iOS: How to access the `UIKeyboard`?

问题:

I want to get a pointer reference to UIKeyboard *keyboard to the keyboard on screen so that I can add a transparent subview to it, covering it completely, to achieve the effect of disabling the UIKeyboard without hiding it.

In doing this, can I assume that there's only one UIKeyboard on the screen at a time? I.e., is it a singleton? Where's the method [UIKeyboard sharedInstance]. Brownie points if you implement that method via a category. Or, even more brownie points if you convince me why it's a bad idea to assume only one keyboard and give me a better solution.

回答1:

Try this:

// my func
- (void) findKeyboard {

    // Locate non-UIWindow.
    UIWindow *keyboardWindow = nil;
    for (UIWindow *testWindow in [[UIApplication sharedApplication] windows]) {
        if (![[testWindow class] isEqual:[UIWindow class]]) {
           keyboardWindow = testWindow;
           break;
       }
    }

    // Locate UIKeyboard.  
    UIView *foundKeyboard = nil;
    for (UIView *possibleKeyboard in [keyboardWindow subviews]) {

        // iOS 4 sticks the UIKeyboard inside a UIPeripheralHostView.
        if ([[possibleKeyboard description] hasPrefix:@"<UIPeripheralHostView"]) {
            possibleKeyboard = [[possibleKeyboard subviews] objectAtIndex:0];
        }                                                                                

        if ([[possibleKeyboard description] hasPrefix:@"<UIKeyboard"]) {
           foundKeyboard = possibleKeyboard;
           break;
        }
    }
}   

回答2:

How about using -[UIApplication beginIgnoringInteractionEvents]?

Also, another trick to get the view containing the keyboard is to initialize a dummy view with CGRectZero and set it as the inputAccessoryView of your UITextField or UITextView. Then, get its superview. Still, such shenanigans is private/undocumented, but I've heard of apps doing that and getting accepted anyhow. I mean, how else would Instagram be able to make their comment keyboard interactive (dismiss on swipe) like the Messages keyboard?

回答3:

I found that developerdoug's answer wasn't working on iOS 7, but by modifying things slightly I managed to get access to what I needed. Here's the code I used:

-(UIView*)findKeyboard
{
    UIView *keyboard = nil;

    for (UIWindow* window in [UIApplication sharedApplication].windows)
    {
        for (UIView *possibleKeyboard in window.subviews)
        {
            if ([[possibleKeyboard description] hasPrefix:@"<UIPeripheralHostView"])
            {
                keyboard = possibleKeyboard;
                break;
            }
        }
    }

    return keyboard;
}

From what I could make out, in iOS 7 the keyboard is composed of a UIPeripheralHostView containing two subviews: a UIKBInputBackdropView (which provides the blur effect on whatever's underneath the keyboard) and a UIKeyboardAutomatic (which provides the character keys). Manipulating the UIPeripheralHostView seems to be equivalent to manipulating the entire keyboard.

Discaimer: I have no idea whether Apple will accept an app that uses this technique, nor whether it will still work in future SDKs.

回答4:

Be aware, Apple has made it clear that applications which modify private view hierarchies without explicit approval beforehand will be rejected. Take a look in the Apple Developer Forums for various developers' experience on the issue.

If you're just trying to disable the keyboard (prevent it from receiving touches), you might try adding a transparent UIView that is the full size of the screen for the current orientation. If you add it as a subview of the main window, it might work. Apple hasn't made any public method of disabling the keyboard that I'm aware of - you might want to use one of your support incidents with Apple, maybe they will let you in on the solution.

回答5:

For an app I am currently developing I am using a really quick and easy method:

Add this in the header file:

// Add in interface
UIWindow * _window;

// Add as property
@property (strong, nonatomic) IBOutlet UIView * _keyboard;

Then add this code in the bottom of the keyboardWillShow function:

-(void) keyboardWillShow: (NSNotification *) notification {

    .... // other keyboard will show code //

    _window = [UIApplication sharedApplication].windows.lastObject;

    [NSTimer scheduledTimerWithTimeInterval:0.05
                                     target:self
                                   selector:@selector(allocateKeyboard)
                                   userInfo:nil
                                    repeats:NO];
}

This code look for when the keyboard is raised and then allocates the current window. I have then added a timer to allocate the keyboard as there were some issues when allocated immediately.

- (void)allocateKeyboard {

    if (!_keyboard) {
        if (_window.subviews.count) {

            // The keyboard is always the 0th subview
            _keyboard = _window.subviews[0];
        }        
    }
}

We now have the keyboard allocated which gives you direct "access" to the keyboard as the question asks.

Hope this helps

回答6:

Under iOS 8 it appears you have to jump down the chain more than in the past. The following works for me to get the keyboard, although with custom keyboards available and such I wouldn't rely on this working unless you're running in a controlled environment.

- (UIView *)findKeyboard {
    for (UIWindow* window in [UIApplication sharedApplication].windows) {
        UIView *inputSetContainer = [self viewWithPrefix:@"<UIInputSetContainerView" inView:window];
        if (inputSetContainer) {
            UIView *inputSetHost = [self viewWithPrefix:@"<UIInputSetHostView" inView:inputSetContainer];
            if (inputSetHost) {
                UIView *kbinputbackdrop = [self viewWithPrefix:@"<_UIKBCompatInput" inView:inputSetHost];
                if (kbinputbackdrop) {
                    UIView *theKeyboard = [self viewWithPrefix:@"<UIKeyboard" inView:kbinputbackdrop];
                    return theKeyboard;
                }
            }
        }
    }

    return nil;
}


- (UIView *)viewWithPrefix:(NSString *)prefix inView:(UIView *)view {
    for (UIView *subview in view.subviews) {
        if ([[subview description] hasPrefix:prefix]) {
            return subview;
        }
    }

    return nil;
}