将UITapGestureRecognizer添加到子视图

Question

I have been searching for hours ... Needless to say, I'm rather new in programming. My goal is to display a subview programmatically and to remove it by tapping on it.

Already working: Displaying the subview and removing it by tapping on the view (code below).

Doesn't work - whatever I try: Removing the subview by tapping exclusively on the subview.

Thanks for your help!

My .h-file:

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController {

UIImageView *canvas;
UIImageView *square;

}

@property (nonatomic, strong) UIImageView *canvas;
@property (nonatomic, strong) UIImageView *square;
@property (nonatomic) NSUInteger numberOfTouchesRequired;

- (void)handleSingleTap: (UITapGestureRecognizer *)singleTapGestureRecognizer;


@end

My .m-file:

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

@synthesize canvas;
@synthesize square;


- (void)handleSingleTap: (UITapGestureRecognizer *)singleTapGestureRecognizer {

   NSLog(@"tapGesture");

   [square removeFromSuperview];

}

- (void)loadView {

   canvas = [[UIImageView alloc] initWithFrame: [[UIScreen mainScreen] applicationFrame]];

   [canvas setImage:[UIImage imageNamed:@"canvas.png"]];

   self.view = canvas;

   square = [[UIImageView alloc] initWithFrame:CGRectMake(170, 320, 40, 40)];

   [square setImage:[UIImage imageNamed:@"square.png"]];

   [self.view setUserInteractionEnabled:YES];

   [canvas addSubview:square];

   NSLog(@"square");

}

- (void)viewDidLoad {

   [super viewDidLoad];

   UITapGestureRecognizer *singleTapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleSingleTap:)];

   NSLog(@"initialize");

   singleTapGestureRecognizer.numberOfTapsRequired = 1;

   NSLog(@"number of taps");

   [self.view addGestureRecognizer:singleTapGestureRecognizer];

   NSLog(@"square gestureRecognizer");

}


- (void)didReceiveMemoryWarning {
   [super didReceiveMemoryWarning];
   // Dispose of any resources that can be recreated.
}


@end

Answer 1

Instead of

[self.view addGestureRecognizer:singleTapGestureRecognizer];

you should say

[square addGestureRecognizer:singleTapGestureRecognizer];

Answer 2

If you want to remove a subview exclusively, when you tap on that view, then you will need to add tap gesture on that view

[square addGestureRecognizer:singleTapGestureRecognizer];

rather than

[self.view addGestureRecognizer:singleTapGestureRecognizer];

Edit

Also you will need to setUserInteractionEnabled to YES of UIImage because UIImage's setUserInteractionEnabled is default to NO.

[square setUserInteractionEnabled:YES];