iOS中的Autolay問題

Question

我在UIView類型的容器視圖中有一個標籤，圖像和按鈕。容器視圖是UIView類型的supercontainerview的子視圖。所有的佈局都使用autlayout可視格式語言在代碼中完成。我想實現的是當按下按鈕時移除標籤並期待超級容器調整其內容。但目前發生的情況是整個超級容器從屏幕上消失。有人能告訴我爲什麼會發生這種情況嗎？附件是我的代碼示例。

- (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; 

} 

我的方法添加自動佈局屬性

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

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

我的方法去除標籤。

- (IBAction)removeASubview:(id)sender { 

    [helpLabel removeFromSuperview]; 

} 

還有一個問題。相關視圖從其超級視圖中移除時約束對象會發生什麼變化。他們是否存在或被刪除？

Answer 1

您可以添加要在沒有helpLabel和約束可應用於其他約束，但給這個新的較低的優先級，這樣當helpLabel存在，它的約束將支配的觀點，但是當helpLabel是刪除，新的約束將發揮作用。例如：

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

---

順便說一句，如果你想看看發生了什麼，以你的意見helpLabel取出後，用調試器中運行應用程序，點擊暫停按鈕（）暫停應用程序，並在(lldb)調試提示符下，鍵入以下命令：

 
po [[UIWindow keyWindow] recursiveDescription] 

注意，它有時很難確定哪個窗口是的，所以我會經常給各種意見的唯一數字tag屬性，使它更容易。

此外，在相同的命令行，你可以使用下面的命令來確定您的約束曖昧佈局：

 
po [[UIWindow keyWindow] _autolayoutTrace]