Passing js callback function as parameter to Java addJavascriptInterface

Question

Is it possible for arbitrary functional objects in js to be passed to Java side, so java can call that js object? (a callback)

for example, (access is a function that already registered to call a Java function)

access(function(blabla){
    ...
});

Are there any great techniques that can deal with anonymous callback function in java?

what`s mean, @NikolaDespotoski ? is there some bypass style? — ChangWan Hong
– ChangWan Hong, Commented Dec 26, 2011 at 2:46
Try to pass data using JSON string instead returning arbitrary var object.... — Nikola Despotoski
– Nikola Despotoski, Commented Dec 26, 2011 at 2:49

cho · Accepted Answer · 2016-11-15 02:07:53Z

4

You just need some sort of key to reference your individual callback anonymous function. I think this is how jsonp is used sometimes too.

Javascript:

var callbacks = [];
function registerCallback(callback)
{
   callbacks.push(callback);
   return callbacks.length - 1;
}

function getCallback(index)
{
   var callback = callbacks[index];
   callbacks[index] = null;

   TryGCCallbacks();

   return callbacks;
}

//The array index positions must be preserved, but when it's empty, we should restart the array so it doesn't grow forever
function TryGCCallbacks()
{
   var isCallbackRemaining = false;
   for (var i = 0; i < callbacks.length; i++)
   {
      if (callbacks[i] == null) {
         continue;
      }

      isCallbackRemaining = true;
      break;
   }
   if (isCallbackRemaining == false)
   {
      callbacks = []; //reset
   }
}

Java:

@org.xwalk.core.JavascriptInterface
public String TestCallback(String someData, String onSuccess, String onError){
   xwalk.evaluateJavascript("getCallback(" + onSuccess + ")('success');", null);
}

Using this from Javascript:

var onSuccess = registerCallback(function(r) {
   console.log(r);
});

TestCallback('lalala', onSuccess, null);

edited Nov 15, 2016 at 2:07

answered Nov 15, 2016 at 0:47

cho

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3 Comments

Kind Contributor Over a year ago

This is something that should be built into XWalk somehow. This is very handy.

cho Over a year ago

Java : xwalk.post(new Runnable(){ @Override public void run(){ xwalk.evaluateJavascript("(function(){ AndroidStatic.callBack(" + "\"" + result + "\"" + "); })();", null); } });

cho Over a year ago

Javascript : var AndroidStatic = { callBack: function (result) { //alert(result); console.log(result); } };

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