iphone 實現截圖功能

本文摘自：http://blog.sina.com.cn/s/blog_6017de810100q7qt.html

iPhone 使用者同步選取 Home 和鎖屏鍵就能截屏，但在應用裡總不能跳出一行字讓使用者自己按截屏鍵。CocoaChina 會員 “bobgreen” 分享的這段代碼能實現程式內截屏功能，支援 iPhone 4 Retina 高分屏。

UIView *view = [[[[[UIApplication sharedApplication] windows] objectAtIndex:1] subviews] lastObject];//獲得某個window的某個subView
 
    NSInteger index = 0;//用來給儲存的png命名
    for (UIView *subView in [view subviews]) {//遍曆這個view的subViews
        if ([subView isKindOfClass:NSClassFromString(@"UIImageView")] || [subView isKindOfClass:NSClassFromString(@"UIThreePartButton")]) {//找到自己需要的subView
            //支援retina高分的關鍵
            if(UIGraphicsBeginImageContextWithOptions != NULL)
            {
                UIGraphicsBeginImageContextWithOptions(subView.frame.size, NO, 0.0);
            } else {
                UIGraphicsBeginImageContext(subView.frame.size);
            }           
 
            //擷取映像
            [subView.layer renderInContext:UIGraphicsGetCurrentContext()];
            UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
 
            //儲存映像
            NSString *path = [NSHomeDirectory() stringByAppendingFormat:@"/%d.png",index];
            if ([UIImagePNGRepresentation(image) writeToFile:path atomically:YES]) {
                index += 1;
                NSLog(@"Succeeded!");
            }
            else {