android - Using clipRect - explanation -

public class pocii extends activity {       myview mv = new myview(this);       @override      public void oncreate(bundle savedinstancestate) {          super.oncreate(savedinstancestate);          setcontentview(mv);      } }   class myview extends view {       public myview(context context) {         super(context);      }       @override      public void ondraw(canvas canvas) {           paint paint = new paint();           canvas.drawrect(0,0,100,100, paint);          canvas.cliprect(0,0,50,50);     }  } 

my question is, shouldn't above code draw rectangle , crop top left portion? rectangle not getting cropped.

please explain cliprect does. clipping? clip in form of rectangle, given co-ordinates? if so, why above code not working?

canvas.cliprect(left, top, right, bottom) reduces region of screen future draw operations can write to. sets clipbounds spacial intersection of current clipping rectangle , rectangle specified. there lot of variants of cliprect method accept different forms regions , allow different operations on clipping rectangle. if want explicitly set clipping region, try:

canvas.cliprect(left, top, right, bottom, region.op.replace); 

the 5th argument means replace clipping rectangle rather creating intersection previous version.

try moving cliprect statement before drawrect statement. or, try adding:

paint.setcolor(color.yellow); drawrect(0,0,75,75); 

after existing cliprect statement. should draw 50x50 yellow square on had before.

another note: (after long frustration apparently, largely undocumented view/viewgroup/drawing code) found canvas.translate(x,y) adjusts cliprect. interaction of cliprect , drawing matrix confusing. helpful print out:

canvas.getmatrix() 

and

canvas.getclipbounds() 

before , after modifications canvas , before drawing things.