Parse javascript returned value-object from Android app

Question

I'm calling a JavaScript function from my application's WebView. This function returns (if i call it from firebug) for example:

Object {top: 350.171875, left: 129.265625, w: 311, h: 115}

What i want is to get the values of top, left, w and h from my Android application. But when I try to get the values through WebChromeClient onJsAlert() method the value of message parameter is [object Object]. Is there a way to extract the required values of top, left, w, h from [object Object]? i can't find a way to parse [object Object].

Isn't enough something like that? myWebView.loadUrl("javascript:someJsFunction()"); — Antonis
– Antonis, Commented Sep 5, 2013 at 9:50
this will call the javascript function, but you will not be able to get the return value of the function. You need a callback in java with a javascriptinterface. — njzk2
– njzk2, Commented Sep 5, 2013 at 10:12

njzk2 · Accepted Answer · 2013-09-05 10:17:43Z

1

Typically, you can use a JavascriptInterface (see http://developer.android.com/guide/webapps/webview.html).

This can be your callback interface:

public class MyInterface {
    @JavascriptInterface
    public void myCallback(int top, int left, int w, int h) {
        // This is where you receive the values
    }
}

This is how you bind it:

myWebView.addJavascriptInterface(new MyInterface(), "Android");
myWebView.loadUrl("javascript:someJsFunction()");

And this is is how you javascript sends the values :

function someJsFunction() {
    Android.myCallback(dimensions.top, dimensions.left, dimensions.w, dimensions.h);
}

You cannot pass an actual object from javascript to android. You can only pass primitives, strings, and arrays of these.

answered Sep 5, 2013 at 10:17

njzk2

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2 Comments

Antonis Over a year ago

So, if someone has no access to the javascript function to edit it and add as a return value Android.myCallback(...), there is no other way to pass the javascript object to Android.

njzk2 Over a year ago

you can use an eval to pass new javascript to the currently executed : javascript:eval('Android:myCallback(...)')

johnnynotsolucky · Accepted Answer · 2013-09-05 08:17:03Z

1

You should be able to simply do dimensions.top or dimensions.left, etc (Assuming the object is stored in the variable dimensions)

var dimensions = {top: 350.171875, left: 129.265625, w: 311, h: 115}; //Would actually be a call to your function to calculate these dimensions
alert(dimensions.top);

answered Sep 5, 2013 at 8:17

johnnynotsolucky

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