拍摄视图快照而不将其添加到屏幕

Take a snapshot of view without adding it to the screen

我正在尝试从 nib 加载一个视图,对其进行配置,然后拍摄它的快照,而不是将它添加到屏幕上:

+ (void)composeFromNibWithImage:(UIImage*)catImage completion:(CompletionBlock)completion {

    NSArray *nibContents = [[NSBundle mainBundle] loadNibNamed:@"CatNib" owner:nil options:nil];
    CatView *catView = [nibContents firstObject];

    //here, catView is the correct size from the nib, but is blank if inspected with the debugger

    catView.catImageView.image = catImage;
    catView.furButton.selected = YES;    
    UIImage *composite = [UIImage snapshot:catView];
    completion(composite);
}

其中快照是典型的:

+ (UIImage *)snapshot:(UIView *)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, 0.0);
    [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}

但是,catView 和 composite 的大小都正确,但在我逐步执行代码时为空白。如何从从 nib 加载的视图创建 UIImage,而不将视图添加到屏幕?

这感觉有点老套,但我试过了,它确实完成了工作。如果您从主视图后面的笔尖加载视图,您可以截取该层的屏幕截图。只要不是内存密集型视图,用户永远不会知道该视图被添加到超级视图中。

UIGraphicsBeginImageContext(CGSizeMake(catView.frame.size.width, catView.frame.size.height));
CGContextRef context = UIGraphicsGetCurrentContext();
[catView.layer renderInContext:context];
UIImage *screenShot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

因此 运行 在您将 nib 加载到主视图后面后,这段代码。加载后,您可以使用 `[catView removeFromSuperiew]'

将其删除

我前段时间遇到过类似的问题,据我所知,无法拍摄视图的快照,那实际上 屏幕上.我创建了一个解决方法,并将我想要快照的相关视图放置在当前 ViewControllers 视图边界之外,这样您就不会看到它。在这种情况下,可以创建有效的快照。希望这有帮助:)

    UIGraphicsBeginImageContext(view.frame.size);
    [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();