How to correctly handle data management with SharedPreferences? - json

Question

Right now, I am in the process of "optimizing" my app. I am still a beginner, so what I am doing is basically moving methods from my MainActivity.class to their separate class. I believe it's called Encapsulation (Please correct me if I'm wrong).
My application needs to :
Get a YouTube Playlist Link from the YouTube App (with an Intent, android.intent.action.SEND).
Use the link to fetch data from the Google Servers with the YouTubeApi and Volley.
Read the data received and add it to an arrayList<String>.
What my YouTubeUsage.java class is supposed to do, is fetch data with the YouTubeApi and Volley then store the data using SharedPreferences. Once the data is saved, the data is being read in my ConvertActivity.class (It's an activity specifically created for android.intent.action.SEND) with my method getVideoIds() before setting an adapter for my listView in my createRecyclerView() method.
YouTubeUsage.java
public class YoutubeUsage {
private Boolean results = false;
private String mResponse;
private ArrayList<String> videoIds = new ArrayList<>();
String Url;
public String getUrl(String signal) {
String playlistId = signal.substring(signal.indexOf("=") + 1);
this.Url = "https://www.googleapis.com/youtube/v3/playlistItems?part=contentDetails%2C%20snippet%2C%20id&playlistId=" +
playlistId + "&maxResults=25&key=" + "API_KEY";
return this.Url;
}
public void fetch(String Url, final Context context){
RequestQueue queue = Volley.newRequestQueue(context);
StringRequest request = new StringRequest(Request.Method.GET, Url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
sharedPreferences(response, context);
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Log.e("VolleyError", Objects.requireNonNull(error.getMessage()));
}
});
queue.add(request);
}
private void sharedPreferences(String response, Context context){
SharedPreferences m = PreferenceManager.getDefaultSharedPreferences(context);
SharedPreferences.Editor editor = m.edit();
if (m.contains("serverResponse")){
if (!m.getString("serverResponse", "").equals(response)){
editor.remove("serverResponse");
editor.apply();
updateSharedPreferences(response, context);
}
} else{
updateSharedPreferences(response, context);
}
}
private void updateSharedPreferences(String mResponse, Context mContext){
SharedPreferences m = PreferenceManager.getDefaultSharedPreferences(mContext);
SharedPreferences.Editor editor = m.edit();
editor.putString("serverResponse", mResponse);
editor.apply();
}
}
ConvertActivity.java
public class ConvertActivity extends AppCompatActivity {
YoutubeUsage youtubeUsage = new YoutubeUsage();
ArrayList<String> videoIDs = new ArrayList<>();
String Url = "";
ListView listView;
MyCustomAdapter myCustomAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_convert);
listView = findViewById(R.id.listview_convert);
Intent intent = getIntent();
String action = intent.getAction();
String type = intent.getType();
if ("android.intent.action.SEND".equals(action) && "text/plain".equals(type)) {
Url = youtubeUsage.getUrl(Objects.requireNonNull(intent.getStringExtra("android.intent.extra.TEXT")));
}
//I would like to avoid the try/catch below
try {
videoIDs = getVideoIDs(Url, this);
createRecyclerView(videoIDs);
Log.i("ResponseVideoIDs", String.valueOf(videoIDs.size()));
} catch (JSONException e) {
e.printStackTrace();
}
}
private ArrayList<String> getVideoIDs(String Url, Context context) throws JSONException {
ArrayList<String> rawVideoIDs = new ArrayList<>();
youtubeUsage.fetch(Url, context);
SharedPreferences m = PreferenceManager.getDefaultSharedPreferences(context);
String serverResponse = m.getString("serverResponse", "");
JSONObject jsonObject = new JSONObject(serverResponse);
JSONArray jsonArray = jsonObject.getJSONArray("items");
for (int i = 0; i<jsonArray.length(); i++){
JSONObject jsonObject1 = jsonArray.getJSONObject(i);
JSONObject jsonVideoId = jsonObject1.getJSONObject("contentDetails");
rawVideoIDs.add(jsonVideoId.getString("videoId"));
}
return rawVideoIDs;
}
private void createRecyclerView(ArrayList<String> videoIDs){
myCustomAdapter = new MyCustomAdapter(this, videoIDs);
listView.setAdapter(myCustomAdapter);
myCustomAdapter.notifyDataSetChanged();
}
}
Everything works fine, however, my sharedPreferences never gets updated. Which means, if I share a YouTube playlist from the YouTube App to my app with 3 items in it, it will work fine. The Listview will show 3 items with their corresponding IDs as it should. But, if I share a YouTube playlist again, my app will still hold on to the data of the previous playlist I shared (even if I close it), showing the item number and the IDs of the previous link. If i continue to share the same playlist over and over, it will eventually show the correct number of items and the correct IDs.
I could totally put all my methods from the YouTubeUsage.java in my ConvertActivity.class preventing me from using SharedPreferences to transfer data between the two java classes. However, JSON throws an exception. That means I have to encapsulate my code with try/catch. I would like to avoid those since I need to do a lot of operations on the data just received by Volley (check a class size, look for certains strings). I find that doing this in these try/catch don't work like I want. (i.e. outside the try/catch, the values remains the same even if I updated them in the try/catch).
I want to know two things.
How can I correct this problem?
Is this the most efficient way to do this (optimization)? (I though of maybe
converting the VolleyResponse to a string with Gson then store the String file, but I don't know if that's the best way to do it since it's supposed to be
provisional data. It feels like just more of the same).
Thank You!

Answer 1

There is an issue with making assumptions about order of events. Volley will handle requests asynchronously, so it is advisable to implement the observer pattern here.
Create a new Java file that just contains:
interface MyNetworkResponse {
void goodResponse(String responseString);
}
Then make sure ConvertActivity implements MyNetworkResponse and create method:
void goodResponse(String responseString) {
// handle a positive response here, i.e. extract the JSON and send to your RecyclerView.
}
within your Activity.
In your YoutubeUsage constructor, pass in the Activity context (YoutubeUsage) and then store this in a YoutubeUsage instance variable called ctx.
In onCreate, create an instance of YoutubeUsage and pass in this.
In onResponse just call ctx.goodResponse(response).
Amend the following block to:
if ("android.intent.action.SEND".equals(action) && "text/plain".equals(type)) {
Url = youtubeUsage.getUrl(Objects.requireNonNull(intent.getStringExtra("android.intent.extra.TEXT")));
youtubeUsage.fetch(Url);
}
Delete the try/catch from onCreate.
And no need to use SharedPreferences at all.
UPDATE
Try this code:
MyNetworkResponse.java
interface MyNetworkResponse {
void goodResponse(String responseString);
void badResponse(VolleyError error);
}
YoutubeUsage.java
class YoutubeUsage {
private RequestQueue queue;
private MyNetworkResponse callback;
YoutubeUsage(Object caller) {
this.callback = (MyNetworkResponse) caller;
queue = Volley.newRequestQueue((Context) caller);
}
static String getUrl(String signal) {
String playlistId = signal.substring(signal.indexOf("=") + 1);
return "https://www.googleapis.com/youtube/v3/playlistItems?part=contentDetails%2C%20snippet%2C%20id&playlistId=" + playlistId + "&maxResults=25&key=" + "API_KEY";
}
void fetch(String url){
StringRequest request = new StringRequest(Request.Method.GET, url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
callback.goodResponse(response);
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
callback.badResponse(error);
}
});
queue.add(request);
}
}
ConvertActivity.java
public class ConvertActivity extends AppCompatActivity implements MyNetworkResponse {
YoutubeUsage youtubeUsage;
ArrayList<String> videoIDs = new ArrayList<>();
ListView listView;
MyCustomAdapter myCustomAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_convert);
listView = findViewById(R.id.listview_convert);
youtubeUsage = new YoutubeUsage(this);
Intent intent = getIntent();
String action = intent.getAction();
String type = intent.getType();
if ("android.intent.action.SEND".equals(action) && "text/plain".equals(type)) {
String url = YoutubeUsage.getUrl(Objects.requireNonNull(intent.getStringExtra("android.intent.extra.TEXT")));
youtubeUsage.fetch(url);
}
}
private ArrayList<String> getVideoIDs(String serverResponse) throws JSONException {
ArrayList<String> rawVideoIDs = new ArrayList<>();
JSONObject jsonObject = new JSONObject(serverResponse);
JSONArray jsonArray = jsonObject.getJSONArray("items");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject1 = jsonArray.getJSONObject(i);
JSONObject jsonVideoId = jsonObject1.getJSONObject("contentDetails");
rawVideoIDs.add(jsonVideoId.getString("videoId"));
}
return rawVideoIDs;
}
private void createRecyclerView(ArrayList<String> videoIDs) {
myCustomAdapter = new MyCustomAdapter(this, videoIDs);
listView.setAdapter(myCustomAdapter);
myCustomAdapter.notifyDataSetChanged();
}
#Override
public void goodResponse(String responseString) {
Log.d("Convert:goodResp", "[" + responseString + "]");
try {
ArrayList<String> rawVideoIDs = getVideoIDs(responseString);
createRecyclerView(rawVideoIDs);
} catch (JSONException e) {
// handle JSONException, e.g. malformed response from server.
}
}
#Override
public void badResponse(VolleyError error) {
// handle unwanted server response.
}
}