UITextView子类作为自身的委托 [英] UITextView subclass as delegate of itself

问题描述

假设我在 UIView 中添加了 UITextView ，我希望它每次更改其背景颜色内容改变。我可以通过成为 UITextView 的代理并实现 textViewDidChange 来实现。

Let's say I add a UITextView to my UIView, and I want it to change its background color each time the contents change. I can do this by becoming the delegate of the UITextView and implementing textViewDidChange.

如果我经常使用这个行为，创建一个 UITextView 子类是有意义的，我将调用 ColorSwitchingTextView 。它应该包括默认的颜色切换行为，所以任何 UIView 可以简单地添加它而不是标准 UITextView

If I am using this behavior frequently though, it makes sense to create a UITextView subclass, which I will call ColorSwitchingTextView. It should include the color-switching behavior by default, so that any UIView can simply add it instead of a standard UITextView if it wants that behavior.

如何从我的 ColorSwitchingTextView 类中检测内容的更改？我不认为我可以做像 self.delegate = self 。

How do I detect changes in the content from within my ColorSwitchingTextView class? I don't think I can do something like self.delegate = self.

总之， UITextView 子类如何知道其内容何时改变？

In summary, how can a UITextView subclass know when its contents change?

EDIT
看来我可以使用 self.delegate = self ，但是这意味着UIViewController使用 ColorSwitchingTextView 也不能订阅通知。一旦我在视图控制器中使用 switchingTextView.delegate = self ，子类行为不再工作。任何解决方法？我试图得到一个自定义 UITextView ，否则工作像一个常规 UITextView 。

EDIT It seems I can use self.delegate = self, but this means that the UIViewController that uses the ColorSwitchingTextView can not also subscribe to the notifications. Once I use switchingTextView.delegate = self in the view controller, the subclass behavior no longer works. Any workarounds? I'm trying to get a custom UITextView that otherwise works like a regular UITextView.

推荐答案

在您的子类中，监听 UITextViewTextDidChangeNotification 通知并在收到通知时更新背景颜色，像这样：

In your subclass, listen for the UITextViewTextDidChangeNotification notification and update the background color when you receive the notification, like this:

/* 
 * When you initialize your class (in `initWithFrame:` and `initWithCoder:`), 
 * listen for the notification:
 */
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(myTextDidChange)
                                             name:UITextViewTextDidChangeNotification
                                           object:self];

...

// Implement the method which is called when our text changes:
- (void)myTextDidChange 
{
    // Change the background color
}

- (void)dealloc
{
    // Stop listening when deallocating your class:
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

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