UIView drawRect: when you draw a line, the rect area will be clear so the previous drawing is gone
- by snakewa
It is quite hard to tell so I upload an image to show my problem: http://i42.tinypic.com/2eezamo.jpg
Basically in drawRect, I will draw the line from touchesMoved as finger touches and I will call "needsDisplayInRect" for redraw. But I found that the first line is done, the second line will clear the rect part, so some previouse drawing is gone.
Here is my implementation:
enter code here
-(void) drawRect:(CGRect)rect{
//[super drawRect: rect];
CGContextRef context = UIGraphicsGetCurrentContext();
[self drawSquiggle:squiggle at:rect inContext:context];
}
- (void)drawSquiggle:(Squiggle *)squiggle at:(CGRect) rect inContext:(CGContextRef)context
{
CGContextSetBlendMode(context, kCGBlendModeMultiply);
UIColor *squiggleColor = squiggle.strokeColor; // get squiggle's color
CGColorRef colorRef = [squiggleColor CGColor]; // get the CGColor
CGContextSetStrokeColorWithColor(context, colorRef);
NSMutableArray *points = [squiggle points]; // get points from squiggle
// retrieve the NSValue object and store the value in firstPoint
CGPoint firstPoint; // declare a CGPoint
[[points objectAtIndex:0] getValue:&firstPoint];
// move to the point
CGContextMoveToPoint(context, firstPoint.x, firstPoint.y);
// draw a line from each point to the next in order
for (int i = 1; i < [points count]; i++)
{
NSValue *value = [points objectAtIndex:i]; // get the next value
CGPoint point; // declare a new point
[value getValue:&point]; // store the value in point
// draw a line to the new point
CGContextAddLineToPoint(context, point.x, point.y);
} // end for
CGContextStrokePath(context);
}
