Runnable won't wait for function to finish

Question

I'm trying to run every minute a refresh for the UI. I wrote this code where I have an handler and a runnable with postdelay. Inside my runnable I have a call for a function that is returning a Map object. But every time, my runnable continues to the next lines of code before getting back the Map object from the function.

Does anyone know how to fix that?

My Code:

Handler handler = new Handler();
Runnable runnable = new Runnable() {
    @Override
    public void run() {
        Map<String, String> varList = refreshVars(firstname, lastname, id);

        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);

Function:

public Map<String, String> refreshExitVars(final String FN, final String LN, final String IDN){
    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);
                } 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);

    return list;
}

Your get map method is Asynchronous, no function will ever wait for it to return the values. You should probably do some study on how Volley works. — Mohammed Atif, Apr 03 '17 at 15:17

score 0 · Answer 1 · answered Apr 03 '17 at 17:33

As @MohammedAtif pointed out, the request you make in your refreshExitVars() method is asynchronous. That's why you have that responseListener. The onResponse() method of that listener is called when the asynchronous request is completed.

So the easiest way would be to move your /*UI changes related to "newlastdate" and "newcurrentdate"*/ into your onResponse() method instead of trying to return the data.

Runnable won't wait for function to finish

1 Answers1