I want add my data to TableLayout with automatically. I wrote all codes but i get that error what searched everywhere in the internet. Please helpp me

Question

It is the class my MainClass. I had create TableLayout and added one TableRow to my TableLayout. There are 3 TextView in my TableRow. I want to add TableRow automatically when data insert

For That I had created AsyncTask to get data from php and turn it to list(model list) and then want to send it to my table.

public class MainActivity extends AppCompatActivity {
private TableLayout myTable;
private TableRow tr;
private TextView txtId, txtName, txtSurname, txtAge, txtUsername, txtPassword;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    myTable = (TableLayout) findViewById(R.id.myTable);
    String type="geldim";
    BackgroundProcess backgroundProcess=new BackgroundProcess(this);
    backgroundProcess.execute(type);


}

public void setData(List<Test> getList) {
    for (int i = 0; i < getList.size(); i++) {
        tr = new TableRow(this);
        tr.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.FILL_PARENT, TableRow.LayoutParams.WRAP_CONTENT));
        txtId = new TextView(this);
        txtName = new TextView(this);
        txtSurname = new TextView(this);
        txtAge = new TextView(this);
        txtUsername = new TextView(this);
        txtPassword = new TextView(this);
        System.out.println(getList.get(i).getName());
        txtId.setText(getList.get(i).getId());
        txtName.setText(getList.get(i).getName());
        txtSurname.setText(getList.get(i).getSurname());
        txtAge.setText(getList.get(i).getAge());
        txtUsername.setText(getList.get(i).getUsername());
        txtPassword.setText(getList.get(i).getPassword());

        tr.addView(txtId);
        tr.addView(txtName);
        tr.addView(txtSurname);
        tr.addView(txtAge);
        tr.addView(txtUsername);
        tr.addView(txtPassword);
        myTable.addView(tr);
    }
}

}

And it is my background class:

public class BackgroundProcess extends AsyncTask<String,Void,String> {
 Context context;
 private MainActivity mainActivity=new MainActivity();

BackgroundProcess(Context ctx) {
    context = ctx;
}

@Override
protected String doInBackground(String... params) {
    String a=params[0];
    String myLink="http://192.168.31.129/showData.php";

    if(a.equals("geldim")){
        try {
            System.out.println(1111);
            URL url=new URL(myLink);
            HttpURLConnection httpURLConnection= (HttpURLConnection) url.openConnection();
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setRequestMethod("GET");

            int respondCode=httpURLConnection.getResponseCode();
            if(respondCode==HttpURLConnection.HTTP_OK) {
                System.out.println(2223);
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"));

                String result = "";
                String line = "";
                while ((line = bufferedReader.readLine()) != null) {
                    result += line;
                }
                System.out.println(3333);
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();

                return result;
            }else {
                return ("unsuccessful");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }else {
        return  null;
    }
    return  null;


}

@Override
protected void onPreExecute() {
    super.onPreExecute();
}

@Override
protected void onPostExecute(String value) {
    System.out.println(value);
    List<Test> getList=new ArrayList<>();
    if(value!=null){
        try {
            JSONObject object=new JSONObject(value);
            JSONArray array=object.getJSONArray("menim");
            System.out.println("say bu qederdir"+array.length());
            for(int i=0;i<array.length();i++){
                JSONObject result=array.getJSONObject(i);
                Test test=new Test(result.getInt("id"),result.getString("name"),result.getString("surname"),
                        result.getInt("age"),result.getString("username"),result.getString("password"));
                getList.add(test);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(getList);
        mainActivity.setData(getList);
    }
}

@Override
protected void onProgressUpdate(Void... values) {
    super.onProgressUpdate(values);
}

}

I got this error when i run it:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
    at android.view.ViewConfiguration.get(ViewConfiguration.java:431)
    at android.view.View.<init>(View.java:4535)
    at android.view.View.<init>(View.java:4668)
    at android.widget.TextView.<init>(TextView.java:824)
    at android.widget.TextView.<init>(TextView.java:818)
    at android.widget.TextView.<init>(TextView.java:814)
    at android.widget.TextView.<init>(TextView.java:810)
    at com.example.firstprog.TabOne.setData(TabOne.java:110)
    at com.example.firstprog.BackgroundProcess.onPostExecute(BackgroundProcess.java:96)
    at com.example.firstprog.BackgroundProcess.onPostExecute(BackgroundProcess.java:22)
    at android.os.AsyncTask.finish(AsyncTask.java:695)
    at android.os.AsyncTask.-wrap1(Unknown Source:0)
    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:712)
    at android.os.Handler.dispatchMessage(Handler.java:105)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6541)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)