttachInfo;
        if (attachInfo != null) {
            return attachInfo.mHandler;
        }
        return null;
    }

其实都是使用的是mAttachInfo里的handler

void dispatchAttachedToWindow(AttachInfo info, int visibility) {
        mAttachInfo = info;
        if (mOverlay != null) {
            mOverlay.getOverlayView().dispatchAttachedToWindow(info, visibility);
        }
        mWindowAttachCount++;
        // We will need to evaluate the drawable state at least once.
        mPrivateFlags |= PFLAG_DRAWABLE_STATE_DIRTY;
        if (mFloatingTreeObserver != null) {
            info.mTreeObserver.merge(mFloatingTreeObserver);
            mFloatingTreeObserver = null;
        }

        registerPendingFrameMetricsObservers();

        if ((mPrivateFlags&PFLAG_SCROLL_CONTAINER) != 0) {
            mAttachInfo.mScrollContainers.add(this);
            mPrivateFlags |= PFLAG_SCROLL_CONTAINER_ADDED;
        }
        // Transfer all pending runnables.
        if (mRunQueue != null) {
            mRunQueue.executeActions(info.mHandler);
            mRunQueue = null;
        }
        performCollectViewAttributes(mAttachInfo, visibility);
        onAttachedToWindow();

        ListenerInfo li = mListenerInfo;
        final CopyOnWriteArrayList listeners =
                li != null ? li.mOnAttachStateChangeListeners : null;
        if (listeners != null && listeners.size() > 0) {
            // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
            // perform the dispatching. The iterator is a safe guard against listeners that
            // could mutate the list by calling the various add/remove methods. This prevents
            // the array from being modified while we iterate it.
            for (OnAttachStateChangeListener listener : listeners) {
                listener.onViewAttachedToWindow(this);
            }
        }

        int vis = info.mWindowVisibility;
        if (vis != GONE) {
            onWindowVisibilityChanged(vis);
            if (isShown()) {
                // Calling onVisibilityAggregated directly here since the subtree will also
                // receive dispatchAttachedToWindow and this same call
                onVisibilityAggregated(vis == VISIBLE);
            }
        }

        // Send onVisibilityChanged directly instead of dispatchVisibilityChanged.
        // As all views in the subtree will already receive dispatchAttachedToWindow
        // traversing the subtree again here is not desired.
        onVisibilityChanged(this, visibility);

        if ((mPrivateFlags&PFLAG_DRAWABLE_STATE_DIRTY) != 0) {
            // If nobody has evaluated the drawable state yet, then do it now.
            refreshDrawableState();
        }
        needGlobalAttributesUpdate(false);

        notifyEnterOrExitForAutoFillIfNeeded(true);
    }

dispatchAttachedToWindow是给mAttachInfo赋值的

1.当窗口启动的时候view还没有依附到窗口时，mRunQueue是view内部新建的队列，view.post的对象就被存储在mRunQueue
2.开始依附的时候，先指向外部AttachInfo（其实实现在ViewRootImpl中）
3.dispatchAttachedToWindow的时候，如果发现一个view有mRunQueue，先提交到传入的AttachInfo的handler中去处理
3.后续执行onAttachedToWindow/onVisibilityChanged 这2个方法
4.所有view里的handler就是viewrootimpl里面的ViewRootHandler