如何在 android 应用程序中将登录数据与我的 SQLite 数据库进行比较？

Question

I've made a simple login app using a SQLite DB. Now I want to compare my login data (username, password) with my DB to proceed. What should I do in my LoginActivity code to achieve this?

\\This is Registration Activity with SQLite DB "DB"

package com.example.shahxad.myapp;

import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.os.Handler;
public class RegistrationActivity extends AppCompatActivity {
public SQLiteDatabase DB;
public EditText username, email, phone, password;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_registration);
DB = openOrCreateDatabase("DB", MODE_PRIVATE, null);

DB.execSQL("create table if not exists users(REC_ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME varchar(20), EMAIL VARCHAR(20), PHONE integer(10), PASSWORD VARCHAR(20))");
username = (EditText)findViewById(R.id.username);
email = (EditText)findViewById(R.id.email);
phone = (EditText)findViewById(R.id.phone);
password = (EditText)findViewById(R.id.password);
Button reg = (Button) findViewById(R.id.reg);
reg.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        String sql = "insert into users(REC_ID, NAME, EMAIL, PHONE,PASSWORD) values(NULL,'" + username.getText().toString() + "','" + email.getText().toString() + "','" + phone.getText().toString() + "','" + password.getText().toString() + "')";
        DB.execSQL(sql);
        Cursor cursor = DB.rawQuery("select * from users", null);
        cursor.moveToLast();
        String result = cursor.getString(0).toString() + cursor.getString(1).toString() + cursor.getString(2).toString() + cursor.getString(3).toString();
        Toast.makeText(getApplicationContext(), result, Toast.LENGTH_LONG).show();
        Intent intent = new Intent(RegistrationActivity.this, RegSplash.class);
        startActivity(intent);

      }
    });
  }
}

\\This is Login Activity (these are two different activities)

package com.example.shahxad.myapp;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class LoginActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    Button login = (Button) findViewById(R.id.login);
    login.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(LoginActivity.this, AppActivity.class);
            startActivity(intent);
        }
    });
  }
}

Answer 1

Try this,

    public boolean check_login(String u_name, String u_pwd) {

        SQLiteDatabase db = this.getWritableDatabase();
        String select = "SELECT * FROM users WHERE NAME ='" + u_name + "' AND PASSWORD='" + u_pwd + "'";

        Cursor c = db.rawQuery(select, null);

        if (c.moveToFirst()) {
            Log.d(TAG,"User exits");
            return true;
        }

        if(c!=null) {
            c.close();
        }
        db.close();
        return false;
}