objective-c - 以编程方式使用自动布局对齐 NSView

Question

我在以编程方式使用自动布局将 NSView 彼此相邻对齐时遇到问题。为了说明这一点，我做了一个非常简单的示例项目。 DiscView是NSView的子类，它用指定的颜色绘制圆盘。

在下面的示例中，我仅在两个 subview 之一上添加自动布局约束，结果正如我所预期的那样(请参见下面的屏幕截图)。

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    DiscView *discViewA = [[DiscView alloc] init];
    DiscView *discViewB = [[DiscView alloc] init];

    discViewA.color = [NSColor blackColor];
    discViewB.color = [NSColor redColor];

    discViewA.translatesAutoresizingMaskIntoConstraints = NO;
    discViewB.translatesAutoresizingMaskIntoConstraints = NO;

    [self.customView addSubview:discViewA];
    [self.customView addSubview:discViewB];

    NSDictionary *discViewDictionary = @{@"discViewA" : discViewA,
                                         @"discViewB" : discViewB};

    [self.customView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[discViewA]|" options:0
                                                                           metrics:nil
                                                                              views:discViewDictionary]];

    [self.customView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[discViewA]|" options:0
                                                                            metrics:nil
                                                                              views:discViewDictionary]];
}

但是，如果我尝试使用一些附加约束并排显示两个 subview ，我只会看到一个红色圆盘。也就是说，就好像红色圆盘直接绘制在黑色圆盘之上。

[self.customView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[discViewA]-[discViewB]|" options:0
                                                                               metrics:nil
                                                                                  views:discViewDictionary]];

[self.customView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[discViewA]|" options:0
                                                                                metrics:nil
                                                                                  views:discViewDictionary]];

[self.customView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[discViewB]|" options:0
                                                                                metrics:nil
                                                                                  views:discViewDictionary]];

这里可能出了什么问题？

Answer 1

[self.customView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[discViewA][discViewB]|" 
                                                                        options:NSLayoutFormatAlignAllTop | NSLayoutFormatAlignAllBottom 
                                                                          views:discViewDictionary]];


[self.customView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[discViewA]|" options:0
                                                                        metrics:nil
                                                                          views:discViewDictionary]];

试试这个。这可能有帮助。如果没有，就按照别人的建议去做，并像这样施加限制。

[self.customView addConstraint:[NSLayoutConstraint constraintWithItem:discViewA
                                                                attribute:NSLayoutAttributeWidth
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:self.customView
                                                                attribute:NSLayoutAttributeWidth
                                                               multiplier:0.5f
                                                                 constant:0.f]];