Iphone CGContextFilllellipseInRect:无效的上下文

当我启动我的应用程序时，我不断得到这个cgContextFilllellipseInrect:invalid context错误。我的应用程序只是为了让圆圈变得“可捏”

调试器向我显示以下内容：

[Session started at 2010-05-23 18:21:25 +0800.]
2010-05-23 18:21:27.140 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.144 Erase[8045:207] New value of counter is 1
2010-05-23 18:21:27.144 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.144 Erase[8045:207] New value of counter is 2
2010-05-23 18:21:27.144 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.144 Erase[8045:207] New value of counter is 3
2010-05-23 18:21:27.145 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.145 Erase[8045:207] New value of counter is 4
2010-05-23 18:21:27.148 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.149 Erase[8045:207] New value of counter is 5
2010-05-23 18:21:27.150 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.150 Erase[8045:207] New value of counter is 6

我有两个问题： 1为什么要更新计数器6次？我删除了行[超级设置需要显示]；但它变成了4倍。 2无效上下文错误是什么

谢谢各位

我不确定这六个调用，但至少有两个调用正在发生，因为框架正在调用drawRect:您也是。您不需要自己调用drawRect:因此不需要重写setNeedsDisplay:。 您应该从drawRect内部调用UIGraphicsGetCurrentContext:。不要缓存它。它可能会失败，因为框架不能保证在每次调用时使用相同的上下文，或者因为您直接调用drawRect，或者两者都调用；我不知道是哪个。

---

你好，马塞洛，谢谢你的回复。通过1删除对setNeedsDisplay的覆盖2将CGContextRef上下文放在drawRect:方法中，完全按照您所说的做了。然而，我仍然接到2个电话，当我启动应用程序时，屏幕上有一个巨大的椭圆形，它与屏幕的宽度和高度相匹配。知道吗？这个巨大的椭圆是由于第二个调用计数器==1，它随后调用第二个椭圆代码并使用框架传递的rect。它基本上是建议你画整个屏幕。您是否曾调用setNeedsDisplay:或setNeedsDisplayInRect:？这可能是这两个电话的原因。

//
//  ImageView.m
//  Erase
//

#import "ImageView.h"
#import "EraseViewController.h"

@implementation ImageView


-(void)setNewRect:(CGRect)anotherRect{
    newRect = anotherRect;
}

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        newRect = CGRectMake(0,0,0,0);
        ref = UIGraphicsGetCurrentContext();
    }
    return self;
}



- (void)drawRect:(CGRect)rect {
    static int counter = 0;
    CGRect veryNewRect = CGRectMake(30.0, 210.0, 60.0, 60.0);
    NSLog(@"I'm being redrawn.");

    if (counter == 0){
        CGContextFillEllipseInRect(ref, veryNewRect);
    }
    else{
        CGContextFillEllipseInRect(ref, rect);
    }

    counter++;
    NSLog(@"New value of counter is %d", counter);
}

- (void)setNeedsDisplay{
    [super setNeedsDisplay];
    [self drawRect:newRect];
}

- (void)dealloc {
    [super dealloc];
}


@end