Cocoa 自动布局约束 - 以编程方式填充可变数量的 View

Question

我希望能够向 super View 添加新 View ，但使它们彼此之间保持恒定的垂直距离。为此，我尝试以编程方式为每个 View 设置约束，但我不知道如何做到这一点。问题是我事先不知道 View 的数量或相对位置。

有没有一种方法可以以编程方式为每个 View 设置约束，以便无论它们相邻的其他 View 如何，自动布局都会保持 View 之间的恒定间距？

Answer 1

这个简短的代码片段可能就是您正在寻找的:

NSMutableArray* newVerticalConstraints = [NSMutableArray array];
UIView* firstView = nil;
UIView* secondView = nil;
UIView* superview = <Your container view>;
NSArray* subviews = [superview subviews];
if ([subviews count] > 0) {
    firstView = [subviews objectAtIndex:0];
    // Add first constraint
    [newVerticalConstraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[firstView]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(firstView)]];

    for (int i = 1; i < [subviews count]; i++) {
        secondView = [subviews objectAtIndex:i];
        [newVerticalConstraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[firstView]-10-[secondView]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(firstView,secondView)]];
        firstView = secondView;
    }

    // Add last constraint
    [newVerticalConstraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[firstView]-10-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(firstView)]];

    [superview removeConstraints:self.verticalConstraints];
    [superview addConstraints:newVerticalConstraints];
    // Save all vertical constraints to be able to remove them
    self.verticalConstraints = newVerticalConstraints;
}