Question

我正在尝试理清事件的运作方式。在关于iTunes U的斯坦福大学课程的视频4中，Alan Cannistraro说有

“3种不同风格的动作方法选择器类型 - （void）actionMethod; - （void）actionMethod：（id）sender; - （void）actionMethod：（id）sender withEvent：（UIEvent *）event;“

我以为我会用一个简单的添加程序来尝试它们 - 你输入2个数字，当你输入时，总和会在第三个UITextField中获得位置。我有一个没有参数签名的方法，它工作正常。当我使用sender参数将其更改为第二个时，代码将停止调用该方法。

这有效：

-(void) setSum {
float a1 = addend1.text.floatValue;
float a2 = addend2.text.floatValue;
float thesum = a1 + a2;
NSString * ssum = [NSString stringWithFormat:@"%g", thesum]; 
sum.text = ssum;
}

-(void)awakeFromNib {
SEL setSumMethod = @selector(setSum);
[addend1 addTarget: self action: setSumMethod forControlEvents: UIControlEventEditingChanged];
[addend2 addTarget: self action: setSumMethod forControlEvents: UIControlEventEditingChanged];
}// awakeFromNib

这会运行，但不会调用setSum：

-(void) setSum:(id) sender {
float a1 = addend1.text.floatValue;
float a2 = addend2.text.floatValue;
float thesum = a1 + a2;
NSString * ssum = [NSString stringWithFormat:@"%g", thesum]; 
sum.text = ssum;
}


-(void)awakeFromNib {
SEL setSumMethod = @selector(setSum:);
[addend1 addTarget: self action: setSumMethod forControlEvents: UIControlEventEditingChanged];
[addend2 addTarget: self action: setSumMethod forControlEvents: UIControlEventEditingChanged];
}// awakeFromNib

所以，问题是其他事件方法类型何时起作用？只有第一个似乎适用。

TIA

标记

Answer 1

很老的问题，我知道......

我刚试过它：

- (void) onField
{
    NSLog(@"onField");
}

- (void) onField:(id) sender
{
    NSLog(@"onField: %@", sender);
}

- (void) onField:(id) sender event:(id)event
{
    NSLog(@"onField: %@\n%@", sender, event);
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    UITextField *field = [[[UITextField alloc] initWithFrame:CGRectMake(0, 100, 100, 100)] autorelease];
    [field setText:@"text"];
    [field addTarget:self action:@selector(onField) forControlEvents:UIControlEventEditingChanged];
    [field addTarget:self action:@selector(onField:) forControlEvents:UIControlEventEditingChanged];
    [field addTarget:self action:@selector(onField:event:) forControlEvents:UIControlEventEditingChanged];
    [window addSubview:field];

    [window makeKeyAndVisible];

    return YES;
}

结果：

2010-11-04 11:35:59.940 Untitled[599:207] onField
2010-11-04 11:35:59.941 Untitled[599:207] onField: <UITextField: 0x6a0c1f0; frame = (0 100; 100 100); text = 'textsfr'; clipsToBounds = YES; opaque = NO; layer = <CALayer: 0x6a0c350>>
2010-11-04 11:35:59.944 Untitled[599:207] onField: <UITextField: 0x6a0c1f0; frame = (0 100; 100 100); text = 'textsfr'; clipsToBounds = YES; opaque = NO; layer = <CALayer: 0x6a0c350>>
(null)

所以它才有效。问题出在其他地方。

如何使用带参数的事件处理程序？

1 个答案: