Develop Reference

RecyclerView chat load more items from top

I am trying to implement pagination in recyclerview to load more chat messages when the user scrolls to top , this is achieved by sending the last message time i.e coversations[0] time to the API , but when the new list is added the old List gets repeated many times . I think this is because i am not updating the time properly , What is the correct way to achieve this?
This is the code i am using, first time i am setting the flag to false and time as empty.
getConvoData(k, " ", "", false);
private String last_msg_time = " ";
private Boolean flag = false;
rv_convo.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (!recyclerView.canScrollVertically(-1)) {
if (conversations != null) {
String time = last_msg_time;
getConvoData(k, " ", time, true);
}
}
}
});
this is the method for fetching conversation Data
private void getConvoData(final String k, final String new_message, final String last_time, final boolean flag) {
final String token1 = Global.shared().tb_token;
final String url = "https://app.aer.media/v2/message_router/_getChat";
final JSONObject jsonBody = new JSONObject();
final ProgressDialog progressDialog = new ProgressDialog(this);
final String mRequestBody = jsonBody.toString();
StringRequest stringRequest = new StringRequest(Request.Method.POST, url, new com.android.volley.Response.Listener<String>() {
#Override
public void onResponse(String response) {
try {
JSONObject jObj = new JSONObject(response);
final JSONObject data = jObj.getJSONObject("data");
conversations = data.getJSONArray("conversation");
JSONObject for_chat = data.getJSONObject("for_chat");
JSONArray jsonArr_chat = new JSONArray();
jsonArr_chat.put(for_chat);
params = (RelativeLayout.LayoutParams) rv_convo.getLayoutParams();
GsonBuilder gsonBuilder = new GsonBuilder();
Gson gson = gsonBuilder.create();
if (!flag) {
convobeans = gson.fromJson(conversations.toString(), convType);
last_msg_time = conversations.getJSONObject(0).getString("time");
Log.d("OldList", convobeans.toString());
adapter = new ChatDetailsAdapter(forChatBeen, convobeans, ChatDetailsActivity.this, forChatBeansList, image, name, initials, new_message, bitmap);
// Collections.reverse(convobeans);
rv_convo.setAdapter(adapter);
rv_convo.smoothScrollToPosition( rv_convo.getAdapter().getItemCount() - 1);
adapter.notifyDataSetChanged();
rv_convo.setNestedScrollingEnabled(true);
} else {
newConvo = gson.fromJson(conversations.toString(), convType);
last_msg_time = conversations.getJSONObject(0).getString("time");
if (newConvo != null && newConvo.size() > 0) {
Log.d("newList", newConvo.toString());
convobeans.addAll(0, newConvo);
adapter.notifyItemChanged(0, newConvo.size());
}
}
}
}
}
Depending on the flag I am updating the list and updating the time as well but the list gets repeated in the RecyclerView due to the previous time being passed , how do I update the time optimally and fetch the new list each time?

This code is used to fetch the data when the user scroll down in a recylerview. Just analyze this code you will get the basic idea.
rvCategory.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
if (dy > 0) {
visibleItemCount = mLinearLayoutManager.getChildCount();
totalItemCount = mLinearLayoutManager.getItemCount();
pastVisiblesItems = mLinearLayoutManager.findFirstVisibleItemPosition();
if (loading) {
if ((visibleItemCount + pastVisiblesItems) >= totalItemCount) {
loading = false;
fetchData();
}
}
}
}
});
Function FetchData()
private void fetchData() {
String url = EndPoints.location + "getMobileData.php?lastData=" + lastData;
JsonObjectRequest jsObjRequest = new JsonObjectRequest
(Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject response) {
try {
lastData = response.getString("last");
JSONArray jArray = response.getJSONArray("response");
if (jArray.length() == 0) {
//Empty condition
} else {
for (int i = 0; i < jArray.length(); i++) {
//Append the chat with the Dataobject of your modelAnd swap the recylerview view with new data
//Example
}
adapter.swap(rvHomeModel.createHomeList(DataPathsHome, true));
}
} catch (JSONException e) {
e.printStackTrace();
}
loading = true;
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
// TODO Auto-generated method stub
loading = true;
Toast.makeText(CategoryView.this, "No internet connection", Toast.LENGTH_LONG).show();
}
});
// Add a request (in this example, called stringRequest) to your RequestQueue.
MySingleton.getInstance(this).addToRequestQueue(jsObjRequest);
}
Create a function called swap in your adapter class that accept the new dataset
public void swap(List<rvHomeModel> list) {
//Check your previouse dataset used in adapter is empty or not
if (rvHomeModels!= null) {
rvHomeModels.clear();
rvHomeModels.addAll(list);
} else {
rvHomeModels = list;
}
notifyDataSetChanged();
}
At server
1. Get the previous value
2. Do the database operation and get the chats id < of previous
2. Create a JSON Object contain
{
last:last_chat_id,
response:{
//Your chat
}
}
This is not a perfect solution for this question. But you will get the basic idea about what you are looking for.

Simple push notification without gcm like things

I want to implement a push notification in android app without gcm like things.I want to handle all action from my side(android) .
Till now I have a json response.Which i am trying to use in push notification.and my push notification works on click event.But i have no idea how it check or excute json response automatically(periodically). Here is my current code for json respone (using volley lib.).
public class MainActivity extends AppCompatActivity {
// Log tag
int total_time = 1000 * 60 * 60 * 24; // total one day you can change
int peroid_time = 5000; // one hour time is assumed to make request
private static final String TAG = MainActivity.class.getSimpleName();
private static String url = "http://my_url/Service.asmx/GetNotifications";
private ProgressDialog pDialog;
private List<Notifications> noteList = new ArrayList<Notifications>();
private ListView listView;
private Custom_Adapter_N adapter;
EditText ed1,ed2,ed3;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.list_note);
adapter = new Custom_Adapter_N(this, noteList);
listView.setAdapter(adapter);
new CountDownTimer(peroid_time, total_time) {
public void onTick(long millisUntilFinished) {
// make request to web and get reponse and show notification.
MakingWebRequest();
Toast.makeText(MainActivity.this, " Tesitng the data", Toast.LENGTH_LONG).show();
}
public void onFinish() {
//
}
}.start();
// pDialog = new ProgressDialog(this);
// // Showing progress dialog before making http request
// pDialog.setMessage("Loading...");
// pDialog.show();
ed1=(EditText)findViewById(R.id.editText);
ed2=(EditText)findViewById(R.id.editText2);
ed3=(EditText)findViewById(R.id.editText3);
Button b1=(Button)findViewById(R.id.button);
}
// //on create
// #Override
// public void onDestroy() {
// super.onDestroy();
// hidePDialog();
// }
private void hidePDialog() {
if (pDialog != null) {
pDialog.dismiss();
pDialog = null;
}
}
public void MakingWebRequest() {
StringRequest stringRequest = new StringRequest(Request.Method.POST, url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
Log.d(TAG, response.toString());
hidePDialog();
try {
JSONArray jsonarray = new JSONArray(response);
for (int i = 0; i < jsonarray.length(); i++) {
JSONObject obj = jsonarray.getJSONObject(i);
// Notifications note = new Notifications();
// note.setNotificationId(obj.getString("NotificationId"));
// note.setNotification(obj.getString("Notification"));
String excep = obj.getString("NotificationId");
String message1 = obj.getString("Notification");
NotificationManager notif=(NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
NotificationCompat.Builder builder = new NotificationCompat.Builder(MainActivity.this);
Notification notify=new Notification(R.drawable.push,message1,System.currentTimeMillis());
PendingIntent pending= PendingIntent.getActivity(getApplicationContext(), 0, new Intent(), 0);
notify = builder.setContentIntent(pending)
.setStyle(new NotificationCompat.BigTextStyle().bigText(message1))
.setSmallIcon(R.drawable.push).setTicker(excep).setWhen(System.currentTimeMillis())
.setAutoCancel(true).setContentTitle(message1)
.setContentText(message1).build();
// notif.notify(NOTIFICATION, notify);
notif.notify(0, notify);
// String id = obj.getString("Exception");
// String message1 = obj.getString("Message");
// Toast.makeText(Notification1.this, id.toString(), Toast.LENGTH_LONG).show();
// Toast.makeText(Notification1.this, message1.toString(), Toast.LENGTH_LONG).show();
// adding movie to movies array
// noteList.add(note);
}
} catch (JSONException e) {
e.printStackTrace();
}
// notifying list adapter about data changes
// so that it renders the list view with updated data
adapter.notifyDataSetChanged();
}
//.... you rest code
// add your notification here
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
hidePDialog();
}
}
)
{
#Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
return params;
}
};
RequestQueue requestQueue = Volley.newRequestQueue(MainActivity.this);
requestQueue.add(stringRequest);
}
}

This solution is referred as short term because its running on UI thread. You can do the same in service for background working.
For running it in servic look here how service start and works.
public class MainActivity extends Activity {
int total_time = 1000 * 60 * 60 * 24; // total one day you can change
int peroid_time = 1000 * 60 * 60; // one hour time is assumed to make request
// reduced the time while testing
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new CountDownTimer(peroid_time, total_time) {
public void onTick(long millisUntilFinished) {
// make request to web and get reponse and show notification.
MakingWebRequest();
}
public void onFinish() {
//
}
}.start();
}
void MakingWebRequest() {
StringRequest stringRequest = new StringRequest(Request.Method.POST, url,
new Response.Listener<String>() {
//.... you rest code
// add your notification here
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
hidePDialog();
}
});
RequestQueue requestQueue = Volley.newRequestQueue(MainActivity.this);
requestQueue.add(stringRequest);
}
}

JSON Download # onCreateView leaves recyclerView empty

if (isConnected()) {
Event eInstance = new Event();
theEvents = eInstance.downloadEvents(eventsNightlife, getActivity());
rAdapter = new RecyclerAdapter(theEvents);
recyclerView.setAdapter(rAdapter);
progrsBar.setVisibility(View.GONE);
....
This is part of the code that runs at "onCreateView". The method downloadEvents uses Volley to download JSON data, extract it and return a list of items (theEvents). Now when my app starts, the recycler view is empty. If I go to my home screen out of the app and then run my app again, this time the data sometimes gets downloaded.
I debugged step by step, and at first launch (i mean when the app is not just resuming), theEvents is empty, so the download didn't return or manage to return anything...
Suggestions on how to execute things before the UI has been shown to the user or what actually needs to be done to approach this task better?
Also, I use a swipeRefreshLayout and at its onRefresh method I do:
public void onRefresh() {
Event eInstance = new Event();
theEvents = eInstance.downloadEvents(eventsNightlife, getActivity());
rAdapter.notifyDataSetChanged();
swipeRefreshLayout.setRefreshing(false);
}
but it doesn't work. I also tried to
rAdapter = new RecyclerAdapter(theEvents);
rAdapter.notifyDataSetChanged();
recyclerView.swapAdapter(rAdapter, false);
still not working.
EDIT: My downloadEvents method implementing Volley:
public List<Event> downloadEvents(String urlService, Context context) {
eventsList = new ArrayList<>();
RequestQueue requestQueue = Volley.newRequestQueue(context);
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest
(Request.Method.GET, urlService, null, new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
try {
String durationStr = null;
for (int i = 0; i < response.length(); i++) {
JSONObject eventJson = response.getJSONObject(i);
String title = eventJson.getString("EventTitle");
String body = eventJson.getString("EventBody");
String date = eventJson.getString("EventDate");
String time = eventJson.getString("EventTime");
int duration = Integer.parseInt(eventJson.getString("EventDuration"));
if (duration > 60) {
durationStr = "Duration: " + duration / 60 + " h";
} else if (duration < 60) {
durationStr = "Duration: " + duration + " m";
}
String place = eventJson.getString("EventPlace");
String organ = eventJson.getString("Organization");
Event event = new Event(title, body, date, time, durationStr, place, organ);
eventsList.add(event);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Log.e("VOLLEY ERROR", "" + error);
}
}
);
requestQueue.add(jsonArrayRequest);
return eventsList;
}

You can use EventBus for your purpose that is a simple and truth way.
Here, i write an example for how to use EventBus with volley.
Consider that i want to download some data.
This is the class that my download methods is inside it (you can add more methods to it in the future):
Im used volley to download my data:
// Download methods is inside volley
public class MyDownloader{
public static void downloadData(){
DownloadDataEvent dlDataEvent=new DownloadDataEvent();
List<String> myResult=new ArrayList<>();
...
#Override
public void onResponse(JSONArray response) {
super.onResponse(response);
if(respone!=null){
// Do what i want with my received data
dlDataEvent.setData(response);
}
// Post my event by EventBus
EventBus.getDefault().post(dlDataEvent);
...
}
}
}
This is my event:
public class DownloadDataEvent{
private JSONArray mData;
public void setData(JSONArray data){
mData=data;
}
public JSONArray setData(){
return mData;
}
}
Now i want to use my downloadData() method inside my MainActivity:
(I called my downloadData method inside onCreate.)
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
...
// I have to register this class for EventBus subscriber:
if(!EventBus.getDefault().isRegister(this)){
EventBus.getDefault().registerSticky(this);
}
// Call my downloadData method
if(isConnected()){
MyDownloader.downloadData();
}
}
// And for receive the data through EventBus, i have to create a
// method (subscriber) in this template:
public void onEventMainThread(DownloadDataEvent downloadDataEvent){
JSONArray result=downloadDataEvent.getData();
// Do what i want with my received data
}
}
you can create more than one subscriber every where you want to use received data.
I passed JSONArray to my DownloadDataEvent that it is not good. you can deserialize your received data and pass it to your DownloadDataEvent.
I used Volley to download data
Maybe my descriptions were confusing, but EventBus is a well-known library and is very easy to use.

ListView: how to notify the user about new fetched data with sound and vibration?

I've added my MainActivity below, the application fetches data from a database and refreshes automatically and on swipe down.
My question is, how on earth can it notify the user about "new" fetched inserts via sound and vibration?
To be more specific regarding the definition of "new inserts", the application starts with 0 data in it, once refreshed a php call from the database gets a new JSON string and is decoded in the app and appears on the listview.
public class MainActivity extends AppCompatActivity implements SwipeRefreshLayout.OnRefreshListener {
private int mInterval = 5000; // 5 seconds by default, can be changed later
private Handler mHandler;
private String TAG = MainActivity.class.getSimpleName();
private String URL = "http://10.0.0.2:0080/stringtest2.php?offset=";
private SwipeRefreshLayout swipeRefreshLayout;
private ListView listView;
private SwipeListAdapter adapter;
private List<Order> orderList;
// initially offset will be 0, later will be updated while parsing the json
private int offSet = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listView);
//RelativeLayout.LayoutParams layout_description = new RelativeLayout.LayoutParams(50,10);
//Rl.setLayoutParams(layout_description);
swipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_refresh_layout);
orderList = new ArrayList<>();
adapter = new SwipeListAdapter(this, orderList);
listView.setAdapter(adapter);
swipeRefreshLayout.setOnRefreshListener(this);
/**
* Showing Swipe Refresh animation on activity create
* As animation won't start on onCreate, post runnable is used
*/
swipeRefreshLayout.post(new Runnable() {
#Override
public void run() {
swipeRefreshLayout.setRefreshing(true);
fetchOrders();
}
}
);
mHandler = new Handler();
startRepeatingTask();
}
/**
* This method is called when swipe refresh is pulled down
*/
Runnable mStatusChecker = new Runnable() {
#Override
public void run() {
//updateStatus(); //this function can change value of mInterval.
mHandler.postDelayed(mStatusChecker, mInterval);
}
};
void startRepeatingTask() {
mStatusChecker.run();
}
void stopRepeatingTask() {
mHandler.removeCallbacks(mStatusChecker);
}
//added code start here
Runnable mAutoRefreshRunnable = new Runnable() {
#Override
public void run() {
fetchOrders();
mHandler.postDelayed(mAutoRefreshRunnable, 60000);
}
};
#Override
protected void onResume() {
super.onResume();
mHandler.postDelayed(mAutoRefreshRunnable, 60000);
}
#Override
protected void onPause(){
super.onPause();
mHandler.removeCallbacks(mAutoRefreshRunnable);
}
//added code ends here
#Override
public void onRefresh() {
fetchOrders();
}
/**
* Fetching movies json by making http call
*/
private void fetchOrders() {
// showing refresh animation before making http call
swipeRefreshLayout.setRefreshing(true);
// appending offset to url
String url = URL + offSet;
// Volley's json array request object
JsonArrayRequest req = new JsonArrayRequest(url,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
Log.d(TAG, response.toString());
if (response.length() > 0) {
// looping through json and adding to order list
for (int i = 0; i < response.length(); i++) {
try {
JSONObject orderObj = response.getJSONObject(i);
int rank = orderObj.getInt("rank");
String title = orderObj.getString("title");
Order m = new Order(rank, title);
orderList.add(0, m);
// updating offset value to highest value
if (rank >= offSet)
offSet = rank;
} catch (JSONException e) {
Log.e(TAG, "JSON Parsing error: " + e.getMessage());
}
}
adapter.notifyDataSetChanged();
}
// stopping swipe refresh
swipeRefreshLayout.setRefreshing(false);
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Log.e(TAG, "Server Error: " + error.getMessage());
Toast.makeText(getApplicationContext(), "Can't connect to database", Toast.LENGTH_LONG).show();
// stopping swipe refresh
swipeRefreshLayout.setRefreshing(false);
}
});
// Adding request to request queue
MyApplication.getInstance().addToRequestQueue(req);
}
}

After you fetch new data, there is a place you need to call notifyDataSetChanged() to let the listview update its content.
right after that call, you can use Vibrator to start a vibration
Vibrator v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
// Vibrate for 500 milliseconds
v.vibrate(500);
see: http://developer.android.com/reference/android/os/Vibrator.html
To play sound, you need a MediaPlayer:
MediaPlayer mp = MediaPlayer.create(this, yourSoundFile);
mp.start();

How can implement offline caching of json in Android?

I am working on a articles application like techcrunch I am parsing data from json.
I am parsing title,author and image from json.
Articles are displayed in list-view.
I want to do offline caching means when there is no internet user can read the articles.
Here is my code-
public class OneFragment extends Fragment {
public OneFragment(){}
private static final String TAG = OneFragment.class.getSimpleName();
// Movies json url
private static String URL = "http://url";
private ProgressDialog pDialog;
private List<Movie> movieList = new ArrayList<Movie>();
private ListView listView;
private CustomListAdapter adapter;
int current_page = 0;
int mPreLast;
SwipeRefreshLayout swipeView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View rootView = inflater.inflate(R.layout.swip, container, false);
swipeView = (SwipeRefreshLayout) rootView.findViewById(R.id.swipe);
swipeView.setColorScheme(android.R.color.holo_blue_dark, android.R.color.holo_blue_light, android.R.color.holo_green_light, android.R.color.holo_green_dark);
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Loading...");
pDialog.show();
pDialog.setCancelable(false);
swipeView.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
#Override
public void onRefresh() {
// TODO Auto-generated method stub
swipeView.setRefreshing(true);
Log.d("Swipe", "Refreshing Number");
( new Handler()).postDelayed(new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
swipeView.setRefreshing(false);
onStart();
}
}, 3000);
}
});
listView = (ListView) rootView.findViewById(R.id.list49);
listView.setOnScrollListener(new AbsListView.OnScrollListener()
{
#Override
public void onScrollStateChanged(AbsListView absListView, int i)
{
}
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)
{
int lastItem = firstVisibleItem + visibleItemCount;
if(lastItem == totalItemCount){
if (mPreLast != lastItem)
{
mPreLast = lastItem;
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Loading more articles...");
pDialog.show();
//pDialog.setCancelable(false);
onStart();
}
}
}
});
listView.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int Position,
long offset) {
// TODO Auto-generated method stub
Movie item = (Movie) adapter.getItem(Position);
Intent intent = new Intent(rootView.getContext(), SingleArticle.class);
single.title = item.getTitle();
single.author = item.getAuthor();
startActivity(intent);
}
});
//pDialog = new ProgressDialog(this);
// Showing progress dialog before making http request
return rootView;
}
#Override
public void onStart(){
super.onStart();
// calling adapter changes here, just
// to avoid getactivity()null
// increment current page
current_page += 1;
// Next page request
URL = "http://url" + current_page;
//adapter = new CustomListAdapter(this, movieList);
int currentPosition = listView.getFirstVisiblePosition();
adapter = new CustomListAdapter(getActivity(), movieList);
listView.setAdapter(adapter);
listView.setSelectionFromTop(currentPosition + 1, 0);
// changing action bar color
//getActivity().getActionBar().setBackground(
//new ColorDrawable(Color.parseColor("#1b1b1b")));
// Creating volley request obj
JsonArrayRequest movieReq = new JsonArrayRequest(URL,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
Log.d(TAG, response.toString());
hidePDialog();
// Parsing json
for (int i = 0; i < response.length(); i++) {
try {
JSONObject obj = response.getJSONObject(i);
Movie movie = new Movie();
movie.setTitle(obj.getString("title"));
movie.setAuthor(obj.getString("author"));
// adding movie to movies array
movieList.add(movie);
adapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
}
},new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
new AlertDialog.Builder(getActivity())
.setTitle("No Connectivity ")
.setMessage("Please check your internet connectivity!")
.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// continue with delete
}
})
//.setNegativeButton(android.R.string.no, new DialogInterface.OnClickListener() {
//public void onClick(DialogInterface dialog, int which) {
// do nothing
//}
//})
.setIcon(android.R.drawable.ic_dialog_alert)
.show();
hidePDialog();
}
});
AppController.getInstance().addToRequestQueue(movieReq);
//listView.setAdapter(adapter);
}
private View getActionBar() {
// TODO Auto-generated method stub
return null;
}
#Override
public void onDestroy() {
super.onDestroy();
hidePDialog();
}
private void hidePDialog() {
if (pDialog != null) {
pDialog.dismiss();
pDialog = null;
}
}
}

This probably isn't the best way to do it, but it worked for me.
You might find this helpful: http://www.vogella.com/tutorials/JavaSerialization/article.html
I had to do the same in some project. This is what I did:
public final class cacheThis {
private cacheThis() {}
public static void writeObject(Context context, String fileName, Object object) throws IOException {
FileOutputStream fos = context.openFileOutput(fileName, Context.MODE_PRIVATE);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(object);
oos.flush();
oos.close();
fos.close();
}
public static Object readObject(Context context, String fileName) throws IOException,
ClassNotFoundException {
FileInputStream fis = context.openFileInput(fileName);
ObjectInputStream ois = new ObjectInputStream(fis);
Object object = ois.readObject();
fis.close();
return object;
}
}
To write to file:
cacheThis.writeObject(YourActivity.this, fileName, movieList);
To read from file:
movieList.addAll((List<Movie>) cacheThis.readObject(
VideoActivity.this, fileName));
You have to have your Movie class implements Serializable

You must save the json offline. It can be Db or file system. I will prefer to go with Db part.
The approach is ,every time you get data from server save first in you db then from db you can show it to your UI.
Inserting in Db can be slow but you can use beginTransaction and other methods which will make it lighting fast.
Now How can you save data in Db. You have two ways
You can parse json first and create the table structure for name,url and other fields then run the query
Or store the whole json in Db without parsing .By using GSON or other json parsers this approch will be quite helpful.

I saw you are using Volley. Volley has built-in HTTP Cache mechanism.
So the easiest way is to support HTTP cache headers in your backend. It is very easy and it is transparent to the client side. Volley does the hard work. You can find information here
If you don't have access to the URL you use, you must use internal database to support your application. ContentProvider API is the best way to do that. And the following library is a great library to construct a database and write to it.
https://github.com/TimotheeJeannin/ProviGen
Basically you need to write every item that you pull from the internet to the database and the ListView should show the items from the database using ContentProvider you have just created. When the user opens the app, show the data from the database and then immediately try to pull the new data from your backend.