子类化 UIImageView 并添加 UIControl答案

【问题标题】：Subclassing UIImageView and adding a UIControl子类化 UIImageView 并添加 UIControl
【发布时间】：2013-01-15 20:02:03
【问题描述】：

我正在尝试对 UIImageView 进行子类化以向其添加 UIControl，以便我知道它何时被选中：

-(id)initWithSize:(CGSize)size OffImage:(UIImage *)offImage onImage:(UIImage *)onImage
{
    if (self) {
        [self setTranslatesAutoresizingMaskIntoConstraints:NO];
        self.userInteractionEnabled = TRUE;

        [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[self(80)]"
                                                                     options:0
                                                                     metrics:@{@"WIDTH" : [NSNumber numberWithFloat:size.width]}
                                                                       views:NSDictionaryOfVariableBindings(self)]];

        [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[self(90)]"
                                                                     options:0
                                                                     metrics:@{@"HEIGHT" : [NSNumber numberWithFloat:size.height]}
                                                                       views:NSDictionaryOfVariableBindings(self)]];

        self.offImage = offImage;
        self.onImage = onImage;
        self.selected = FALSE;

        UIControl *control = [[UIControl alloc] init];
        [control setTranslatesAutoresizingMaskIntoConstraints:NO];
        self.control = control;

        [self addSubview:control];

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

    }

    return self;
}

当我尝试添加约束以使 UIControl 与子类 UIImageView 的大小相同时，我收到一条错误消息，提示 self.control 没有超级视图：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse constraint format: 
Unable to interpret '|' character, because the related view doesn't have a superview 
H:|[control]| 
            ^'

如果我通过创建 UIImageView 来做同样类型的事情，然后创建 UIControl 和 [imageView addsubview:control]，它就可以正常工作。为什么当我尝试将相同的代码添加到init 方法时它会崩溃？

【问题讨论】：

标签： ios objective-c uiimageview autolayout nslayoutconstraint

【解决方案1】：

您是如何创建 imageView 子类对象的？在这段代码中没有[Super init..]

【讨论】：

呸，就是这样，谢谢！我忘了self = [super init]。现在我觉得很傻。