How do you set the tab order in iOS?

Solution 1:

@sprocket's answer was only somewhat helpful. Just because something works out of the box doesn't mean you should stop thinking about a better way -- or even the right way -- of doing something. As he noticed the behavior is undocumented but fits our needs most of the time.

This wasn't enough for me though. Think of a RTL language and tabs would still tab left-to-right, not to mention the behavior is entirely different from simulator to device (device doesn't focus the first input upon tab). Most importantly though, Apple's undocumented implementation seems to only consider views currently installed in the view hierarchy.

Think of a form in form of (no pun intended) a table view. Each cell holds a single control, hence not all form elements may be visible at the same time. Apple would just cycle back up once you reached the bottommost (on screen!) control, instead of scrolling further down. This behavior is most definitely not what we desire.

So here's what I've come up with. Your form should be managed by a view controller, and view controllers are part of the responder chain. So you're perfectly free to implement the following methods:

#pragma mark - Key Commands

- (NSArray *)keyCommands
{
    static NSArray *commands;

    static dispatch_once_t once;
    dispatch_once(&once, ^{
        UIKeyCommand *const forward = [UIKeyCommand keyCommandWithInput:@"\t" modifierFlags:0 action:@selector(tabForward:)];
        UIKeyCommand *const backward = [UIKeyCommand keyCommandWithInput:@"\t" modifierFlags:UIKeyModifierShift action:@selector(tabBackward:)];

        commands = @[forward, backward];
    });

    return commands;
}

- (void)tabForward:(UIKeyCommand *)command
{
    NSArray *const controls = self.controls;
    UIResponder *firstResponder = nil;

    for (UIResponder *const responder in controls) {
        if (firstResponder != nil && responder.canBecomeFirstResponder) {
            [responder becomeFirstResponder]; return;
        }
        else if (responder.isFirstResponder) {
            firstResponder = responder;
        }
    }

    [controls.firstObject becomeFirstResponder];
}

- (void)tabBackward:(UIKeyCommand *)command
{
    NSArray *const controls = self.controls;
    UIResponder *firstResponder = nil;

    for (UIResponder *const responder in controls.reverseObjectEnumerator) {
        if (firstResponder != nil && responder.canBecomeFirstResponder) {
            [responder becomeFirstResponder]; return;
        }
        else if (responder.isFirstResponder) {
            firstResponder = responder;
        }
    }

    [controls.lastObject becomeFirstResponder];
}

Additional logic for scrolling offscreen responders visible beforehand may apply.

Another advantage of this approach is that you don't need to subclass all kinds of controls you may want to display (like UITextFields) but can instead manage the logic at controller level, where, let's be honest, is the right place to do so.

Solution 2:

I'm interested in solving the same problem, although so far the default order, which appears to be left to right, then top to bottom, is the one I want.

I tested the hypothesis that the cursor moves in depth-first order through the tree of subviews and superview, but that is not true. Changing the order of subviews without changing their location didn't change the order of fields traversed by tab presses.

One possibly useful feature is that the text field delegate's textFieldShouldBeginEditing method appears to be called for every text field in the application's window. If that returns NO, then the text field won't be chosen, so if you can define your desired order and make only the right one return YES, that might solve your problem.