how to validate a user

Question

i am creating a logging app in which the user enters the username and password. if the username and password is present in the database then the user is taken to new page via intent else an error is thrown.

MAIN PAGE

package com.loginappdemo;

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainPage extends Activity {
    EditText un, pw;
    Button login, register;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final DataBaseHandler db = new DataBaseHandler(this);
        un = (EditText) findViewById(R.id.username);
        pw = (EditText) findViewById(R.id.password);
        login = (Button) findViewById(R.id.login);
        login.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                String a=un.getText().toString();
                String b=pw.getText().toString();
                String data=db.selectData(a, b);


            }
        });
        register = (Button) findViewById(R.id.register);
        register.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent i = new Intent(MainPage.this, NewLogin.class);
                startActivity(i);

            }
        });

    }
} 

DATABASEHANDLER CLASS

package com.loginappdemo;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class DataBaseHandler extends SQLiteOpenHelper {
    private static final String username = "username";
    private static final String password = "password";
    private static final String id = "id";
    private static final String db_name = "LOGINDEMO";
    private static final String table_name = "LOGINDETAILS";
    private static final int db_version = 1;
    private static final String create_table = " CREATE TABLE " + table_name
            + "(" + id + " INTEGER PRIMARY KEY AUTOINCREMENT, " + username
            + " VARCHAR(200)," + password + " VARCHAR(200) " + " ) ";

    public DataBaseHandler(Context context) {
        super(context, db_name, null, db_version);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        // TODO Auto-generated method stub
db.execSQL(create_table);
    }

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        // TODO Auto-generated method stub

    }
public long insertData(String name,String password1){
    SQLiteDatabase db=getWritableDatabase();
    ContentValues cv=new ContentValues();
    cv.put(username, name);
    cv.put(password, password1);
    long id=db.insert(table_name, null, cv);
    return id;

}
public String selectData(String name,String password1){
    SQLiteDatabase db=getWritableDatabase();
    String[] col={ username, password};
    String[] args={ name, password1};
    StringBuffer b=new StringBuffer();
    Cursor cursor=db.query(table_name, col, username + " =?  AND "  +password+ " =? ", args, null, null, null);
    String s1= cursor.getString(1);
    String s2=cursor.getString(2);
    b.append(s1 + " " + s2 + "\n" );
    return b.toString();

}
}

Answer 1

Try with this way,

boolean res = dbh.GetData(s1, s2);
if(res == true) {
    Intent in=new Intent(LoginActivity.this,nextActivity.class);
    startActivity(in);                      
} 
else {                  
    Toast.makeText(MainActivity.this, "Login failed", Toast.LENGTH_SHORT).show();
}

dbh is your DataBaseHandler class object and then

public boolean GetData(String uname, String pass)
{
    SQLiteDatabase dbc = this.getReadableDatabase();
    Cursor c1 =  dbc.query(
            TABLE_MIS2,
            null,
            DatabaseHandler.KEY_USERID  + "=? AND " + DatabaseHandler.KEY_PWD + "=?",
            new String[] { uname, pass },
            null,
            null,
            null);
    return (c1.getCount() >= 1);
}

Replace the variable name with your variable and and try.

Answer 2

You can do it either way,

public int selectData(String name,String password1)
{
    SQLiteDatabase db=getWritableDatabase();
    String[] col={ username, password};
    String[] args={ name, password1};
    StringBuffer b=new StringBuffer();
    Cursor cursor=db.query(table_name, col, username + " =?  AND "  +password+ " =? ", args, null, null, null);
    cursor.moveToFirst();
    return cursor.getCount();
}

In onClick() method

if ( db.selectData(a, b) > 0 ) 
{
     // Launch second Activity  
}
else
{
     // Display Toast Msg "Invalid Username/Password";
}