Android final exam inventory (7): SQLite (below)

I won’t talk too much about this article, but I’ll just write a code for logging in and registering SQLite, because this is actually the best test in the exam. Registration is like adding data to a data table, and logging in is to query data from a data table.

XML file for login registration

activity_login.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#E6E6E6"
    android:orientation="vertical"
    android:padding="10dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="15dp"
        android:background="@android:color/white"
        android:orientation="horizontal">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:text="账号:"
            android:textColor="#000"
            android:textSize="20sp" />
        <EditText

            android:id="@+id/et_account"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:background="@null"
            android:padding="10dp" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:background="@android:color/white"
        android:orientation="horizontal">
        <TextView
            android:id="@+id/tv_password"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:text="密码:"
            android:textColor="#000"
            android:textSize="20sp" />

        <EditText
            android:id="@+id/et_password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:background="@null"
            android:inputType="textPassword"
            android:padding="10dp" />
    </LinearLayout>


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <Button
            android:id="@+id/btn_login"
            android:layout_weight="1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="25dp"
            android:background="#3C8DC4"
            android:text="登录"
            android:textColor="@android:color/white"
            android:textSize="20sp" />
        <Button
            android:id="@+id/btn_reg"
            android:layout_weight="1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="25dp"
            android:background="#3C8DC4"
            android:text="注册"
            android:textColor="@android:color/white"
            android:textSize="20sp" />
    </LinearLayout>

</LinearLayout>

activity_register.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#E6E6E6"
    android:orientation="vertical"
    android:padding="10dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="15dp"
        android:background="@android:color/white"
        android:orientation="horizontal">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:text="账号:"
            android:textColor="#000"
            android:textSize="20sp" />
        <EditText

            android:id="@+id/et_account"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:background="@null"
            android:padding="10dp" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:background="@android:color/white"
        android:orientation="horizontal">
        <TextView
            android:id="@+id/tv_password"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:text="密码:"
            android:textColor="#000"
            android:textSize="20sp" />

        <EditText
            android:id="@+id/et_password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:background="@null"
            android:inputType="textPassword"
            android:padding="10dp" />
    </LinearLayout>


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <Button
            android:id="@+id/btn_reg"
            android:layout_weight="1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="25dp"
            android:background="#3C8DC4"
            android:text="注册"
            android:textColor="@android:color/white"
            android:textSize="20sp" />
        <Button
            android:id="@+id/btn_back"
            android:layout_weight="1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="25dp"
            android:background="#3C8DC4"
            android:text="返回"
            android:textColor="@android:color/white"
            android:textSize="20sp" />
    </LinearLayout>

</LinearLayout>

UsersHelper inherits the custom class of SQLiteOpenHelper

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

public class UsersHelper extends SQLiteOpenHelper {

    public UsersHelper(@Nullable Context context) {
        super(context, "user.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE user(id INTEGER PRIMARY KEY AUTOINCREMENT,account VARCHAR(20),password VARCHAR(20))");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

Logic code for login and registration

LoginActivitiy.Java

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

import java.util.Map;

public class LoginActivity extends AppCompatActivity {
    private EditText et_account, et_password;
    private Button btn_login;
    UsersHelper usersHelper;
    SQLiteDatabase db;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        et_account = (EditText)findViewById(R.id.et_account);
        et_password = (EditText)findViewById(R.id.et_password);
        usersHelper=new UsersHelper(LoginActivity.this);
        btn_login = findViewById(R.id.btn_login);
        btn_login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String zh=et_account.getText().toString().trim();
                String mm=et_password.getText().toString().trim();
                db=usersHelper.getReadableDatabase();
                Cursor cursor = db.rawQuery("select * from user where account=? and password=?", new String[]{zh, mm});
                if (cursor.getCount()>0){
                    Toast.makeText(LoginActivity.this,"登录成功",Toast.LENGTH_SHORT).show();
                }else {
                    Toast.makeText(LoginActivity.this,"没有账号",Toast.LENGTH_SHORT).show();
                }
            }
        });
        findViewById(R.id.btn_reg).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(LoginActivity.this,RegisterActivity.class);
                startActivity(intent);
            }
        });
    }
}

registered logic code

RegisterActivity.Java
 

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentValues;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class RegisterActivity extends AppCompatActivity {
    private EditText et_account, et_password;
    private Button btn_reg;
    UsersHelper usersHelper;
    SQLiteDatabase db;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);
        et_account = (EditText)findViewById(R.id.et_account);
        et_password = (EditText)findViewById(R.id.et_password);
        usersHelper=new UsersHelper(RegisterActivity.this);
        btn_reg = findViewById(R.id.btn_reg);
        btn_reg.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String zh=et_account.getText().toString().trim();
                String mm=et_password.getText().toString().trim();
                db=usersHelper.getReadableDatabase();
                ContentValues values=new ContentValues();
                values.put("account",zh);
                values.put("password",mm);
                db.insert("user",null,values);
                db.close();
                Toast.makeText(RegisterActivity.this,"注册成功",Toast.LENGTH_SHORT).show();
            }
        });
        findViewById(R.id.btn_back).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });
    }
}