在Android中需要經(jīng)常對用戶手勢進(jìn)行判斷，在判斷手勢時需要精細(xì)的分清楚每個觸摸事件以及每個View對事件的接收情況，在View，ViewGroup，Activity中都可以接收事件，在對事件進(jìn)行處理時onInterceptTouchEvent、dispatchTouchEvent及onTouchEvent這三個函數(shù)的調(diào)用順序及關(guān)系需要好好理清楚。原理代碼有點多，如果不對著具體事例，理解起來很難。下面對著代碼進(jìn)行分析。代碼地址為：https://github.com/huangtianyu/DispatchTouchEvent，記得幫忙點Star

MainActivity.java

[java] view plaincopy

package?com.zqc.dispatchtouchevent;??

??

import?android.app.Activity;??

import?android.os.Bundle;??

import?android.util.Log;??

import?android.view.MotionEvent;??

import?android.view.View;??

??

import?static?com.zqc.dispatchtouchevent.Constants.TAG;??

??

public?class?MainActivity?extends?Activity?implements?View.OnTouchListener?{??

????private?MyView?myView;??

????@Override??

????protected?void?onCreate(Bundle?savedInstanceState)?{??

????????super.onCreate(savedInstanceState);??

????????Log.e(TAG,?"MainActivity?onCreate");??

????????setContentView(R.layout.activity_main);??

????????myView?=?(MyView)?findViewById(R.id.myview);??

????????myView.setOnTouchListener(MainActivity.this);??

????}??

????@Override??

????public?boolean?dispatchTouchEvent(MotionEvent?ev)?{??

????????Log.e(TAG,?"MainActivity?dispatchTouchEvent");??

????????return?super.dispatchTouchEvent(ev);??

????}??

????@Override??

????public?boolean?onTouchEvent(MotionEvent?event)?{??

????????Log.e(TAG,?"MainActivity?onTouchEvent");??

????????switch?(event.getAction())?{??

????????????case?MotionEvent.ACTION_DOWN:??

????????????????Log.e(TAG,?"MainActivity?onTouchEvent?ACTION_DOWN");??

????????????????break;??

????????????case?MotionEvent.ACTION_MOVE:??

????????????????Log.e(TAG,?"MainActivity?onTouchEvent?ACTION_MOVE");??

????????????????break;??

????????????case?MotionEvent.ACTION_CANCEL:??

????????????????Log.e(TAG,?"MainActivity?onTouchEvent?ACTION_CANCEL");??

????????????????break;??

????????????case?MotionEvent.ACTION_UP:??

????????????????Log.e(TAG,?"MainActivity?onTouchEvent?ACTION_UP");??

????????????????break;??

????????????default:??

????????????????Log.e(TAG,?"MainActivity?onTouchEvent?"?+?event.getAction());??

????????????????break;??

????????}??

????????return?super.onTouchEvent(event);??

????}??

????@Override??

????protected?void?onResume()?{??

????????Log.e(TAG,?"MainActivity?onResume");??

????????super.onResume();??

????}??

????@Override??

????protected?void?onPause()?{??

????????Log.e(TAG,?"MainActivity?onPause");??

????????super.onPause();??

????}??

????@Override??

????public?boolean?onTouch(View?v,?MotionEvent?event)?{??

????????Log.e(TAG,?"MainActivity?onTouch");??

????????switch?(event.getAction()?&?MotionEvent.ACTION_MASK)?{??

????????????case?MotionEvent.ACTION_DOWN:??

????????????????Log.e(TAG,?"MainActivity?onTouch?ACTION_DOWN");??

????????????????break;??

????????????case?MotionEvent.ACTION_MOVE:??

????????????????Log.e(TAG,?"MainActivity?onTouch?ACTION_MOVE");??

????????????????break;??

????????????case?MotionEvent.ACTION_CANCEL:??

????????????????Log.e(TAG,?"MainActivity?onTouch?ACTION_CANCEL");??

????????????????break;??

????????????case?MotionEvent.ACTION_UP:??

????????????????Log.e(TAG,?"MainActivity?onTouch?ACTION_UP");??

????????????????break;??

????????????default:??

????????????????Log.e(TAG,?"MainActivity?onTouchEvent?"?+?event.getAction());??

????????????????break;??

????????}??

????????return?false;??

????}??

}??

MyView.java

[java] view plaincopy

package?com.zqc.dispatchtouchevent;??

??

import?android.content.Context;??

import?android.util.AttributeSet;??

import?android.util.Log;??

import?android.view.GestureDetector;??

import?android.view.MotionEvent;??

import?android.widget.TextView;??

??

import?static?com.zqc.dispatchtouchevent.Constants.MY_GESTURE_TAG;??

import?static?com.zqc.dispatchtouchevent.Constants.TAG;??

??

??

public?class?MyView?extends?TextView?{??

????private?Context?mContext;??

????//private?GestureDetector?mGesture;??

??

????public?MyView(Context?context)?{??

????????this(context,?null);??

????}??

??

????public?MyView(Context?context,?AttributeSet?attrs)?{??

????????super(context,?attrs);??

????????Log.e(TAG,?"MyView");??

????????mContext?=?context;??

????????//手勢初始化??

???????//?mGesture?=?new?GestureDetector(mContext,?mGestureListener);??

????}??

??

????@Override??

????public?boolean?onTouchEvent(MotionEvent?event)?{??

????????Log.e(TAG,?"MyView?onTouchEvent");??

????????switch?(event.getAction())?{??

????????????case?MotionEvent.ACTION_DOWN:??

????????????????Log.e(TAG,?"MyView?onTouchEvent?ACTION_DOWN");??

????????????????break;??

????????????case?MotionEvent.ACTION_MOVE:??

????????????????Log.e(TAG,?"MyView?onTouchEvent?ACTION_MOVE");??

????????????????break;??

????????????case?MotionEvent.ACTION_CANCEL:??

????????????????Log.e(TAG,?"MyView?onTouchEvent?ACTION_CANCEL");??

????????????????break;??

????????????case?MotionEvent.ACTION_UP:??

????????????????Log.e(TAG,?"MyView?onTouchEvent?ACTION_UP");??

????????????????break;??

????????????default:??

????????????????Log.e(TAG,?"MyView?onTouchEvent?"?+?event.getAction());??

????????????????break;??

????????}??

//????????設(shè)置手勢監(jiān)聽??

???????//?mGesture.onTouchEvent(event);??

????????return?super.onTouchEvent(event);??

????}??

??

????@Override??

????public?boolean?dispatchTouchEvent(MotionEvent?event)?{??

????????Log.e(TAG,?"MyView?dispatchTouchEvent");??

????????return?super.dispatchTouchEvent(event);??

????}??

}??

MyViewGroup.java

[java] view plaincopy

package?com.zqc.dispatchtouchevent;??

??

import?android.content.Context;??

import?android.util.AttributeSet;??

import?android.util.Log;??

import?android.view.MotionEvent;??

import?android.widget.RelativeLayout;??

??

import?static?com.zqc.dispatchtouchevent.Constants.TAG;??

??

public?class?MyViewGroup?extends?RelativeLayout?{??

????public?MyViewGroup(Context?context)?{??

????????this(context,?null);??

????}??

??

????public?MyViewGroup(Context?context,?AttributeSet?attrs)?{??

????????super(context,?attrs);??

????????Log.e(TAG,?"MyViewGroup");??

????}??

??

????@Override??

????public?boolean?onInterceptTouchEvent(MotionEvent?ev)?{??

????????Log.e(TAG,?"MyViewGroup?onInterceptTouchEvent");??

????????return?super.onInterceptTouchEvent(ev);??

????}??

??

????@Override??

????public?boolean?dispatchTouchEvent(MotionEvent?ev)?{??

????????Log.e(TAG,?"MyViewGroup?dispatchTouchEvent");??

????????return?super.dispatchTouchEvent(ev);??

????}??

??

????@Override??

????public?boolean?onTouchEvent(MotionEvent?event)?{??

????????Log.e(TAG,?"MyViewGroup?onTouchEvent");??

????????switch?(event.getAction())?{??

????????????case?MotionEvent.ACTION_DOWN:??

????????????????Log.e(TAG,?"MyViewGroup?onTouchEvent?ACTION_DOWN");??

????????????????break;??

????????????case?MotionEvent.ACTION_MOVE:??

????????????????Log.e(TAG,?"MyViewGroup?onTouchEvent?ACTION_MOVE");??

????????????????break;??

????????????case?MotionEvent.ACTION_CANCEL:??

????????????????Log.e(TAG,?"MyViewGroup?onTouchEvent?ACTION_CANCEL");??

????????????????break;??

????????????case?MotionEvent.ACTION_UP:??

????????????????Log.e(TAG,?"MyViewGroup?onTouchEvent?ACTION_UP");??

????????????????break;??

????????????default:??

????????????????Log.e(TAG,?"MyViewGroup?onTouchEvent?"?+?event.getAction());??

????????????????break;??

????????}??

????????return?super.onTouchEvent(event);??

????}??

}??

Contants.java

[java] view plaincopy

package?com.zqc.dispatchtouchevent;??

??

public?class?Constants?{??

??

????public?final?static?String?TAG?=?"MY_LOG";??

????public?final?static?String?MY_GESTURE_TAG?=?"GESTURE_TAG";??

}??

在代碼中將每個函數(shù)分別列出并加上Log輸出，這樣對著Log日志進(jìn)行分析，則一目了然。

1.讓所有的onInterceptTouchEvent、dispatchTouchEvent及onTouchEvent均返回super.onTouchEvent即均返回false時，輕輕點擊MyView然后快速抬起，查看相應(yīng)的Log：

?

通過Log能清楚的查看代碼執(zhí)行的流程，具體流程如下：

DOWN事件：MainActivity.dispatchTouchEvent->MyViewGroup.dispatchTouchEvet->MyViewGroup.onInterceptTouchEvent->MyView.dispatchTouchEvent->setOnTouchListener.onTouch->MyView.onTouchEvent->MyViewGroup.onTouchEvent->MainActivity.onTouchEvent

UP事件：MainActivity.dispatchTouchEvent->MainActivity.onTouchEvent

從上面流程可以看出，點擊事件最先傳給窗口Activity的dispatchTouchEvent函數(shù)進(jìn)行事件分發(fā)，然后對于View類，是先傳給對應(yīng)的父View的dispatchTouchEvent進(jìn)行事件分發(fā)，然后在傳給里面點擊的View。當(dāng)down事件沒有被各個view消費時，最終會調(diào)用Acitivity的onTouchEvent，并在在Down后續(xù)的UP事件不在傳給MyViewGroup和MyView，直接傳給MainAcitivity。所以當(dāng)事件沒有被窗口中的View消費時，最終都是給了該窗口Activity類中的onTouchEvent事件處理。從Log中也可以看出setOnTouchListener中的onTouch事件是在對應(yīng)View的onTouchEvent事件之前被執(zhí)行。

2.當(dāng)MainAcivity中dispathTouchEvent返回true時，輕輕點擊MyView，查看對應(yīng)Log：

通過Log可以看到當(dāng)窗口Activity的dispatchTouchEvent返回true時，DOWN事件沒有往View中傳，也就沒有調(diào)用任何的onTouchEvent事件，UP事件也是走到Activity的dispatchTouchEvent時也就結(jié)束了。

3.重新置Activity中dispatchTouchEvent返回false，然后置ViewGroup中onInterceptTouchEvent返回true時，輕輕點擊MyView查看對應(yīng)Log：

這時DOWN事件和UP事件的執(zhí)行流程如下：

DOWN事件：MainActivity.dipatchTouchEvent->MyViewGroup.dispatchTouchEvent->MyViewGroup.onInterceptTouchEvent->MyViewGroup.onTouchEvent->MainActivity.onTouchEvent.

UP事件:MainActiviy.dispatchTouchEvent->MainActivity.onTouchEvent.

從Log中可以看出，當(dāng)onInterceptTouchEvent返回true時，事件即被MyViewGroup攔截了，這時事件就直接傳給MyViewGroup.onTouchEvent，不在往子View傳，由于MyViewGroup.onTouchEvent返回的是false，即MyViewGroup并沒有消費事件，這時事件會傳給窗口Activity，UP事件會傳給最后一個接受Down事件的窗口或View。

4.當(dāng)MyView中onTouchEvent返回true時，即MyView會消費傳給他的事件。輕點MyView查看對應(yīng)的Log：

繼續(xù)分析DOWN事件的流程：

DOWN事件：MainActivity.dispatchTouchEvent->MyViewGroup.dispatchTouchEvet->MyViewGroup.onInterceptTouchEvent->MyView.dispatchTouchEvent->setOnTouchListener.onTouch->MyView.onTouchEvent

UP事件：MainActivity.dispatchTouchEvent->MyViewGroup.dispatchTouchEvet->MyViewGroup.onInterceptTouchEvent->MyView.dispatchTouchEvent->setOnTouchListener.onTouch->MyView.onTouchEvent

從上面的執(zhí)行流程可以看出當(dāng)事件被MyView消費后，事件不會在往上傳，后續(xù)的UP事件也直接通過dispatchTouchEvent分發(fā)給對應(yīng)的View，這里還是提一下，在MainAcitivy中設(shè)置的setOnTouchListener中的onTouch事件是在MyView自身的onTouchEvent事件之前被執(zhí)行，因而設(shè)置的setOnTouchEvent的onTouch函數(shù)還是會被執(zhí)行。

先只分析這幾種場景，MOVE事件和UP事件一樣只要DOWN事件被某個View消耗了，那么MOVE事件也就直接傳到這個View。可以下載代碼運行后，在MyView上面滑動下看下Log，具體Log我也貼一份。

情況1：

情況2：

下面對著Android源碼來具體分析View的觸摸事件到底是怎么執(zhí)行的。首先根據(jù)Log可以最先接收到消息的是Activity的dispatchTouchEvent，在該處設(shè)置斷點，然后查看對應(yīng)的調(diào)用方法棧（你會發(fā)現(xiàn)在調(diào)到MainActivity的dispatchTouchEvent時，前面已經(jīng)調(diào)用了很多方法），如下：

由于Android系統(tǒng)啟動后會先啟動Zygote進(jìn)程，該進(jìn)程會在手機開機后一直運行，Android中的幾個系統(tǒng)服務(wù)都是由Zygote進(jìn)程fork出來的，一個應(yīng)用在啟動時所分配到的進(jìn)程也是由Zygote進(jìn)程fork出來的，通常說一個應(yīng)用的起點是Application里面的onCreate函數(shù)，其實真正的起點是ActivityThread里面的main函數(shù)，看到這個main函數(shù)是不是有種熟悉的感覺啊。在main函數(shù)中初始化了應(yīng)用程序的主線程，同時初始化了主線程的消息隊列，并調(diào)用了Looper.loop()函數(shù)使主線程不斷的對消息隊列進(jìn)行循環(huán)檢測，有消息則進(jìn)行處理。點擊事件產(chǎn)生一個消息，該消息傳到InputEventReceiver后，由InputEventReceiver的繼承類WindowInputEventReceiver去處理，WindowInputEventReceiver類是ViewRootImpl類的內(nèi)部類，查看對應(yīng)代碼如下：

ViewRootImpl.java

[java] view plaincopy

final?class?WindowInputEventReceiver?extends?InputEventReceiver?{??

????public?WindowInputEventReceiver(InputChannel?inputChannel,?Looper?looper)?{??

????????super(inputChannel,?looper);??

????}??

??

????@Override??

????public?void?onInputEvent(InputEvent?event)?{??

????????enqueueInputEvent(event,?this,?0,?true);??

????}??

??

????@Override??

????public?void?onBatchedInputEventPending()?{??

????????if?(mUnbufferedInputDispatch)?{??

????????????super.onBatchedInputEventPending();??

????????}?else?{??

????????????scheduleConsumeBatchedInput();??

????????}??

????}??

??

????@Override??

????public?void?dispose()?{??

????????unscheduleConsumeBatchedInput();??

????????super.dispose();??

????}??

}??

查看代碼可以當(dāng)點擊消息過來時，直接調(diào)用ViewRootImpl類中的enqueueInputEvent(event,this,0,true)方法:

ViewRootImpl.java

[java] view plaincopy

void?enqueueInputEvent(InputEvent?event,??

????????InputEventReceiver?receiver,?int?flags,?boolean?processImmediately)?{??

????adjustInputEventForCompatibility(event);??

????QueuedInputEvent?q?=?obtainQueuedInputEvent(event,?receiver,?flags);??

??

????//?Always?enqueue?the?input?event?in?order,?regardless?of?its?time?stamp.??

????//?We?do?this?because?the?application?or?the?IME?may?inject?key?events??

????//?in?response?to?touch?events?and?we?want?to?ensure?that?the?injected?keys??

????//?are?processed?in?the?order?they?were?received?and?we?cannot?trust?that??

????//?the?time?stamp?of?injected?events?are?monotonic.??

????QueuedInputEvent?last?=?mPendingInputEventTail;??

????if?(last?==?null)?{??

????????mPendingInputEventHead?=?q;??

????????mPendingInputEventTail?=?q;??

????}?else?{??

????????last.mNext?=?q;??

????????mPendingInputEventTail?=?q;??

????}??

????mPendingInputEventCount?+=?1;??

????Trace.traceCounter(Trace.TRACE_TAG_INPUT,?mPendingInputEventQueueLengthCounterName,??

????????????mPendingInputEventCount);??

??

????if?(processImmediately)?{??

????????doProcessInputEvents();??

????}?else?{??

????????scheduleProcessInputEvents();??

????}??

}??

由于processImmediately為true，因而是立即處理，即直接調(diào)用doProcessInputEvents();

ViewRootImpl.java

[java] view plaincopy

void?doProcessInputEvents()?{??

????//?Deliver?all?pending?input?events?in?the?queue.??

????while?(mPendingInputEventHead?!=?null)?{??

????????QueuedInputEvent?q?=?mPendingInputEventHead;??

????????mPendingInputEventHead?=?q.mNext;??

????????if?(mPendingInputEventHead?==?null)?{??

????????????mPendingInputEventTail?=?null;??

????????}??

????????q.mNext?=?null;??

??

????????mPendingInputEventCount?-=?1;??

????????Trace.traceCounter(Trace.TRACE_TAG_INPUT,?mPendingInputEventQueueLengthCounterName,??

????????????????mPendingInputEventCount);??

??

????????long?eventTime?=?q.mEvent.getEventTimeNano();??

????????long?oldestEventTime?=?eventTime;??

????????if?(q.mEvent?instanceof?MotionEvent)?{??

????????????MotionEvent?me?=?(MotionEvent)q.mEvent;??

????????????if?(me.getHistorySize()?>?0)?{??

????????????????oldestEventTime?=?me.getHistoricalEventTimeNano(0);??

????????????}??

????????}??

????????mChoreographer.mFrameInfo.updateInputEventTime(eventTime,?oldestEventTime);??

??

????????deliverInputEvent(q);??

????}??

??

????//?We?are?done?processing?all?input?events?that?we?can?process?right?now??

????//?so?we?can?clear?the?pending?flag?immediately.??

????if?(mProcessInputEventsScheduled)?{??

????????mProcessInputEventsScheduled?=?false;??

????????mHandler.removeMessages(MSG_PROCESS_INPUT_EVENTS);??

????}??

}??

z之后調(diào)用了deliverInputEvent(q)

ViewRootImpl.java

[java] view plaincopy

private?void?deliverInputEvent(QueuedInputEvent?q)?{??

????Trace.asyncTraceBegin(Trace.TRACE_TAG_VIEW,?"deliverInputEvent",??

????????????q.mEvent.getSequenceNumber());??

????if?(mInputEventConsistencyVerifier?!=?null)?{??

????????mInputEventConsistencyVerifier.onInputEvent(q.mEvent,?0);??

????}??

??

????InputStage?stage;??

????if?(q.shouldSendToSynthesizer())?{??

????????stage?=?mSyntheticInputStage;??

????}?else?{??

????????stage?=?q.shouldSkipIme()???mFirstPostImeInputStage?:?mFirstInputStage;??

????}??

??

????if?(stage?!=?null)?{??

????????stage.deliver(q);??

????}?else?{??

????????finishInputEvent(q);??

????}??

}??

在這里初始化了一個InputStage類的實例，然后調(diào)用了該類的deliver(q)，具體方法如下：

[java] view plaincopy

/**?

?????*?Base?class?for?implementing?a?stage?in?the?chain?of?responsibility?

?????*?for?processing?input?events.?

?????*?<p>?

?????*?Events?are?delivered?to?the?stage?by?the?{@link?#deliver}?method.??The?stage?

?????*?then?has?the?choice?of?finishing?the?event?or?forwarding?it?to?the?next?stage.?

?????*?</p>?

?????*/??

????abstract?class?InputStage?{??

????????private?final?InputStage?mNext;??

??

????????protected?static?final?int?FORWARD?=?0;??

????????protected?static?final?int?FINISH_HANDLED?=?1;??

????????protected?static?final?int?FINISH_NOT_HANDLED?=?2;??

??

????????/**?

?????????*?Creates?an?input?stage.?

?????????*?@param?next?The?next?stage?to?which?events?should?be?forwarded.?

?????????*/??

????????public?InputStage(InputStage?next)?{??

????????????mNext?=?next;??

????????}??

??

????????/**?

?????????*?Delivers?an?event?to?be?processed.?

?????????*/??

????????public?final?void?deliver(QueuedInputEvent?q)?{??

????????????if?((q.mFlags?&?QueuedInputEvent.FLAG_FINISHED)?!=?0)?{??

????????????????forward(q);??

????????????}?else?if?(shouldDropInputEvent(q))?{??

????????????????finish(q,?false);??

????????????}?else?{??

????????????????apply(q,?onProcess(q));??

????????????}??

????????}??

??

????????/**?

?????????*?Marks?the?the?input?event?as?finished?then?forwards?it?to?the?next?stage.?

?????????*/??

????????protected?void?finish(QueuedInputEvent?q,?boolean?handled)?{??

????????????q.mFlags?|=?QueuedInputEvent.FLAG_FINISHED;??

????????????if?(handled)?{??

????????????????q.mFlags?|=?QueuedInputEvent.FLAG_FINISHED_HANDLED;??

????????????}??

????????????forward(q);??

????????}??

??

????????/**?

?????????*?Forwards?the?event?to?the?next?stage.?

?????????*/??

????????protected?void?forward(QueuedInputEvent?q)?{??

????????????onDeliverToNext(q);??

????????}??

??

????????/**?

?????????*?Applies?a?result?code?from?{@link?#onProcess}?to?the?specified?event.?

?????????*/??

????????protected?void?apply(QueuedInputEvent?q,?int?result)?{??

????????????if?(result?==?FORWARD)?{??

????????????????forward(q);??

????????????}?else?if?(result?==?FINISH_HANDLED)?{??

????????????????finish(q,?true);??

????????????}?else?if?(result?==?FINISH_NOT_HANDLED)?{??

????????????????finish(q,?false);??

????????????}?else?{??

????????????????throw?new?IllegalArgumentException("Invalid?result:?"?+?result);??

????????????}??

????????}??

??

????????/**?

?????????*?Called?when?an?event?is?ready?to?be?processed.?

?????????*?@return?A?result?code?indicating?how?the?event?was?handled.?

?????????*/??

????????protected?int?onProcess(QueuedInputEvent?q)?{??

????????????return?FORWARD;??

????????}??

??

????????/**?

?????????*?Called?when?an?event?is?being?delivered?to?the?next?stage.?

?????????*/??

????????protected?void?onDeliverToNext(QueuedInputEvent?q)?{??

????????????if?(DEBUG_INPUT_STAGES)?{??

????????????????Log.v(TAG,?"Done?with?"?+?getClass().getSimpleName()?+?".?"?+?q);??

????????????}??

????????????if?(mNext?!=?null)?{??

????????????????mNext.deliver(q);??

????????????}?else?{??

????????????????finishInputEvent(q);??

????????????}??

????????}??

??

????????protected?boolean?shouldDropInputEvent(QueuedInputEvent?q)?{??

????????????if?(mView?==?null?||?!mAdded)?{??

????????????????Slog.w(TAG,?"Dropping?event?due?to?root?view?being?removed:?"?+?q.mEvent);??

????????????????return?true;??

????????????}?else?if?((!mAttachInfo.mHasWindowFocus??

????????????????????&&?!q.mEvent.isFromSource(InputDevice.SOURCE_CLASS_POINTER))?||?mStopped??

????????????????????||?(mPausedForTransition?&&?!isBack(q.mEvent)))?{??

????????????????//?This?is?a?focus?event?and?the?window?doesn't?currently?have?input?focus?or??

????????????????//?has?stopped.?This?could?be?an?event?that?came?back?from?the?previous?stage??

????????????????//?but?the?window?has?lost?focus?or?stopped?in?the?meantime.??

????????????????if?(isTerminalInputEvent(q.mEvent))?{??

????????????????????//?Don't?drop?terminal?input?events,?however?mark?them?as?canceled.??

????????????????????q.mEvent.cancel();??

????????????????????Slog.w(TAG,?"Cancelling?event?due?to?no?window?focus:?"?+?q.mEvent);??

????????????????????return?false;??

????????????????}??

??

????????????????//?Drop?non-terminal?input?events.??

????????????????Slog.w(TAG,?"Dropping?event?due?to?no?window?focus:?"?+?q.mEvent);??

????????????????return?true;??

????????????}??

????????????return?false;??

????????}??

??

????????void?dump(String?prefix,?PrintWriter?writer)?{??

????????????if?(mNext?!=?null)?{??

????????????????mNext.dump(prefix,?writer);??

????????????}??

????????}??

??

????????private?boolean?isBack(InputEvent?event)?{??

????????????if?(event?instanceof?KeyEvent)?{??

????????????????return?((KeyEvent)?event).getKeyCode()?==?KeyEvent.KEYCODE_BACK;??

????????????}?else?{??

????????????????return?false;??

????????????}??

????????}??

????}??

對應(yīng)方法棧可以看出，進(jìn)過一些列調(diào)用最終會調(diào)用到ViewPostImeInputStage類的processPointerEvent方法.

ViewRootImpl.java

[java] view plaincopy

private?int?processPointerEvent(QueuedInputEvent?q)?{??

????final?MotionEvent?event?=?(MotionEvent)q.mEvent;??

??

????mAttachInfo.mUnbufferedDispatchRequested?=?false;??

????boolean?handled?=?mView.dispatchPointerEvent(event);??

????if?(mAttachInfo.mUnbufferedDispatchRequested?&&?!mUnbufferedInputDispatch)?{??

????????mUnbufferedInputDispatch?=?true;??

????????if?(mConsumeBatchedInputScheduled)?{??

????????????scheduleConsumeBatchedInputImmediately();??

????????}??

????}??

????return?handled???FINISH_HANDLED?:?FORWARD;??

}??

在該方法中調(diào)用了mView的dispatchPointerEvent，這個mView的初始化可以查看Activity的創(chuàng)建代碼，在Activity創(chuàng)建的時候會給Activity設(shè)置一個根布局也就是DecorView，這里的mView就是DecorView，這個DecorView是PhoneWindow的私有內(nèi)部類，它繼承于FrameLayout并實現(xiàn)了RootViewSurfaceTaker接口，但是該方法是View類的一個final方法，子類無法覆寫，直接查看View中的相應(yīng)代碼即可。代碼如下：

View.java

[java] view plaincopy

/**?

?*?Dispatch?a?pointer?event.?

?*?<p>?

?*?Dispatches?touch?related?pointer?events?to?{@link?#onTouchEvent(MotionEvent)}?and?all?

?*?other?events?to?{@link?#onGenericMotionEvent(MotionEvent)}.??This?separation?of?concerns?

?*?reinforces?the?invariant?that?{@link?#onTouchEvent(MotionEvent)}?is?really?about?touches?

?*?and?should?not?be?expected?to?handle?other?pointing?device?features.?

?*?</p>?

?*?

?*?@param?event?The?motion?event?to?be?dispatched.?

?*?@return?True?if?the?event?was?handled?by?the?view,?false?otherwise.?

?*?@hide?

?*/??

public?final?boolean?dispatchPointerEvent(MotionEvent?event)?{??

????if?(event.isTouchEvent())?{??

????????return?dispatchTouchEvent(event);??

????}?else?{??

????????return?dispatchGenericMotionEvent(event);??

????}??

}??

繼續(xù)查看DecorView類中的dispatchTouchEvent方法，代碼如下：

PhoneWindow.java

[java] view plaincopy

@Override??

public?boolean?dispatchTouchEvent(MotionEvent?ev)?{??

????final?Callback?cb?=?getCallback();??

????return?cb?!=?null?&&?!isDestroyed()?&&?mFeatureId?<?0???cb.dispatchTouchEvent(ev)??

????????????:?super.dispatchTouchEvent(ev);??

}??

這個getCallback也就是當(dāng)前的Activity，當(dāng)當(dāng)前Activity沒有destroy的時候即調(diào)用該Activity的dispatchTouchEvent，這里代碼就回到了應(yīng)用層了，框架層完成了很多操作，這些操作只有查看源碼才知道，這里終于回到了我們編寫代碼的地方了。當(dāng)然這之后還是會通過框架層將對應(yīng)的Touch事件傳給對應(yīng)的ViewGroup和View。下面先看下Activity中dispatchTouchEvent的代碼：

Activity.java

[java] view plaincopy

/**?

?*?Called?to?process?touch?screen?events.??You?can?override?this?to?

?*?intercept?all?touch?screen?events?before?they?are?dispatched?to?the?

?*?window.??Be?sure?to?call?this?implementation?for?touch?screen?events?

?*?that?should?be?handled?normally.?

?*?

?*?@param?ev?The?touch?screen?event.?

?*?

?*?@return?boolean?Return?true?if?this?event?was?consumed.?

?*/??

public?boolean?dispatchTouchEvent(MotionEvent?ev)?{??

????if?(ev.getAction()?==?MotionEvent.ACTION_DOWN)?{??

????????onUserInteraction();??

????}??

????if?(getWindow().superDispatchTouchEvent(ev))?{//這個getWindow就是PhoneWindow，也就是通過PhoneWindow繼續(xù)對touch事件進(jìn)行分發(fā)。??

????????return?true;??

????}//當(dāng)上面返回true，也就是View把事件消費了，那么就不再調(diào)用Activity的onTouchEvent函數(shù)了。??

????return?onTouchEvent(ev);??

}??

果然這里又回到了框架層，這里getWindow就是PhoneWindow，繼續(xù)查看PhoneWindow的代碼：

PhoneWindow.java

[java] view plaincopy

@Override??

public?boolean?superDispatchTouchEvent(MotionEvent?event)?{??

????return?mDecor.superDispatchTouchEvent(event);??

}??

這里把事件就傳給了DecorView進(jìn)行分發(fā)。

PhoneWindow.java->DecorView

[java] view plaincopy

public?boolean?superDispatchTouchEvent(MotionEvent?event)?{??

????return?super.dispatchTouchEvent(event);??

}??

前面說過DecorView繼承于FrameLayout，這里super.dispatchTouchEvent就是調(diào)用了FrameLayout里面的dispatchTouchEvent，而FrameLayout類中并未重寫dispatchTouchEvent，因而直接調(diào)用的是ViewGroup中的dispatchTouchEvent。繼續(xù)查看代碼：

ViewGroup.java

[java] view plaincopy

/**?

?*?{@inheritDoc}?

?*/??

@Override??

public?boolean?dispatchTouchEvent(MotionEvent?ev)?{??

????if?(mInputEventConsistencyVerifier?!=?null)?{??

????????mInputEventConsistencyVerifier.onTouchEvent(ev,?1);??

????}??

??

????//?If?the?event?targets?the?accessibility?focused?view?and?this?is?it,?start??

????//?normal?event?dispatch.?Maybe?a?descendant?is?what?will?handle?the?click.??

????if?(ev.isTargetAccessibilityFocus()?&&?isAccessibilityFocusedViewOrHost())?{??

????????ev.setTargetAccessibilityFocus(false);??

????}??

??

????boolean?handled?=?false;??

????if?(onFilterTouchEventForSecurity(ev))?{??

????????final?int?action?=?ev.getAction();??

????????final?int?actionMasked?=?action?&?MotionEvent.ACTION_MASK;??

??

????????//?Handle?an?initial?down.??

????????if?(actionMasked?==?MotionEvent.ACTION_DOWN)?{??

????????????//?Throw?away?all?previous?state?when?starting?a?new?touch?gesture.??

????????????//?The?framework?may?have?dropped?the?up?or?cancel?event?for?the?previous?gesture??

????????????//?due?to?an?app?switch,?ANR,?or?some?other?state?change.??

????????????cancelAndClearTouchTargets(ev);??

????????????resetTouchState();??

????????}??

??

????????//?Check?for?interception.??

????????final?boolean?intercepted;??

????????if?(actionMasked?==?MotionEvent.ACTION_DOWN??

????????????????||?mFirstTouchTarget?!=?null)?{??

????????????final?boolean?disallowIntercept?=?(mGroupFlags?&?FLAG_DISALLOW_INTERCEPT)?!=?0;??

????????????if?(!disallowIntercept)?{??

????????????????intercepted?=?onInterceptTouchEvent(ev);??

????????????????ev.setAction(action);?//?restore?action?in?case?it?was?changed??

????????????}?else?{??

????????????????intercepted?=?false;??

????????????}??

????????}?else?{??

????????????//?There?are?no?touch?targets?and?this?action?is?not?an?initial?down??

????????????//?so?this?view?group?continues?to?intercept?touches.??

????????????intercepted?=?true;??

????????}??

??

????????//?If?intercepted,?start?normal?event?dispatch.?Also?if?there?is?already??

????????//?a?view?that?is?handling?the?gesture,?do?normal?event?dispatch.??

????????if?(intercepted?||?mFirstTouchTarget?!=?null)?{??

????????????ev.setTargetAccessibilityFocus(false);??

????????}??

??

????????//?Check?for?cancelation.??

????????final?boolean?canceled?=?resetCancelNextUpFlag(this)??

????????????????||?actionMasked?==?MotionEvent.ACTION_CANCEL;??

??

????????//?Update?list?of?touch?targets?for?pointer?down,?if?needed.??

????????final?boolean?split?=?(mGroupFlags?&?FLAG_SPLIT_MOTION_EVENTS)?!=?0;??

????????TouchTarget?newTouchTarget?=?null;??

????????boolean?alreadyDispatchedToNewTouchTarget?=?false;??

????????if?(!canceled?&&?!intercepted)?{??

??

????????????//?If?the?event?is?targeting?accessiiblity?focus?we?give?it?to?the??

????????????//?view?that?has?accessibility?focus?and?if?it?does?not?handle?it??

????????????//?we?clear?the?flag?and?dispatch?the?event?to?all?children?as?usual.??

????????????//?We?are?looking?up?the?accessibility?focused?host?to?avoid?keeping??

????????????//?state?since?these?events?are?very?rare.??

????????????View?childWithAccessibilityFocus?=?ev.isTargetAccessibilityFocus()??

??????????????????????findChildWithAccessibilityFocus()?:?null;??

??

????????????if?(actionMasked?==?MotionEvent.ACTION_DOWN??

????????????????????||?(split?&&?actionMasked?==?MotionEvent.ACTION_POINTER_DOWN)??

????????????????????||?actionMasked?==?MotionEvent.ACTION_HOVER_MOVE)?{??

????????????????final?int?actionIndex?=?ev.getActionIndex();?//?always?0?for?down??

????????????????final?int?idBitsToAssign?=?split???1?<<?ev.getPointerId(actionIndex)??

????????????????????????:?TouchTarget.ALL_POINTER_IDS;??

??

????????????????//?Clean?up?earlier?touch?targets?for?this?pointer?id?in?case?they??

????????????????//?have?become?out?of?sync.??

????????????????removePointersFromTouchTargets(idBitsToAssign);??

??

????????????????final?int?childrenCount?=?mChildrenCount;??

????????????????if?(newTouchTarget?==?null?&&?childrenCount?!=?0)?{??

????????????????????final?float?x?=?ev.getX(actionIndex);??

????????????????????final?float?y?=?ev.getY(actionIndex);??

????????????????????//?Find?a?child?that?can?receive?the?event.??

????????????????????//?Scan?children?from?front?to?back.??

????????????????????final?ArrayList<View>?preorderedList?=?buildOrderedChildList();??

????????????????????final?boolean?customOrder?=?preorderedList?==?null??

????????????????????????????&&?isChildrenDrawingOrderEnabled();??

????????????????????final?View[]?children?=?mChildren;??

????????????????????for?(int?i?=?childrenCount?-?1;?i?>=?0;?i--)?{??

????????????????????????final?int?childIndex?=?customOrder??

??????????????????????????????????getChildDrawingOrder(childrenCount,?i)?:?i;??

????????????????????????final?View?child?=?(preorderedList?==?null)??

??????????????????????????????????children[childIndex]?:?preorderedList.get(childIndex);??

??

????????????????????????//?If?there?is?a?view?that?has?accessibility?focus?we?want?it??

????????????????????????//?to?get?the?event?first?and?if?not?handled?we?will?perform?a??

????????????????????????//?normal?dispatch.?We?may?do?a?double?iteration?but?this?is??

????????????????????????//?safer?given?the?timeframe.??

????????????????????????if?(childWithAccessibilityFocus?!=?null)?{??

????????????????????????????if?(childWithAccessibilityFocus?!=?child)?{??

????????????????????????????????continue;??

????????????????????????????}??

????????????????????????????childWithAccessibilityFocus?=?null;??

????????????????????????????i?=?childrenCount?-?1;??

????????????????????????}??

??

????????????????????????if?(!canViewReceivePointerEvents(child)??

????????????????????????????????||?!isTransformedTouchPointInView(x,?y,?child,?null))?{??

????????????????????????????ev.setTargetAccessibilityFocus(false);??

????????????????????????????continue;??

????????????????????????}??

??

????????????????????????newTouchTarget?=?getTouchTarget(child);??

????????????????????????if?(newTouchTarget?!=?null)?{??

????????????????????????????//?Child?is?already?receiving?touch?within?its?bounds.??

????????????????????????????//?Give?it?the?new?pointer?in?addition?to?the?ones?it?is?handling.??

????????????????????????????newTouchTarget.pointerIdBits?|=?idBitsToAssign;??

????????????????????????????break;??

????????????????????????}??

??

????????????????????????resetCancelNextUpFlag(child);??

????????????????????????if?(dispatchTransformedTouchEvent(ev,?false,?child,?idBitsToAssign))?{??

????????????????????????????//?Child?wants?to?receive?touch?within?its?bounds.??

????????????????????????????mLastTouchDownTime?=?ev.getDownTime();??

????????????????????????????if?(preorderedList?!=?null)?{??

????????????????????????????????//?childIndex?points?into?presorted?list,?find?original?index??

????????????????????????????????for?(int?j?=?0;?j?<?childrenCount;?j++)?{??

????????????????????????????????????if?(children[childIndex]?==?mChildren[j])?{??

????????????????????????????????????????mLastTouchDownIndex?=?j;??

????????????????????????????????????????break;??

????????????????????????????????????}??

????????????????????????????????}??

????????????????????????????}?else?{??

????????????????????????????????mLastTouchDownIndex?=?childIndex;??

????????????????????????????}??

????????????????????????????mLastTouchDownX?=?ev.getX();??

????????????????????????????mLastTouchDownY?=?ev.getY();??

????????????????????????????newTouchTarget?=?addTouchTarget(child,?idBitsToAssign);??

????????????????????????????alreadyDispatchedToNewTouchTarget?=?true;??

????????????????????????????break;??

????????????????????????}??

??

????????????????????????//?The?accessibility?focus?didn't?handle?the?event,?so?clear??

????????????????????????//?the?flag?and?do?a?normal?dispatch?to?all?children.??

????????????????????????ev.setTargetAccessibilityFocus(false);??

????????????????????}??

????????????????????if?(preorderedList?!=?null)?preorderedList.clear();??

????????????????}??

??

????????????????if?(newTouchTarget?==?null?&&?mFirstTouchTarget?!=?null)?{??

????????????????????//?Did?not?find?a?child?to?receive?the?event.??

????????????????????//?Assign?the?pointer?to?the?least?recently?added?target.??

????????????????????newTouchTarget?=?mFirstTouchTarget;??

????????????????????while?(newTouchTarget.next?!=?null)?{??

????????????????????????newTouchTarget?=?newTouchTarget.next;??

????????????????????}??

????????????????????newTouchTarget.pointerIdBits?|=?idBitsToAssign;??

????????????????}??

????????????}??

????????}??

??

????????//?Dispatch?to?touch?targets.??

????????if?(mFirstTouchTarget?==?null)?{??

????????????//?No?touch?targets?so?treat?this?as?an?ordinary?view.??

????????????handled?=?dispatchTransformedTouchEvent(ev,?canceled,?null,??

????????????????????TouchTarget.ALL_POINTER_IDS);??

????????}?else?{??

????????????//?Dispatch?to?touch?targets,?excluding?the?new?touch?target?if?we?already??

????????????//?dispatched?to?it.??Cancel?touch?targets?if?necessary.??

????????????TouchTarget?predecessor?=?null;??

????????????TouchTarget?target?=?mFirstTouchTarget;??

????????????while?(target?!=?null)?{??

????????????????final?TouchTarget?next?=?target.next;??

????????????????if?(alreadyDispatchedToNewTouchTarget?&&?target?==?newTouchTarget)?{??

????????????????????handled?=?true;??

????????????????}?else?{??

????????????????????final?boolean?cancelChild?=?resetCancelNextUpFlag(target.child)??

????????????????????????????||?intercepted;??

????????????????????if?(dispatchTransformedTouchEvent(ev,?cancelChild,??

????????????????????????????target.child,?target.pointerIdBits))?{??

????????????????????????handled?=?true;??

????????????????????}??

????????????????????if?(cancelChild)?{??

????????????????????????if?(predecessor?==?null)?{??

????????????????????????????mFirstTouchTarget?=?next;??

????????????????????????}?else?{??

????????????????????????????predecessor.next?=?next;??

????????????????????????}??

????????????????????????target.recycle();??

????????????????????????target?=?next;??

????????????????????????continue;??

????????????????????}??

????????????????}??

????????????????predecessor?=?target;??

????????????????target?=?next;??

????????????}??

????????}??

??

????????//?Update?list?of?touch?targets?for?pointer?up?or?cancel,?if?needed.??

????????if?(canceled??

????????????????||?actionMasked?==?MotionEvent.ACTION_UP??

????????????????||?actionMasked?==?MotionEvent.ACTION_HOVER_MOVE)?{??

????????????resetTouchState();??

????????}?else?if?(split?&&?actionMasked?==?MotionEvent.ACTION_POINTER_UP)?{??

????????????final?int?actionIndex?=?ev.getActionIndex();??

????????????final?int?idBitsToRemove?=?1?<<?ev.getPointerId(actionIndex);??

????????????removePointersFromTouchTargets(idBitsToRemove);??

????????}??

????}??

??

????if?(!handled?&&?mInputEventConsistencyVerifier?!=?null)?{??

????????mInputEventConsistencyVerifier.onUnhandledEvent(ev,?1);??

????}??

????return?handled;??

}??

代碼有點多，通過調(diào)試可知將會調(diào)用dispatchTransformedTouchEvent，查看代碼如下：

ViewGroup.java

[java] view plaincopy

/**?

?*?Transforms?a?motion?event?into?the?coordinate?space?of?a?particular?child?view,?

?*?filters?out?irrelevant?pointer?ids,?and?overrides?its?action?if?necessary.?

?*?If?child?is?null,?assumes?the?MotionEvent?will?be?sent?to?this?ViewGroup?instead.?

?*/??

private?boolean?dispatchTransformedTouchEvent(MotionEvent?event,?boolean?cancel,??

????????View?child,?int?desiredPointerIdBits)?{??

????final?boolean?handled;??

??

????//?Canceling?motions?is?a?special?case.??We?don't?need?to?perform?any?transformations??

????//?or?filtering.??The?important?part?is?the?action,?not?the?contents.??

????final?int?oldAction?=?event.getAction();??

????if?(cancel?||?oldAction?==?MotionEvent.ACTION_CANCEL)?{??

????????event.setAction(MotionEvent.ACTION_CANCEL);??

????????if?(child?==?null)?{??

????????????handled?=?super.dispatchTouchEvent(event);??

????????}?else?{??

????????????handled?=?child.dispatchTouchEvent(event);??

????????}??

????????event.setAction(oldAction);??

????????return?handled;??

????}??

??

????//?Calculate?the?number?of?pointers?to?deliver.??

????final?int?oldPointerIdBits?=?event.getPointerIdBits();??

????final?int?newPointerIdBits?=?oldPointerIdBits?&?desiredPointerIdBits;??

??

????//?If?for?some?reason?we?ended?up?in?an?inconsistent?state?where?it?looks?like?we??

????//?might?produce?a?motion?event?with?no?pointers?in?it,?then?drop?the?event.??

????if?(newPointerIdBits?==?0)?{??

????????return?false;??

????}??

??

????//?If?the?number?of?pointers?is?the?same?and?we?don't?need?to?perform?any?fancy??

????//?irreversible?transformations,?then?we?can?reuse?the?motion?event?for?this??

????//?dispatch?as?long?as?we?are?careful?to?revert?any?changes?we?make.??

????//?Otherwise?we?need?to?make?a?copy.??

????final?MotionEvent?transformedEvent;??

????if?(newPointerIdBits?==?oldPointerIdBits)?{??

????????if?(child?==?null?||?child.hasIdentityMatrix())?{??

????????????if?(child?==?null)?{??

????????????????handled?=?super.dispatchTouchEvent(event);??

????????????}?else?{??

????????????????final?float?offsetX?=?mScrollX?-?child.mLeft;??

????????????????final?float?offsetY?=?mScrollY?-?child.mTop;??

????????????????event.offsetLocation(offsetX,?offsetY);??

??

????????????????handled?=?child.dispatchTouchEvent(event);??

??

????????????????event.offsetLocation(-offsetX,?-offsetY);??

????????????}??

????????????return?handled;??

????????}??

????????transformedEvent?=?MotionEvent.obtain(event);??

????}?else?{??

????????transformedEvent?=?event.split(newPointerIdBits);??

????}??

??

????//?Perform?any?necessary?transformations?and?dispatch.??

????if?(child?==?null)?{??

????????handled?=?super.dispatchTouchEvent(transformedEvent);??

????}?else?{??

????????final?float?offsetX?=?mScrollX?-?child.mLeft;??

????????final?float?offsetY?=?mScrollY?-?child.mTop;??

????????transformedEvent.offsetLocation(offsetX,?offsetY);??

????????if?(!?child.hasIdentityMatrix())?{??

????????????transformedEvent.transform(child.getInverseMatrix());??

????????}??

??

????????handled?=?child.dispatchTouchEvent(transformedEvent);??

????}??

??

????//?Done.??

????transformedEvent.recycle();??

????return?handled;??

}??

在該函數(shù)中調(diào)用了child.dispatchTouchEvent()，這里便走到了子View的dispatchTouchEvent中。子View也就是MyView，也就走到了TextView的dispathTouchEvent中，由于TextView并未重寫dispathTouchEvent，因而直接進(jìn)入View的dispatchTouchEvent中，代碼如下：

View.java

[java] view plaincopy

/**?

?*?Pass?the?touch?screen?motion?event?down?to?the?target?view,?or?this?

?*?view?if?it?is?the?target.?

?*?

?*?@param?event?The?motion?event?to?be?dispatched.?

?*?@return?True?if?the?event?was?handled?by?the?view,?false?otherwise.?

?*/??

public?boolean?dispatchTouchEvent(MotionEvent?event)?{??

????//?If?the?event?should?be?handled?by?accessibility?focus?first.??

????if?(event.isTargetAccessibilityFocus())?{??

????????//?We?don't?have?focus?or?no?virtual?descendant?has?it,?do?not?handle?the?event.??

????????if?(!isAccessibilityFocusedViewOrHost())?{??

????????????return?false;??

????????}??

????????//?We?have?focus?and?got?the?event,?then?use?normal?event?dispatch.??

????????event.setTargetAccessibilityFocus(false);??

????}??

??

????boolean?result?=?false;??

??

????if?(mInputEventConsistencyVerifier?!=?null)?{??

????????mInputEventConsistencyVerifier.onTouchEvent(event,?0);??

????}??

??

????final?int?actionMasked?=?event.getActionMasked();??

????if?(actionMasked?==?MotionEvent.ACTION_DOWN)?{??

????????//?Defensive?cleanup?for?new?gesture??

????????stopNestedScroll();??

????}??

??

????if?(onFilterTouchEventForSecurity(event))?{??

????????//noinspection?SimplifiableIfStatement??

????????ListenerInfo?li?=?mListenerInfo;??

????????if?(li?!=?null?&&?li.mOnTouchListener?!=?null??

????????????????&&?(mViewFlags?&?ENABLED_MASK)?==?ENABLED??

????????????????&&?li.mOnTouchListener.onTouch(this,?event))?{//在這里就調(diào)用了setOnTouchListener中的onTouch函數(shù)，如果有一個消費了，那么result=true??

????????????result?=?true;??

????????}??

??

????????if?(!result?&&?onTouchEvent(event))?{//當(dāng)上面的result為true時，子View的onTouchEvent便不會執(zhí)行了。??

????????????result?=?true;??

????????}??

????}??

??

????if?(!result?&&?mInputEventConsistencyVerifier?!=?null)?{??

????????mInputEventConsistencyVerifier.onUnhandledEvent(event,?0);??

????}??

??

????//?Clean?up?after?nested?scrolls?if?this?is?the?end?of?a?gesture;??

????//?also?cancel?it?if?we?tried?an?ACTION_DOWN?but?we?didn't?want?the?rest??

????//?of?the?gesture.??

????if?(actionMasked?==?MotionEvent.ACTION_UP?||??

????????????actionMasked?==?MotionEvent.ACTION_CANCEL?||??

????????????(actionMasked?==?MotionEvent.ACTION_DOWN?&&?!result))?{??

????????stopNestedScroll();??

????}??

??

????return?result;??

}??

在該函數(shù)中看到了在MainActivity中設(shè)置的setOnTouchListener對應(yīng)的Listener接口，當(dāng)setListener中的onTouch返回true時，MyView本身的onTouchEvent便不被調(diào)用。接下來看下View的onTouchEvent代碼：

View.java

[java] view plaincopy

public?boolean?onTouchEvent(MotionEvent?event)?{??

????????final?float?x?=?event.getX();??

????????final?float?y?=?event.getY();??

????????final?int?viewFlags?=?mViewFlags;??

????????final?int?action?=?event.getAction();??

??

????????if?((viewFlags?&?ENABLED_MASK)?==?DISABLED)?{??

????????????if?(action?==?MotionEvent.ACTION_UP?&&?(mPrivateFlags?&?PFLAG_PRESSED)?!=?0)?{??

????????????????setPressed(false);??

????????????}??

????????????//?A?disabled?view?that?is?clickable?still?consumes?the?touch??

????????????//?events,?it?just?doesn't?respond?to?them.??

????????????return?(((viewFlags?&?CLICKABLE)?==?CLICKABLE??

????????????????????||?(viewFlags?&?LONG_CLICKABLE)?==?LONG_CLICKABLE)??

????????????????????||?(viewFlags?&?CONTEXT_CLICKABLE)?==?CONTEXT_CLICKABLE);??

????????}??

??

????????if?(mTouchDelegate?!=?null)?{//一個View還可以設(shè)置TouchDelegate，也可以在TouchDelegate的onTouchEvent里面處理點擊事件??

????????????if?(mTouchDelegate.onTouchEvent(event))?{??

????????????????return?true;??

????????????}??

????????}??

??

????????if?(((viewFlags?&?CLICKABLE)?==?CLICKABLE?||??

????????????????(viewFlags?&?LONG_CLICKABLE)?==?LONG_CLICKABLE)?||??

????????????????(viewFlags?&?CONTEXT_CLICKABLE)?==?CONTEXT_CLICKABLE)?{??

????????????switch?(action)?{??

????????????????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;??

??

????????????????case?MotionEvent.ACTION_DOWN:??

????????????????????mHasPerformedLongPress?=?false;??

??

????????????????????if?(performButtonActionOnTouchDown(event))?{??

????????????????????????break;??

????????????????????}??

??

????????????????????//?Walk?up?the?hierarchy?to?determine?if?we're?inside?a?scrolling?container.??

????????????????????boolean?isInScrollingContainer?=?isInScrollingContainer();??

??

????????????????????//?For?views?inside?a?scrolling?container,?delay?the?pressed?feedback?for??

????????????????????//?a?short?period?in?case?this?is?a?scroll.??

????????????????????if?(isInScrollingContainer)?{??

????????????????????????mPrivateFlags?|=?PFLAG_PREPRESSED;??

????????????????????????if?(mPendingCheckForTap?==?null)?{??

????????????????????????????mPendingCheckForTap?=?new?CheckForTap();??

????????????????????????}??

????????????????????????mPendingCheckForTap.x?=?event.getX();??

????????????????????????mPendingCheckForTap.y?=?event.getY();??

[java] view plaincopy

//這個注意下，這里會調(diào)用ViewRootImpl內(nèi)部函數(shù)也就是后面的MOVE為啥知道前面DOWN了??

postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout()); } else { // Not inside a scrolling container, so show the feedback right away setPressed(true, x, y);

[java] view plaincopy

//這個去檢查是否有長按事件??

checkForLongClick(0); } break; case MotionEvent.ACTION_CANCEL: setPressed(false); removeTapCallback(); removeLongPressCallback(); mInContextButtonPress = false; mHasPerformedLongPress = false; mIgnoreNextUpEvent = false; break; case MotionEvent.ACTION_MOVE: drawableHotspotChanged(x, y); // Be lenient about moving outside of buttons if (!pointInView(x, y, mTouchSlop)) { // Outside button removeTapCallback(); if ((mPrivateFlags & PFLAG_PRESSED) != 0) { // Remove any future long press/tap checks removeLongPressCallback(); setPressed(false); } } break; } return true; } return false; }這里僅分析下DOWN事件的處理，這里會先處理按鈕自身的一些事件，具體事件見如下代碼：

[java] view plaincopy

/**?

?*?Performs?button-related?actions?during?a?touch?down?event.?

?*?

?*?@param?event?The?event.?

?*?@return?True?if?the?down?was?consumed.?

?*?

?*?@hide?

?*/??

protected?boolean?performButtonActionOnTouchDown(MotionEvent?event)?{??

????if?(event.getToolType(0)?==?MotionEvent.TOOL_TYPE_MOUSE?&&??

????????(event.getButtonState()?&?MotionEvent.BUTTON_SECONDARY)?!=?0)?{??

????????showContextMenu(event.getX(),?event.getY(),?event.getMetaState());??

????????mPrivateFlags?|=?PFLAG_CANCEL_NEXT_UP_EVENT;??

????????return?true;??

????}??

????return?false;??

}??

然后判斷當(dāng)前View的父View是否在滾動，如果不在滾動就調(diào)用postDelayed：

View.java

[java] view plaincopy

public?boolean?postDelayed(Runnable?action,?long?delayMillis)?{??

????final?AttachInfo?attachInfo?=?mAttachInfo;??

????if?(attachInfo?!=?null)?{??

????????return?attachInfo.mHandler.postDelayed(action,?delayMillis);??

????}??

????//?Assume?that?post?will?succeed?later??

????ViewRootImpl.getRunQueue().postDelayed(action,?delayMillis);??

????return?true;??

}??

將action延遲一段時間，用于后續(xù)判斷（是否長按事件，后續(xù)MOVE事件，UP事件）。

轉(zhuǎn)載于:https://www.cnblogs.com/Free-Thinker/p/8915919.html

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