An explanation of the Android event process

An explanation of the Android event process

There are many blogs on the web about the Android event distribution mechanism and processing mechanism, but seen times, always feel a little bit vaguely, so specifically to take out a day of events to pro-test, to like me, the vast number of entry programmers in detail about the story behind the Android event, say not much, on dry.

The entire Android event process is mainly involved in dispatchtouchevent (), Onintercepttouchevent (),

Ontouchevent () These three methods, the following table illustrates the functions and distribution scenarios of these three methods:

Table 1:

Method name	Explanation of work Solution	Activity	ViewGroup	View
Dispatchtouchevent ()	Event distribution	YES	YES	YES
Onintercepttouchevent ()	Event interception	NO	YES	NO
Ontouchevent ()	Event handling	YES	YES	YES

First analyze the touch event: When all touch events occur, the dispatchtouchevent () Party of the current activity is called

method to distribute the event, the activity's Dispatchtouchevent () method will eventually call the Phonewindow class

Superdispatchtouchevent method, the final logic is that the activity calls the ViewGroup class.

Dispatchtouchevent () for tunnel distribution events (distributed externally by layout elements), such as the distribution process in this case

For Touchtraining, Touchviewgroup, TouchView, it's important to note that when you're in Activit

Dispatchtouchevent () directly returns the specific Boolean value (either True or false), the touch event is directly

Consumption in this method, the event distribution process will not be carried out again, so must be in the activity of the Dispatchtouchevrent

Returns Super.dispatchtouchevent () for the event distribution process. The following example illustrates the analysis:

First in defining your own view and viewgroup, rewrite table 1 the event flow methods that they each support, and I'll customize the viewgroup here

Inherit the LinearLayout (as long as you inherit the same viewgroup), and then add the custom in the activity's layout file, respectively

The event flow method that it supports in the activity.

Activity_touchtrain.xml

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TouchView (Custom view Class)

@Overridepublic boolean dispatchtouchevent (Motionevent event) {LOG.E (TAG, "Dispatchtouchevent distribution Event" +    Toucheventutil.gettouchaction (Event.getaction ())); Return Super.dispatchtouchevent (event);} @Overridepublic boolean ontouchevent (motionevent ev) {LOG.E (TAG, "ontouchevent handling Event" + toucheventutil.gettouchaction (    Ev.getaction ())); return super.ontouchevent (EV);}

Touchviewgroup (Custom ViewGroup Class)

@Overridepublic boolean dispatchtouchevent (motionevent ev) {LOG.E (TAG, "Dispatchtouchevent distribution event" + Toucheventutil.gett    Ouchaction (Ev.getaction ())); return super.dispatchtouchevent (EV);} @Overridepublic boolean onintercepttouchevent (motionevent ev) {LOG.E (TAG, "onintercepttouchevent intercept event" +    Toucheventutil.gettouchaction (Ev.getaction ())); return super.onintercepttouchevent (EV);} @Overridepublic boolean ontouchevent (motionevent ev) {LOG.E (TAG, "ontouchevent handling Event" + toucheventutil.gettouchaction (    Ev.getaction ())); return super.ontouchevent (EV);}

Touchtraining (Activity)

@Overridepublic boolean dispatchtouchevent (motionevent ev) {LOG.E (TAG, "Dispatchtouchevent distribution Event" +    Toucheventutil.gettouchaction (Ev.getaction ())); return super.dispatchtouchevent (EV);} @Overridepublic boolean ontouchevent (motionevent ev) {LOG.E (TAG, "ontouchevent handling Event" + toucheventutil.gettouchaction (    Ev.getaction ())); return super.ontouchevent (EV);}

Toucheventutils (tool class, getting the current event type)

Public static string gettouchaction (Int actionid)  {    string  actionName =  "unknow:id="  + actionId;    switch  (ActionId)  {        case MotionEvent.ACTION_DOWN:             actionName =  "Action_down";             break;         case motionevent.action_move:             actionname =  "Action_move";             break;        case motionevent.action_up:             actionName =  "Action_up";              break;        case motionevent.action_cancel:             actionName =  "Action_cancel" ;            break;         case MotionEvent.ACTION_OUTSIDE:             actionName =  "Action_outside";             break;    }    return actionname;}

Case analysis

Scenario 1

Conditions
Control Name	Dispatchtouchevent return value	Onintercepttouchevent return value	Ontouchevent return value
Touchtraining	Super.dispatchtouchevent (EV)	----	Super.ontouchevent (EV)
Touchviewgroup	False	Super.onintercepttouchevent (EV)	Super.ontouchevent (EV)
TouchView	Super.dispatchtouchevent (EV)	----	Super.ontouchevent (EV)

Operation Result:

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining E/touchviewgroup:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining e/touchtraining:ontouchevent Handling Event Action_down

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_up

Com.training.cj.mytraining e/touchtraining:ontouchevent Handling Event Action_up

Result Analysis: The touch event begins, calling Touchtraining's dispatchtouchevent to distribute the event Touchviewgroup

The Dispatchtouchevent,touchviewgroup Dispatchtouchevent returns false, the event stops passing down, the same

When the event is not consumed, it is returned to Touchtraining because the event is from Touchtraining (Activity)

Ontouchevent for consumption.

Scenario 2

Conditions
Control Name	Dispatchtouchevent return value	Onintercepttouchevent return value	Ontouchevent return value
Touchtraining	Super.dispatchtouchevent (EV)	----	Super.ontouchevent (EV)
Touchviewgroup	True	Super.onintercepttouchevent (EV)	Super.ontouchevent (EV)
TouchView	Super.dispatchtouchevent (EV)	----	Super.ontouchevent (EV)

Operation Result:

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining E/touchviewgroup:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_up

Com.training.cj.mytraining E/touchviewgroup:dispatchtouchevent Distributing Events Action_up

Results analysis: The touch event was continuously distributed to Touchviewgroup by Touchtraining's dispatchtouchevent,

Touchviewgroup's dispatchtouchevent return True,touchviewgroup in Dispatchtouchevent

Fees from Touchtraining's dispatchtouchevent distribution of events.

Scenario 3

Conditions
Control Name	Dispatchtouchevent return value	Onintercepttouchevent return value	Ontouchevent return value
Touchtraining	Super.dispatchtouchevent (EV)	----	Super.ontouchevent (EV)
Touchviewgroup	Super.onintercepttouchevent (EV)	True	Super.ontouchevent (EV)
TouchView	Super.dispatchtouchevent (EV)	----	Super.ontouchevent (EV)

Operation Result:

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining E/touchviewgroup:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining e/touchviewgroup:onintercepttouchevent Intercept Event Action_down

Com.training.cj.mytraining e/touchviewgroup:ontouchevent Handling Event Action_down

Com.training.cj.mytraining e/touchtraining:ontouchevent Handling Event Action_down

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_up

Com.training.cj.mytraining e/touchtraining:ontouchevent Handling Event Action_up

Result Analysis: Touch event occurs, call Touchtraining dispatchtouchevent distribution event to Touchviewgroup

The dispatchtouchevent of the Dispatchtouchevent,touchviewgroup return super.onintercepttouchevent (EV) into

The row event is distributed, and the event is passed down to Touchviewgroup's Onintercepttouchevent,touchviewgroup onintercepttouchevent returns True, The event was intercepted and passed on to Touchviewgroup's ontouchevent for consumption, Touchviewgroup's ontouchevent returned to Super.dispatchtouchevent (EV), The ontouchevent that the touch event was not consumed and returned to the parent control was consumed because Touchviewgroup's touch event came from Touchtraining, so the last Consumed by the ontouchevent of Touchtraining.

Scenario 4

condition
control name	dispatchtouchevent return value	onintercepttouchevent return value	ontouchevent return value
touchtraining	super.dispatchtouchevent (EV)	----	super.ontouchevent (EV)
Tou Chviewgroup	super.onintercepttouchevent (EV)	false	super.ontouchevent (EV)
TouchView	super.dispatchtouchevent (EV) /td>	----	super.ontouchevent (EV)

Operation Result:

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining E/touchviewgroup:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining e/touchviewgroup:onintercepttouchevent Intercept Event Action_down

Com.training.cj.mytraining E/touchview:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining e/touchview:ontouchevent Handling Event Action_down

Com.training.cj.mytraining e/touchviewgroup:ontouchevent Handling Event Action_down

Com.training.cj.mytraining e/touchtraining:ontouchevent Handling Event Action_down

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_up

Com.training.cj.mytraining e/touchtraining:ontouchevent Handling Event Action_up

Result Analysis: Touch event occurred, call touchtraining dispatchtouchevent distribution event to Touchviewgroup Dispatchtouchevent, Touchviewgroup's dispatchtouchevent returns to Super.onintercepttouchevent (EV), Continue distributing down passing events to Touchviewgroup's Onintercepttouchevent,touchviewgroup Onintercepttouchevent returns false, Continue distributing the Dispatchtouchevent return super.dispatchtouchevent (EV) of the Dispatchtouchevent,touchview that passed the event down to Touchview, Continuing to distribute the Ontouchevent return super.ontouchevent (EV) of the Ontouchevent,touchview that passed the event down to Touchview, the event is not consumed, Returned to the higher Touchviewgroup ontouchevent for consumption, touchviewgroup

Ontouchevent returns to Super.ontouchevent (EV) and continues to return to the ontouchevent of the upper touchtraining for consumption.

Scenario 5:

Conditions
Control Name	Dispatchtouchevent return value	Onintercepttouchevent return value	Ontouchevent return value
Touchtraining	Super.dispatchtouchevent (EV)	----	Super.ontouchevent (EV)
Touchviewgroup	Super.onintercepttouchevent (EV)	False	Super.ontouchevent (EV)
TouchView	True	----	Super.ontouchevent (EV)

Operation Result:

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining E/touchviewgroup:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining e/touchviewgroup:onintercepttouchevent Intercept Event Action_down

Com.training.cj.mytraining E/touchview:dispatchtouchevent Distributing Events Action_down

Com.training.cj.mytraining e/touchview:ontouchevent Handling Event Action_down

Com.training.cj.mytraining E/touchtraining:dispatchtouchevent Distributing Events Action_up

Com.training.cj.mytraining E/touchviewgroup:dispatchtouchevent Distributing Events Action_up

Com.training.cj.mytraining e/touchviewgroup:onintercepttouchevent Intercept Event action_up

Com.training.cj.mytraining E/touchview:dispatchtouchevent Distributing Events Action_up

Com.training.cj.mytraining e/touchview:ontouchevent Handling Event Action_up

Result Analysis: Touch event occurred, call touchtraining dispatchtouchevent distribution event to Touchviewgroup Dispatchtouchevent, The method returns Super.dispatchtouchevent (EV), continuing to distribute the event to Touchviewgroup's Onintercepttouchevent, which returns false, Continue distributing events to Touchview Dispatchtouchevent, the method returns Super.dispatchtouchevent (EV), continuing to distribute events to ontouchevent, because Ontouchevent returns true , which indicates a consumption event, and the touch event terminates.

Well, the touch event analysis for this issue is over here, and there's a little detail to note that the Ontouchevent method in view and view group is returned by default False,view The onintercepttouchevent in group also returns false by default. So the above 5 scenarios describe all of the touch event delivery possibilities. Understanding the distribution and consumption mechanisms of the touch event is better for our custom controls, although we should try not to rewrite the Dispatchtouchevent method when customizing the control.

This post reference blog: http://www.cnblogs.com/sunzn/archive/2013/05/10/3064129.html

This article is from the "Programmer's Life" blog, be sure to keep this source http://geektraining.blog.51cto.com/10814565/1706173

An explanation of the Android event process