Question

确保UIScrollView中的子视图使用autolayout一个接一个地水平堆叠的最佳方法是什么？子视图的数量会有所不同，所以我不能使用IB，但必须以编程方式进行。我理解布局约束如何工作，但解决它的最佳方法是什么？每次更新子视图的数量时，循环所有子视图并更新每个视图的约束？如果是这样，是否有一个简单的解决方案来引用布局约束中的前一个兄弟，或者我是否必须保留对前一个兄弟的引用？

Answer 1

我为应用编写了以下方法。可能不是最漂亮，但它完成了工作。它将视图作为一个数组来解决引用前一个视图的问题。它还使用透明的间隔视图来均匀地隔开它们，但您可以轻松地将它们取出来。

+(void)spaceViews:(NSArray*)views evenlyInContainer:(UIView*)container {

    UIView* lastSpacer = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 10, 10)];
    lastSpacer.translatesAutoresizingMaskIntoConstraints = NO;
    [lastSpacer addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[lastSpacer(10)]" options:NSLayoutFormatDirectionLeadingToTrailing metrics:nil views:NSDictionaryOfVariableBindings(lastSpacer)]];
    [container addSubview:lastSpacer];

    [container addConstraint:[NSLayoutConstraint constraintWithItem:container attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:lastSpacer attribute:NSLayoutAttributeLeading multiplier:1.f constant:0]];


    for (int i = 0; i < [views count]; i++) {
        [container addSubview:views[i]];

        [container addConstraint:[NSLayoutConstraint constraintWithItem:lastSpacer attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:views[i] attribute:NSLayoutAttributeLeading multiplier:1.f constant:0]];

        UIView* spacerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 10, 10)];
        [spacerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[spacerView(10)]" options:NSLayoutFormatDirectionLeadingToTrailing metrics:nil views:NSDictionaryOfVariableBindings(spacerView)]];


        spacerView.translatesAutoresizingMaskIntoConstraints = NO;
        [spacerView setBackgroundColor:[UIColor blueColor]];
        [container addSubview:spacerView];
        [container addConstraint:[NSLayoutConstraint constraintWithItem:spacerView attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:views[i] attribute:NSLayoutAttributeTrailing multiplier:1.f constant:0]];

        [container addConstraint:[NSLayoutConstraint constraintWithItem:spacerView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:container attribute:NSLayoutAttributeCenterY multiplier:1.f constant:0]];

        [container addConstraint:[NSLayoutConstraint constraintWithItem:views[i] attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:container attribute:NSLayoutAttributeCenterY multiplier:1.f constant:0]];

        if (lastSpacer) {
            [container addConstraint:[NSLayoutConstraint constraintWithItem:spacerView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:lastSpacer attribute:NSLayoutAttributeWidth multiplier:1.f constant:0]];
        }
        lastSpacer = spacerView;
    }
    [container addConstraint:[NSLayoutConstraint constraintWithItem:lastSpacer attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:container attribute:NSLayoutAttributeTrailing multiplier:1.f constant:0]];
}

使用自动布局

1 个答案: