是否可以将Java方法的引用传递给GWT中的javascript

Question

I'm trying to implement multi-threading in client side by using VKthread with GWT,

my problem that i need to pass a reference for java method to thread invoker in java script, so that when the thread is executed, it call the java method

here's my code:

static JavaScriptObject sum() {

    return flipName();
}

static native JavaScriptObject flipName() /*-{
    console.log("asd");
}-*/;


native String Excec() /*-{

    $wnd.vkthread
            .exec(
                    @com.tradeos.b2b.industries.freight.data.freightTrade.marketplace.builders.client.MarketPlaceQuoteResultsPanel::sum()(), //function to execute in a threads
                    [], //arguments for the function
                    function(data) { // callback function;
                        var foo = data;
                        console.log(foo);
                    });

}-*/;

If i passed a javascript method to $wnd.vkthread it works well, but when trying to pass java method it doesn't work!

Answer 1

In your snippet, you are calling your method ( ::sum()() ), to get a reference to the method, remove the last pair of parentheses. You should also wrap it into $entry :

$wnd.vkthread
        .exec(
                $entry(@com.tradeos.b2b.industries.freight.data.freightTrade.marketplace.builders.client.MarketPlaceQuoteResultsPanel::sum()), //function to execute in a threads
                [], //arguments for the function
                function(data) { // callback function;
                    var foo = data;
                    console.log(foo);
                });

Answer 2

You need to export your method:

public static native void exportStaticMethod() /*-{
       $wnd.sum =
           $entry(@com.tradeos.b2b.industries.freight.data.freightTrade.marketplace.builders.client.MarketPlaceQuoteResultsPanel::sum());
}-*/;

Now you can use $wnd.sum instead of your Java method which is convenient if you plan to call it in more than one place.

If you only use it once, you can simply wrap it into $entry() directly in your JSNI method.

The documentation explains it: Calling a Java Method from Handwritten JavaScript