Automated iOS form component for tabbing through text fields and auto scrolling/sizing scroll views

OrderedForm.h

//
//  OrderedForm.h
//  KSLClassifieds
//
//  Created by Dustin Graham on 11/4/11.
//  Copyright (c) 2011 __MyCompanyName__. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "StandardInputAccessory.h"

@interface OrderedForm : NSObject <UITextFieldDelegate, UITextViewDelegate, StandardInputAccessoryDelegate>{
    float _scrollFrameHeight;
    BOOL _keyboardShown;
}

@property (nonatomic, strong) NSMutableArray *orderedResponders;
@property (nonatomic, strong) UIScrollView *scrollView;
@property (nonatomic, strong) StandardInputAccessory *inputAccessory;
@property(nonatomic, strong) id activeField;

- (id)initWithOrderedResponders:(NSArray *)responders scrollView:(UIScrollView *)formContainer;
@end

OrderedForm.m

//
//  OrderedForm.m
//  KSLClassifieds
//
//  Created by Dustin Graham on 11/4/11.
//  Copyright (c) 2011 __MyCompanyName__. All rights reserved.
//

#import "OrderedForm.h"

#define KEYBOARD_FIELD_PADDING 25.0f

@interface OrderedForm ()



- (void)registerForKeyboardNotifications;

- (void)scrollToActiveField;
@end

@implementation OrderedForm
@synthesize orderedResponders, inputAccessory;
@synthesize activeField = _activeField;
@synthesize scrollView = _scrollView;

- (id)initWithOrderedResponders:(NSArray *)responders scrollView:(UIScrollView *)formContainer {
    self = [super init];
    if (self) {
        // custom initialization
        self.orderedResponders = [[NSMutableArray alloc] init];
        inputAccessory = [[StandardInputAccessory alloc] init];
        inputAccessory.delegate = self;
        for (id formElement in responders) {
            if ([formElement conformsToProtocol:@protocol(UITextInput)] || [formElement conformsToProtocol:@protocol(UITextInputTraits)]) {
                [formElement setInputAccessoryView:inputAccessory];
                [formElement performSelector:@selector(setDelegate:) withObject:self];
                [self.orderedResponders addObject:formElement];
            }
        }
        self.scrollView = formContainer;
        [self registerForKeyboardNotifications];
    }
    return self;
}

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)setActiveField:(id)activeField {
    _activeField = activeField;
    int index = [self.orderedResponders indexOfObject:activeField];
    if (index == 0) {
        [inputAccessory hasPrevious:NO];
        [inputAccessory hasNext:YES];
    } else if (index == [self.orderedResponders count] - 1) {
        [inputAccessory hasPrevious:YES];
        [inputAccessory hasNext:NO];
    } else {
        [inputAccessory hasPrevious:YES];
        [inputAccessory hasNext:YES];
    }
}

#pragma mark - first responder methods
- (void)enableNextResponder {
    if (self.activeField) {
        NSInteger indexOfActiveField = [self.orderedResponders indexOfObject:self.activeField];
        indexOfActiveField++;

        UITextField *nextResponder = [self.orderedResponders objectAtIndex:indexOfActiveField];
        [nextResponder becomeFirstResponder];
        [self scrollToActiveField];
    }
}

- (void)enablePrevResponder {
    if (self.activeField) {
        NSInteger indexOfActiveField = [self.orderedResponders indexOfObject:self.activeField];
        indexOfActiveField--;

        UITextField *previousResponder = [self.orderedResponders objectAtIndex:indexOfActiveField];
        [previousResponder becomeFirstResponder];
        [self scrollToActiveField];
    }
}

#pragma mark - UITextFieldDelegate methods
- (void)textFieldDidBeginEditing:(UITextField *)textField {
    self.activeField = textField;
}

- (void)textFieldDidEndEditing:(UITextField *)textField {
    self.activeField = nil;
}

#pragma mark - UITextViewDelegate methods
- (void)textViewDidBeginEditing:(UITextView *)textView {
    self.activeField = textView;
}

- (void)textViewDidEndEditing:(UITextView *)textView {
    self.activeField = nil;
}

- (void)inputAccessory:(StandardInputAccessory *)accessory pushedButton:(int)which {

    if (which == PREVIOUS_BUTTON) {
        [self enablePrevResponder];
    } else if (which == NEXT_BUTTON) {
        [self enableNextResponder];
    } else {
        [self.orderedResponders makeObjectsPerformSelector:@selector(resignFirstResponder)];
    }
}

#pragma mark - ScrollView and Keyboard management

- (void)scrollToActiveField {
    if (self.activeField) {
        CGPoint point = ((UIView *) _activeField).frame.origin;
        point = [((UIView *) _activeField) convertPoint:point toView:_scrollView];
        CGPoint lowerPoint = CGPointMake(point.x, point.y + ((UIView *) _activeField).frame.size.height);
        CGPoint upperPoint = point;
        if (!([_scrollView pointInside:upperPoint withEvent:nil] && [_scrollView pointInside:lowerPoint withEvent:nil])) {
                point.x = 0;
            if (_activeField == [self.orderedResponders objectAtIndex:0]) {
                point.y = 0;
            } else {
                if (((UIView *) _activeField).frame.size.height + 25.0f < _scrollView.frame.size.height) {
                    point.y -= _scrollView.frame.size.height - ((UIView *) _activeField).frame.size.height - 25.0f;
                }
                if (point.y > _scrollView.contentSize.height - _scrollView.bounds.size.height)
                        point.y = _scrollView.contentSize.height - _scrollView.bounds.size.height;
            }
            [_scrollView setContentOffset:point animated: YES];
        }
    }
}

- (void)registerForKeyboardNotifications {
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWasShown:)
                                                 name:UIKeyboardDidShowNotification object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification object:nil];
}

- (void)keyboardWasShown:(NSNotification *)notification {
    if (_keyboardShown)
        return;

    CGFloat keyboardOriginY = [[notification.userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].origin.y - 44.0f - 20.0f;
    // TODO: Why does 20 work here?

    // Resize the scroll view
    CGRect scrollFrame = _scrollView.frame;
    // Save the original height of the scroll view so we can restore it when the keyboard is hidden
    _scrollFrameHeight = scrollFrame.size.height;
    scrollFrame.size.height = keyboardOriginY;
    _scrollView.frame = scrollFrame;

    [self scrollToActiveField];

    _keyboardShown = YES;
}


- (void)keyboardWillHide:(NSNotification *)notification {
    NSTimeInterval animationDuration = [[notification.userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];

    // Reset the height of the scroll view to its original value
    [UIView animateWithDuration:animationDuration animations:^{
        CGRect scrollFrame = _scrollView.frame;
        scrollFrame.size.height = _scrollFrameHeight;
        _scrollView.frame = scrollFrame;
    }];

    _keyboardShown = NO;
}

@end