目标 C：从 UIButton 类的子类创建的按钮不起作用

Question

我正在创建 UIButton 的子类，以便创建自己的自定义按钮。我的代码如下：

//interface file (subclass of uIButton
@interface UICustomButton : UIButton 
{
    Answer *answer;
    NSString *btnType;
}

@property (nonatomic, retain) Answer *answer;
@property (nonatomic, assign) NSString *btnType;

- (id)initWithAnswer:(Answer *)ans andButtonType:(NSString *)type andFrame:(CGRect)frame; 
- (void)buttonPressed;

@end


//Implementation file (.m)
@implementation UICustomButton
@synthesize answer,btnType;

- (id)initWithAnswer:(Answer *)ans andButtonType:(NSString *)type andFrame:(CGRect)frame; 
{
    self = [super initWithFrame:frame];
    if (self) 
    {
        self = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, frame.size.width, frame.size.height)];
        self.backgroundColor = [UIColor colorWithHexString:@"#E2E4E7"];

    }

    [self addTarget:self action:@selector(buttonPressed) forControlEvents:UIControlStateNormal];

    self.answer = ans;
    self.btnType = type;

    return self;
}

我在使上述代码正常工作时遇到了一些问题。我有两个问题

1) 按钮没有响应选择器方法“buttonPressed”

2) 我在 'self.answer = ans' 和 'self.btnType = type' 行中遇到运行时错误堆栈跟踪如下：

-[UIButton setAnswer:]: unrecognized selector sent to instance 0x614ebc0
2011-06-23 00:55:27.038 onethingaday[97355:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIButton setAnswer:]: unrecognized selector sent to instance 0x614ebc0'

我在这里做错了什么？

Answer 1

发生这种情况是因为您在 init 方法中创建的是 UIButton 类型对象，而不是 UICustomButton 类型

self = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, frame.size.width, frame.size.height)];

尝试将您的 init 方法替换为

- (id)initWithAnswer:(Answer *)ans andButtonType:(NSString *)type andFrame:(CGRect)frame; 
{
    self = [self initWithFrame:CGRectMake(0, 0, frame.size.width, frame.size.height)];
    if (self) 
    {
        self.backgroundColor = [UIColor colorWithHexString:@"#E2E4E7"];

        [self addTarget:self action:@selector(buttonPressed) forControlEvents:UIControlEventTouchUpInside];

        self.answer = ans;
        self.btnType = type;
    }

    return self;
}

这将导致self 成为UICustomButton 类型的对象。

此外，当您使用 addTarget:action:forControlEvents: 方法将目标添加到按钮时，您使用的 UIControlState 参数类型错误

你应该使用下面的值：

UIControlEventTouchDown
UIControlEventTouchDownRepeat
UIControlEventTouchDragInside
UIControlEventTouchDragOutside
UIControlEventTouchDragEnter
UIControlEventTouchDragExit
UIControlEventTouchUpInside
UIControlEventTouchUpOutside
UIControlEventTouchCancel

---

编辑： UIButton 子类化注意事项

网络上的许多参考资料都说您不应该继承 UIButton 类，但不仅有人说为什么，而且让我深感恼火的是 UIButton Class Reference 根本没有说明它。

如果你以UIWebView Class Reference 为例，它明确指出你不应该继承UIWebView

子类化注释 UIWebView 类 不应该被子类化。

UIButton 的重要之处在于它继承自 UIControl，UIControl Class Reference 本身提供了一个简单明了的解释

子类化注释你可能想要 为任一扩展 UIControl 子类 有两个原因：

• 观察或修改调度 给目标的行动信息 特殊事件
• 提供定制 跟踪行为（例如， 更改突出显示的外观）

因此，这意味着您可以子类化 UIButton，但您应该小心您正在做的事情。只需将其子类化以更改其行为而不是不其外观。要修改UIButton 的外观，您应该使用为此提供的接口方法，例如：

setTitle:forState:
setBackgroundImage:forState:
setImage:forState:

值得一读的参考资料

• UIView 编程指南：View and Window Architecture -> Tips for Using Views Effectively -> Do Not Customize Controls by Embedding Subviews

来源：my post here

Answer 2

不确定这是否在之前的文档中，但无论如何这些是+ (id)buttonWithType:(UIButtonType)buttonType 上的当前注释...

在我看来，只要您使用init 而不是buttonWithType，子类化就可以了。不过，我还没有亲自尝试过。

讨论这个方法是一个方便的构造函数，用于创建 具有特定配置的按钮对象。它是 UIButton 的子类， 此方法不会返回您的子类的实例。如果你想 要创建特定子类的实例，您必须分配/初始化 直接按钮。

当创建一个自定义按钮时——该按钮的类型为 UIButtonTypeCustom——按钮的框架设置为 (0, 0, 0, 0) 最初。在将按钮添加到界面之前，您应该 将框架更新为更合适的值。

Answer 3

如果您想在用户与您的按钮交互时获得通知，只需子类化 UIButton 并实现这些方法：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSLog(@"touchesBegan");
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSLog(@"touchesEnded");
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSLog(@"touchesCancelled");
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSLog(@"touchesMoved");
}

不需要初始化方法。

Answer 4

编辑

这个答案可以追溯到几年前，而且情况已经发生了变化——Apple 文档现在明确提到了子类化并给出了一些提示。

因此，以下答案可能与当前的发展无关或错误，如果您对当前的技术水平感兴趣，可能会被忽略。

---

UIButton 不应该被子类化。

您最好创建一个类别并定义一个提供所需按钮的工厂方法（正确调用buttonWithType:）。 initWithFrame: 无论如何都不是初始化按钮的正确方法。

Answer 5

//
//  BtnClass.m

#import "BtnClass.h"

@implementation BtnClass

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code


    }
    return self;
}

//added custum properities to button
-(id)initWithCoder:(NSCoder *)aDecoder
{
    NSLog(@"initWithCoder");
    self = [super initWithCoder: aDecoder];
    if (self) {
        // Initialization code

        _numberOfItems=[[UILabel alloc]initWithFrame:CGRectMake(40, 8, 160, 30)];
        _numberOfItems.textAlignment=NSTextAlignmentLeft;
        _numberOfItems.font = [UIFont boldSystemFontOfSize:18.0];
        _numberOfItems.textColor = [UIColor darkGrayColor];
        [self addSubview:_numberOfItems];
        _leftImage=[[UIImageView alloc]initWithFrame:CGRectMake(10, 10, 25, 25)];
        [self addSubview:_leftImage];
        _rightImage=[[UIImageView alloc]initWithFrame:CGRectMake(280, 10, 15, 15)];
        [self addSubview:_rightImage];
        [self setImage:[UIImage imageNamed:@"list-bg2-1.png"] forState:UIControlStateNormal];
        [_rightImage setImage:[UIImage imageNamed:@"carat.png"]];
        self.backgroundColor=[UIColor blackColor];


        if(self.tag==1)
        {
            [_leftImage setImage:[UIImage imageNamed:@"notes-icon.png"]];

        }
        if(self.tag==2)
        {
            [_leftImage setImage:[UIImage imageNamed:@"photos-icon.png"]];

        }
        if(self.tag==3)
        {
            [_leftImage setImage:[UIImage imageNamed:@"videos-icon.png"]];

        }


    }
    return self;
}

//selected method of uibutton
-(void)setSelected:(BOOL)selected
{

    [super setSelected:selected];


    if(selected)
    {
        [self setImage:nil forState:UIControlStateNormal];
        _numberOfItems.textColor = [UIColor whiteColor];

        [_rightImage setImage:[UIImage imageNamed:@"carat-open.png"]];

        if(self.tag==1)
        {
            [_leftImage setImage:[UIImage imageNamed:@"white-notes-icon.png"]];
        }
        else if(self.tag==2)
        {

            [_leftImage setImage:[UIImage imageNamed:@"white-photo-icon.png"]];

        }
        else
        {
            [_leftImage setImage:[UIImage imageNamed:@"white-video-icon.png"]];

        }

    }
    else{

        _numberOfItems.textColor = [UIColor darkGrayColor];

        if(self.tag==1)
        {
            [_leftImage setImage:[UIImage imageNamed:@"notes-icon.png"]];

        }
        if(self.tag==2)
        {
            [_leftImage setImage:[UIImage imageNamed:@"photos-icon.png"]];

        }
        if(self.tag==3)
        {
            [_leftImage setImage:[UIImage imageNamed:@"videos-icon.png"]];

        }

        [self setImage:[UIImage imageNamed:@"list-bg2-1.png"] forState:UIControlStateNormal];

        [_rightImage setImage:[UIImage imageNamed:@"carat.png"]];

    }
}
/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
}
*/

@end