UIControl - 更改分配的选择器：addTarget& removeTarget [英] UIControl - changing assigned selectors: addTarget & removeTarget

问题描述

我在界面中使用了10个按钮，需要不时更改按钮的选择器。

I'm using 10 buttons in my interface and need, from time to time, to change the button's selector.

我需要使用：

-(void)removeTarget:(id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents 

之前，我可以使用：

-(void)addTarget:(id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents 

我担心，如果我改变选择器使用addTarget：方法不使用removeTarget：方法，我将本质上堆叠选择器为我的UIButton触发时按下。 p>

I'm concerned that if I change the selector using the addTarget: method sans the removeTarget: method that I'll essentially "stack up" selectors for my UIButton to fire when it is pressed.

推荐答案

是的，您应该在将新目标分配给按钮之前，始终删除先前添加的目标。像这样---

Yes you should always remove the previously add target before assigning the new target to the button. Like this---

UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [btn setFrame:CGRectMake(50, 50, 200, 50)];

    [btn setTag:101];
    [btn addTarget:self action:@selector(method1) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];


    btn = (UIButton *)[self.view viewWithTag:101];
    [btn removeTarget:self action:@selector(method1) forControlEvents:UIControlEventTouchUpInside];
    [btn addTarget:self action:@selector(method2) forControlEvents:UIControlEventTouchUpInside];

现在如果你这样做

btn = (UIButton *)[self.view viewWithTag:101];
        [btn addTarget:self action:@selector(method2) forControlEvents:UIControlEventTouchUpInside];

那么将调用method1和method2方法。

then both the methods method1 and method2 will be called.

希望这有帮助。

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