How do collect data from a specific database using cursor . I get an illegal argument exception. I want to show the bio data of the person logged in

Question

//error from the logcat

  Caused by: java.lang.IllegalArgumentException: the bind value at index 1 is null
    at android.database.sqlite.SQLiteProgram.bindString(SQLiteProgram.java:183)
    at android.database.sqlite.SQLiteProgram.bindAllArgsAsStrings(SQLiteProgram.java:219)
    at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:49)
    at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1967)
    at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1906)
    at com.example.covidapp.DBelper.biopage(DBelper.java:182)
    at com.example.covidapp.profilepage.onCreate(profilepage.java:52)

//This function is to get the userdetails from the user

public class Register extends AppCompatActivity {
Button nextpage;
DBelper DB;
public TextInputLayout firstname, middlename, lastname, gender, dob;
CheckBox male, female, other;
String id;
public String firstnametxt, middlenametxt, lastnametxt, dobtxt, gendertxt;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.registerscreen);
    nextpage = findViewById(R.id.nexttbtn);
    firstname = findViewById(R.id.firstname);
    middlename = findViewById(R.id.middlename);
    lastname = findViewById(R.id.lastname);
    male = findViewById(R.id.m);
    female = findViewById(R.id.f);
    other = findViewById(R.id.o);
    dob = findViewById(R.id.dob);
    user user = new user();
    usermodel info = new usermodel();
    id = UUID.randomUUID().toString();
    user.setuser(id);
    DB = new DBelper(this);
    // patient patient;
    nextpage.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            patient patient;
            firstnametxt = firstname.getEditText().getText().toString().toUpperCase().trim();
            middlenametxt = middlename.getEditText().getText().toString().toUpperCase().trim();
            lastnametxt = lastname.getEditText().getText().toString().toUpperCase().trim();
            dobtxt = dob.getEditText().getText().toString().toUpperCase().trim();
            //datagetter get = new datagetter();
            //get.setFirstname(firstnametxt);
            if (male.isChecked()) {
                gendertxt = male.getText().toString().toUpperCase().trim();
            }
            if (female.isChecked()) {
                gendertxt = male.getText().toString().toUpperCase().trim();
            }
            if (other.isChecked()) {
                gendertxt = male.getText().toString().toUpperCase().trim();
            }
            patient = new patient(firstnametxt);
            DB.getter(patient);

            if ((!validatefirstname(firstnametxt) | !validatemiddlename(middlenametxt) | !validatelastname(lastnametxt) | !validatedob(dobtxt))) {

            } else {
                if (male.isChecked() && female.isChecked()) {
                    Toast.makeText(Register.this, "Select Only One Gender", Toast.LENGTH_LONG).show();
                } else if (male.isChecked() && female.isChecked()) {
                    Toast.makeText(Register.this, "Select Only One Gender", Toast.LENGTH_LONG).show();
                } else if (female.isChecked() && other.isChecked()) {
                    Toast.makeText(Register.this, "Select Only One Gender", Toast.LENGTH_LONG).show();
                } else if (male.isChecked() && other.isChecked()) {
                    Toast.makeText(Register.this, "Select Only One Gender", Toast.LENGTH_LONG).show();
                } else {
                    DB.getbio(firstnametxt, middlenametxt, lastnametxt, dobtxt, gendertxt);
                    Intent intent = new Intent(Register.this, Register2.class);
                    startActivity(intent);
                }
            }
        }
    });
}

public String getid() {
    return id;
}

public boolean validatefirstname(String val) {

    if (val.equals("")) {
        firstname.setError("Field is empty");
        return false;
    } else if (!val.matches("[a-zA-Z]+")) {
        firstname.setError("Field Should Only Contain Alphabets");
        return false;
    } else {
        firstname.setError(null);
        firstname.setErrorEnabled(false);
        return true;
    }
}

public boolean validatemiddlename(String val) {
    if (val.equals("")) {
        middlename.setError(null);
        middlename.setErrorEnabled(false);
        return true;
    } else if (!val.matches("[a-zA-Z]+")) {
        middlename.setError("Field Should Only Contain Alphabets");
        return false;
    } else {
        middlename.setError(null);
        middlename.setErrorEnabled(false);
        return true;
    }
}

public boolean validatelastname(String val) {
    if (val.equals("")) {
        lastname.setError("Field is empty");
        return false;
    } else if (!val.matches("[a-zA-Z]+")) {
        lastname.setError("Field Should Only Contain Alphabets");
        return false;
    } else {
        lastname.setError(null);
        lastname.setErrorEnabled(false);
        return true;
    }
}

public boolean validatedob(String val) {
    SimpleDateFormat date = new SimpleDateFormat("dd/mm/yyyy");
    Date d;
    if (val.equals("")) {
        dob.setError("Field is empty");
        return false;
    } else if (val.matches("[0-9]{2}[/]{2}[0-9]{2}[0-9]{1}[0-9]{4}")) {
        return true;
    } else {
        dob.setError(null);
        dob.setErrorEnabled(false);
        return true;
    }
}

}

//code for the getter and setter methods

public class datagetter {
private String  firstname ;
public datagetter(String firstname){
    this.firstname = firstname;
}

public void setFirstname(String firstname) {
    this.firstname = firstname;
}

public String getFirstname() {
    return firstname;
}
public datagetter(){

}}

//fucntion in the databasehelper class to get information from the table containing the name of the account logged in

    public Cursor biopage() {
    model u = new model();
    String s = u.getfirstname();
    datagetter g = new datagetter();
    data user = new data();
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery("select * from USERDATA_BIO ", null);
    StringBuilder firstName = new StringBuilder();
    String lastName;
    String x = g.getFirstname();
    // datagetter data = new datagetter();
    // Log.i("data",data.getFirstname());
    //   System.out.println(data.getFirstname());
    if (cursor.moveToNext()) {
        get = cursor.getString(1);
        firstName.append(cursor.getString(1));

    }
    Log.i(x, "values of firstname");
    Cursor cursor1 = db.rawQuery("select * from USERDATA_BIO where firstname = ?  ", new String[]{g.getFirstname()});
    return cursor1;
}

//class that shows the activity that would show the info of the user logged in

public class profilepage extends AppCompatActivity {
Button logout,bio,personal,account,appoint;
DBelper DB;
TextView fname,lname,mname;
protected void onCreate( Bundle savedInstanceState ){
    super.onCreate( savedInstanceState);
    setContentView( R.layout.profilepage);
    logout = findViewById( R.id.logbtn);
    DB = new DBelper(this);
    fname = findViewById(R.id.fnametext);
    lname = findViewById(R.id.lnametext);
    mname = findViewById(R.id.middlenametext);
    bio = findViewById(R.id.biobtn);
    personal = findViewById(R.id.perbtn);
    account = findViewById(R.id.accbtn);
    appoint = findViewById(R.id.appbtn);
    appoint.setOnClickListener(new View.OnClickListener(){
       public void onClick(View view){
           Intent intent= new Intent(profilepage.this,appointment.class);
           startActivity(intent);

       }
    });
    personal.setOnClickListener(new View.OnClickListener(){
       public void onClick(View view ){
           Intent intent = new Intent(profilepage.this, personal.class);
           startActivity(intent);
       }
    });
    account.setOnClickListener(new View.OnClickListener(){
        public void onClick(View view ){
            Intent intent = new Intent(profilepage.this, account.class);
            startActivity(intent);
        }
    });
    bio.setOnClickListener(new View.OnClickListener(){
       public void onClick(View view ){
           Intent intent = new Intent(profilepage.this, biopage.class);
           startActivity(intent);
       }
    });
    Cursor cursor = DB.biopage();
    StringBuilder stringname  = new StringBuilder();
    StringBuilder stringlast=new StringBuilder();
    StringBuilder middle = new StringBuilder();
    while(cursor.moveToNext()){
        stringname.append(cursor.getString(2));
        middle.append(cursor.getString(2));
        stringlast.append(cursor.getString(3));
    }
    mname.setText(middle);
    fname.setText(stringname);
    lname.setText(stringlast);
    logout.setOnClickListener( new View.OnClickListener(){
        public void onClick(View view){
            Intent intent = new Intent(profilepage.this,MainActivity.class);
            startActivity(intent);
        }
    });
}

}