无法在 NewPad 9.3.5 上将 UIView 转换为 UIImage

Question

使用- (nullable UIView *)resizableSnapshotViewFromRect:(CGRect)rect afterScreenUpdates:(BOOL)afterUpdates withCapInsets:(UIEdgeInsets)从包含AVCaptureVideoPreviewLayer的UIView中进行快照，然后我想将结果（UIView *）转换为UIImage，并显示它，但是UIImage一直是空的。

CGRect frame = CGRectMake(0, 0, 768, 893);
UIView *photo = [self.cameraView resizableSnapshotViewFromRect:frame afterScreenUpdates:YES withCapInsets:UIEdgeInsetsZero];

UIGraphicsBeginImageContextWithOptions(photo.bounds.size, NO, [[UIScreen mainScreen] scale]);
[photo drawViewHierarchyInRect:photo.bounds afterScreenUpdates:YES];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

UIImageView * iv = [[UIImageView alloc] initWithImage:image];
[iv setFrame:CGRectMake(0, 0, image.size.width, image.size.height)];
[self addSubview:iv];

CALayer * layer = [iv layer];
layer.borderWidth = 2.0f;
layer.borderColor = [[UIColor orangeColor] CGColor];

有人知道为什么不能得到正确的 UIImage 吗？

Xcode Version 8.2.1 (8C1002) MacOS Sierra 10.12.3(16D32) Deployment Target 9.3 iPad iOS 9.3.5

Answer 1

我不知道这个的Objective-C-version，但是尝试自己将它转换为Obj-C，并添加这段代码：

let context = UIGraphicsGetCurrentContext()
photo.layer.render(in:context!)

在后面加上

[photo drawViewHierarchyInRect:photo.bounds afterScreenUpdates:YES];

但之前

UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

Answer 2

使用以下方法（未经测试）：

- (UIImage *)renderViewToImage:(UIView *)view
{
    UIImage* image = nil;

    UIGraphicsBeginImageContext(view.bounds.size);          
    [view.layer renderInContext: UIGraphicsGetCurrentContext()];        
    image = UIGraphicsGetImageFromCurrentImageContext();            
    UIGraphicsEndImageContext();

    return image
}

然后调用：

UIImage *img = [self renderViewToImage:photo]

您可能希望将其设为UIView 的类别。