UIControl 子类 - 事件调用两次 [英] UIControl Subclass - Events called twice

问题描述

我目前正在研究自定义 UIControl 子类.要跟踪触摸，我使用以下方法:

I'm currently working on a custom UIControl Subclass. To track the touches I use the following Method:

- (BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event {
 NSLog(@"Start");
 CGPoint location = [touch locationInView:self];
 if ([self touchIsInside:location] == YES) {
    //Touch Down
    [self sendActionsForControlEvents:UIControlEventTouchDown];
    return YES;
 }
 else {
    return NO;
 }  
}

这按预期工作，@"Start" 只记录一次.下一步是我使用 UIControlEventTouchDown 添加一个 Target 和一个 Selector.

This works as expected and @"Start" is loged exactely once. The next step is that I add a Target and a Selector with UIControlEventTouchDown.

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

这也有效，并且调用了 action: 方法.但那是我的问题.该动作被调用两次.我究竟做错了什么?我只使用 [self sendActionsForControlEvents:UIControlEventTouchDown]; 一次，目标操作被调用两次.我的代码有什么问题?

This works also and the action: method is called. But that's my problem. The action is called twice. What am I doing wrong? I just use [self sendActionsForControlEvents:UIControlEventTouchDown]; once and the target action is called twice. What's wrong with my code?

桑德罗·迈耶

推荐答案

第一次调用 action 方法会在您调用后由事件调度程序自动发生:

The first call to the action method happens automatically by the event dispatcher once you've called:

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

注册处理程序.

所以当你打电话时:

//Touch Down
[self sendActionsForControlEvents:UIControlEventTouchDown];

您正在生成对您的处理程序(以及任何其他连接的)的第二个调用.

you are generating the second call to your handler (and any others that are hooked up).

所以看起来你不需要动作处理程序和 beginTracking - 使用其中之一.

So it seems like you don't need both the action handler and the beginTracking - use one or the other.

更新:

根据您的评论和进一步思考:由于您是 UIControl 的子类，我认为您可能不想为自己注册事件处理程序.

Given your comment and further thought: since you are a subclass of UIControl, I think you probably don't want to be registering for event handlers for yourself.

相反，您应该专门使用:

Instead you should exclusively use:

- (BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event;
- (BOOL)continueTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event;
- (void)endTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event;
- (void)cancelTrackingWithEvent:(UIEvent *)event;   // event may be nil if cancelled for non-event reasons, e.g. removed from window

也是 tracking 实例变量.

所以我认为您不应该发布活动或收听活动.此外，如果它不在您的视野中，是否真的有可能获得 beginTrackingWithTouch 事件?似乎不会.所以我认为你不需要测试来看看它是否在你的视野中.

So I think you should not be posting events or listening to events. Further, is it actually possible to get a beginTrackingWithTouch event if it's not in your view? Doesn't seem like it would be. So I don't think you need the testing to see if it's in your view.

所以我认为有必要退后一步思考您正在尝试做什么并重新阅读 UIControl 文档.具体:

So I think it might be worth stepping back and thinking about what you are trying to do and re-reading UIControl documentation. Specifically:

子类化注释你可能想扩展一个 UIControl 子类两个原因之一:

Subclassing Notes You may want to extend a UIControl subclass for either of two reasons:

观察或修改动作消息到目标的分派特定事件为此，覆盖sendAction:to:forEvent:，评估传入的选择器、目标对象或 UIControlEvents 位掩码，然后按要求进行.

To observe or modify the dispatch of action messages to targets for particular events To do this, override sendAction:to:forEvent:, evaluate the passed-in selector, target object, or UIControlEvents bit mask, and proceed as required.

提供自定义跟踪行为(例如，更改突出显示外观)为此，请覆盖以下一项或全部方法:beginTrackingWithTouch:withEvent:,continueTrackingWithTouch:withEvent:, endTrackingWithTouch:withEvent:.

To provide custom tracking behavior (for example, to change the highlight appearance) To do this, override one or all of the following methods: beginTrackingWithTouch:withEvent:, continueTrackingWithTouch:withEvent:, endTrackingWithTouch:withEvent:.

第一部分是让您的 UIControl 子类为您的控件的客户端或用户执行目标操作处理的非标准处理(尽管这听起来不像您想要做的)你真的没有给出高层次的描述).

The first part is for having your UIControl subclass do non-standard handling of target action processing for clients or users of your control (that doesn't sound like what you are trying to do, though you didn't really give a high-level description).

第二部分听起来更像是您想要做的 - UIControl 子类中的自定义跟踪.

The second part sounds more like what you are wanting to do - custom tracking within your UIControl subclass.

这篇关于UIControl 子类 - 事件调用两次的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！