GWT-JSNI在外部JS库中传递JavaScriptObject

Question

I'm desesperatly trying to create an Anno object in a JSNI method but I have a strange problem : the code in the jsni method doesn't work but if I do the same in my browser console, it works fine.

Java Part

I'm using a JSONArray in wich I add some JSONObject (with all the elements, according to Anno doc). Here's my JSNI method :

// I'm using the getJavaScriptObject() on my JSONArray
private static native void launch( JavaScriptObject steps )/*-{
        var anno = new $wnd.Anno(steps);
        anno.chainIndex().show();
                                                            }-*/;

Browser Part

Just to be clear, the method is called on a onShow event, so all the ressources are loaded and rendered. So when the element is displayed and the function called, I have this error in my console :

Couldn't find Anno.target 'h1'. --- anno.js:265

NB : In Anno.js, h1 is the dafault value of target.

But my steps value is right and when I do the same commands in the console it works :

var testAnno = new Anno([{
    content: "namespinnerFrequencyA",
    position: "center-right",
    target: ".dataAuto0"
},{
    content: "chooseFrequencyB",
    position: "top",
    target: ".dataAuto1"}]);
testAnno.show();

I don't understand why it works in one case and not in the other. I've also tried to use JSON.stringify then JSON.parse but it doesn't work either.

---

EDIT :

I figured something out. While debugging anno.js I figured something : when I initialized Anno in the console, the local scope look like this (bigger image here ) :

But when I use the jsni method, the local scope is absolutely different, my parameter is stored as an actual array instead of being processed normally (bigger image here ) :

Answer 1

The problem is that GWT code runs in an iframe (for sandboxing/isolation) and Anno only supports array types from the same browsing context.

See http://perfectionkills.com/instanceof-considered-harmful-or-how-to-write-a-robust-isarray/ and http://web.mit.edu/jwalden/www/isArray.html for descriptions of the problem.

ECMAScript 5.1 added an Array.isArray() function that solves that issue and has wide browser support (back up to IE9): https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray
And jQuery has one too, which makes it incomprehensible (to me) that Anno doesn't use it instead of using the broken if arg.__proto__ is Array.prototype (unless it's by design). So first things first: file an issue on Anno.

As a workaround, it should be possible to use $wnd.Array.apply($wnd.Array, steps) to copy your array into an array from the top window.

Answer 2

It seems to me that the error message says it cant find the target dom element and not that it cant find the target property. Is the element there when your code is fired? make sure it is and get back to me.