安卓第五次作业

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="hhh.com.can">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="点餐管理系统"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">

        </activity>

        <activity android:name=".find">

        </activity>

        <activity android:name=".login">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>

        <activity android:name=".register">

        </activity>

        <activity android:name=".add">

        </activity>

        <activity android:name=".alt">

        </activity>
    </application>

</manifest>

package hhh.com.can;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class register extends AppCompatActivity implements View.OnClickListener {
    private Button bt_register;
    private EditText et_ID,et_password;
    private String username,password;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);

        et_ID = (EditText) findViewById(R.id.et_ID);
        et_password = (EditText) findViewById(R.id.et_password);
        bt_register = (Button) findViewById(R.id.bt_register);
        bt_register.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.bt_register:
                username = et_ID.getText().toString().trim();
                password = et_password.getText().toString().trim();
                if(username.equals("") || password.equals("")){
                    Toast.makeText(this,"请完善信息！",Toast.LENGTH_SHORT).show();
                    return;
                }else {

                        userService userService = new userService(this);
                        Boolean flag = userService.CheckIsDataAlreadyInDBorNot(username);
                        if(flag==Boolean.TRUE){
                            Toast.makeText(this,"该用户已存在！",Toast.LENGTH_SHORT).show();
                            return;
                        }else {
                            user user = new user();
                            user.setUsername(username);
                            user.setPassword(password);
                            userService.register(user);
                            Toast.makeText(this,"注册成功",Toast.LENGTH_SHORT).show();
                            finish();

                    }
                }
                break;
        }
    }
}

package hhh.com.can;

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

/**
 * 用户登录注册处理类
 */
public class userService {
    private DBHelper dbHelper;
    public userService(Context context){
        dbHelper=new DBHelper(context);
    }

    //登录用，检测账号密码是否与数据库中的信息匹配
    public boolean login(String username,String password){
        SQLiteDatabase sdb=dbHelper.getReadableDatabase();
        String sql="select * from user where username=? and password=?";
        Cursor cursor=sdb.rawQuery(sql, new String[]{username,password});
        if(cursor.moveToFirst()==true){
            cursor.close();
            return true;
        }
        return false;
    }
    //注册用，将相应的账号密码写入数据库
    public boolean register(user user){
        SQLiteDatabase sdb=dbHelper.getReadableDatabase();
        String sql="insert into user(username,password) values(?,?)";
        Object obj[]={user.getUsername(),user.getPassword()};
        sdb.execSQL(sql, obj);
        return true;
    }

    //检测该账号的用户是否存在
    public boolean CheckIsDataAlreadyInDBorNot(String value) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        String Query = "select * from user where username =?";
        Cursor cursor = db.rawQuery(Query, new String[]{value});
        if (cursor.getCount() > 0) {
            cursor.close();
            return true;
        }
        cursor.close();
        return false;
    }
}