【发布时间】：2013-08-14 00:10:06
【问题描述】：
我正在尝试使用可调整大小的图像作为按钮背景。
UIImage *image = [UIImage imageNamed:@"btn_prev_secondary"];
UIEdgeInsets edgeInsets = UIEdgeInsetsMake(30.0f, 25.0f, 29.0f, 9.0f);
UIImage *resizeableImage = [image resizableImageWithCapInsets:edgeInsets];
// What I'd like to do:
[self.backButton setBackgroundImage:resizeableImage forState:UIControlStateNormal];
// This works (but doesn't do what I want)
// [self.backButton setImage:resizeableImage forState:UIControlStateNormal];
// Also works (also doesn't do what I want)
// [self.backButton setImage:image forState:UIControlStateNormal];
当我运行这段代码时，我的按钮背景设置正确，但出现各种日志错误：
Aug 13 17:05:25 MyApp <Error>: CGContextSaveGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextSetBlendMode: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextSetAlpha: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextTranslateCTM: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextScaleCTM: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextGetCTM: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextSaveGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextClipToRect: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextDrawTiledImage: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextRestoreGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextGetCTM: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextSaveGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextClipToRect: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextDrawTiledImage: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextRestoreGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextGetCTM: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextSaveGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextClipToRect: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextDrawTiledImage: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextRestoreGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextGetCTM: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextSaveGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextClipToRect: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextDrawTiledImage: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextRestoreGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextGetCTM: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextSaveGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextClipToRect: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextDrawTiledImage: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextRestoreGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextGetCTM: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextSaveGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextClipToRect: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextDrawTiledImage: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextRestoreGState: invalid context 0x0
Aug 13 17:05:25 MyApp <Error>: CGContextRestoreGState: invalid context 0x0
这是 Cocoa 错误还是我做错了什么（以及如果我正在做的事情如何纠正）？
【问题讨论】：
-
什么是self.backButton？
-
self.backButton 是在故事板上定义的 UIButton。
-
我复制并粘贴了您的代码，对我来说效果很好。你怎么知道是这段代码导致了错误？
-
有趣！我想是这段代码，因为如果我更改或注释该特定行，我看不到错误 - 只有在我使用可调整大小的图像时才会发生。也许我对视图所做的事情与这个问题有关——我从情节提要中对其进行实例化，然后将其动画推送到导航堆栈上。此导航控制器位于占据屏幕子部分的容器视图中。我会试着去掉复杂性，看看它什么时候开始抱怨。
标签： ios objective-c cocoa uibutton core-graphics