Question

我正在尝试扩展UIButton类以添加一些方法，但是当我尝试初始化对象时遇到了一些问题。

-(id)init{

UIImage* image = [UIImage imageNamed:@"button_background.png"];    
CGRect frame=  CGRectMake(100.0, 70.0, 45.0 ,45.0);

self.frame = frame;

[self setTitle:@"title" forState:UIControlStateNormal];
[self setBackgroundImage:image forState:UIControlStateNormal];
[self setImage:image forState:UIControlStateNormal];

NSLog(@"type: %d",self.buttonType);
NSLog(@"x: %f\ny: %f\nwidth: %f\nheight: %f",frame.origin.x, frame.origin.y ,frame.size.width, frame.size.height);
NSLog(@"x: %f\ny: %f\nwidth: %f\nheight: %f",self.frame.origin.x, self.frame.origin.y ,self.frame.size.width, self.frame.size.height);

if(self != nil){
    //
}
return self;

}

接缝工作正常，执行期间没有警告或错误。但是在控制台中出现了frame和self.frame的值之间的一些不一致，当然按钮不会出现在屏幕上。

type: 0
x: 100.000000
y: 70.000000
width: 45.000000
height: 45.000000

x: 0.000000
y: 0.000000
width: 0.000000
height: -1.998576

请帮助我，我已经忘记了！：\

Answer 1

当你在Objective-C中进行子类化时，你必须（1）覆盖指定的初始化器（2）调用超类的指定初始化器。你没有。

你应该这样做：

/** 
 * \brief Convenience class method to replace button method of UIButton
 */
+(id)myButton
{
    MyButton* myButton = [[MyButton alloc] 
                              initWithFrame:CGMakeRect(100.0, 70.0, 45.0, 45.0)];
    return [myButton autorelaase];
}

-(id)initWithFrame:(CGRect)f
{
    if(self = [super initWithFrame:f])
    {
        UIImage* image = [UIImage imageNamed:@"button_background.png"];    

        [self setTitle:@"title" forState:UIControlStateNormal];
        [self setBackgroundImage:image forState:UIControlStateNormal];
        [self setImage:image forState:UIControlStateNormal];

        NSLog(@"type: %d",self.buttonType);
        NSLog(@"x: %f\ny: %f\nwidth: %f\nheight: %f", NSStringFromCGRect(frame));
        NSLog(@"x: %f\ny: %f\nwidth: %f\nheight: %f", NSStringFromCGRect(self.frame));
    }
    return self;
}

希望这会有所帮助。如果您需要更多信息，请告诉我。

Answer 2

在您记录的那一刻，您没有将按钮添加到任何视图。无论如何，代码必须看起来像这样吗？

-(id)init{



if(self != nil){
    UIImage* image = [UIImage imageNamed:@"button_background.png"];    
CGRect frame=  CGRectMake(100.0, 70.0, 45.0 ,45.0);

self.frame = frame;

[self setTitle:@"title" forState:UIControlStateNormal];
[self setBackgroundImage:image forState:UIControlStateNormal];
[self setImage:image forState:UIControlStateNormal];

NSLog(@"type: %d",self.buttonType);
NSLog(@"x: %f\ny: %f\nwidth: %f\nheight: %f",frame.origin.x, frame.origin.y ,frame.size.width, frame.size.height);
NSLog(@"x: %f\ny: %f\nwidth: %f\nheight: %f",self.frame.origin.x, self.frame.origin.y ,self.frame.size.width, self.frame.size.height);
}
return self;

顺便问一下，你不要忘记调用超类init吗？

Answer 3

我刚才回答了一个非常相似的问题： How to create a very custom uibutton like UITableViewCellStyleSubtitle in iOS

像其他人一样指出，UIButton是一个类集群，所以你可能不想将它子类化。但是，您可能会发现创建UIButton类别更容易，而不是子类化UIControl。

iOS编程：扩展UIButton类的问题

3 个答案: