Android event distribution (6) -- ACTION_DOWN consumption Verification

Android event distribution (6) -- ACTION_DOWN consumption Verification
MainActivity is as follows:

Package cn. c; import android. OS. bundle; import android. app. activity; import android. view. motionEvent;/*** Demo Description: * analyzes the Android event distribution and processing mechanism **. In this example, three custom views are involved. they are: * The layout of the outermost layer MyFrameLayout * the layout of the inner layer MyLinearLayout * The Custom button MyButton of the innermost layer ** mentioned a very important thing in the dispatchTouchEvent () source code analysis: * If a View does not process the ACTION_DOWN event, that is, false is returned for the event (the event is not consumed) * Subsequent ACTION_MOVE and ACTION_UP operations will not be passed to the View; that is to say, this View does not have * the qualification to process ACTION_MOVE and ACTION_UP. * This issue is verified here. * ** in the onTouchEvent () method of MyButton, false is directly returned. * Then we can see that MyButton only processes ACTION_DOWN. * Similarly, MyFrameLayout and MyLinearLayout directly return false for Touch events; they cannot process * ACTION_MOVE and ACTION_UP **/public class MainActivity extends Activity {@ Override public void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. main); System. out. println (==> MainActivity calls onCreate (); System. out. println (------------------------------------------------);} @ Override public boolean dispatchTouchEvent (MotionEvent ev) {System. out. println (==> MainActivity calls dispatchTouchEvent (); System. out. println (==> super. dispatchTouchEvent () returns true by default); System. out. println (--------------------------------------------------); return super. dispatchTouchEvent (ev) ;}@ Overridepublic void onUserInteraction () {System. out. println (==> MainActivity calls onUserInteraction (); System. out. println (--------------------------------------------------); super. onUserInteraction () ;}@ Overridepublic boolean onTouchEvent (MotionEvent event) {switch (event. getAction () {case MotionEvent. ACTION_DOWN: System. out. println (==> MainActivity calls onTouchEvent () ---> ACTION_DOWN); break; case MotionEvent. ACTION_MOVE: System. out. println (==> MainActivity calls onTouchEvent () ---> ACTION_MOVE); break; case MotionEvent. ACTION_UP: System. out. println (==> MainActivity calls onTouchEvent () ---> ACTION_UP); default: break;} System. out. println (super. onTouchEvent () returns false by default, indicating that the event is not consumed); System. out. println (--------------------------------------------------); return super. onTouchEvent (event );}}

MyFrameLayout is as follows:

Package cn. c; import android. content. context; import android. util. attributeSet; import android. view. motionEvent; import android. widget. frameLayout; public class extends FrameLayout {public MyFrameLayout (Context context, AttributeSet attrs) {super (context, attrs);} @ Overridepublic boolean dispatchTouchEvent (MotionEvent ev) {super. dispatchTouchEvent (ev); System. out. println (the dispatchTouchEvent () is called in the outer MyFrameLayout; System. out. println (super. dispatchTouchEvent () returns true by default to continue distribution); System. out. println (--------------------------------------------------); return super. dispatchTouchEvent (ev); // return false;} // overwrite from ViewGroup @ Overridepublic boolean onInterceptTouchEvent (MotionEvent ev) {System. out. println (calling onInterceptTouchEvent () in the outer MyFrameLayout); System. out. println (super. onInterceptTouchEvent () returns false by default to prevent interception); System. out. println (--------------------------------------------------); return super. onInterceptTouchEvent (ev);} // Note: // 1 ViewGroup is a subclass of View // The onTouchEvent () method in 2 ViewGroup returns false @ Overridepublic boolean onTouchEvent (MotionEvent event) by default) {super. onTouchEvent (event); switch (event. getAction () {case MotionEvent. ACTION_DOWN: System. out. println (calling onTouchEvent () ---> ACTION_DOWN) in the outer MyFrameLayout; break; case MotionEvent. ACTION_MOVE: System. out. println (the outer MyFrameLayout calls onTouchEvent () ---> ACTION_MOVE); break; case MotionEvent. ACTION_UP: System. out. println (calling onTouchEvent () ---> ACTION_UP in the outer MyFrameLayout); default: break;} System. out. println (super. onTouchEvent () returns false by default, indicating that the event is not consumed); System. out. println (--------------------------------------------------); return super. onTouchEvent (event); // return true ;}}

 

MyLinearLayout is as follows:

Package cn. c; import android. content. context; import android. util. attributeSet; import android. view. motionEvent; import android. widget. linearLayout; public class MyLinearLayout extends LinearLayout {public MyLinearLayout (Context context, AttributeSet attrs) {super (context, attrs) ;}@ Overridepublic boolean dispatchTouchEvent (MotionEvent ev. dispatchTouchEvent (ev); System. out. println (calls dispatchTouchEvent () in the inner MyLinearLayout); System. out. println (super. dispatchTouchEvent () returns true by default to continue distribution); System. out. println (--------------------------------------------------); return super. dispatchTouchEvent (ev); // return false;} // overwrite from ViewGroup @ Overridepublic boolean onInterceptTouchEvent (MotionEvent ev) {super. onInterceptTouchEvent (ev); System. out. println (calls onInterceptTouchEvent () in the inner MyLinearLayout); System. out. println (super. onInterceptTouchEvent () returns false by default to prevent interception); System. out. println (--------------------------------------------------); return super. onInterceptTouchEvent (ev);} // Note: // 1 ViewGroup is a subclass of View // The onTouchEvent () method in 2 ViewGroup returns false @ Overridepublic boolean onTouchEvent (MotionEvent event) by default) {switch (event. getAction () {case MotionEvent. ACTION_DOWN: System. out. println (calls onTouchEvent () ---> ACTION_DOWN in the inner MyLinearLayout); break; case MotionEvent. ACTION_MOVE: System. out. println (calls onTouchEvent () ---> ACTION_MOVE in the inner MyLinearLayout); break; case MotionEvent. ACTION_UP: System. out. println (calls onTouchEvent () ---> ACTION_UP in the inner MyLinearLayout); default: break;} System. out. println (super. onTouchEvent () returns false by default, indicating that the event is not consumed); System. out. println (--------------------------------------------------); return super. onTouchEvent (event );}}

 

MyButton is as follows:

Package cn. c; import android. content. context; import android. util. attributeSet; import android. view. motionEvent; import android. widget. button; public class MyButton extends Button {public MyButton (Context context, AttributeSet attrs) {super (context, attrs) ;}@ Overridepublic boolean dispatchTouchEvent (MotionEvent event) {System. out. println (call dispatchTouchEvent () in the Custom Button); System. out. println (super. dispatchTouchEvent returns true by default); System. out. println (--------------------------------------------------); return super. dispatchTouchEvent (event);} @ Overridepublic boolean onTouchEvent (MotionEvent event) {switch (event. getAction () {case MotionEvent. ACTION_DOWN: System. out. println (call onTouchEvent () ---> ACTION_DOWN); break; case MotionEvent in the Custom Button. ACTION_MOVE: System. out. println (call onTouchEvent () ---> ACTION_MOVE); break; case MotionEvent in the Custom Button. ACTION_UP: System. out. println (call onTouchEvent () ---> ACTION_UP); break; default: break;} System. out. println (--------------------------------------------------); // return false; return true ;}}

     
     
   
    
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