DrawRect does not refresh the screen

Question

I have this code in the drawRect method

float aValue = .0167f; float fValue = 20; for(int i=1; i<=6; i++) { CGContextSelectFont(context, "Arial", fValue, kCGEncodingMacRoman); CGContextSetCharacterSpacing(context, 0); CGContextSetTextDrawingMode(context, kCGTextFill); NSString *hString = [[NSString alloc] initWithFormat:@"%i",i]; CGContextSetRGBFillColor(context, 1, 1, 1, aValue); CGContextShowTextAtPoint(context, i*25, i*16, [hString UTF8String], [hString length]); aValue += 0.167; fValue += 1; } 

I call a method using NSTimer like this

 staticTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(refreshUIView) userInfo:nil repeats:YES]; 

here is refreshUIView

 -(void)refreshUIView { [self setNeedsDisplay]; } 

The problem is that drawRect does not clear the screen; it just writes what was last written on the screen.

Answer 1

Call at the beginning of drawRect: after getting the context.

 CGContextClearRect( context , [self bounds] ); 

Or call [super drawRect:]; if clearsContextBeforeDrawing set.