Android - How to generate touch event from javascript?

Question

Is it possible to generate a touch event in javascript that'll invoke the onTouchEvent() function in my android WebView?

I tried with the following javascript code which generates both touchstart and touchend events, but my webview onTouchEvent() function does not get invoked.

try{
var evt = document.createEvent('TouchEvent');
evt.initTouchEvent('touchstart', true, true);
evt.view = window;
evt.altKey = false;
evt.ctrlKey = false;
evt.shiftKey = false;
evt.metaKey = false;
this.dispatchEvent(evt);

var evt1 = document.createEvent('TouchEvent');
evt1.initTouchEvent('touchend', true, true);
evt1.view = window;
evt1.altKey = false;
evt1.ctrlKey = false;
evt1.shiftKey = false;
evt1.metaKey = false;
this.dispatchEvent(evt1); 

}
catch(e)
{
    alert(e);
}

Is something missing from my code, or do the javascript events not even get into the android framework?

Thx

Kirk B. · Accepted Answer · 2012-10-11 04:17:32Z

2

Not sure how you plan to use the touch event, and also not sure you can bubble touch events from the rendered dom up to the containing webview control's handler, but you could try this approach:

1) Add a javascript interface to your web view and expose a simple object of a class that captures your dom-generated events:

(inside onCreate of ContainerActivity)

this.mWebView.addJavascriptInterface
    ( new JavascriptContainer() {
        final private WebView mView = ContainerActivity.this.mWebView;

        @Override
        public void captureEvent(final String sDetails) {
            // do what you want with the details and webview...
        }
    }
    , "appReceiver"
    );

2) Capture touch events or click event (or whatever) in your rendered html and use javascript to delegate them to the exposed global "appReceiver":

if (window.appReceiver !== undefined) {
    window.appReceiver.captureEvent('blah blah: ' + event.x + ':' + event.y);
    ...
}

answered Oct 11, 2012 at 4:17

Kirk B.

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2 Comments

Gubatron Over a year ago

I can confirm this will work, I was going to answer the same. @sofarsogood on your WebView you add whatever object you want to have access on the JavaScript side using myWebView.addJavascriptInterface(aJavaObjectIWillUseInJavaScript,"myJavaObject"); Then on JavaScript, register an event listener that will use myJavaObject.someMethod(param1,param2,...) to trigger the desired behavior in Android-land.

Kirk B. Over a year ago

I should also note the security issue this approach incurs... Any javascript rendered in your webview can call your exposed global captureEvent() method -- make sure to validate the passed-in arguments.

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