Transparent Background with a Modal UIViewControll

问题:

I have a dilema, I want to present to the user a semi-transparent view.

I found out by experimenting that if I simply pushed the transparent view to the top of my NavigationController's stack, that it would not render the transparency level I wanted. So I decided to simply add the view as a subview of the current view at the top of the stack.

This solution works, the view below is still visible, and the View is 'semi-modal'. The problem is, if the parent view inherits from UITableViewController (as mine does), then the view I 'push' onto it, does not cover the navigation bar at the top.

I really don't want to get into a situation where I am forced to enable / disable controls on the navigation bar every time I push this view, so I was wondering, if anyone knew of any solutions that I could use so that the view I push onto the UITableViewController will actually 'push over' the navigation bar?

回答1:

Funny, I was just doing the same thing yesterday. Unfortunately it seems to be impossible. Once the modal view controller is in place, the previous view becomes hidden. See this previous question on the topic.

You can still use the view controller and NIB files you have set up - here's my sample code

- (void)showUpgrade {
    [self.upgradeVC viewWillAppear:NO];
    [self.view addSubview:self.upgradeVC.view];
    [self.upgradeVC viewDidAppear:NO];
}

- (void)hideUpgrade {
    [self.upgradeVC viewWillDisappear:NO];
    [self.upgradeVC.view removeFromSuperview];
    [self.upgradeVC viewDidDisappear:NO];
}

- (UpgradeViewController *)upgradeVC {
    if (_upgradeVC == nil) {
        _upgradeVC = [[UpgradeViewController alloc] initWithNibName:[NSString stringWithFormat:@"UpgradeView_%@", self.deviceType] bundle:nil];
        _upgradeVC.delegate = self;
    }
    return _upgradeVC;
}

You will need to store a reference to the parent view controller in the modal view controller so that you can access the -hide method. I did this through a delegate.

It would also be easy to add some animation to -show and -hide if you want it to animate up from the bottom of the screen - I was just too lazy to do this.

回答2:

iOS 8 added the UIModalPresentationOverFullScreen presentation style. Set this as the presented view controller’s modalPresentationStyle. For more advanced needs, look into creating a custom presentation controller.

回答3:

There is now a way to achieve this using iOS7 custom transitions :

MyController * controller = [MyController new];
[controller setTransitioningDelegate:self.transitionController];
controller.modalPresentationStyle = UIModalPresentationCustom;
[self controller animated:YES completion:nil];

To create your custom transition, you need 2 things :

• A TransitionDelegate object (implementing <UIViewControllerTransitionDelegate>)
• An "AnimatedTransitioning" object (implementing <UIViewControllerAnimatedTransitioning>)

You can find more informations on custom transitions in this tutorial : http://www.doubleencore.com/2013/09/ios-7-custom-transitions/

回答4:

Try this:

ViewController *vc = [[ViewController alloc] init];
[vc setModalPresentationStyle:UIModalPresentationOverCurrentContext];
[self presentViewController:vc animated:YES completion:nil];

回答5:

Have you tried looping over the Modal View Controller's subviews and setting the background color to clear for every view? This is a DFS recursive function.

- (void)setBackgroundToClearForView:(UIView *)view {
    if ([view subviews]) {
        for (UIView *subView in [view subviews]) {
            [self setBackgroundToClearForView:subView];
        }
    }

    if ([view respondsToSelector:@selector(setBackgroundColor:)]) {
        [view performSelector:@selector(setBackgroundColor:)
                   withObject:[UIColor clearColor]];
    }
}

To use it call:

[self setBackgroundToClearForView:self.view];

in viewDidLoad.

回答6:

This will do the trick.. Try this one.

// for clear color or you can easily adjust the alpha here
 YourVC *vc=[[YourVC alloc]initWithNibName:@"YourVC" bundle:nil] ;
 vc.view.backgroundColor = [UIColor clearColor];
 self.modalPresentationStyle = UIModalPresentationCurrentContext;
 [self presentViewController:vc animated:NO completion:nil];

So that the view will be full screen unlike UIModalPresentationFormSheet..