android 中view 的OnTouchListener和OnClickListener的区别

有时候会迷惑，OnTouchListener和OnClickListener究竟有什么区别。 通过源码分析一下。

一，OnTouchListener的触发逻辑

代码在View类 中

    public boolean dispatchTouchEvent(MotionEvent event) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onTouchEvent(event, 0);
        }

        if (onFilterTouchEventForSecurity(event)) {
            //noinspection SimplifiableIfStatement
            ListenerInfo li = mListenerInfo;
            if (li != null && li.mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED
                    && li.mOnTouchListener.onTouch(this, event)) {
                return true;
            }

            if (onTouchEvent(event)) {
                return true;
            }
        }

        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
        }
        return false;
    }

分发touch事件时 先判断mOnTouchListener.onTouch() 是否处理了 事件，如果方法返回true(处理了)，则不向下传递。

所以OnTouchListener 的触发时机是：手指一触摸就会触发。 action_down的时候就会触发。而且touchListener的字面意思"触碰监听"也比较贴切 。

二，OnClickListener的触发逻辑

代码也在View类 中

public boolean onTouchEvent(MotionEvent event) {
...
if (((viewFlags & CLICKABLE) == CLICKABLE ||
                (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_UP:
                    boolean prepressed = (mPrivateFlags & PREPRESSED) != 0;
                    if ((mPrivateFlags & 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);
                       }

                        if (!mHasPerformedLongPress) {
                            // 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();//触发点
                                }
                            }
                        }
...
}

下面看触发点performClick()

    public boolean performClick() {
        sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);

        ListenerInfo li = mListenerInfo;
        if (li != null && li.mOnClickListener != null) {
            playSoundEffect(SoundEffectConstants.CLICK);
            li.mOnClickListener.onClick(this);//触发点击事件
            return true;
        }

        return false;
    }

在onTouch()的事件处理的逻辑中，手指抬起 action_up 时，符合click的条件，则触发mOnClickListener的逻辑。

总结：

OnTouchListener的触发点：action_down 手指按下时

OnClickListener的触发点：action_up 手指抬起时

OnTouchListener 处理逻辑在OnClickListener之前,  所以OnTouchListener 的onTouch（）如果返回true, 则 onTouchEvent ()中所有逻辑失效，当然OnClickListener也不会触发。