UITextField, automatically move to next after 1 ch

问题:

Scenario: I have 4 UITextFields that only accept 1 character. Easy.

Problem: After I enter the 1 character, I want the next TextField to become active automatically without having to press next (i.e. I'm using the UIKeyboardTypeNumberPad, and theres no NEXT button. (I KNOW I can actually create a next button programmatically, but I dont want to go that far, just need the next field to become active automatically after the 1 character is entered.

#define MAX_LENGTH 1

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSCharacterSet *myCharSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
    for (int i = 0; i < [string length]; i++) {
    unichar c = [string characterAtIndex:i];
        if (![myCharSet characterIsMember:c]) {
            return NO;
        }
    }
        NSUInteger newLength = [textField.text length] + [string length] - range.length;
        return (newLength > 1) ? NO : YES;
}


-(BOOL)textFieldShouldReturn:(UITextField *)textField {
    if (textField == pc1) {
        [pc2 becomeFirstResponder];
    }else if (textField == pc2) {
        [pc3 becomeFirstResponder];
    }else if (textField == pc3) {
        [pc4 becomeFirstResponder];
    }else if (textField == pc4) {
        [textField resignFirstResponder];
    }
    return YES;
}

回答1:

I arrived at a solution by modifying some code I found here: http://www.thepensiveprogrammer.com/2010/03/customizing-uitextfield-formatting-for.html

First set the your view controller to be the delegate of the textfields.

Then do something like this:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{   
    BOOL shouldProcess = NO; //default to reject
    BOOL shouldMoveToNextField = NO; //default to remaining on the current field

    int insertStringLength = [string length];
    if(insertStringLength == 0){ //backspace
        shouldProcess = YES; //Process if the backspace character was pressed
    }
    else {
        if([[textField text] length] == 0) {
            shouldProcess = YES; //Process if there is only 1 character right now
        }
    }

    //here we deal with the UITextField on our own
    if(shouldProcess){
        //grab a mutable copy of what's currently in the UITextField
        NSMutableString* mstring = [[textField text] mutableCopy];
        if([mstring length] == 0){
            //nothing in the field yet so append the replacement string
            [mstring appendString:string];

            shouldMoveToNextField = YES;
        }
        else{
            //adding a char or deleting?
            if(insertStringLength > 0){
                [mstring insertString:string atIndex:range.location];
            }
            else {
                //delete case - the length of replacement string is zero for a delete
                [mstring deleteCharactersInRange:range];
            }
        }

        //set the text now
        [textField setText:mstring];

        [mstring release];

        if (shouldMoveToNextField) {
            //
            //MOVE TO NEXT INPUT FIELD HERE
            //
        }
    }

    //always return no since we are manually changing the text field
    return NO;
}

回答2:

I know this is a very old question, but here's my approach for allowing a single numeric value only across four UITextFields, and automatically 'tabbing' to the next one (pin1-pin4 each represents a PIN number digit lol, and are retained as properties):

-(BOOL)textFieldShouldReturn:(UITextField*)textField;
{
    if (textField == pin1)
    {
        [pin2 becomeFirstResponder];
    }
    else if (textField == pin2)
    {
        [pin3 becomeFirstResponder];
    }
    else if (textField == pin3)
    {
        [pin4 becomeFirstResponder];
    }

    return NO;
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    // This allows numeric text only, but also backspace for deletes
    if (string.length > 0 && ![[NSScanner scannerWithString:string] scanInt:NULL])
        return NO;

    NSUInteger oldLength = [textField.text length];
    NSUInteger replacementLength = [string length];
    NSUInteger rangeLength = range.length;

    NSUInteger newLength = oldLength - rangeLength + replacementLength;

    // This 'tabs' to next field when entering digits
    if (newLength == 1) {
        if (textField == pin1)
        {
            [self performSelector:@selector(setNextResponder:) withObject:pin2 afterDelay:0.2];
        }
        else if (textField == pin2)
        {
            [self performSelector:@selector(setNextResponder:) withObject:pin3 afterDelay:0.2];
        }
        else if (textField == pin3)
        {
            [self performSelector:@selector(setNextResponder:) withObject:pin4 afterDelay:0.2];
        }
    }
    //this goes to previous field as you backspace through them, so you don't have to tap into them individually
    else if (oldLength > 0 && newLength == 0) {
        if (textField == pin4)
        {
            [self performSelector:@selector(setNextResponder:) withObject:pin3 afterDelay:0.1];
        }
        else if (textField == pin3)
        {
            [self performSelector:@selector(setNextResponder:) withObject:pin2 afterDelay:0.1];
        }
        else if (textField == pin2)
        {
            [self performSelector:@selector(setNextResponder:) withObject:pin1 afterDelay:0.1];
        }
    }

    return newLength <= 1;
}

- (void)setNextResponder:(UITextField *)nextResponder
{
    [nextResponder becomeFirstResponder];
}

回答3:

UPDATED CODE FOR SWIFT 3

@IBOutlet weak var tf1: UITextField!
@IBOutlet weak var tf2: UITextField!
@IBOutlet weak var tf3: UITextField!
@IBOutlet weak var tf4: UITextField!
override func viewDidLoad() {
    super.viewDidLoad()
    tf1.delegate = self
    tf2.delegate = self
    tf3.delegate = self
    tf4.delegate = self


    tf1.addTarget(self, action: #selector(self.textFieldDidChange(textField:)), for: UIControlEvents.editingChanged)
    tf2.addTarget(self, action: #selector(self.textFieldDidChange(textField:)), for: UIControlEvents.editingChanged)
    tf3.addTarget(self, action: #selector(self.textFieldDidChange(textField:)), for: UIControlEvents.editingChanged)
    tf4.addTarget(self, action: #selector(self.textFieldDidChange(textField:)), for: UIControlEvents.editingChanged)

}
override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(true)
    tf1.becomeFirstResponder()

}
func textFieldDidChange(textField: UITextField){

    let text = textField.text

    if text?.utf16.count==1{
        switch textField{
        case tf1:
            tf2.becomeFirstResponder()
        case tf2:
            tf3.becomeFirstResponder()
        case tf3:
            tf4.becomeFirstResponder()
        case tf4:
            tf4.resignFirstResponder()
        default:
            break
        }
    }else{

    }
}

回答4:

Swift 4.x

textField.addTarget(self, action: #selector(self.textFieldDidChange(textField:)), for: .editingChanged)

---

@objc func textFieldDidChange(textField: UITextField)
{
    let text = textField.text
    if text?.utf16.count == 1 {
        switch textField {
        case txtOtpNumber1:
            txtOtpNumber2.becomeFirstResponder()
        case txtOtpNumber2:
            txtOtpNumber3.becomeFirstResponder()
        case txtOtpNumber3:
            txtOtpNumber4.becomeFirstResponder()
        case txtOtpNumber4:
            txtOtpNumber4.resignFirstResponder()
        default:
            break
        }
    } else {
        switch textField {
        case txtOtpNumber4:
            txtOtpNumber3.becomeFirstResponder()
        case txtOtpNumber3:
            txtOtpNumber2.becomeFirstResponder()
        case txtOtpNumber2:
            txtOtpNumber1.becomeFirstResponder()
        case txtOtpNumber1:
            txtOtpNumber1.resignFirstResponder()
        default:
            break
        }
    }
}

_{PS. Chetan's answer updated for the current Swift.}

回答5:

Although it is an old question, I just came cross it and I came with simpler solution. assuming we doing this for pass code so each box (UITextField) max length is one char.

- (BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    if (![string isEqualToString:@""]) {
        textField.text = string;
        if ([textField isEqual:self.txtField1]) {
            [self.txtField2 becomeFirstResponder];
        }else if ([textField isEqual:self.txtField2]){
            [self.txtField3 becomeFirstResponder];
        }else if ([textField isEqual:self.txtField3]){
            [self.txtField4 becomeFirstResponder];
        }else{
            [textField resignFirstResponder];
        }
        return NO;
    }
    return YES;
}

-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField{
    if (textField.text.length > 0) {
        textField.text = @"";
    }
    return YES;
}