How does evaluateJavascript work?

Question

I\'m trying to use the new evaluateJavascript method in Android 4.4, but all I ever get back is a null result:

webView1.evaluateJavascript(\"return \\\"test\         


        

Answer 1

OK, so it turns out the result here is the result of the Javascript call - as if one were entering the command into a Javascript console.

So in order to get a result, it needs to be wrapped in a function:

webView1.evaluateJavascript("(function() { return \"this\"; })();", new ValueCallback() {
    @Override
    public void onReceiveValue(String s) {
        Log.d("LogName", s); // Prints 'this'
    }
});

This will also work:

webView1.evaluateJavascript("window.variable = \"asd\";", new ValueCallback() {
    @Override
    public void onReceiveValue(String s) {
        Log.d("LogName", s); // Prints asd
    }
});

The method also handles Javascript objects:

webView1.evaluateJavascript("(function() { return { var1: \"variable1\", var2: \"variable2\" }; })();", new ValueCallback() {
    @Override
    public void onReceiveValue(String s) {
        Log.d("LogName", s); // Prints: {"var1":"variable1","var2":"variable2"}
    }
});