视图快照不呈现

Question

我正在尝试获取另一个控制器在动画中使用的视图的快照。我正在使用以下代码，但是除了该视图的背景颜色外，我什么也看不到，其子视图（两个按钮，一个文本视图和标签）都没有：

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    FirstPageController *fpController = [self.storyboard instantiateViewControllerWithIdentifier:@"FirstPage"];
    UIGraphicsBeginImageContext(fpController.view.bounds.size);
    NSLog(@"%@",fpController.view.subviews);
    [fpController.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGSize destinationSize = CGSizeMake(90, 122);
    UIGraphicsBeginImageContext(destinationSize);
    [viewImage drawInRect:CGRectMake(0,0,destinationSize.width,destinationSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    self.imageView2 = [[UIImageView alloc] initWithImage:newImage];
    self.imageView2.center = self.view.center;
    [self.view addSubview:self.imageView2];
     NSLog(@"%@",NSStringFromCGSize(self.imageView2.image.size));
}

我已经记录了所有相关内容，fpcontroller，imageView，image以及所有内容都正确记录。

编辑后：如果我切换到当前控制器的视图，则可以正常工作，因此我认为这与获取不在屏幕上的视图的快照有关。可以做吗？

Answer 1

希望这对您有帮助：

 CGSize textcontent =CGSizeMake(width, height);
UIGraphicsBeginImageContext(textcontent);
if ([UIScreen instancesRespondToSelector:@selector(scale)] && [[UIScreen mainScreen] scale] == 2.0f)
{
    UIGraphicsBeginImageContextWithOptions(textcontent, YES, 1.0f);
}
else
{
    UIGraphicsBeginImageContext(textcontent);
}
    [image.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return viewImage;

Answer 2

UIGraphicsBeginImageContextWithOptions(fpController.view.bounds.size, NO, 0.0);

UIGraphicsBeginImageContextWithOptions(destinationSize, NO, 0.0);

使用这两行代替UIGraphicsBeginImageContext(fpController.view.bounds.size);

 UIGraphicsBeginImageContext(destinationSize); respectively 

希望对您有帮助

Answer 3

我找到了一种使这项工作的方法，尽管它似乎是一个黑客。我添加了要渲染的视图作为视图的子视图，执行渲染，然后删除视图。从来没有在屏幕上看到它，所以从视觉上看很好。我只是想知道是否有更好的方法。

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    self.fpController = [self.storyboard instantiateViewControllerWithIdentifier:@"FirstPage"];
    [self.view insertSubview:self.fpController.view belowSubview:self.view];
    UIGraphicsBeginImageContext(self.fpController.view.bounds.size);
    [self.fpController.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    [self.fpController.view removeFromSuperview];
    self.imageView2 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 90, 122)];
    self.imageView2.image = viewImage;
    [self.pageView insertSubview:self.imageView2 belowSubview:self.imageView];
}