Comment by Arunavh Krishnan on "Runnable won't wait for function to finish"

The problem is with the asynchronous nature of the request.

After you make the request, you don't wait for the response. The code continues to run (this is an asynchronous piece of code).

When the request is finally processed, you get your response in onResponse method. But this piece of code was non-blocking. It means it doesn't guarantee that onResponse will be called before you return the list. You have already returned the list (* which is a map not list) from the function refershExitVars and at that point of time onResponse wasn't even called and hence your map is empty.

Solution : You cannot simply return values from a non-blocking method. You need a Callback.

When you call refreshExitVars you need to pass it a Callback. Once onResponse is called and you have your map ready (not empty), you can use this Callback to transfer your map data back to the caller.

//create a callback interface

interface Callback { void onData(Map<String, String> mappedData); }

Handler handler = new Handler(); Runnable runnable = new Runnable() { @Override public void run() {

            //pass the callback as a param
        refreshVars(firstname, lastname, id, new Callback() {
                //Override
                void onData(Map<String, String> mappedData) {
                    //This will be called from the onResponse method on refreshExitVars

                    //do whatever you want with your data here. It won’t be empty.
                }
        };);

        String newlastdate = varList.get("newlastdate");
        String newcurrentdate = varList.get("newcurrentdate");

        /*UI changes related to "newlastdate" and "newcurrentdate"*/

        }
        handler.postDelayed(this, 60000);
    }
};
handler.postDelayed(runnable, 60000);

public void refreshExitVars(final String FN, final String LN, final String IDN, final Callback callback){ final Map<String, String> list = new HashMap<>(); Response.Listener<String> responseListener = new Response.Listener<String>() { @Override public void onResponse(String response) {

        try {
            JSONObject jsonResponse = new JSONObject(response);
            boolean success = jsonResponse.getBoolean("success");
            if (success) {
                String nlastdate = jsonResponse.getString("date");
                String ncurrentdate = jsonResponse.getString("currentdate");

                list.put("newlastdate", nlastdate);
                list.put("newcurrentdate", ncurrentdate);

                    //Use the callback object to transfer data.
                    callback.onData(list);

            } else {
                int ErrorCode = jsonResponse.getInt("errorcode");
                AlertDialog.Builder builder;
                builder = new AlertDialog.Builder(Exit.this);
                            builder.setMessage("" + ErrorCode)
                                    .setNegativeButton("Close", new DialogInterface.OnClickListener() {
                                        @Override
                                        public void onClick(DialogInterface dialog, int which) {
                                            this.finish();
                                        }
                                    })
                                    .create()
                                    .show();
            }

            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    };

    RequestUIChanges requestUIChanges = new RequestUIChanges(FN, LN, IDN, responseListener);
    RequestQueue queue = Volley.newRequestQueue(Exit.this);
    queue.add(requestUIChanges);

//No value should be returned from here.
//return list;

}

// Check out the bold text. Correct any syntax errors. I've just typed it here.

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