XCode 自动布局无法与 UIScrollView 一起用于水平分页

Question

我正在尝试使用 AutoLayout 创建水平分页。这是代码。

 UIView *newsView = [[UIView alloc] initWithFrame:CGRectZero];
    newsView.backgroundColor = [UIColor redColor];

    UIView *anotherNewsView = [[UIView alloc] initWithFrame:CGRectZero];
    anotherNewsView.backgroundColor = [UIColor blueColor];

    self.scrollView.translatesAutoresizingMaskIntoConstraints = NO;
    newsView.translatesAutoresizingMaskIntoConstraints = NO;
    anotherNewsView.translatesAutoresizingMaskIntoConstraints = NO;

    self.scrollView.pagingEnabled = YES;

    [self.scrollView addSubview:newsView];
    [self.scrollView addSubview:anotherNewsView];
 [self.scrollView addConstraint:[NSLayoutConstraint constraintWithItem:newsView
                                                                    attribute:NSLayoutAttributeTop
                                                                    relatedBy:NSLayoutRelationEqual
                                                                       toItem:self.scrollView
                                                                    attribute:NSLayoutAttributeTop
                                                                   multiplier:1.0f
                                                                     constant:0.0f]];

    [self.scrollView addConstraint:[NSLayoutConstraint constraintWithItem:newsView
                                                                attribute:NSLayoutAttributeBottom
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:self.scrollView
                                                                attribute:NSLayoutAttributeBottom
                                                               multiplier:1.0f
                                                                 constant:0.0f]];

    [self.scrollView addConstraint:[NSLayoutConstraint constraintWithItem:newsView
                                                                attribute:NSLayoutAttributeLeading
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:self.scrollView
                                                                attribute:NSLayoutAttributeLeading
                                                               multiplier:1.0f
                                                                 constant:0.0f]];
//
    [self.scrollView addConstraint:[NSLayoutConstraint constraintWithItem:newsView
                                                                attribute:NSLayoutAttributeTrailing
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:anotherNewsView
                                                                attribute:NSLayoutAttributeLeading
                                                               multiplier:1.0f
                                                                 constant:0.0f]];
//    
    [self.scrollView addConstraint:[NSLayoutConstraint constraintWithItem:anotherNewsView
                                                                attribute:NSLayoutAttributeTop
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:self.scrollView
                                                                attribute:NSLayoutAttributeTop
                                                               multiplier:1.0f
                                                                 constant:0.0f]];

    [self.scrollView addConstraint:[NSLayoutConstraint constraintWithItem:anotherNewsView
                                                                attribute:NSLayoutAttributeBottom
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:self.scrollView
                                                                attribute:NSLayoutAttributeBottom
                                                               multiplier:1.0f
                                                                 constant:0.0f]];

    [self.scrollView addConstraint:[NSLayoutConstraint constraintWithItem:anotherNewsView
                                                                attribute:NSLayoutAttributeTrailing
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:self.scrollView
                                                                attribute:NSLayoutAttributeTrailing
                                                               multiplier:1.0f
                                                                 constant:0.0f]];

    [self.scrollView addConstraint:[NSLayoutConstraint constraintWithItem:newsView
                                                                attribute:NSLayoutAttributeWidth
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:anotherNewsView
                                                                attribute:NSLayoutAttributeWidth
                                                               multiplier:0.99f
                                                                 constant:0.0f]];

但我只看到scrollView，我将背景设置为青色。

Answer 1

问题是您的视图现在的配置宽度和高度为零。

尝试为它们添加一些高度限制，例如：

NSArray *heightConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[view(height)]" options:0 metrics:@{ @"height":@(CGRectGetHeight(self.scrollView.frame)) } views:@{ @"view":newsView }];
[self.scrollView addConstraints: heightConstraints];

[self.scrollView addConstraints: [NSLayoutConstraint constraintsWithVisualFormat:@"H:[newsView(width)]" options:0 metrics:@{ @"width":@(CGRectGetWidth(self.scrollView.frame)) } views:@{ @"newsView":newsView]];

[self.scrollView addConstraints: [NSLayoutConstraint constraintsWithVisualFormat:@"H:[anotherNewsView(width)]" options:0 metrics:@{ @"width":@(CGRectGetWidth(self.scrollView.frame)) } views:@{ @"anotherNewsView":anotherNewsView }]];

您也可以查看我的其他回答之一。

重要的是 scrollview 中的视图必须有自己的宽度和高度。这就是 scrollView 计算其 contentSize 的方式。如果没有，contentSize 将是 CGSizeZero，您将看不到您的观点。

希望对您有所帮助！如果您需要更多帮助，请告诉我。

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