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我在 UIView 类型的容器视图中有一个标签、图像和按钮。容器视图又是 UIView 类型的超级容器视图的子视图。所有布局都是使用 autlayout 视觉格式语言在代码中完成的。我想要实现的是在按下按钮时删除标签并期望超级容器调整其内容的大小。但目前发生的是整个超级容器从屏幕上消失了。有人能告诉我为什么会这样吗？附件是我的代码示例。

- (void)viewDidLoad {
    [super viewDidLoad];


    superContainer = [[UIView alloc] initWithFrame:CGRectZero];
    superContainer.backgroundColor = [UIColor orangeColor];

    [self.view addSubview:superContainer];


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

    [superContainer addSubview:Container];

    NSDictionary *sViews = NSDictionaryOfVariableBindings(Container);

    [superContainer addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10.0-[Container]-10.0-|" options:0 metrics:nil views:sViews]];

    [superContainer addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10.0-[Container]-10.0-|" options:0 metrics:nil views:sViews]];


    CGSize temp1 = [superContainer systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];


    superContainer.frame = CGRectMake(superContainer.frame.origin.x, superContainer.frame.origin.y, temp1.width, temp1.height);


    closeButton = [UIButton buttonWithType:UIButtonTypeCustom];
    //[closeButton setImage: forState:UIControlStateNormal];
    [closeButton setBackgroundImage:[UIImage imageNamed:@"closebox.png"] forState:UIControlStateNormal];
    [closeButton addTarget:self action:@selector(hide:) forControlEvents:UIControlEventTouchUpInside];
    NSLog(@"Close button frame is %@",NSStringFromCGRect(closeButton.frame));
    //closeButton.frame = CGRectMake(0, 10, 32, 32);
    [Container addSubview:closeButton];


    helpLabel = [[UILabel alloc] init];
    NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:@"This is sample Text. This is sample Text.This is sample Text. This is sample Text.This is sample Text. This is sample Text.This is sample Text. This is sample Text.This is sample Text. This is sample Text. "];
    helpLabel.attributedText = attrString;


    helpLabel.numberOfLines = 0;
    helpLabel.backgroundColor = [UIColor greenColor];
    [Container addSubview:helpLabel];


    helpImageView = [[UIImageView alloc] init];
    helpImageView.image = [UIImage imageNamed:@"testimage.png"];
    NSLog(@"frame of imageview is %@",NSStringFromCGRect(helpImageView.frame));
    [Container addSubview:helpImageView];

    dismissButton = [UIButton buttonWithType:UIButtonTypeCustom];
    [dismissButton setTitle:@"Dismiss" forState:UIControlStateNormal];
    [[dismissButton titleLabel] setLineBreakMode:NSLineBreakByWordWrapping];
    dismissButton.backgroundColor = [UIColor blueColor];
    [Container addSubview:dismissButton];

    [Container setClipsToBounds:YES];

    [self addAutoLayoutProperties];

    NSDictionary *views = NSDictionaryOfVariableBindings(helpLabel,helpImageView,dismissButton,closeButton);

    NSDictionary *metrics = @{@"buttonHeight":@32.0};

    // Horizontal layout - for helplabel
    [Container addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-5.0-[helpLabel(400)]-5.0-|" options:NSLayoutFormatAlignAllLeft|NSLayoutFormatAlignAllRight metrics:metrics views:views]];
    // Horizontal layout - for helpImageView
    [Container addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[helpImageView]|" options:NSLayoutFormatAlignAllLeft|NSLayoutFormatAlignAllRight metrics:metrics views:views]];
    // Horizontal layout - for dismissButton
    [Container addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-[dismissButton]-|" options:NSLayoutFormatAlignAllCenterX|NSLayoutFormatAlignAllCenterY metrics:metrics views:views]];
    // Horizontal layout - for dismissButton
    [Container addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[closeButton]-1.0-|" options:0 metrics:metrics views:views]];

    // Vertical layout

    [Container addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-1.0-[closeButton]" options:0 metrics:metrics views:views]];

    [Container addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-buttonHeight-[helpLabel]-5.0-[helpImageView]-5.0-[dismissButton]-5.0-|" options:0 metrics:metrics views:views]];

    CGSize temp = [Container systemLayoutSizeFittingSize:UILayoutFittingExpandedSize];


    Container.frame = CGRectMake(Container.frame.origin.x, Container.frame.origin.y, temp.width, temp.height);

    superContainer.center = self.view.center;

}

我添加自动布局属性的方法

-(void)addAutoLayoutProperties {
    helpLabel.translatesAutoresizingMaskIntoConstraints = NO;
    helpImageView.translatesAutoresizingMaskIntoConstraints = NO;
    dismissButton.translatesAutoresizingMaskIntoConstraints = NO;
    closeButton.translatesAutoresizingMaskIntoConstraints = NO;

    superContainer.translatesAutoresizingMaskIntoConstraints = NO;
    Container.translatesAutoresizingMaskIntoConstraints = NO;
}

我删除标签的方法。

- (IBAction)removeASubview:(id)sender {

    [helpLabel removeFromSuperview];

}

还有一个问题。当相关视图从其父视图中移除时，约束对象会发生什么。它们在那里存在还是被删除？

4

1 回答 1

1

您可以添加另一个约束，该约束应该在没有helpLabel及其约束的情况下应用，但给这个新约束一个较低的优先级，这样当helpLabel存在时，它的约束将控制视图，但是当helpLabel被删除时，新的约束将出现玩。例如：

[container addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-buttonHeight@500-[helpImageView]" options:0 metrics:metrics views:views]];

顺便说一句，如果您想查看helpLabel删除后视图发生了什么，请使用调试器运行应用程序，点击暂停按钮 ( 暂停) 以暂停应用程序，然后在(lldb)调试器提示符下键入以下命令：

po [[UIWindow keyWindow] recursiveDescription]

请注意，有时很难确定哪个窗口是哪个窗口，因此我会经常为各种视图提供唯一的数字tag属性以使其更容易。

此外，在同一命令行中，您可以使用以下命令来识别约束中的模棱两可的布局：

po [[UIWindow keyWindow] _autolayoutTrace]
于 2013-08-17T14:54:34.627 回答