public class MainActivity extends AppCompatActivity {
        String username ;
        String password;

        public void doLgin(View view) {
            if(Build.VERSION.SDK_INT >= 10){
                StrictMode.ThreadPolicy policy = StrictMode.ThreadPolicy.LAX;
                StrictMode.setThreadPolicy(policy);
            }

            username = ((EditText)findViewById(R.id.editTextUsername)).getText().toString();
            password = ((EditText)findViewById(R.id.editTextPassword)).getText().toString();

            try {

                HttpClient httpClient = new DefaultHttpClient();
                HttpGet httpPost = new HttpGet("http://182.18.163.39/m/login.php?username=" + username + "&key=" + password);
                HttpResponse response = httpClient.execute(httpPost);
                HttpEntity entity = response.getEntity();

                String responseString = EntityUtils.toString(entity);
                JSONArray jsonarray = new JSONArray(responseString);
                JSONObject jsonObj = new JSONObject();
                jsonObj.put("Result", jsonarray);
                String error = jsonObj.getJSONArray("Result").getJSONObject(0).toString();
                String errormsg = "{"Error":"Problem with authentication,Please login."}";

                if (error.equalsIgnoreCase(errormsg)) {
                    Toast.makeText(getApplicationContext(), "Invalid username or password", Toast.LENGTH_SHORT).show();

                } else {
    //                Toast.makeText(getApplicationContext(), "Success", Toast.LENGTH_SHORT).show();
                   Intent i = new Intent(MainActivity.this, Main2Activity.class);

                   startActivity(i);

                }
            }

public class Main2Activity extends AppCompatActivity {

    MainActivity m = new MainActivity();
    String user = m.username;
    String pass = m.password;

    String JSON_URL = "http://182.18.163.39/m/list.php?username=admin&key=admin";
    ListView listView;
    java.util.List<List> tktList;

    String link;
    Button logoutbt;
    Button ubt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        logoutbt = (Button)findViewById(R.id.lbt);
        logoutbt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                SharedPreferences SM = getSharedPreferences("userrecord", 0);
                SharedPreferences.Editor edit = SM.edit();
                edit.putBoolean("username", false);
                edit.commit();

                Intent intent = new Intent(Main2Activity.this, MainActivity.class);
                startActivity(intent);
                finish();
            }
        });

        //initializing listview and hero list
        listView = (ListView) findViewById(R.id.listView);
        tktList = new ArrayList<>();

        //this method will fetch and parse the data
        loadHeroList();
    }

    private void loadHeroList() {
        //getting the progressbar
        final ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressBar);

        //making the progressbar visible
        progressBar.setVisibility(View.VISIBLE);

        //creating a string request to send request to the url
        StringRequest stringRequest = new StringRequest(Request.Method.GET, JSON_URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        //hiding the progressbar after completion
                        progressBar.setVisibility(View.INVISIBLE);

                        try {

                            JSONArray jsonarray = new JSONArray(response);
                            for (int i = 0; i < jsonarray.length(); i++) {
                                JSONObject jsonobject = jsonarray.getJSONObject(i);
                                String name = jsonobject.getString("Sno");
                                String Tktid = jsonobject.getString("TKTID");
                                link = jsonobject.getString("Link");

                                List list = new List(jsonobject.getString("Sno"), jsonobject.getString("TKTID"),jsonobject.getString("Link"));
                                tktList.add(list);

                                Log.i("website content", name);
                                Log.i("website content", Tktid);
                                Log.i("website content", link);

                            }

                            //creating custom adapter object
                            ListViewAdapter adapter = new ListViewAdapter(tktList, getApplicationContext());


                            //adding the adapter to listview
                            listView.setAdapter(adapter);

                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        //displaying the error in toast if occurrs
                        Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_SHORT).show();
                    }
                });

        //creating a request queue
        com.android.volley.RequestQueue requestQueue = Volley.newRequestQueue(this);

        //adding the string request to request queue
        requestQueue.add(stringRequest);
    }
}

MainActivity m = new MainActivity();
    String user = m.username;
    String pass = m.password;