Ios – Prevent user from setting cursor position on UITextField

iosiphoneobjective c

I have an UITextField constructed using the storyboard. I want to not allow the user to change the position of the cursor and keep it always at the end of the text into the text field.

I tried to change the position of the cursor at the touchdown event, but when selecting the text field and then change the position of the cursor by touching the text field again, the position is changed:

- (IBAction)amountBoxTouchDown:(id)sender {
    UITextPosition *start = [amountBox positionFromPosition:[amountBox beginningOfDocument] offset:amountBox.text.length];
    UITextPosition *end = [amountBox positionFromPosition:start
                                                   offset:0];
    [amountBox setSelectedTextRange:[amountBox textRangeFromPosition:start toPosition:end]];
}

Does anyone know a solution? Thanks

Best Answer

Simply create a subclass of UITextField and override the closestPositionToPoint method:

- (UITextPosition *)closestPositionToPoint:(CGPoint)point{
    UITextPosition *beginning = self.beginningOfDocument;
    UITextPosition *end = [self positionFromPosition:beginning offset:self.text.length];
    return end;
}

Now the user will be unable to move cursor, it will be always in the end of field.

SWIFT:

override func closestPosition(to point: CGPoint) -> UITextPosition? {
    let beginning = self.beginningOfDocument
    let end = self.position(from: beginning, offset: self.text?.count ?? 0)
    return end
}

Related Solutions

Ios – Control cursor position in UITextField

Controlling cursor position in a UITextField is complicated because so many abstractions are involved with input boxes and calculating positions. However, it's certainly possible. You can use the member function setSelectedTextRange:

[input setSelectedTextRange:[input textRangeFromPosition:start toPosition:end]];

Here's a function which takes a range and selects the texts in that range. If you just want to place the cursor at a certain index, just use a range with length 0:

+ (void)selectTextForInput:(UITextField *)input atRange:(NSRange)range {
    UITextPosition *start = [input positionFromPosition:[input beginningOfDocument] 
                                                 offset:range.location];
    UITextPosition *end = [input positionFromPosition:start
                                               offset:range.length];
    [input setSelectedTextRange:[input textRangeFromPosition:start toPosition:end]];
}

For example, to place the cursor at idx in the UITextField input:

    [Helpers selectTextForInput:input 
                        atRange:NSMakeRange(idx, 0)];

Objective-c – How to determine the cursor position of a UITextField

Clever bit with the keyboards. My immediate thought is that perhaps that you shouldn't allow the user to move the cursor in the first place.

This isn't without precedent in the iPhone UI. The telephone keypad view, for example, restricts the user to sequential input. I have also found this technique useful for currency input. Anywhere with input that has a very rigid syntax, basically, seems like a candidate for this kind of treatment. Might work well for your situation.

Not sure if this is the best method, but here's how I do it:

A UITextField to capture input and a UILabel to display the input. The text field is hidden but is sent becomeFirstResponder to trigger the keyboard. As the user types, delegate methods do their thing to format the text, if necessary (as with currency), and update the UILabel, which provides the user feedback on their input.

Depending upon the situation, you may wish to style the UILabel in such a way that makes it clear the user can't use it as they would a selectable text field while reassuring them that it is, in fact, their input.

With 11 characters in play, I can see how curser editing might be useful. Still, phone numbers are often in that same range and I never have a problem with the sequential editor in the Phone app.

Best Answer

Related Solutions

Ios – Control cursor position in UITextField

Objective-c – How to determine the cursor position of a UITextField

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