OPENHELPER

- Step 1: Create utils/OpenHelper.java
+ Create a database with two 2 line

private static final String DATABASE_NAME = "DB_USER";
private static final int DATABASE_VERSION = 1;

+ Create a new table in database with commands

private static final String TABLE_ACCOUNT = "ACCOUNT";
private static final String COLUMN_ID = "_id";
private static final String COLUMN_ACC = "tentaikhoan";
private static final String COLUMN_PASSWORD = "matkhau";
private static final String COLUMN_NAME = "hoten";

+ Detail coding:

 	public class OpenHelper extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "DB_USER";
    private static final int DATABASE_VERSION = 1;

    private static final String TABLE_ACCOUNT = "ACCOUNT";
    private static final String COLUMN_ID = "_id";
    private static final String COLUMN_ACC = "tentaikhoan";
    private static final String COLUMN_PASSWORD = "matkhau";
    private static final String COLUMN_NAME = "hoten";

    private static Context context;
    static SQLiteDatabase db;
    private OpenHelper openHelper;

    public OpenHelper(Context context){
	super(context,DATABASE_NAME,null,DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
	sqLiteDatabase.execSQL("CREATE TABLE " + TABLE_ACCOUNT + " ("
	        + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
	        + COLUMN_ACC + " TEXT NOT NULL, "
	        + COLUMN_PASSWORD + " TEXT NOT NULL, "
	        + COLUMN_NAME + " TEXT NOT NULL);");
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
	sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + TABLE_ACCOUNT);
	onCreate(sqLiteDatabase);
    }
}

- Step 2: Direction development 

+ Create button to presentation functionality:
+ Create a new object to save database
+ View result 
+ Delete All data of database

- Step 3: Design activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="vn.udn.dut.openhelpera.MainActivity">
    <EditText
	android:id="@+id/edtUserName"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:padding="10dp"
	android:background="@android:color/transparent"
	android:hint="username" />

    <EditText
	android:id="@+id/edtPass"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:padding="10dp"
	android:background="@android:color/transparent"
	android:hint="password" />

    <EditText
	android:id="@+id/edtName"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:padding="10dp"
	android:background="@android:color/transparent"
	android:hint="name" />

    <Button
	android:id="@+id/btnCreate"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:text="@string/tkmoi" />

    <Button
	android:id="@+id/btnList"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:text="@string/danh_sach" />

    <Button
	android:id="@+id/btnDeleteAll"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:text="@string/xoa_het" />
    <Button
	android:id="@+id/btnLogin"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:text="Login" />
    <ListView
	android:id="@+id/lvUser"
	android:layout_width="match_parent"
	android:layout_height="wrap_content">
    </ListView>
</LinearLayout>

- Picture description

- Step 2: Create Object User in package bean

public class User {
    private String username;
    private String password;
    private String fullname;

    public User() {
    }

    public User(String username, String password, String fullname) {
	this.username = username;
	this.password = password;
	this.fullname = fullname;
    }

    public String getUsername() {
	return username;
    }

    public String getPassword() {
	return password;
    }

    public String getFullname() {
	return fullname;
    }

    public void setUsername(String username) {
	this.username = username;
    }

    public void setPassword(String password) {
	this.password = password;
    }

    public void setFullname(String fullname) {
	this.fullname = fullname;
    }
}

- Step 3: Create new adapter call ModelDemo

package vn.udn.dut.openhelpera;

import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.appindexing.Thing;
import com.google.android.gms.common.api.GoogleApiClient;

import java.util.ArrayList;
import java.util.List;

import vn.udn.dut.openhelpera.adapter.ModelDemo;
import vn.udn.dut.openhelpera.bean.User;

import static android.R.layout.simple_list_item_1;

public class MainActivity extends AppCompatActivity {

private Button btnCreate, btnList, btnDeleteAll;
private ListView lvUser;
private EditText edtUser, edtPass, edtName;
private Button mBtnLogin;

private ModelDemo model = new ModelDemo(this);
private ArrayList<User> listItems;
private List<String> listUsername;
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

lvUser = (ListView) findViewById(R.id.lvUser);

edtUser = (EditText) findViewById(R.id.edtUser);
edtPass = (EditText) findViewById(R.id.edtPass);
edtName = (EditText) findViewById(R.id.edtName);

btnCreate = (Button) findViewById(R.id.btnCreate);
btnList = (Button) findViewById(R.id.btnList);
btnDeleteAll = (Button) findViewById(R.id.btnDeleteAll);
mBtnLogin = (Button) findViewById(R.id.btnLogin);

listItems = new ArrayList<>();
listUsername = new ArrayList<>();

btnCreate.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
	model.open();
	model.addItem(new User(edtUser.getText().toString(), edtPass.getText().toString(), edtName.getText().toString()));
	model.close();
	resetForm();
    }
});

btnList.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
	model.open();
	listItems = model.getList();
	for(int i = 0;i<listItems.size();i++){
	    listUsername.add(new String(listItems.get(i).getFullname()));
	}
	model.close();
	showListView(listUsername);
    }
});

btnDeleteAll.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
	model.open();
	model.delAll();
	model.close();
    }
});
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
}

/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
public Action getIndexApiAction() {
Thing object = new Thing.Builder()
	.setName("Main Page") // TODO: Define a title for the content shown.
	// TODO: Make sure this auto-generated URL is correct.
	.setUrl(Uri.parse("http://[ENTER-YOUR-URL-HERE]"))
	.build();
return new Action.Builder(Action.TYPE_VIEW)
	.setObject(object)
	.setActionStatus(Action.STATUS_TYPE_COMPLETED)
	.build();
}

@Override
public void onStart() {
super.onStart();

// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client.connect();
AppIndex.AppIndexApi.start(client, getIndexApiAction());
}

@Override
public void onStop() {
super.onStop();

// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
AppIndex.AppIndexApi.end(client, getIndexApiAction());
client.disconnect();
}

public void showListView(List<String> list){
ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, list);
lvUser.setAdapter(adapter);
}

public void resetForm(){
edtUser.setText("");
edtPass.setText("");
edtName.setText("");
}
}

- Step 4: Picture