How to check for no blanks fields and prompt the user if there is any (Java Android Application)

Question

Okay so I have this login / register function on a same page. So far everything is working but I am trying to make a check whereby if the user does not enter anything when he click login or register , it will prompt the user a message with a toast like "1 or more field is left empty. please check and try again" . Please advise me . thanks

package mdad.project;

import com.example.manandhowproject.R;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class Login extends Activity {


SQLiteDatabase db;
        Button btnLogin, btnSignUp;
        EditText etUsername, etPassword;
        SQLiteOpenHelper dbhelper;
        Cursor cursor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        etUsername = (EditText)findViewById(R.id.etUsername);
        etPassword = (EditText)findViewById(R.id.etPassword);
        Button button = (Button)findViewById(R.id.btnLogin);

        button.setOnClickListener(new OnClickListener(){
            public void onClick (View V){
            if(login(etUsername.getText().toString(), etPassword.getText().toString()) == 1){
                Toast.makeText(getApplicationContext(), "Log In Success ! ", Toast.LENGTH_LONG).show();
                Intent msg1 = new Intent(Login.this, Userreg.class);
                startActivity(msg1);
            }else{
                Toast.makeText(getApplicationContext(), "Error Logging In, Please Try Again", Toast.LENGTH_LONG).show();
            }

            }
        });

        Button btnSignUp = (Button) findViewById (R.id.btnSignUp);
        btnSignUp.setOnClickListener(new OnClickListener (){
            public void onClick (View V) {
                Toast.makeText(getApplicationContext(), "Sign Up Success ! ", Toast.LENGTH_LONG).show();

                String username= etUsername.getText().toString();
                String password= etPassword.getText().toString();
                String sql = "insert into Registration (Username ,Password) values( '"+username+"','"+password+"')";
                String result = updateTable(sql);
                etUsername.setText("");
                etPassword.setText("");
            }});

        String sql="create table if not exists Registration (recld integer PRIMARY KEY autoincrement, Username text, Password text)"; 
        String result = createDatabase(sql, "Reg.db");

    }

    public int login(String username, String password){

        String[] selectionArgs = new String[]{username, password};
        try
        {
            int i = 0;
            Cursor c = null;
            c = db.rawQuery("select * from Registration where username=? and password=?", selectionArgs);
            c.moveToFirst();
            i = c.getCount(); 
            c.close(); 
            return i;
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        return 0;
    }
    String createDatabase(String sql, String dbName) {
        try{
            System.out.println(sql);
            db = SQLiteDatabase.openOrCreateDatabase("sdcard/" + dbName,null);
            db.beginTransaction();
            db.execSQL(sql);
            db.setTransactionSuccessful();
            db.endTransaction();
        }

        catch (Exception e){
            Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();
            System.out.println(e.toString());
            return ("error open DB");
        }

        return "";
    }

    String updateTable(String sql)
     {
     try{
     System.out.println(sql);
     db.beginTransaction();
     db.execSQL(sql);
     db.setTransactionSuccessful();
     db.endTransaction();

     }catch (Exception e) { System.out.println(e.toString());
     return ("Error updating DB");
     }
     return ("DB updated");
     }





    @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();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

Answer 1

you can check the length of the edit texts before they are submitted

as you do the check

if(etUsername.getText().toString(), etPassword.getText().toString()) == 1

before the above line check for blanks like this

if(etUsername.getText().toString().trim().length()==0) {
    etUsername.setError("this field should be filled");
    return;
} else if(etPassword.getText().toString().trim().length()==0) {
    etPassword.setError("this field should be filled");
    return;
}

then you can contune what you are already did