Question

我添加UIView，其大小等于屏幕大小，而不是UIImageView添加到此视图。我想将此UIImageView设置在UIView的正中心。因此，我以编程方式执行此操作，无法通过故事板进行约束。以下是我的代码：

UIView* viewForImage = [[UIView alloc] initWithFrame:screenRect];
CGRect rect = CGRectMake(0, 0, 100, 200);
UIImageView* imgcoverView = [[UIImageView alloc] initWithFrame:rect];
imgcoverView.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.9];
imgcoverView.image = imgView.image;
[viewForImage addSubview:imgcoverView];

Answer 1

imgcoverView.center = CGPointMake(viewForImage.frame.size.width/2,viewForImage.frame.size.height/2) ;

Answer 2

请考虑设备的不同方向。我认为最好添加两个中心约束。

NSLayoutConstraint *xCenterConstraint = [NSLayoutConstraint constraintWithItem:imgcoverView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:viewForImage attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0];
[viewForImage addConstraint:xCenterConstraint];

NSLayoutConstraint *yCenterConstraint = [NSLayoutConstraint constraintWithItem:imgcoverView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:viewForImage attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0];
[viewForImage addConstraint:yCenterConstraint];

Answer 3

imgcoverView.frame = 
           CGRectMake(viewForImage.frame.origin.x + (viewForImage.frame.size.width - imgcoverView.frame.size.width)/2, 
                      viewForImage.frame.origin.y + (viewForImage.frame.size.height - imgcoverView.frame.size.height)/2,
                      imgcoverView.frame.size.width,
                      imgcoverView.frame.size.height);

Answer 4

你可以通过约束来做到这一点！

在容器中仅设置两个约束水平中心，在容器中设置垂直中心

在视图中心的UIView内添加UIImageView

4 个答案: