Question

我是使用代码自动布局的新手。

addConstaints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-16-[v0]-16-|",options:NSLayoutFormatOptions(), metrics:nil ,views:["v0":thumbnailImageView]))

addConstaints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-16-[v0]-16-|",options:NSLayoutFormatOptions(), metrics:nil ,views:["v0":thumbnailImageView]))

Iam尝试使用下面的代码在Objective C中实现上面的swift代码但是app在加载时崩溃并且出现以下错误

由于未捕获的异常终止应用＆＃39; NSInvalidArgumentException＆＃39;，原因：＆＃39;无法解析约束格式：期待一个观点 H：| -16- [v0] -16- | ^＆＃39;

    [self addConstraints:[NSLayoutConstraint 
constraintsWithVisualFormat:@"H:|-16-[v0]-16-|" 
options:0 
metrics:nil 
views:NSDictionaryOfVariableBindings(thumbnailImageView)]];

    [self addConstraints:[NSLayoutConstraint
constraintsWithVisualFormat:@"V:|-16-[v0]-16-|" 
options:0 
metrics:nil 
views:NSDictionaryOfVariableBindings(thumbnailImageView)]];

.....

UIImageView * thumbnailImageView = [[UIImageView alloc] init];
        thumbnailImageView.backgroundColor = [UIColor greenColor];
        thumbnailImageView.translatesAutoresizingMaskIntoConstraints = false;

        [self addSubview:thumbnailImageView];


        thumbnailImageView.frame = CGRectMake(0, 0, 100, 100);

Answer 1

NSDictionaryOfVariableBindings生成与Objective-C变量名匹配的变量绑定。所以你需要把约束写为

[self addConstraints:[NSLayoutConstraint 
constraintsWithVisualFormat:@"H:|-16-[thumbnailImageView]-16-|" 
options:0 
metrics:nil 
views:NSDictionaryOfVariableBindings(thumbnailImageView)]];

或者您只需跳过NSDictionaryOfVairableDBindings并使用：

[self addConstraints:[NSLayoutConstraint 
constraintsWithVisualFormat:@"H:|-16-[v0]-16-|" 
options:0 
metrics:nil 
views:@{ @"v0" : thumbnailImageView } ];

这有点像Swift版本。（目前没有编译器方便，所以第二部分可能会出现一些小的语法错误。请尽快检查。）

Answer 2

您错误地使用了需要传递变量名称的宏NSDictionaryOfVariableBindings

/ *这个宏是用于制作视图词典的助手 + constraintsWithVisualFormat：选择：指标：观点：。 NSDictionaryOfVariableBindings（v1，v2，v3）相当于 [NSDictionary dictionaryWithObjectsAndKeys：v1，@“v1”，v2，@“v2”，v3， @“v3”，nil]; * /

 [self addConstraints:[NSLayoutConstraint 
constraintsWithVisualFormat:@"H:|-16-[thumbnailImageView]-16-|" 
options:0 
metrics:nil 
views:NSDictionaryOfVariableBindings(thumbnailImageView)]];

    [self addConstraints:[NSLayoutConstraint
constraintsWithVisualFormat:@"V:|-16-[thumbnailImageView]-16-|" 
options:0 
metrics:nil 
views:NSDictionaryOfVariableBindings(thumbnailImageView)]];

Objective C相当于Swift addConstraints？

2 个答案: