IOS-移除imageView

Question

屏幕上有一张图片需要在停留的时候全屏。

    UILongPressGestureRecognizer *hold = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(hold:)];
    hold.minimumPressDuration = 0;

    [self.photoImageView addGestureRecognizer:hold];

监听器：

-(void)hold:(UILongPressGestureRecognizer *)sender{
    UIImageView *img = [[UIImageView alloc] initWithImage:self.photo];
    img.userInteractionEnabled = NO;

    if(sender.state == UIGestureRecognizerStateBegan){
        NSLog(@"state began");
        [self.view addSubview:img];
    } else if (sender.state == UIGestureRecognizerStateEnded){
        NSLog(@"state ended");
        [img removeFromSuperview];
    }
}

图片成功添加到屏幕中，只有 [img removeFromSuperview]好像没有响应。

结束状态的NSlog也正常。

Answer 1

-(void)hold:(UILongPressGestureRecognizer *)sender{
    //每次响应函数 img都是一个新alloc出来的UIImageView
    UIImageView *img = [[UIImageView alloc] initWithImage:self.photo];
    img.userInteractionEnabled = NO;

    if(sender.state == UIGestureRecognizerStateBegan){
        NSLog(@"state began");
        //添加新alloc出来的UIImageView，可以看到界面效果
        [self.view addSubview:img];
    } else if (sender.state == UIGestureRecognizerStateEnded){
        NSLog(@"state ended");
       //remove 新alloc出来的UIImageView当然没有效果，它还没有被add进去
        [img removeFromSuperview];
    }
}

改成这样

-(void)hold:(UILongPressGestureRecognizer *)sender{
    if(sender.state == UIGestureRecognizerStateBegan){
        NSLog(@"state began");
        UIImageView *img = [[UIImageView alloc] initWithImage:self.photo];
        img.userInteractionEnabled = NO;
        img.tag = kTAG_PHOTO_IMAGE_VIEW
        [self.view addSubview:img];
    } else if (sender.state == UIGestureRecognizerStateEnded){
        NSLog(@"state ended");
        UIImageView *img = (UIImageView *)[self.view viewWithTag:kTAG_PHOTO_IMAGE_VIEW];
        [img removeFromSuperview];
    }
}