Helper classes to be used with (DRF-Android)[https://github.com/101Loop/DRF-Android]

APIErrorListener.java

package com.example.drfUser;

import android.content.Context;
import android.util.Log;
import android.widget.Toast;

import com.android.volley.VolleyError;
import com.civilmachines.drfapi.DjangoErrorListener;

import org.json.JSONObject;

public class APIErrorListener extends DjangoErrorListener {
    private static final String TAG = "APIErrorListener";
    private Context context;

    public APIErrorListener(Context context) {
        this.context = context;
    }

    @Override
    public void onNetworkError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onMethodNotAllowedError(String message) {
        defaultErrorListener(message);
    }

    @Override
    public void onAuthFailureError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onBadRequestError(String message) {
        defaultErrorListener(message);
    }

    @Override
    public void onBadRequestError(JSONObject response) {
        defaultErrorListener("Bad Request. Data sent in incorrect format!");
    }

    @Override
    public void onDefaultError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onDefaultHTMLError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onDefaultJsonError(JSONObject response) {
        defaultErrorListener("Some JSON Error occurred.");
    }

    @Override
    public void onForbiddenError(String message) {
        defaultErrorListener(message);
    }

    @Override
    public void onNoConnectionError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onNonJsonError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onNotFoundError(String message) {
        defaultErrorListener(message);
    }

    @Override
    public void onParseError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onServerError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onTimeoutError(String response) {
        defaultErrorListener(response);
    }

    @Override
    public void onUnprocessableEntityError(String message) {
        defaultErrorListener(message);
    }

    @Override
    public void onUnprocessableEntityError(JSONObject response) {
        defaultErrorListener("Unprocessable Entity");
    }

    @Override
    public void onUnsupportedMediaTypeError(String message) {
        defaultErrorListener(message);
    }

    public void defaultErrorListener(String message) {
        Log.e(TAG, "defaultErrorListener: " + message);
        Toast.makeText(context, message, Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onErrorResponse(VolleyError error) {
        try {
            super.onErrorResponse(error);
        } catch (Exception e) {
            Toast.makeText(context, "Can't connect to the server.", Toast.LENGTH_SHORT).show();
            Log.e(TAG, "onErrorResponse: " + error.getMessage());
        }
    }
}

VolleySingleton.java

package com.example.drfUser;

import android.app.Application;
import android.content.Context;
import android.text.TextUtils;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.Volley;

public class VolleySingleton extends Application {
    public static final String TAG = VolleySingleton.class
            .getSimpleName();

    private RequestQueue mRequestQueue;

    private static VolleySingleton mInstance;
    private static Context mCtx;

    @Override
    public void onCreate() {
        super.onCreate();
        mInstance = this;
    }

    public VolleySingleton() {
        // required constructor

    }

    private VolleySingleton(Context context) {
        mCtx = context;
        mRequestQueue = getRequestQueue();
    }

    public static synchronized VolleySingleton getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new VolleySingleton(context);
        }

        return mInstance;
    }

    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            mRequestQueue = Volley.newRequestQueue(getApplicationContext());
        }

        return mRequestQueue;
    }

    public <T> void addToRequestQueue(Request<T> req, String tag) {
        // set the default tag if tag is empty
        req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
        getRequestQueue().add(req);
    }

    public <T> void addToRequestQueue(Request<T> req) {
        req.setTag(TAG);
        getRequestQueue().add(req);
    }

    public void cancelPendingRequests(Object tag) {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(tag);
        }
    }
}