iPhone 应用里实现截屏功能的代码

iPhone 用户同时按下 Home 和锁屏键就能截屏，但在应用里总不能跳出一行字让用户自己按截屏键，支持高清分辨率：
UIView *view = [[[[[UIApplication sharedApplication] windows] objectAtIndex:1] subviews] lastObject];//获得某个window的某个subView

    NSInteger index = 0;//用来给保存的png命名
    for (UIView *subView in [view subviews]) {//遍历这个view的subViews
        if ([subView isKindOfClass:NSClassFromString(@"UIImageView")] || [subView isKindOfClass:NSClassFromString(@"UIThreePartButton")]) {//找到自己需要的subView
            //支持retina高分的关键
            if(UIGraphicsBeginImageContextWithOptions != NULL)
            {
                UIGraphicsBeginImageContextWithOptions(subView.frame.size, NO, 0.0);
            } else {
                UIGraphicsBeginImageContext(subView.frame.size);
            }            

            //获取图像
            [subView.layer renderInContext:UIGraphicsGetCurrentContext()];
            UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();

            //保存图像
            NSString *path = [NSHomeDirectory() stringByAppendingFormat:@"/%d.png",index];
            if ([UIImagePNGRepresentation(image) writeToFile:path atomically:YES]) {
                index += 1;
                NSLog(@"Succeeded!");
            }
            else {
                NSLog(@"Failed!");
            }
        }
    }

第二种方式

UIImage* image = nil;

#if TARGET_IPHONE_SIMULATOR

    CGSize imageSize = [view bounds].size;

    if (NULL != UIGraphicsBeginImageContextWithOptions)

        UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);

    else

        UIGraphicsBeginImageContext(imageSize);

    CGContextRef context = UIGraphicsGetCurrentContext();

    [view.layer renderInContext:context];  

    image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

#else

    CGImageRef screen = UIGetScreenImage();

    image = [UIImage imageWithCGImage:screen];

#endif