Carrying and reusing information (json string) from an AsyncTask?

Issue

I have created a simple android app with 3 TextViews and then run an AsyncTask Task via a different class the next step would be to carry the information over and make the task reusable.

The Task will consume a String (URL) and the context of the MainActivity.

The Task will make a simple REST Request (GET) and retrieve a json string.

I have then created another class that which gets the json response and creates a .json file saves it to

..../0/Notes/launch.json

The folder "Notes is created by myself via file.mkdirs().

In the MainActivity I created an InputStream to read the .json file saved by the AsyncTask but once I try to open it, it gives me a FileNotFoundException.

Here's the code of my MainActivity.class

package com.example.root.example;

import android.Manifest;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.widget.ImageView;
import android.widget.TextView;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 200);
    String url = "https://api.spacexdata.com/v3/launches/upcoming"; //Copy the url and open it in your browser to see the json.

    AsyncCall asyncCall = new AsyncCall(getApplicationContext());
    asyncCall.myAsyncTask(url);

   try {
        InputStream inputStream = this.getAssets().open("launch.json");
        int size = inputStream.available();
        byte[] buffer = new byte[size];
        inputStream.read(buffer);
        inputStream.close();
        String jsonStringFromFile= new String(buffer,"UTF-8");
        JSONObject launchObject = new JSONObject(jsonStringFromFile);
        System.out.println(launchObject.get("flight_number"));
    } catch (IOException e) {
        e.printStackTrace();
    } catch (JSONException e) {
        e.printStackTrace();
    }
  }
}

This is the AsyncCall.class (making and retrieving the json etc..)

package com.example.root.example;

import android.content.Context;
import android.os.AsyncTask;
import android.os.Environment;

import java.io.IOException;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class AsyncCall {

FileCreator fileCreator = new FileCreator();
private final Context myContext;

public AsyncCall(final Context context) {
    myContext = context;
}

public void myAsyncTask(final String url) {

    AsyncTask asyncTask = new AsyncTask() {
        @Override
        protected Object doInBackground(Object[] objects) {
            OkHttpClient okHttpClient = new OkHttpClient();
            Request request = new Request.Builder()
                    .url(url)
                    .build();
            Response response = null;
            try {
                response = okHttpClient.newCall(request).execute();
                fileCreator.generateFile(myContext, myContext.getString(R.string.fileName), response.body().string());

            } catch (IOException ioe) {
                ioe.getMessage();
            }
            return null;
        }
    }.execute();
  }
}

what am I trying to archive? I'm trying to save information (json here) and make it reusable just as the Falcon 9.

The issue lies in carrying information over to a different class. If there's an alternative solution (other than saving a .json file) to fix this issue then please don't hesitate to post it.

This is just my first issue, the second issue appears once you open the api link and see that there are a few more than just one JSON String (0,1,2,3,4... upcoming missions).

I have no clue in any way to tacle the first let alone the second problem and have started over a few times, a while ago multiple times.

Solution

Within your Activity, you can get the JSON like so

OkHttpClient okHttpClient = new OkHttpClient();
Request request = new Request.Builder().url(url).build();
okHttpClient.newCall(request).enqueue(new Callback() {
    @Override
    public void onResponse(Call call, final Response response) throws IOException {  
        try {
            final String responseData = response.body().string();
            JSONObject json = new JSONObject(responseData);

            String flightNumber = json.getString("flight_number");
            // TODO: Load number into a TextView
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
});

Looking at your API response, though, you'll actually need new JSONArray(responseData), and you would have to loop over that to get each individual object's flight number

Answered By - OneCricketeer