截图在iOS5中运行良好，但在iOS4中运行不正常

Question

Xcode4.2，SDK为5.0

已添加QuartzCore.framework。

#import <QuartzCore/QuartzCore.h>
@property (retain, nonatomic) IBOutlet UIImageView *imageView;

-(UIImage*)getShot
{
    CGSize imageSize = CGSizeMake(320, 460);
    UIGraphicsBeginImageContext(imageSize); 
    [imageView.layer renderInContext:UIGraphicsGetCurrentContext()]; 
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    return viewImage;
}

它在iOS5中运行良好，但在iOS4中运行不正确。

我是否使用

UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0) 

或

UIGraphicsBeginImageContext(imageSize)

没有帮助。

Answer 1

- (UIImage*) takeScreenshot
{
        if (iosVersionIsAtLeast(4.0))
                UIGraphicsBeginImageContextWithOptions(self.frame.size, NO, 0.0);
        else
                UIGraphicsBeginImageContext(self.frame.size);
        [self.layer renderInContext:UIGraphicsGetCurrentContext()];

        // save to UIImage
        UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        return screenshot;
}