滚动到前沿的 IOS-9 UIStackView 问题答案

【问题标题】：IOS-9 UIStackView issue in scrolling to leading edge滚动到前沿的 IOS-9 UIStackView 问题
【发布时间】：2015-08-04 10:04:51
【问题描述】：

我正在尝试为UIStackView 实现滚动，其中有两个按钮可以水平添加和删除视图。我将scroll.contentSize 更改为UIStackView 的大小，因此当堆栈大小大于ScrollView 的大小时，可以滚动堆栈视图。但是在滚动时，我无法到达堆栈视图的开头。滚动时无法到达开始时的少数视图，但可以到达最后的视图。

//In load view
    scroll = [[UIScrollView alloc]initWithFrame:CGRectMake(25,100, screen.size.width-50, 50)];
    scroll.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:scroll];
    scroll.scrollEnabled = YES;
    scroll.delegate = self;
    cus.center = CGPointMake(scroll.frame.size.width/2, scroll.frame.size.height/2);
    [scroll addSubview:cus];

    stack = [[UIStackView alloc]init];
    stack.axis = UILayoutConstraintAxisHorizontal;
    stack.distribution = UIStackViewDistributionEqualSpacing;
    stack.spacing = 30;
    stack.alignment = UIStackViewAlignmentLeading;
    stack.translatesAutoresizingMaskIntoConstraints = NO;
    [scroll addSubview:stack];

    [stack.centerXAnchor constraintEqualToAnchor:scroll.centerXAnchor].active = YES;
    [stack.centerYAnchor constraintEqualToAnchor:scroll.centerYAnchor].active = YES;

    a = 0;//this is used to count no of views currently present
//Completion of load view

    -(void)addOn//Action performing when clicking on add button.
    {
        UIView *vampire = [[UIView alloc]init];
        vampire.backgroundColor = [UIColor blackColor];
        [vampire.widthAnchor constraintEqualToConstant:40].active = YES;
        [vampire.heightAnchor constraintEqualToConstant:40].active = YES;
        vampire.layer.cornerRadius = 20;
        a = (int)stack.subviews.count;
        [stack addArrangedSubview:vampire];
        float contentWidth = ((a-1)*30+(a*40));
        scroll.contentSize = CGSizeMake(contentWidth,vampire.frame.size.height);
    }


    -(void)removeOn//Action performing when clicking on remove button.
    {
        if(a >=0)
        {
            remove.userInteractionEnabled = NO;
        UIView *view = stack.arrangedSubviews[a];
        [UIView animateWithDuration:.2
                              delay:0
                            options:UIViewAnimationOptionCurveEaseInOut
                         animations:^{
                             view.hidden = YES;

                         } completion:^(BOOL finished) {
                              a--;
                             [view removeFromSuperview];
                             float contentWidth = ((a-1)*30+(a*40));
                             scroll.contentSize = CGSizeMake(contentWidth,view.frame.size.height);
                             remove.userInteractionEnabled = YES;
                         }];
                   }
    }

【问题讨论】：

iOS 9 是否仍处于 NDA 之下，因为它仍处于测试阶段？我认为你最好在 Apple Developer 网站上问这些类型的问题，否则你将违反 Apple 的 T&C。
感谢您的帮助，我会在 Apple Developer 网站上提出这些问题。
不，Apple 公开发布的信息没有保密协议！当所有新 API 和所有 WWDC 会话都已公开发布且无需登录时，它们怎么可能处于 NDA 之下？
您可能应该尝试使用其他约束类型而不是 centerX。看起来您的 stackView 在后缘有一些额外的填充，与 centerX 约束相结合，导致您的堆栈视图不断居中，即使它比滚动视图更宽。
你找到解决办法了吗？

标签： ios objective-c ios9 uistackview

【解决方案1】：

@maheswar-chinnu，你可以试试ScrollableStackView：https://github.com/gurhub/ScrollableStackView

它是 Objective-C 和 Swift 兼容的库。可通过CocoaPods 获得。

示例代码 (Swift)

import ScrollableStackView

var scrollable = ScrollableStackView(frame: view.frame)
view.addSubview(scrollable)

// add your views with 
let rectangle = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 55))
rectangle.backgroundColor = UIColor.blue
scrollable.stackView.addArrangedSubview(rectangle)
// ...

示例代码（Objective-C）

@import ScrollableStackView

ScrollableStackView *scrollable = [[ScrollableStackView alloc] initWithFrame:self.view.frame];
scrollable.stackView.distribution = UIStackViewDistributionFillProportionally;
scrollable.stackView.alignment = UIStackViewAlignmentCenter;
scrollable.stackView.axis = UILayoutConstraintAxisVertical;
[self.view addSubview:scrollable];

UIView *rectangle = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 55)];
[rectangle setBackgroundColor:[UIColor blueColor]];

// add your views with
[scrollable.stackView addArrangedSubview:rectangle]; 
// ...

【讨论】：