Question

在为UIButton定义回调时，我列出了同一动作的几个事件

在目标中，我希望能够区分触发回调的事件

[button addTarget:self action:@selector(callback:) forControlEvents:UIControlEventTouchDown | UIControlEventTouchCancel];

-(void)callback:(UIButton *)button
{
  // need to be able to distinguish between the events
if (event == canceled)
{
}
if (event == touchDown)
{
}
... etc
}

Answer 1

您可以更改操作以采用事件参数，如下所示：

[button addTarget:self action:@selector(callback:event:) forControlEvents:UIControlEventTouchDown | UIControlEventTouchCancel];

-(void)callback:(UIButton *)button (UIEvent*)event {
    ...
}

向回调添加第二个参数将使Cocoa将事件传递给您，以便您可以检查触发回调的内容。

编辑：不幸的是，cocoa does not send you a UIControlEvent，因此找出导致回调的控件事件并不像检查事件类型那么简单。 UIEvent为您提供了一系列触摸，您可以分析这些触摸是否为UITouchPhaseCancelled触摸。这可能不是最方便的做事方式，因此设置多个回调以向您提供正确的类型可能会更好：

[button addTarget:self action:@selector(callbackDown:) forControlEvents:UIControlEventTouchDown];
[button addTarget:self action:@selector(callbackCancel:) forControlEvents:UIControlEventTouchCancel];

-(void)callbackDown:(UIButton*) btn {
    [self callback:btn event:UIControlEventTouchDown];
}
-(void)callbackCancel:(UIButton*) btn {
    [self callback:btn event:UIControlEventTouchCancel];
}
-(void)callback:(UIButton*)btn event:(UIControlEvent) event {
    // Your actual callback
}

Answer 2

最好做到以下几点：

[button addTarget:self action:@selector(callback1) forControlEvents:UIControlEventTouchDown];
[button addTarget:self action:@selector(callback2) forControlEvents:UIControlEventTouchCancel];

当然：

-(void)callback1:(UIButton *)button
{
}

-(void)callback2:(UIButton *)button
{
}

Answer 3

您可以从知道控件事件的第三/第四种方法调用回调：

- (void)buttonTouchDown:(UIButton*)button {
    [self callback:(UIButton*)button forControlEvent:UIControlEventTouchDown];
}


- (void)buttonTouchCancel:(UIButton*)button {
    [self callback:(UIButton*)button forControlEvent:UIControlEventTouchCancel];
}

-(void)callback:(UIButton *)button forControlEvent:(UIControlEvents)controlEvents {
    if (controlEvents == UIControlEventTouchDown) {
       <#do something#>
    }
    if (controlEvents == UIControlEventTouchCancel) {
       <#do something#>
    }
}

Answer 4

如果每个事件需要不同的行为，则应考虑为每个事件编写不同的回调。

如何区分UIButton回调操作的触发事件

4 个答案: