iOS: How to detect the escape/control keys on a ha

问题:

I'm trying to figure out how to detect that the Escape (and other key combinations like Ctrl and alt) have been pressed on a bluetooth keyboard attached to an iOS device.

Some answers seem to suggest this isn't possible. However there are apps in the Appstore that do this (for example iSSH) so I assume it is possible using the public APIs somehow.

I've tried creating my own UITextInput however this receives nothing when the Escape key is pressed. The only part of the API I can see where the iPad might respond is when VoiceOver is enabled (Escape works as back in Safari), so I'm wondering if there's a way in via the accessibility API?

I've also tried to see if there's something I can observe from NSNotificationCenter that might help, but have yet to find anything.

Suggestions welcome, I've been hacking away at this for a day and I'm at a bit of a loss now.

回答1:

You can do this now in iOS 7. For example, to implement the escape key, override UITextView and place the following methods in your class:

- (NSArray *) keyCommands {
    UIKeyCommand *esc = [UIKeyCommand keyCommandWithInput: UIKeyInputEscape modifierFlags: 0 action: @selector(esc:)];
    return [[NSArray alloc] initWithObjects: esc, nil];
}

- (void) esc: (UIKeyCommand *) keyCommand {
    // Your custom code goes here.
}

You don't need to check to be sure you are on iOS 7, since earlier versions of the OS won't call the keyCommands method.

回答2:

There are no public APIs for what you intend to accomplish, so this may lead to a rejection.

If you are willing to risk it, you can try this. Wich basically intercepts all events sent to your App by overwriting sendEvent: in your UIApplication.

回答3:

AFAIK this is not possible using public API. I've done a bit of searching and the esc key is not recognized. The only thing that I didn't do is to try iSSH (it costs 9€ :-), but if you read the description on the AppStore it seems clear that ESC key on a hardware (bluetooth) keyboard doesn't work:

• Exhaustive key configuration support. Has arrow keys (by pop-up or by toolbar). ctrl, alt, esc, tab, shift, Fn keys (1-10), ` key, PgUp, PgDown and for those keys not listed provides multiple means to add them.

• Bluetooth keyboard support for arrow keys, function keys and a remapping of the ctrl key through option key mapping in either X11/VNC server or terminal. When enabled, an Option+key press maps to equivalent Ctrl+key press.

As you can see, in the second line the ESC key is not mentioned. Moreover, I've found this (old) post.

EDIT:

As your last updates, I've found a way to "hide" the _gsEvent inside the binary. I don't know if Apple static analyser can find it, however. The trick is simple...create the _gsEvent selector (and other private selectors) at runtime!

-(void)sendEvent:(UIEvent *)event
{

    SEL aSelector = NSSelectorFromString([self theSelector]);
    if ([event respondsToSelector:aSelector]) {

        NSLog(@"Event: %@", event.description);
    }

    [super sendEvent:event];
}

-(NSString *)theSelector
{
    // compose the keyword as you prefer
    NSString *sel = [NSString stringWithFormat:@"%@g%@%@ent", @"_", @"s", @"Ev"];
    return sel;
}

I've tried to search inside the binary and I don't find the _gsEvent keyword, obviously because it's created only at runtime.
Hope this helps.