I have a fragment that calls a helper class in order to make a jsonRequest with Volley.
Upon response, the helper class creates a custom object, but in order to set it up, it needs to check some values stored in Shared Preferences.
The problem is that I can't access getSharedPreferences inside the helper class.
public class MyDataHandler {
ArrayList<MyItem> itemsArrayList = new ArrayList<>();
public List<MyItem> getAll(Boolean completed, String current, final MyAsyncResponse callBack) {
String url = "https://my.api/" + current;
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(
Request.Method.GET,
url,
null,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
for (int i = 0; i < response.length(); i++) {
try {
JSONObject jsonObject = response.getJSONObject(i);
MyItem myItem = new MyItem();
if (!completed) {
SharedPreferences sharedPreferences = getSharedPreferences("MyApp", MODE_PRIVATE); // this doesn't work
if (sharedPreferences.getBoolean("someKey", false)) {
// set properties in MyItem
}
}
itemsArrayList.add(myItem);
} catch (JSONException e) {
e.printStackTrace();
}
}
if (null != callBack) callBack.processFinished(itemsArrayList);
}
},
new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
}
}
);
AppController.getInstance().addToRequestQueue(jsonArrayRequest);
return itemsArrayList;
}
How can I access Shared Preferences if this class isn't attached to any particular activity?
I assume that you are instantiating MyDataBaseHandler as "getAll" is a non static function
create a constructor and a member variable like this :-
MyDataBaseHandler{
Context context;
public MyDataHandler(Context context){ //pass your activity here
this.context=context;
}
// write rest of your code
}
now you can use this context member variable and access your shared perefrence using context.getSharedPreference("MyApp", Context.MODE_PRIVATE).
Related
i am new to Android,here is class Question bank returns list of json obj received from an api
ArrayAsyncResponse in interface containing only one method process complete ,i readed that http request is asynchronous but unable to relate
Question is model class
case 1) when there is no ArrayAsyncResponse interface exist and i return the list to main activity and print it it shows empty list but when i make call to callback.processComplete() and then return list followed by printing ,it shows data
case2 )if i pass null in this function callback.processComplete() then again returned list is empty
so what basically Interface is helping us
public class QuestionBank {
ArrayList questionArrayList = new ArrayList<>();
private String url = "https://raw.githubusercontent.com/curiousily/simple-quiz/master/script/statements-data.json";
public List<Question> getQuestions(final AnswerListAsyncResponse callBack) {
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(
Request.Method.GET,
url,
(JSONArray) null,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
for (int i = 0; i < response.length(); i++) {
try {
Question question = new Question();
question.setAnswer(response.getJSONArray(i).get(0).toString());
question.setAnswerTrue(response.getJSONArray(i).getBoolean(1));
//Add question objects to list
questionArrayList.add(question);
//Log.d("Hello", "onResponse: " + question.getAnswer());
// Log.d("JSON", "onResponse: " + response.getJSONArray(i).get(0));
//Log.d("JSON2", "onResponse: " + response.getJSONArray(i).getBoolean(1));
} catch (JSONException e) {
e.printStackTrace();
}
}
if (null != callBack) callBack.processFinished(questionArrayList);
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
}
});
AppController.getInstance().addToRequestQueue(jsonArrayRequest);
return questionArrayList;
}
public class MainActivity extends AppCompatActivity {
private QuestionBank questionBank;
List<Question> questionList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
questionBank=new QuestionBank();
questionList=questionBank.getQuestions(new AnswerListAsyncResponse() {
#Override
public void processFinished(ArrayList<Question> questionsArrayList) {//this function triggers when response is received from api
Log.d("inside", "processFinished: "+questionsArrayList);
}
});
Log.d("sync response", "questionLIst: "+questionList);
}
}
Sorry I can't write this in comment, but I think I can help you.
I don't understand well your question. but I think you need to get a Listener of the async in your class activity.
You can do that with EventBus, like this : https://github.com/greenrobot/EventBus
I created a parent activity and Fragments are added to parent activity.
But i need to call a function (HTTP request) in parent activity and return the result in fragment activity. But i am able to access the function from fragment using
String stage = ((TabActivity)getActivity()).fetchStage(tabid,"12");
But the value is not receiving in fragments stage variable..
my TabActivity Function:
public String fetchStage(String tabid,String userId){
Log.e("URL","http://35.184.41.163/phpmyadmin/app/demo/getstage.php?tabid="+tabid+"&userid="+userId);
RestClientHelper.getInstance().get("http://35.184.41.163/phpmyadmin/app/demo/getstage.php?tabid="+tabid+"&userid="+userId, new RestClientHelper.RestClientListener() {
#Override
public void onSuccess(String response) {
try {
Log.e("onSUcess Stage","onSUcess Stage");
JSONObject stageresponse = new JSONObject(response);
JSONArray posts = stageresponse.optJSONArray("stage");
for (int i = 0; i < posts.length(); i++) {
JSONObject post = posts.optJSONObject(i);
stage = post.optString("stage");
Log.e("onSUcess FOR","onSUcess FOR"+stage);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
#Override
public void onError(String error) {
Log.e("onError Stage","onError Stage");
stage = "stage1";
}
});
Log.e("STAGE",stage);
return stage;
}
Your rest client is doing the network call asynchronously. So, your onSuccess isCalling after sometime. You should declare a public function in your fragment and call that from the onSuccess method.
You could supply an instance of RestClientListener to fetchStage.
The method signature would become:
fetchStage(String tabId, String userId, RestClientHelper.RestClientListener listener);
and when you call it from the Fragment you'd write:
((TabActivity)getActivity()).fetchStage(
tabid,
"12",
new RestClientHelper.RestClientListener () {
// this anonymous class has access to your instance members
#Override
public void onSuccess(String response) {
// ...
MyFragment.this.stage = ...
}
#Override
public void onError(String error) {
MyFragment.this.stage = "stage 1";
}
});
This is widely used in Android; e.g setting a LocationListener to a LocationManager.
I want to get string from arraylist inside oncreateview fragment but i cant figure itout since no position index has been pass. get(position) return error.
String price = arrayList.get(position).getPrice();
i need to get string price and settext for price.this is my main concern.
this values should return from arraylist.
this is response JSON array from volley using mysingleton.
Single Product Response: [{"price":"75","date":"2017-07-13 03:25:31","pk_i_id":"4"}]
this main activty fragment
public class MainActivityFragment extends Fragment {
private TextView product,price,date,title;
private String product_id;
ArrayList<ProductItem> arrayList = new ArrayList<>();
Context context;
public MainActivityFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_main_activity, container, false);
product = (TextView) view.findViewById(R.id.tv1);
title = (TextView) view.findViewById(R.id.tvTitle);
price = (TextView) view.findViewById(R.id.tvPrice);
date = (TextView) view.findViewById(R.id.tvDate);
if (getArguments() != null) {
Log.i(TAG, "getArgument is not null");
product_id = getArguments().getString("product_id");
ProductBackgroundTask productBackgroundTask = new ProductBackgroundTask(this.getActivity(), product_id);
arrayList = productBackgroundTask.getList();
String price = arrayList.get(position).getPrice();
// Log.d(TAG, "price: " + price);
product.setText(product_id);
// price.setText(price);
}else {
Log.i(TAG, "getArgument is null");
}
return view;
}
}
this is task to get arraylist using volley
public class ProductBackgroundTask {
private Context context;
ArrayList<ProductItem> arrayList = new ArrayList<>();
String json_url = "phpfile.php";
private String product_id;
public ProductBackgroundTask(Context context, String product_id) {
this.context = context;
this.product_id = product_id;
}
public ArrayList<ProductItem> getList(){
StringRequest stringRequest = new StringRequest(Request.Method.POST, json_url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
Log.d(TAG, "Single Product Response: " + response);
try {
JSONArray jsonarr = new JSONArray(response);
for (int i = 0; i < jsonarr.length(); i++) {
JSONObject jsonobj = jsonarr.getJSONObject(i);
ProductItem productItem = new ProductItem(jsonobj.getString("price"), jsonobj.getString("date"), jsonobj.getInt("pk_i_id"));
arrayList.add(productItem);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
}
}){
#Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String,String> params = new HashMap<>();
params.put("product_id", product_id);
return params;
}
};
MySingleton.getInstance(context).addToRequestQueue(stringRequest);
return arrayList;
}
}
and this is class of array list
public class ProductItem {
private String Price,Date;
private int ProductId;
public ProductItem(String Price, String Date, int ProductId){
this.setPrice(Price);
this.setDate(Date);
this.setProductId(ProductId);
}
public int getProductId() {
return ProductId;
}
public void setProductId(int productId) {
ProductId = productId;
}
public String getPrice() {
return Price;
}
public void setPrice(String price) {
Price = price;
}
public String getDate() {
return Date;
}
public void setDate(String date) {
Date = date;
}
Clearly in your oncreate you haven’t initialized the product item and you cannot parse the complete list.You can try two to solve this
1.Pass specific item number instead of position i.e
say if you want to show 4th item then position=3
2.Or write a loop like this to parse entire arrayList like this
for(ProductItem productItem:arrayList){
String price = productItem.getPrice();
// Log.d(TAG, "price: " + price);
product.setText(product_id);
price.setText(price);
}
Mistake you're doing is that in the MainActivityFragment your trying to assign the value to the arrayList even before the data is added to the arrayList in the ProductBackgroundTask-getList. That's the reason you are getting the list null all the time. Try to use interfaces.
1.Make your MainActivityFragment implement the interface.
2.Set the value to the interface method once you get the data from the server.
3.Get the data in the MainActivityFragment inside interface method and do all the operation you're doing inside the onCreateView method.
Now your arraylist will have the data whatever you received from the server.
Below is the link for the example on interfaces if you haven't used them before. He is doing exactly as your requirement.
https://www.justinmccandless.com/post/setting-up-a-callback-function-in-android/
Allow me. The arrayList that you return from getList isn't populated at the time you call String price = arrayList.get(position).getPrice();. The server call using volley takes some time to process and that's when the onResponse gets called. This happens AFTER you've returned the arrayList which is in fact empty.
The sequence of events is as follows.
• Call to arrayList = productBackgroundTask.getList(); which returns an empty ArrayList.
• String price = arrayList.get(position).getPrice();
Now after a while..
• onResponse inside getList() gets called.
Do you now see why it's empty?
Simple Solution: • Define a simple interface ProductListener alongside ProductBackgroundTask. (With only a single abstract method onProducts).
• Instantiate it inside the Fragment's onCreateView using an anonymous class and pass it to the constructor of ProductListener to save it for later use. Do whatever you want to do with the products inside the onProducts method. (Since that will be called with the actual data)
• Call its onProducts method with the data that's parsed and fetched inside the onResponse method.
ProductBackgroundTask code:
public class ProductBackgroundTask {
private Context context;
// I removed the instance ArrayList since that can be made
// local.
// Here, we add a reference to our callback interface as we can use it later.
private ProductListener listener;
String json_url = "http://192.168.43.55/android/v1/productList.php";
private String product_id;
// Instantiate this class using an additional listener argument
// which would be a concrete implementation of our interface.
public ProductBackgroundTask(Context context, String product_id, ProductListener listener) {
this.context = context;
this.product_id = product_id;
this.listener = listener;
}
// getList should not return anything,
// so I keep the return as void.
public void getList() {
StringRequest stringRequest = new StringRequest(Request.Method.POST, json_url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
ArrayList<ProductItem> arrayList = new ArrayList<>();
Log.d(TAG, "Single Product Response: " + response);
try {
JSONArray jsonarr = new JSONArray(response);
for (int i = 0; i < jsonarr.length(); i++) {
JSONObject jsonobj = jsonarr.getJSONObject(i);
ProductItem productItem = new ProductItem(jsonobj.getString("price"), jsonobj.getString("date"), jsonobj.getInt("pk_i_id"));
arrayList.add(productItem);
}
// Notice this line here, this is what
// calls the callback with the products.
listener.onProducts(arrayList);
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
}
}){
#Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String,String> params = new HashMap<>();
params.put("product_id", product_id);
return params;
}
};
MySingleton.getInstance(context).addToRequestQueue(stringRequest);
}
}
// Callback interface, we would need a concrete implementation
// of this and pass that to the constructor of ProductBackgroundTask.
interface ProductListener {
void onProducts(ArrayList<ProductItem> products);
}
The code inside onCreateView:
ProductBackgroundTask productBackgroundTask = new ProductBackgroundTask(this.getActivity(), product_id, new ProductListener() {
// This method will be called with the needed products.
// Give an anonymous class implementation of our interface
// right here since we won't be using it anymore.
public void onProducts(ArrayList<ProductItem> products) {
// Get the price you want.
String str = arrayList.get(0).getPrice();
// Use str wherever necessary. Use the UI thread here if you need
// to change any visible elements on the screen.
}
});
// Simply call this method to get the ball rolling.
productBackgroundTask.getList();
This is a concrete implementation of the this answer and you won't be changing much code.
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.
I have the following code successfully loading from SharedPreferences
List<MyObject> oList = new ArrayList<MyObject>();
// Get JSON Data from storage.
HashSet<String> oStrings = new HashSet<String>();
oStrings = (HashSet<String>) oSharedPrefs.getStringSet(IConstants.MY_OBJECT_LIST, null);
if (oStrings != null && oStrings.size() > 0)
{
Gson oGson = new Gson();
for (String strJSONObject : oStrings)
{
MyObject oObject = oGson.fromJson(strJSONObject, MyObject.class);
oList.add(oObject);
}
}
return oList;
The problem is, this is running on the UI thread & as the SharedPreferences JSON strings get larger, this can cause my app to pause for a few seconds.
How would I go about loading this data in the background then retrieving the object list?
You can use a AsyncTask for this:
public class LoadFromShared extends AsyncTask<Void, Void, List<MyObject>>{
private OnLoadingDoneListener mListener;
public interface OnLoadingDoneListener{
public void onDone(List<MyObject> result);
}
public void setOnLoadingDoneListener(OnLoadingDoneListener listener){
this.mListener = listener;
}
#Override
protected List<MyObject> doInBackground(Void... params) {
List<MyObject> oList = new ArrayList<MyObject>();
// Get JSON Data from storage.
HashSet<String> oStrings = new HashSet<String>();
oStrings = (HashSet<String>) oSharedPrefs.getStringSet(IConstants.MY_OBJECT_LIST, null);
if (oStrings != null && oStrings.size() > 0)
{
Gson oGson = new Gson();
for (String strJSONObject : oStrings)
{
MyObject oObject = oGson.fromJson(strJSONObject, MyObject.class);
oList.add(oObject);
}
}
return oList;
}
protected void onPostExecute(List<MyObject> result) {
if(mListener!=null={
mListener.onDone(result);
}
};
}
An then in your main:
LoadFromShared loader = new LoadFromShared();
loader.setOnLoadingDoneListener(new OnLoadingDoneListener(){
#Override
onDone(List<MyObject> result){
//do your stuff here
}
};);
loader.execute();
No guarantee for correct typing ;)