Question

I have successfully integrated the three20 framework in my project,
and I have extended the TTPhotoViewController to add some further
functionality.

Now I need to add some subviews to the TTPhotoView loaded by the
TTPhotoViewController. In particular I would like to add that subviews
after every TTPhotoView as been loaded. These subviews represents
sensible area over the image so they should scale proportionally with
the image.
The user can tap a subview to get extra info about the image.

I don’t know how to implement this behavior. Should I extend the
TTPhotoView and make sure that the TTPhotoViewController use this
extended version instead of its TTPhotoView?

Could someone point me to the right direction?
Thank you

Answer 1

Solved subclassing the TTPhotoView (TapDetectingPhotoView) and then adding all my subviews to that subclass.
The main problem was represented by the photo switching, because the TTPhotoViewController (in particular its inner TTScrollView) reuse the TTPhotoView during switching operation.
So for example if you add your subview to your TTPhotoView subclass and try to switch to the next photo, your subview will probably be here, because the TTPhotoView is reused.
To solve this problem I decided to add and remove all my subviews every time a photo switch occur (see TTPhotoViewController::didMoveToPhoto).
In this way I’m sure that every photoview has its subviews.

Here my implementation (only remarkable methods)
Hope these help!

PhotoViewController.h:

#import "TapDetectingPhotoView.h"


@interface PhotoGalleryController : TTPhotoViewController <TTScrollViewDelegate, TapDetectingPhotoViewDelegate> {

    NSArray *images;
}
@property (nonatomic, retain) NSArray *images;
@end

PhotoViewController.m:

#import "PhotoGalleryController.h"

@implementation PhotoGalleryController
@synthesize images;

- (void)viewDidLoad { // fill self.images = ... }

- (TTPhotoView*)createPhotoView {
    TapDetectingPhotoView *photoView = [[TapDetectingPhotoView alloc] init];
    photoView.tappableAreaDelegate = self;

    return [photoView autorelease];
}

#pragma mark -
#pragma mark TTPhotoViewController

- (void)didMoveToPhoto:(id<TTPhoto>)photo fromPhoto:(id<TTPhoto>)fromPhoto {
    [super didMoveToPhoto:photo fromPhoto:fromPhoto];

    TapDetectingPhotoView *previousPhotoView = (TapDetectingPhotoView *)[_scrollView pageAtIndex:fromPhoto.index];
    TapDetectingPhotoView *currentPhotoView = (TapDetectingPhotoView *)[_scrollView pageAtIndex:photo.index];

    // destroy the sensible areas from the previous photoview, because the photo could be reused by the TTPhotoViewController!
    if (previousPhotoView)
        previousPhotoView.sensibleAreas = nil;

    // if sensible areas has not been already created, create new
    if (currentPhotoView && currentPhotoView.sensibleAreas == nil) {
        currentPhotoView.sensibleAreas = [[self.images objectAtIndex:photo.index] valueForKey:@"aMap"];
        [self showSensibleAreas:YES animated:YES];
    }
}


#pragma mark -
#pragma mark TappablePhotoViewDelegate

// show a detail view when a sensible area is tapped
- (void)tapDidOccurOnSensibleAreaWithId:(NSUInteger)ids {
    NSLog(@"SENSIBLE AREA TAPPED ids:%d", ids); 
    // ..push new view controller...
}

TapDetectingPhotoView.h:

#import "SensibleAreaView.h"

@protocol TapDetectingPhotoViewDelegate;

@interface TapDetectingPhotoView : TTPhotoView <SensibleAreaViewDelegate> {
    NSArray *sensibleAreas;
    id <TapDetectingPhotoViewDelegate> tappableAreaDelegate;
}

@property (nonatomic, retain) NSArray *sensibleAreas;
@property (nonatomic, assign) id <TapDetectingPhotoViewDelegate> tappableAreaDelegate;
@end


@protocol TapDetectingPhotoViewDelegate <NSObject>
@required
- (void)tapDidOccurOnSensibleAreaWithId:(NSUInteger)ids;
@end

TapDetectingPhotoView.m:

#import "TapDetectingPhotoView.h"


@interface TapDetectingPhotoView (Private)
- (void)createSensibleAreas;
@end


@implementation TapDetectingPhotoView

@synthesize sensibleAreas, tappableAreaDelegate;


- (id)init {
    return [self initWithSensibleAreas:nil];
}

- (id)initWithFrame:(CGRect)frame {
    return [self initWithSensibleAreas:nil];
}

// designated initializer
- (id)initWithSensibleAreas:(NSArray *)areasList {
    if (self = [super initWithFrame:CGRectZero]) {
        self.sensibleAreas = areasList;
        [self createSensibleAreas];
    }

    return self;
}

- (void)setSensibleAreas:(NSArray *)newSensibleAreas {
    if (newSensibleAreas != self.sensibleAreas) {
        // destroy previous sensible area and ensure that only sensible area's subviews are removed
        for (UIView *subview in self.subviews)
            if ([subview isMemberOfClass:[SensibleAreaView class]])
                [subview removeFromSuperview];

        [newSensibleAreas retain];
        [sensibleAreas release];
        sensibleAreas = newSensibleAreas;
        [self createSensibleAreas];
    }
}

- (void)createSensibleAreas {
    SensibleAreaView *area;
    NSNumber *areaID;
    for (NSDictionary *sensibleArea in self.sensibleAreas) {
        CGFloat x1 = [[sensibleArea objectForKey:@"nX1"] floatValue];
        CGFloat y1 = [[sensibleArea objectForKey:@"nY1"] floatValue];

        area = [[SensibleAreaView alloc] initWithFrame:
            CGRectMake(
                x1, y1, 
                [[sensibleArea objectForKey:@"nX2"] floatValue]-x1, [[sensibleArea objectForKey:@"nY2"] floatValue]-y1
            )
    ];

        areaID = [sensibleArea objectForKey:@"sId"];
        area.ids = [areaID unsignedIntegerValue]; // sensible area internal ID
        area.tag = [areaID integerValue];
        area.delegate = self;
        [self addSubview:area];
        [area release];
    }
}

// to make sure that if the zoom factor of the TTScrollView is > than 1.0 the subviews continue to respond to the tap events
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event { 
    UIView *result = nil;
    for (UIView *child in self.subviews) {
        CGPoint convertedPoint = [self convertPoint:point toView:child];
        if ([child pointInside:convertedPoint withEvent:event]) {
            result = child;
        }
    }

    return result;
}

#pragma mark -
#pragma mark TapDetectingPhotoViewDelegate methods

- (void)tapDidOccur:(SensibleAreaView *)aView {
    NSLog(@"tapDidOccur ids:%d tag:%d", aView.ids, aView.tag);
    [tappableAreaDelegate tapDidOccurOnSensibleAreaWithId:aView.ids];
}

SensibleAreaView.h:

@protocol SensibleAreaViewDelegate;

@interface SensibleAreaView : UIView {
    id <SensibleAreaViewDelegate> delegate;
    NSUInteger ids;
    UIButton *disclosureButton;
}

@property (nonatomic, assign) id <SensibleAreaViewDelegate> delegate;
@property (nonatomic, assign) NSUInteger ids;
@property (nonatomic, retain) UIButton *disclosureButton;

@end


@protocol SensibleAreaViewDelegate <NSObject>
@required
- (void)tapDidOccur:(SensibleAreaView *)aView;
@end

SensibleAreaView.m:

#import "SensibleAreaView.h"

@implementation SensibleAreaView

@synthesize delegate, ids, disclosureButton;


- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        self.userInteractionEnabled = YES;

        UIColor *color = [[UIColor alloc] initWithWhite:0.4 alpha:1.0]; 
        self.backgroundColor = color;
        [color release];

        UIButton *button = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
        [button addTarget:self action:@selector(buttonTouched) forControlEvents:UIControlEventTouchUpInside];
        CGRect buttonFrame = button.frame;
        // set the button position over the right edge of the sensible area
        buttonFrame.origin.x = frame.size.width - buttonFrame.size.width + 5.0f;
        buttonFrame.origin.y = frame.size.height/2 - 10.0f;
        button.frame = buttonFrame;
        button.autoresizingMask = UIViewAutoresizingFlexibleTopMargin |UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleLeftMargin |UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleWidth |UIViewAutoresizingFlexibleHeight;
        self.disclosureButton = button;
        [self addSubview:button];

        // notification used to make sure that the button is properly scaled together with the photoview. I do not want the button looks bigger if the photoview is zoomed, I want to preserve its default dimensions
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(zoomFactorChanged:) name:@"zoomFactorChanged" object:nil];
    }

    return self;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesBegan:touches withEvent:event];

    if ([[touches anyObject] tapCount] == 1)
        [delegate tapDidOccur:self];
}


- (void)buttonTouched {
[delegate tapDidOccur:self];
}

- (void)zoomFactorChanged:(NSNotification *)message {
    NSDictionary *userInfo = [message userInfo];
    CGFloat factor = [[userInfo valueForKey:@"zoomFactor"] floatValue];
    BOOL withAnimation = [[userInfo valueForKey:@"useAnimation"] boolValue];

    if (withAnimation) {
        [UIView beginAnimations:nil context:nil];
        [UIView setAnimationDuration:0.18];
    }

    disclosureButton.transform = CGAffineTransformMake(1/factor, 0.0, 0.0, 1/factor, 0.0, 0.0);

    if (withAnimation)
        [UIView commitAnimations];
}


- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self name:@"zoomFactorChanged"   object:nil];
    [disclosureButton release];
    [super dealloc];
}