Is there a way to change the color of the text inside a textfield as you are typing?

Question

I am looking to change the colour of the font if the text length of the textfield is less than 4. But I only want it to show up when I have finished typing (Gone off the text field).

I have this

if ([_username.text length] < 4){
    _username.textColor = [UIColor redColor];
}
else{
    _username.textColor = [UIColor blackColor];
}

But I don't know what I have to "put it inside of" (New to objective C - Don't know the lingo).

I have tried this but it doesn't work properly as when you return to the text field the font stays red. I want it so that when you are typing it is allways black. And also it only becomes red if you hit the return (Next) key.

- (BOOL)textFieldShouldReturn:(UITextField *)textField 

---

Also why is this not working?

if (textField == _confirm) {
        int resultantLength = textField.text.length + string.length - range.length;
        
        NSLog(@"Length After Additions And Subtractions Will Be: %i letters", resultantLength);
        
        if (![_confirm.text isEqualToString:_password.text]) {
            textField.textColor = [UIColor redColor];
            [_next setEnabled:NO];

        }else{
            [_next setEnabled:YES];
        }
    }

Answer 1

If you'd like to wait til the user is done add this:

- (void)textFieldDidEndEditing:(UITextField *)textField {
    if (textField.text.length < 4){
        textField.textColor = [UIColor redColor];
    }
    else{
        textField.textColor = [UIColor blackColor];
    }
}

If you'd like to do it in real time:

- (BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    int resultantLength = textField.text.length + string.length - range.length;

    NSLog(@"Length After Additions And Subtractions Will Be: %i letters", resultantLength);

    if (resultantLength < 4){
        textField.textColor = [UIColor redColor];
    }
    else{
        textField.textColor = [UIColor blackColor];
    }

    return YES;
}

Note that this will affect any textField that uses the same delegate. If you'd like to only respond to a specific textField, for example _username, do this:

- (BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    if (textField == _username) {
        int resultantLength = textField.text.length + string.length - range.length;

        NSLog(@"Length After Additions And Subtractions Will Be: %i letters", resultantLength);

        if (resultantLength < 4){
            textField.textColor = [UIColor redColor];
        }
        else{
            textField.textColor = [UIColor blackColor];
        }
    }
    return YES;
}

Make sure your ViewController is set up for UITextFieldDelegate protocol and it is the delegate of your textField

Answer 2

To change the text color on every key press, do this:

[myTextField addTarget:self action:@selector(textFieldDidChange:)
                  forControlEvents:UIControlEventEditingChanged];

//....

- (void)textFieldDidChange:(UITextField *)textField
{
    if (textField.text.length > 4) {
      //change color
    } else {
       //change to another color
    }
}

Answer 3

You have to use NSAttributedString. Scan through the word and find the range of your character or letter and change its color.

- (IBAction)colorWord:(id)sender {
NSMutableAttributedString * string = [[NSMutableAttributedString alloc]initWithString:self.text.text];

NSArray *words=[self.text.text componentsSeparatedByString:@" "];

for (NSString *word in words) {        
    if ([word hasPrefix:@"@"]) {
        NSRange range=[self.text.text rangeOfString:word];
        [string addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:range];           
    }
}
[self.text setAttributedText:string];

}

The code above will work for changing the color of a specific word in a sentence. I'm sure you can do the same for a character in a word.

Good luck!

ERID: Here's where I got the code snip-it from. There's also a working app, so you can have a look. AttributedStringOneWord

Answer 4

You can implement the UITextFieldDelegate methods:

1. -textFieldDidEndEditing:
   • to set red color if needed
2. -textFieldShouldBeginEditing:
   • to reset to black color (incase the text was red and you came back to edit)

Example:

-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
    //to set font color to black when user begins editing the textField
    [textField setTextColor:[UIColor blackColor]];

    return YES;
}

-(void)textFieldDidEndEditing:(UITextField *)textField
{
    //for implementing the red font color logic
    NSString *strCurrent = textField.text;

    if (strCurrent.length < 4) {
        [textField setTextColor:[UIColor redColor]];
    } else {
        [textField setTextColor:[UIColor blackColor]];
    }
}

---

Since you're new...
Note:

1. Set delegate for the textField object
   • [textFieldObject setDelegate:self];
2. In the .h of your class file, declare the protocol <UITextFieldDelegate>
   • example: @interface ViewController : UIViewController <UITextFieldDelegate>