I want to draw line between 2 points. But UIGraphicsGetCurrentContext() is return null
ViewController.m
self.drawLine.firstPoint = self.btnPointOne.bounds.origin;
self.drawLine.secondPoint = self.btnPointTwo.bounds.origin;
[self.drawLine drawRect:self.drawWatchModeView.bounds];
DrawLine.h
@interface DrawLine : UIView{
CGContextRef context;
}
@property (assign, nonatomic) CGPoint firstPoint;
@property (assign, nonatomic) CGPoint secondPoint;
DrawLine.m
- (id)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
}
return self;
}
- (void)drawRect:(CGRect)rect {
context = UIGraphicsGetCurrentContext();
// Drawing code
CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
//line width
CGContextSetLineWidth(context, 1.0);
CGContextMoveToPoint(context, self.firstPoint.x, self.firstPoint.y);
CGContextAddLineToPoint(context, self.secondPoint.x, self.secondPoint.y);
// and now draw the Path!
CGContextStrokePath(context);
}
But it error
CGContextSetStrokeColorWithColor: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextSetLineWidth: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextMoveToPoint: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextAddLineToPoint: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextDrawPath: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextSetStrokeColorWithColor: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextSetLineWidth: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextMoveToPoint: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextAddLineToPoint: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextDrawPath: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextSetStrokeColorWithColor: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextSetLineWidth: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextMoveToPoint: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextAddLineToPoint: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextDrawPath: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextSetStrokeColorWithColor: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextSetLineWidth: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextMoveToPoint: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextAddLineToPoint: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
CGContextDrawPath: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
I try to UIViewControllerBasedStatusBarAppearance
set YES
it not work for me I try to remove UIViewControllerBasedStatusBarAppearance
it not work for me
You can't just call drawRect:
whenever you want, so your line:
[self.drawLine drawRect:self.drawWatchModeView.bounds];
needs to change to ask the OS to run a draw cycle. When that happens the drawing context will be setup and everything will be ready. When you run it explicitly that context doesn't exist. So, change that line to:
[self.drawLine setNeedsDisplay];
or
[self.drawLine setNeedsDisplayInRect:self.drawWatchModeView.bounds];
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