android - Switching activities gives me a null pointer exception -

code switch activities:

intent myintent=new intent(context,timezones.class); context.startactivity(myintent); 

once part of code has been hit, null pointer exception here (specifically 2nd line):

protected void ondraw(canvas canvas) { canvas.drawcolor(color.white); } 

i tried adding boolean stop canvas drawing anything:

intent myintent=new intent(context,timezones.class); context.startactivity(myintent); dontdraw = true;   protected void ondraw(canvas canvas) {     if (dontdraw == false)     {         canvas.drawcolor(color.white);     } } 

using boolean, activity timezones runs, frozen.

thanks in advance!