LKM LKM - 4 months ago 125
Javascript Question

iPad Web App: Detect Virtual Keyboard Using JavaScript in Safari?

I'm writing a web app for the iPad (not a regular App Store app - it's written using HTML, CSS and JavaScript). Since the keyboard fills up a huge part of the screen, it would make sense to change the app's layout to fit the remaining space when the keyboard is shown. However, I have found no way to detect when or whether the keyboard is shown.

My first idea was to assume that the keyboard is visible when a text field has focus. However, when an external keyboard is attached to an iPad, the virtual keyboard does not show up when a text field receives focus.

In my experiments, the keyboard also did not affect the height or scrollheight of any of the DOM elements, and I have found no proprietary events or properties which indicate whether the keyboard is visible.


I found a solution which works, although it is a bit ugly. It also won't work in every situation, but it works for me. Since I'm adapting the size of the user interface to the iPad's window size, the user is normally unable to scroll. In other words, if I set the window's scrollTop, it will remain at 0.

If, on the other hand, the keyboard is shown, scrolling suddenly works. So I can set scrollTop, immediately test its value, and then reset it. Here's how that might look in code, using jQuery:

    $('input').bind('focus',function() {
        var keyboard_shown = $(window).scrollTop() > 0;

        $('#test').append(keyboard_shown?'keyboard ':'nokeyboard ');

Normally, you would expect this to not be visible to the user. Unfortunately, at least when running in the Simulator, the iPad visibly (though quickly) scrolls up and down again. Still, it works, at least in some specific situations.

I've tested this on an iPad, and it seems to work fine.