我如何知道UITextField的文本是否已被用户修改

Question

I work on a project for iPhone iOS 4 and Xcode 4.

There is a method to know if the text of a UITextField ha been modified by the user?

For example,I have 2 UITextField, textFieldA and textFieldB, and suppose that textField contains some text as "abc".

The user first tap in textFieldA (keyboard opens), and then in textFieldB. How can I know if the text in textFieldA has been modified by the user?

Thank you.

Answer 1

How about: First subscribe to the text field delegate in your header file with:
<UITextFieldDelegate>

Then somewhere in your implementation file (.m), you can add: myTextField.delegate = self;

Now you can access the delegate methods for text fields. This means you can now use:

    -(void)textFieldDidBeginEditing:(UITextField *)textField

and -(void)textFieldDidEndEditing:(UITextField *)textField

Why not store the value of your text field in textFieldDidBeginEditing and compare it to it's value in textFieldDidEndEditing? `

Answer 2

Better to have the text field send a UIControlEventValueChanged action message to your controller. This way you don't need to wonder if the user actually edited the text field. You can either wire the target/action in IB or do it programmatically:

[myTextField addTarget:self 
                action:@selector(textFieldValueChanged:)
      forControlEvents:UIControlEventValueChanged];

Then implement the appropriate action in the target:

- (IBAction)textFieldValueChanged:(UITextField *)sender {
    // text field value was changed
}

This is discussed in more detail for this question

Answer 3

将操作连接到文本字段并选择“值已更改”事件，然后每次用户更改文本字段的值（文本）时，将执行该操作

Answer 4

You will have to implement the uitextfielddelegate protocol. Check the documentation for more details.