Reading and writing from and to a JSON file

Question

In Android, I have 2 activities. Mainactivity takes input from 2 edittext (USERNAME-PASSWORD) and writes them to file.json located in asset folder , Output activity has 2 textview , which will read the values (USERNAME-PASSWORD)from file.json and set the text to TextView. This is how far I tried.

MainActivity.java

package com.example.io;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;

import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;

import android.view.View;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.annotation.*;
import com.fasterxml.jackson.databind.*;

import com.google.android.material.navigation.NavigationView;

import androidx.core.view.GravityCompat;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.ActionBarDrawerToggle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.EditText;

import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.InputStreamReader;

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener
{

    private EditText et1,et2;
    private Button b;
    String e1,e2;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        et1 = (EditText) findViewById(R.id.et1);
        et2 = (EditText) findViewById(R.id.et2);
        b = (Button) findViewById(R.id.b);

        e1=et1.getText().toString().trim();
        e2=et2.getText().toString().trim();

        b.setOnClickListener(new View.OnClickListener()
        {
            BufferedReader reader = null;
            DataOutputStream dos = null;
            BufferedWriter writer = null;

            @Override
            public void onClick(View v)
            {

                //ObjectMapper mapper = new ObjectMapper();
                try
                {
                    JSONObject jsonObject = new JSONObject();
                    jsonObject.put("id",et1);
                    jsonObject.put("password",et2);

                    String FILENAME = "file.json";

                    String string = jsonObject.toString();

                    FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
                    fos.write(string.getBytes());
                    fos.close();

                    Intent intent = new Intent(MainActivity.this,Output.class);
                    startActivity(intent);
                }
                catch (Exception e)
                {
                    e.printStackTrace();
                    System.out.println(e.getMessage());
                }
            }
        });
    }

    @Override
    public void onBackPressed()
    {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START))
        {
            drawer.closeDrawer(GravityCompat.START);
        }
        else
        {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings)
        {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item)
    {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_input)
        {
            // Handle the camera action
        }
        else if (id == R.id.nav_output)
        {
            Intent intent = new Intent(MainActivity.this,Output.class);
            startActivity(intent);
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

Output.java

package com.example.io;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;



import com.google.android.material.navigation.NavigationView;

import androidx.core.view.GravityCompat;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.ActionBarDrawerToggle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;

import org.json.JSONArray;
import org.json.JSONObject;

import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;

import org.json.simple.parser.JSONParser;

public class Output extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener
{
    private TextView tv1;
    private TextView tv2;

    String id,password;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_output);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);



        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        tv1 = findViewById(R.id.tv1);
        tv2 = findViewById(R.id.tv2);
        String json = null;

        try
        {
            /*JSONParser jsonParser = new JSONParser();
            JSONArray jsonArray = (JSONArray) jsonParser.parse(new FileReader("C:\\Users\\I\\Desktop\\IO\\app\\src\\main\\assets\\file.json"));
            JSONObject jsonObject = jsonArray.getJSONObject(0);
            Functions functions = new Functions();
            Bundle bundle = functions.MakeBundleFromJSON(jsonObject);*/

            /*InputStream is =  Output.this.getAssets().open("file.json");
            int size = is.available();
            byte[] buffer = new byte[size];
            is.read(buffer);
            is.close();
            json = new String(buffer, "UTF-8");*/
            InputStream is = getAssets().open("file.json");
            int size = is.available();
            byte[] buffer = new byte[size];
            is.read(buffer);
            is.close();
            json = new String(buffer, "UTF-8");

            System.out.println(json);

            JSONObject obj = new JSONObject(json);


            tv1.setText(obj.getString("id"));
            tv2.setText(obj.getString("password"));
        }
        catch (Exception e)
        {
            e.printStackTrace();
            System.out.println(e.getMessage());
        }
    }

    @Override
    public void onBackPressed()
    {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START))
        {
            drawer.closeDrawer(GravityCompat.START);
        }
        else
        {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.output, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings)
        {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item)
    {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_input)
        {
            // Handle the camera action
            Intent intent = new Intent(Output.this,MainActivity.class);
            startActivity(intent);
        }
        else if (id == R.id.nav_output)
        {

        }


        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

My problem is I can't see any output in Output activity.

here is log If u need a closer look see here in git

Answer 1

You can store the data in Shared Preference from your activity and the data will still persists when your application is closed.

You can visit the below link to Android developers official website Shared Preference

Hope it helps.