Transparent UIImageView in front of all the UI

问题

After the first launch of my app i want to show the user a little tutorial, to explain the functionality of my app.

So i need to set a transpalent UIImageView with some arrow and labels, where the main UI(more specificly,tableviewcontroller in navigationviewcontroller in a tabbarcontroler) is stil visible behind the tutorial image.

And,because tutorial consists of several images,I want to add a tap gesture that will switch to another image.

I tried just to add an UIImageView to my tabbarcontroller,and andd a gesturerecogniser to that, but it doesn't react to my tap's,it just works,like if there were no ImageView - selects's the roe in table,pushes the buttons.

   -(void)nextTap:(UIGestureRecognizer*)nextTap
{
    //Show another image
}
-(void)showTutorial
{
    NSLog(@"Show tutorial");
    UIImageView *tutorialImage = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"BG"]];
    [self.navigationController.tabBarController.view addSubview:tutorialImage];
    UITapGestureRecognizer *nextTap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(nextTap:)];
    [tutorialImage addGestureRecognizer:nextTap];
}

Can anybody tell me, where should i add my view than,for it to work properly?

回答1:

you should set tutorialImage.userInteractionEnabled = YES The default value of UIImageView's userInteractionEnabled property is NO, it prevent UIImageView receive any touch event even gestures

回答2:

do it with another UIWindow!

Like this:

-(void)showTutorial
{
    NSLog(@"Show tutorial");


    CGRect screenBounds = [UIScreen mainScreen].bounds;
    UIWindow *anotherWindow = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, screenBounds.size.width, screenBounds.size.height)];
    anotherWindow.windowLevel = UIWindowLevelAlert+1;
    [anotherWindow makeKeyAndVisible];

    // make the background of the new window black alpha 0.5
    anotherWindow.backgroundColor = [UIColor colorWithRed:0 green:0 blue:0 alpha:0.5];

    // add a test-image (icon)
    UIImageView *image = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"icon.png"]];
    [anotherWindow addSubview:image];

    UIImageView *tutorialImage = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"BG"]];
    [anotherWindow addSubview:tutorialImage];
    UITapGestureRecognizer *nextTap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(nextTap:)];
    [tutorialImage addGestureRecognizer:nextTap];
}

EDITED! now it should work also in your case.