检测UITextfield中的文本更改 [英] Detecting a change to text in UITextfield

问题描述

我希望能够检测到某些文本是否在 UITextField 中更改，以便我可以启用 UIButton 保存更改。

I would like to be able to detect if some text is changed in a UITextField so that I can then enable a UIButton to save the changes.

推荐答案

利用UITextFieldTextDidChange通知或在文本字段上设置委托并注意textField：shouldChangeCharactersInRange：replacementString。

Take advantage of the UITextFieldTextDidChange notification or set a delegate on the text field and watch for textField:shouldChangeCharactersInRange:replacementString.

如果你想通过通知观察变化，你需要在你的代码中注册这样的通知：

If you want to watch for changes with a notification, you'll need something like this in your code to register for the notification:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textFieldDidChange:) name:UITextFieldTextDidChangeNotification object:theTextField];

此处theTextField是您要观看的UITextField实例。其中self是上面代码中的实例的类必须实现textFieldDidChange，如下所示：

Here theTextField is the instance of UITextField that you want to watch. The class of which self is an instance in the code above must then implement textFieldDidChange, like so:

- (void)textFieldDidChange:(NSNotification *)notification {
    // Do whatever you like to respond to text changes here.
}

如果文本字段比观察者寿命长，那么你必须取消注册以获取观察者的dealloc方法中的通知。实际上即使文本字段没有超过观察者，这也是一个好主意。

If the text field is going to outlive the observer, then you must deregister for notifications in the observer's dealloc method. Actually it's a good idea to do this even if the text field does not outlive the observer.

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    // Other dealloc work
}

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