java - Why OnTouchListener is not set for me? -

i working on custom view called canvasview. view allows me draw stuff on outside of ondraw method. this:

public class canvasview extends view {     private arraylist<shape> shapes;     private paint paint;      public canvasview (context c) {         super(c);         init ();     }      public canvasview(context context, attributeset attrs) {         super (context, attrs);         init ();     }      public canvasview(context context, attributeset attrs, int defstyleattr) {         super (context, attrs, defstyleattr);         init ();     }     private void init () {         shapes = new arraylist<> ();         paint = new paint ();         paint.setstrokewidth (5);         paint.setcolor (color.black);     }      //focus on method, think others irrelevant     @override     public void setontouchlistener (final ontouchlistener listener) {         final ontouchlistener baselistener = new ontouchlistener () {             @override             public boolean ontouch(view v, motionevent event) {                 float x = event.getx ();                 float y = event.gety ();                 if (x < 18 || x > getwidth () - 18 || y < 18 ||                         y > getheight () - 18)                     return false;                  return true;             }         };          super.setontouchlistener (new ontouchlistener () {             @override             public boolean ontouch(view v, motionevent event) {                 if (baselistener.ontouch (v, event)) {                     if (listener != null) {                         return listener.ontouch (v, event);                     } else {                         return true;                     }                 }                 return false;             }         });     }      @override     protected void ondraw (canvas c) {         super.ondraw (c);         (shape s : shapes) {             s.draw (c);         }         //draw border. irrelevant         c.drawline (3, 3, getwidth () - 3, 3, paint);         c.drawline (3, getheight () - 3, getwidth () - 3, getheight () - 3, paint);         c.drawline (3, 3, 3, getheight () - 3, paint);         c.drawline (getwidth () - 3, 3, getwidth () - 3, getheight () - 3, paint);          //draw inner border         c.drawline (18, 18, getwidth () - 18, 18, paint);         c.drawline (18, getheight () - 18, getwidth () - 18, getheight () - 18, paint);         c.drawline (18, 18, 18, getheight () - 18, paint);         c.drawline (getwidth () - 18, 18, getwidth () - 18, getheight () - 18, paint);     }      public void addshape (shape s) {         shapes.add (s);     }      public void clear () {         shapes.clear ();     } } 

explanation:

shape interface method:

public void draw (canvas c); 

focus on setontouchlistener override. overrode method because want limit user not touch borders of canvasview. can see, first invoke baselistener check whether touch in bounds. , invoke listener passed in constructor. practice?

anyway, set ontouchlistener of canvasview in oncreate method:

canvas.setontouchlistener (new view.ontouchlistener () {         @override         public boolean ontouch(view v, final motionevent event) {             if (point1 != null && point2 != null) {                 throw new illegalstateexception ("both point1 , point2 not null");             }              if (point1 == null) {                 point1 = new pointf (event.getx (), event.gety ());             } else { //point2 null                 point2 = new pointf (event.getx (), event.gety ());                 canvas.addshape (new shape () {                     @override                     public void draw(canvas c) {                         c.drawline (point1.x, point1.y, point2.x, point2.y, paint);                     }                 });                 canvas.setontouchlistener (null);             }              canvas.addshape (new shape () {                 @override                 public void draw(canvas c) {                     c.drawcircle (event.getx (), event.gety (), 13, paint);                 }             });              return true;         }     }); 

explanation:

point1 , point2 fields declared in activity class. when user touches screen, 1 of them instantiated , little circle drawn @ point. when user touches second time, point2 instantiated , line drawn between 2 points.

when run app , touch screen, nothing drawn! think setonclicklistener override not written correctly. can tell me why?

the ondraw method of view called when view first created. cause called again, need mark view “dirty” (changes have been made) using invalidate() function on view, every time contents of view change.

thus, convenient place call function after adding shape view in addshape function.

 public void addshape (shape s) {         shapes.add (s);         this.invalidate();     }