UIScrollView 具有自动布局的错误 contentSize

Question

我在情节提要中有一个类似这样的 iOS 屏幕：

如果我在模拟器中尝试此操作，我无法滚动到第二个 UIView（我使用分页）。我知道发生这种情况是因为 contentSize 的宽度为 320，但我不知道如何使用自动布局来解决它，也不知道如何让它在每个设备位置（横向、纵向）上工作。我只需要在 UIScrollView 中显示一个 UIView。谢谢。

Answer 1

这是可以解决的，应该可以很好地与自动布局一起使用。

NSDictionary *views = NSDictionaryOfVariableBindings(scrollView, subview1, subview2);

// Constraint the scrollview frame within its parent
[parentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[scrollView]|" options:0 metrics: 0 views:viewsDictionary]];
[parentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[scrollView]|" options:0 metrics: 0 views:viewsDictionary]];

// Determine the scrollview's contentSize using its content
[scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[subview1]|" options:0 metrics: 0 views:viewsDictionary]];
[scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[subview1][subview2]|" options:0 metrics: 0 views:viewsDictionary]];
[scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[subview2]|" options:0 metrics: 0 views:viewsDictionary]];

// Set the children width using the outer view
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:subview1 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:parentView attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:subview2 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:parentView attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];

// Set the children height manually
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:subview1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:80.0]];
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:subview2 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:80.0]];

如果您遇到问题，请告诉我。这种方式会有适应屏幕方向、屏幕大小、状态栏高度变化等的优势。

以上示例假设您要将孩子的高度设置为固定高度（80 像素）。要使其垂直填满屏幕，您宁愿执行与宽度相同的操作。

这还假设scrollview、subview1 和subview2 都将其translatesAutoresizingMaskIntoConstraints 属性设置为NO。

它也会不在滚动视图中垂直对齐子视图。如果你想这样做，你可以让他们每个人都驻留在他们自己的 container 视图中，如下所示：

// Set the containers' width & height using the outer view
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:containerview1 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:parentView attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:containerview2 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:parentView attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];

[parentView addConstraint:[NSLayoutConstraint constraintWithItem:containerview1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:parentView attribute:NSLayoutAttributeHeight multiplier:1.0 constant:0.0]];
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:containerview2 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:parentView attribute:NSLayoutAttributeHeight multiplier:1.0 constant:0.0]];

// Set the children height manually
[containerview1 addConstraint:[NSLayoutConstraint constraintWithItem:subview1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:80.0]];
[containerview2 addConstraint:[NSLayoutConstraint constraintWithItem:subview2 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:80.0]];

// Align them vertically
[containerview1 addConstraint:[NSLayoutConstraint constraintWithItem:subview1 attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:containerview1 attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0.0]];
[containerview2 addConstraint:[NSLayoutConstraint constraintWithItem:subview2 attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:containerview2 attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0.0]];

// Set the width to equal that of their container
[containerview1 addConstraint:[NSLayoutConstraint constraintWithItem:subview1 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:containerview1 attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];
[containerview2 addConstraint:[NSLayoutConstraint constraintWithItem:subview2 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:containerview2 attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];

Answer 2

试试这样的：

[_scrollView setContentSize:CGSizeMake(640, _scrollView.frame.size.height)];

关于自动布局：有时最好不要使用它们。

考虑屏幕方向的代码：

float screenWidth = [UIScreen mainScreen].bounds.size.width;
[_scrollView setContentSize:CGSizeMake(screenWidth * 2, _scrollView.frame.size.height)];

要捕捉设备旋转的那一刻，您应该在视图控制器中使用这种方法：

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation
{
    // Remove current subviews

    for(UIView *subview in _scrollView.subviews)
    {
        [subview removeFromSuperview];
    }

    // Fill scroll view with subviews resized for screen size
    // ...
}