工程文件

https://download.csdn.net/download/qq_45688164/51971151

前端框架

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="5dp"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tv_username"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:text="用户名："
        android:textSize="30sp" />

    <EditText
        android:id="@+id/et_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_toRightOf="@id/tv_username"
        android:background="@drawable/shape_editext"
        android:minLines="2" />


    <EditText
        android:id="@+id/et_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/et_username"
        android:layout_alignLeft="@id/et_username"
        android:layout_marginTop="10dp"
        android:background="@drawable/shape_editext"
        android:inputType="textPassword"
        android:minLines="2"
        android:textSize="30sp" />

    <TextView
        android:id="@+id/tv_choiceB"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@id/et_password"
        android:text="密    码："
        android:textSize="30sp" />

    <EditText
        android:id="@+id/et_age"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/et_password"
        android:layout_alignLeft="@id/et_password"
        android:layout_marginTop="10dp"
        android:background="@drawable/shape_editext"
        android:minLines="2" />

    <TextView
        android:id="@+id/tv_age"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@id/et_age"
        android:text="年    龄："
        android:textSize="30sp" />

    <Button
        android:id="@+id/bt_save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/tv_age"
        android:layout_alignTop="@id/bt_query"
        android:text="保存"
        android:textSize="23sp" />

    <Button
        android:id="@+id/bt_query"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/et_age"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="10dp"
        android:layout_toRightOf="@id/bt_save"
        android:text="查询"
        android:textSize="23sp" />

    <Button
        android:id="@+id/bt_update"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/et_age"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="10dp"
        android:layout_toRightOf="@id/bt_query"
        android:text="修改"
        android:textSize="23sp" />

    <Button
        android:id="@+id/bt_delete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/et_age"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="10dp"
        android:layout_toRightOf="@id/bt_update"
        android:text="删除"
        android:textSize="23sp" />

    <TextView
        android:id="@+id/tv_show"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/bt_save"
        android:text=""
        android:scrollbars="vertical"
        android:singleLine="false"
        android:textSize="20sp" />

</RelativeLayout>

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentResolver;
import android.os.Bundle;
import android.text.method.ScrollingMovementMethod;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private UsersDao dao;
    private User user;
    private EditText et_username, et_password, et_age;
    private Button bt_save, bt_query, bt_update, bt_delete;
    private ArrayList<User> datas;
    private ArrayList datas_jiexi;

    private TextView tv_show;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //创建数据库
        init();
        dao = new UsersDao(this);
    }

    public void init() {
        et_username = findViewById(R.id.et_username);
        et_password = findViewById(R.id.et_password);
        et_age = findViewById(R.id.et_age);
        bt_save = findViewById(R.id.bt_save);
        bt_query = findViewById(R.id.bt_query);
        bt_update = findViewById(R.id.bt_update);
        bt_delete = findViewById(R.id.bt_delete);
        tv_show=findViewById(R.id.tv_show);
        tv_show.setMovementMethod(ScrollingMovementMethod.getInstance());

        bt_save.setOnClickListener(this);
        bt_query.setOnClickListener(this);
        bt_update.setOnClickListener(this);
        bt_delete.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.bt_save: {
                //保存插入数据
                user = new User(et_username.getText().toString(), et_password.getText().toString(), Integer.parseInt(et_age.getText().toString()));
                mass(dao.insert(user));
                break;
            }
            case R.id.bt_query: {
                //查询数据
                datas=dao.queryAll();
                String us="";
                for (int i=0;i<datas.size();i++) {
                    us+="\nid:"+datas.get(i).getId()+" name:"+datas.get(i).getName()+" pw:"+datas.get(i).getPasword()+" age:"+datas.get(i).getAge()+"\n";
                }
                tv_show.setText(us);
                break;
            }
            case R.id.bt_update: {
                //修改数据
                user = new User(et_username.getText().toString(), et_password.getText().toString(), Integer.parseInt(et_age.getText().toString()));
                mass(dao.updateUser(user));
                break;
            }
            case R.id.bt_delete: {
                //删除数据
                mass(dao.deleteUser(et_username.getText().toString()));
                break;
            }
            default:
                break;
        }
    }

    public void mass(int flag) {
        if (flag != -1) {
            Toast.makeText(this, "操作成功" + flag, Toast.LENGTH_LONG).show();
        } else {
            Toast.makeText(this, "网络异常", Toast.LENGTH_LONG).show();
        }
    }
}

用户表工具类

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.widget.Toast;

import java.util.ArrayList;

public class UsersDao {
    SQLiteDatabase db;
    MySQLiteOpenHaper sqLite;
    Context context;

    public UsersDao(Context context) {
        sqLite = new MySQLiteOpenHaper(context, "user.db", null, 1);
        this.context = context;
    }

    //增添数据
    public int insert(User user) {
        int flag = -1;
        db = sqLite.getWritableDatabase();
        ContentValues values = new ContentValues();
        // values.put("userno",user.getId());
        values.put("username", user.getName());
        values.put("userpassword", user.getPasword());
        values.put("userage", user.getAge());
        flag = (int) db.insert("user", null, values);
        db.close();
        return flag;
    }

    //删除数据
    public int deleteUser(String username) {
        int flag = -1;
        db = sqLite.getWritableDatabase();
        flag = (int) db.delete("user", "username=?", new String[]{username + ""});
        db.close();
        return flag;
    }
    //更新数据
    public int updateUser(User user) {
        db = sqLite.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("userpassword", user.getPasword());
        values.put("userage", user.getAge());
        int number = db.update("user", values, "username = ?",
                new String[]{user.getName()});
        db.close();
        return number;
    }

    //查询数据
    public ArrayList queryAll() {
        ArrayList list = new ArrayList();
        db = sqLite.getWritableDatabase();
        Cursor cursor = db.query("user", null, null, null, null,
                null, null);
        list = convertFromCursor(cursor);
        return list;
    }

    //将查询数据组织为集合
    private ArrayList convertFromCursor(Cursor cursor) {
        ArrayList<User> list = new ArrayList<User>();
        if (cursor != null && cursor.moveToFirst()) {
            //通过游标遍历整个查询结果集
            do {
                int id = cursor.getInt(cursor.getColumnIndex("userid"));
                String username = cursor.getString(cursor.getColumnIndex("username"));
                String password = cursor.getString(cursor.getColumnIndex("userpassword"));
                int age = cursor.getInt(cursor.getColumnIndex("userage"));
                User user = new User(id, username, password, age);
                list.add(user);
            } while (cursor.moveToNext());
        }
        return list;
    }
}

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

import androidx.annotation.Nullable;

public class MySQLiteOpenHaper extends SQLiteOpenHelper {
    Context context;
    public MySQLiteOpenHaper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
        this.context=context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        String sql = "create table user ("
                + "userid integer primary key autoincrement, "
                + "username text, "
                + "userpassword text, "
                + "userage integer)";
        db.execSQL(sql);
        Toast.makeText(context,"onCreate 以运行",Toast.LENGTH_LONG).show();
    }

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


    }
}

public class User {
    int id;
    String name;
    String pasword;
    int age;
    public User(int id, String name, String pasword, int age) {
        this.id = id;
        this.name = name;
        this.pasword = pasword;
        this.age = age;
    }

    public User(String name, String pasword, int age) {
        this.id = id;
        this.name = name;
        this.pasword = pasword;
        this.age = age;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPasword() {
        return pasword;
    }

    public void setPasword(String pasword) {
        this.pasword = pasword;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pasword='" + pasword + '\'' +
                ", age=" + age +
                '}';
    }

}