Example Analysis of onInterceptTouchEvent, onTouchEvent and onTouch in android Development
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1. OnTouch
OnTouch is a method in the OnTouchListener interface of View that handles events in which View and its subclasses are handled by touch. Of course, the premise is that the touch time can be passed to the specified view. Q1: why can't it be delivered?
/ * * Interface definition for a callback to be invoked when a touch event is * dispatched to this view. The callback will be invoked before the touch * event is given to the view. * / public interface OnTouchListener {/ * * Called when a touch event is dispatched to a view. This allows listeners to * get a chance to respond before the target view. * * @ param v The view the touch event has been dispatched to. * @ param event The MotionEvent object containing full information about * the event. * @ return True if the listener has consumed the event, false otherwise. * / boolean onTouch (View v, MotionEvent event);}
II. OnTouchEvent
OnTouchEvent is also a method defined in view. Handles gesture events passed to view. The types of gesture events include four types of ACTION_DOWN,ACTION_MOVE,ACTION_UP,ACTION_ call events.
/ * Implement this method to handle touch screen motion events. * * @ param event The motion event. * @ return True if the event was handled, false otherwise. * / public boolean onTouchEvent (MotionEvent event) {. …… }
Once the onTouchEvent method is called and returns true, the gesture event ends and is not passed down to the child control. When will Q2:onTouchEvent be called?
III. OnInterceptTouchEvent
OnInterceptTouchEvent is defined in ViewGroup. The layout layout class in Android generally inherits this class. OnInterceptTouchEvent is used to intercept gesture events, and each gesture event calls onInterceptTouchEvent first.
Public boolean onInterceptTouchEvent (MotionEvent ev) {return false;}
If this method returns false, the gesture event is passed to the child control; if true is returned, the onTouchEvent method is called.
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