Passing an array of values from Android Activity to JavaScript in a WebView

Question

I'm using a JS Charts library to draw graphs in a WebView of my Android Application. I want to provide the data from the SQLite database. At this moment I'm stuck on how to pass array of data from Java to JavaScript. The JavaScript part expects something like that:

data = new Array([10, 10], [20, 10]);

I know about the addJavaScriptInterface and I managed to pass single values from my Activity to a WebView. It's only the array that gives me trouble. I thought about something like that:

final class ChartDataLoader {

    public double[][] getData() {
        double[][] data = {{10, 10}, {20, 10}};
        return data;
    }
}

Note that for now I'm just hard-coding the data, but eventually this will be pulled out from a database. So then I expose this to my JS:

webView.addJavascriptInterface(new ChartDataLoader(), "dataLoader");

And finally try to read it in JavaScript:

<html>
<head>
<script type="text/javascript" src="jscharts.js"></script>
</head>

<body>
<div id="chartcontainer">You should see a chart here.</div>

<script type="text/javascript">

 myData = dataLoader.getData(); 
 alert("DataReceived: " + myData.length);
 alert("Element 0 : " + myData[0]);

 var myChart = new JSChart('chartcontainer', 'line');
 myChart.setDataArray(myData);
 myChart.draw();

</script>
</body>
</html>

JavaScript fails on those two alert statements stating:

ERROR/Web Console(2455): Uncaught TypeError: Cannot read property 'length' of undefined at file:///android_asset/chart.html:15

Any hints? I saw some code online where other people convert arrays to a String and then recreate it back in JavaScript but that seems like an overkill to me and I was hoping for a better solution. An alternative is to pass an XML file to the chart library, but again, I thought it would be slow to create a new XML every time a user wants to see a graph.

well, yes ... I think you will have to parse the string and recreate the array in JS. But, I do not see, why that would be such a problem? — LambergaR
– LambergaR, Commented Dec 2, 2010 at 2:27

Ebin Sebastian · Accepted Answer · 2013-02-25 11:00:24Z

5

Remove the line: alert("DataReceived: " + myData.length);

edited Feb 25, 2013 at 11:00

answered Nov 12, 2012 at 9:23

Ebin Sebastian

1,2911 gold badge13 silver badges15 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Swannie · Accepted Answer · 2010-12-02 02:26:57Z

0

To fix the most recent error you need to define myData as a var.

What you talk about at the end of your question (converting arrays to string) is JSON. Any context switch is expensive (e.g. Android to web). The serialisation/de-serialisation probably won't slow you down too much.

answered Dec 2, 2010 at 2:26

Swannie

786 bronze badges

Collectives™ on Stack Overflow

Passing an array of values from Android Activity to JavaScript in a WebView

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related