如何使用 AutoLayout 将 UIButtons 定位在水平线中(环绕，左对齐)?

问题描述

我需要在我的应用程序(iOS 6.0 及更高版本)中以编程方式创建几个不同宽度的 UIButton.

I need to create a couple of UIButtons with various widths programmatically in my app (iOS 6.0 and above).

我想以环绕"样式显示按钮:从左边缘开始，每个按钮应水平放置(按定义的顺序)，如果按钮不适合当前"line"，它应该在前一行下方的左边缘开始新的一行.

I want to display the buttons in a "wrap around" style: Starting from the left edge, each button should be positioned next to each other horizontally (in a defined order), and if a button does not fit in the current "line", it should start a new line on the left edge below the previous line.

注意:我不想要表格/网格，因为按钮有不同的宽度，我希望有一个彼此相邻.

Note: I don't want a table/grid, since the buttons have different widths, and I want to have one right next to each other.

我可以手动计算代码中每个按钮的框架，但我应该使用 AutoLayout(使用以编程方式创建的 NSLayoutConstraints)来代替吗?我究竟需要如何设置它?

I could manually calculate the frame of each button in my code, but should I use AutoLayout (with programmatically created NSLayoutConstraints) instead? How exactly would I need to set it up?

通读 "iOS 6 的第 4 章中级自动布局"by Tutorials" 我不确定使用纯 AutoLayout 是否可以实现我需要的这种环绕"功能.

After reading through Chapter 4 "Intermediate Auto Layout" of "iOS 6 by Tutorials" I am not sure whether using pure AutoLayout could implement this "wrap around" functionality I require.

推荐答案

我目前的解决方案是这样的:没有 AutoLayout，但是为每种情况手动设置正确的约束(第一个按钮，新行中最左边的按钮，任何其他按钮).

My current solution looks like this: No AutoLayout, but manually setting the correct constraints for each case (first button, leftmost button in a new line, any other button).

(我的猜测是直接为每个按钮设置框架会导致比使用 NSLayoutConstraints 更具可读性的代码，无论如何)

(My guess is that setting the frame for each button directly would result in more readable code than using NSLayoutConstraints, anyway)

NSArray *texts = @[ @"A", @"Short", @"Button", @"Longer Button", @"Very Long Button", @"Short", @"More Button", @"Any Key"];

int indexOfLeftmostButtonOnCurrentLine = 0;
NSMutableArray *buttons = [[NSMutableArray alloc] init];
float runningWidth = 0.0f;
float maxWidth = 300.0f;
float horizontalSpaceBetweenButtons = 10.0f;
float verticalSpaceBetweenButtons = 10.0f;

for (int i=0; i<texts.count; i++) {
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [button setTitle:[texts objectAtIndex:i] forState:UIControlStateNormal];
    [button sizeToFit];
    button.translatesAutoresizingMaskIntoConstraints = NO;

    [self.view addSubview:button];

    // check if first button or button would exceed maxWidth
    if ((i == 0) || (runningWidth + button.frame.size.width > maxWidth)) {
        // wrap around into next line
        runningWidth = button.frame.size.width;

        if (i== 0) {
            // first button (top left)
            // horizontal position: same as previous leftmost button (on line above)
            NSLayoutConstraint *horizontalConstraint = [NSLayoutConstraint constraintWithItem:button attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeft multiplier:1.0f constant:horizontalSpaceBetweenButtons];
            [self.view addConstraint:horizontalConstraint];

            // vertical position:
            NSLayoutConstraint *verticalConstraint = [NSLayoutConstraint constraintWithItem:button attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop              multiplier:1.0f constant:verticalSpaceBetweenButtons];
            [self.view addConstraint:verticalConstraint];


        } else {
            // put it in new line
            UIButton *previousLeftmostButton = [buttons objectAtIndex:indexOfLeftmostButtonOnCurrentLine];

            // horizontal position: same as previous leftmost button (on line above)
            NSLayoutConstraint *horizontalConstraint = [NSLayoutConstraint constraintWithItem:button attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:previousLeftmostButton attribute:NSLayoutAttributeLeft multiplier:1.0f constant:0.0f];
            [self.view addConstraint:horizontalConstraint];

            // vertical position:
            NSLayoutConstraint *verticalConstraint = [NSLayoutConstraint constraintWithItem:button attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:previousLeftmostButton attribute:NSLayoutAttributeBottom multiplier:1.0f constant:verticalSpaceBetweenButtons];
            [self.view addConstraint:verticalConstraint];

            indexOfLeftmostButtonOnCurrentLine = i;
        }
    } else {
        // put it right from previous buttom
        runningWidth += button.frame.size.width + horizontalSpaceBetweenButtons;

        UIButton *previousButton = [buttons objectAtIndex:(i-1)];

        // horizontal position: right from previous button
        NSLayoutConstraint *horizontalConstraint = [NSLayoutConstraint constraintWithItem:button attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:previousButton attribute:NSLayoutAttributeRight multiplier:1.0f constant:horizontalSpaceBetweenButtons];
        [self.view addConstraint:horizontalConstraint];

        // vertical position same as previous button
        NSLayoutConstraint *verticalConstraint = [NSLayoutConstraint constraintWithItem:button attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:previousButton attribute:NSLayoutAttributeTop multiplier:1.0f constant:0.0f];
        [self.view addConstraint:verticalConstraint];
    }

    [buttons addObject:button];
}

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