我們熟知View.post()和Handler.post(),雖然最後執行過程還會走到Handler的post()方法中，但是View.post()做了許多額外的工作，所以我認為如非迫不得己，建議直接使用Handler.post()方法，詳情見此文。

如果在android7.0(sdk 24及以上)開發過程中，如果你的view沒有通過addView新增到檢視的時候，就會導致對應view的點選事件無效，以及view.post不執行，可能就是本文原因了，

以下是view.post在sdk版本24及以上的post方法

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;
    }
 

public boolean post(Runnable action) {
        final AttachInfo attachInfo = mAttachInfo;
        if (attachInfo != null) {
            return attachInfo.mHandler.post(action);
        }
        // Assume that post will succeed later
        ViewRootImpl.getRunQueue().post(action);
        return true;
    }
 

其中，getRunQueue()的方法是

   /** 
     *  Returns the queue of runnable for this view.
     *
     * @return the queue of runnables for this view
     */
    private HandlerActionQueue getRunQueue() {
        if (mRunQueue == null) {
            mRunQueue = new HandlerActionQueue();
        }
        return mRunQueue;
    }
 

這個mRunQueue是View類中一個私有變數。

ViewRootImpl可以理解是一個activity的View樹的樹根，每個ViewRootImpl管理對應的DecoView和View樹

ViewRootImpl中的佇列是一個靜態變數，也就是隻有一個這個佇列存在於這個app的生命週期中

static HandlerActionQueue getRunQueue() {
        HandlerActionQueue rq = sRunQueues.get();
        if (rq != null) {
            return rq;
        }
        rq = new HandlerActionQueue();
        sRunQueues.set(rq);
        return rq;
    }

其中，SDK24以上是HandlerActionQueue類中

public void executeActions(Handler handler) {
        synchronized (this) {
            final HandlerAction[] actions = mActions;
            for (int i = 0, count = mCount; i < count; i++) {
                final HandlerAction handlerAction = actions[i];
                handler.postDelayed(handlerAction.action, handlerAction.delay);
            }

            mActions = null;
            mCount = 0;
        }
    }

void executeActions(Handler handler) {
            synchronized (mActions) {
                final ArrayList<HandlerAction> actions = mActions;
                final int count = actions.size();

                for (int i = 0; i < count; i++) {
                    final HandlerAction handlerAction = actions.get(i);
                    handler.postDelayed(handlerAction.action, handlerAction.delay);
                }

                actions.clear();
            }
        }

case MotionEvent.ACTION_UP:
                    boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
                    if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
                        // take focus if we don't have it already and we should in
                        // touch mode.
                        boolean focusTaken = false;
                        if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
                            focusTaken = requestFocus();
                        }

                        if (prepressed) {
                            // The button is being released before we actually
                            // showed it as pressed.  Make it show the pressed
                            // state now (before scheduling the click) to ensure
                            // the user sees it.
                            setPressed(true, x, y);
                       }

                        if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
                            // This is a tap, so remove the longpress check
                            removeLongPressCallback();

                            // Only perform take click actions if we were in the pressed state
                            if (!focusTaken) {
                                // Use a Runnable and post this rather than calling
                                // performClick directly. This lets other visual state
                                // of the view update before click actions start.
                                if (mPerformClick == null) {
                                    mPerformClick = new PerformClick();
                                }
                                if (!post(mPerformClick)) {
                                    performClick();
                                }
                            }
                        }

                        if (mUnsetPressedState == null) {
                            mUnsetPressedState = new UnsetPressedState();
                        }

                        if (prepressed) {
                            postDelayed(mUnsetPressedState,
                                    ViewConfiguration.getPressedStateDuration());
                        } else if (!post(mUnsetPressedState)) {
                            // If the post failed, unpress right now
                            mUnsetPressedState.run();
                        }

                        removeTapCallback();
                    }
                    mIgnoreNextUpEvent = false;
                    break;

而在23及以下版本中，ViewRootImpl的executeActions會頻繁的呼叫，ViewRootImpl中的TraversalRunnable進行呼叫doTraversa來()進行呼叫。而TraversalRunnable是通過Choreographer的postCallBack迴圈呼叫，這個Choreographer通過doScheduleCallback進行一個MSG_DO_SCHEDULE_CALLBACK型別的迴圈操作（它每隔一段時間操作(ms級別)）。詳情請檢視以後的Choreographer文章。

說完了問題原因，解決方法如下：

關於點選事件，首先一定保證對應的view已經addview到父檢視中，這樣可能解決問題，當然不一定滿足業務需求，也不一定能完美解決，那麼可以通過重寫View的對應post方法進行處理，如下

 private Handler mHandler;
    @Override
    public boolean post(Runnable action) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N && action!= null && !isAttachedToWindow()) {
            mHandler = new Handler();
            return mHandler.post(action);
        }
        return super.post(action);
    }

    @Override
    public boolean removeCallbacks(Runnable action) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N && action != null && !isAttachedToWindow()&& mHandler != null) {
            mHandler.removeCallbacks(action);
            return true;
        }
        return super.removeCallbacks(action);
    }