ios - 使用 NSLayoutConstraints 均匀间隔多行任意数量的元素

Question

我对以下场景使用布局约束有疑问。一切都在代码中(没有 Nib 或 Storyboard)。我想创建一个包含任意数量的项目行的 View 。每行包含任意数量的 subview 。

为了创建这个 View ，我想传入一个两层深的数组。第一级数组包含每一行。第二级数组包含每一行中的元素。因此，例如，这可能看起来像这样:

NSArray *elements = @[@[subview1, subview2, subview3], @[subview4], @[subview5, subview6]]

在这个数组中，会有 3 行:

1)第1行: subview 1、 subview 2、 subview 3
2)第2行:subview4
3)第3行: subview 5、 subview 6

我希望这些元素的格式为:

-行都应该是它们父 View 的全宽(为此我们可以假设它是屏幕的大小)
- 一行中的每个元素都应具有相同的宽度，并且它们之间的间距应相同(例如，如果有 4 个元素，则 1&2 和 2&3 之间的间距可以为 10pt)
- 每行之间的垂直间距应相同(例如，每行之间的垂直间距为 10pt)

在上面的场景中，第 1 行将有 3 个等宽的 subview ，第 2 行将有 1 个占据行的整个宽度的 subview ，第 3 行将有 2 个等宽的 subview ，并且将间距相等。

那么，问题是，我该怎么做？!

我已经研究了一段时间，但我的理解似乎并没有好转。帮助将不胜感激!

Answer 1

我认为这样的事情应该可行。我试着做一般的，所以它应该适用于不同数量的行和每行的元素。

#define subviewHeight 44
#define spaceFromTop 10
#define spaceFromSide 10
#define subviewVerticalSpacing 10
#define subviewHorizontalSpacing 10

@implementation ViewController

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    UIButton *subview1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [subview1 setTitle:@"View 1" forState:UIControlStateNormal];
    UIButton *subview2 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [subview2 setTitle:@"View 2" forState:UIControlStateNormal];
    UIButton *subview3 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [subview3 setTitle:@"View 3" forState:UIControlStateNormal];
    UIButton *subview4 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [subview4 setTitle:@"View 4" forState:UIControlStateNormal];
    UIButton *subview5 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [subview5 setTitle:@"View 5" forState:UIControlStateNormal];
    UIButton *subview6 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [subview6 setTitle:@"View 6" forState:UIControlStateNormal];

    NSArray *arrayOfSubviews = @[@[subview1, subview2, subview3], @[subview4], @[subview5, subview6]];

    [self addSubviewsWithConstraints:arrayOfSubviews];

}

-(void)addSubviewsWithConstraints:(NSArray *) arrayOfArrays {
    NSMutableArray *arrayOfViewsDicts = [NSMutableArray array]; // make the views dictionaries needed for the views parameter of constraintsWithVisualFormat:options:metrics:views:. One for each row.

    for (NSArray *array in arrayOfArrays) {
        NSMutableDictionary *dict = [NSMutableDictionary dictionary];
        for (int i = 0; i < array.count; i++) {
            [dict setObject:array[i] forKey:[NSString stringWithFormat:@"view%d",i]];
        }
        [arrayOfViewsDicts addObject:dict];
    }

    for (int i=0; i<arrayOfArrays.count; i++) {
        NSString *formatString = [self makeConstraintsForRowOfSubviews:arrayOfArrays[i] withViewsDict:arrayOfViewsDicts[i]]; // Make the format string for a row of subviews

        for (id subview in arrayOfArrays[i]) {
            [subview setTranslatesAutoresizingMaskIntoConstraints:NO];
            [self.view addSubview:subview];
            NSLayoutConstraint *heightCon = [NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeHeight relatedBy:0 toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:subviewHeight];
            [subview addConstraint:heightCon];

            NSLayoutConstraint *verticalCon = [NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeTop relatedBy:0 toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:spaceFromTop + ((subviewHeight + subviewVerticalSpacing)*i)];
            [self.view addConstraint:verticalCon];
        }
        NSArray *cons = [NSLayoutConstraint constraintsWithVisualFormat:formatString options:NSLayoutFormatAlignAllBottom metrics:nil views:arrayOfViewsDicts[i]];

        [self.view addConstraints:cons];
    }
}


-(NSString *) makeConstraintsForRowOfSubviews:(NSArray *) arrayOfSubviews withViewsDict:(NSDictionary *) viewsDict {
    NSMutableString *formatString = [NSMutableString string];

    for (int i = 0; i<arrayOfSubviews.count; i++) {
        if (i == 0) {
            [formatString appendFormat:@"|-%d-[%@]",spaceFromSide,[viewsDict allKeysForObject:arrayOfSubviews[i]][0]];
        }else{
            [formatString appendFormat:@"-%d-[%@(==view0)]",subviewHorizontalSpacing,[viewsDict allKeysForObject:arrayOfSubviews[i]][0]];
        }
    }

    [formatString appendFormat:@"-%d-|",spaceFromSide];
    return formatString;
}

这段代码产生了这样的结果: