2.20简易记账本四

搭建数据库

首先创建一个DBHelper类

package com.example.myaccountapp;

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

import androidx.annotation.Nullable;

public class DBHelper extends SQLiteOpenHelper {

    private static int DB_VERSION = 1;
    private static String DB_NAME = "account_daily.db";

    public DBHelper(Context context) {
        super(context, DB_NAME ,null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
      String sql="create table account(_id integer primary key autoincrement," +//主键
              "Title varchar(20)," +//Title
              "Date varchar(20)," +//Date
              "Money vaechar(20))";//Money
      db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
}

然后我们写一个类专门存放赋值和取出这些数据的方法，命名为costList

package com.example.myaccountapp;

public class costList {
    private String _id;
    private String Title;
    private String Date;
    private String Money;

    public String getMoney() {
        return Money;
    }

    public void setMoney(String money) {
        Money = money;
    }

    public String getDate() {
        return Date;
    }

    public void setDate(String date) {
        Date = date;
    }

    public String getTitle() {
        return Title;
    }

    public void setTitle(String title) {
        Title = title;
    }

    public String get_id() {
        return _id;
    }

    public void set_id(String _id) {
        this._id = _id;
    }
}

来到MainActivity开始写方法

package com.example.myaccountapp;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.ImageButton;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class MainActivity extends AppCompatActivity {


    private DBHelper helper;
    private  ListView listView;
    private  ImageButton Add;
    private List<costList>list;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        initData();

    }
    //初始化
    private void initData() {
        list=new ArrayList<>();
        SQLiteDatabase db=helper.getReadableDatabase();
        Cursor cursor=db.query("account",null,null,null,null,
                null,null);
        while (cursor.moveToNext()){
            costList clist=new costList();//构造实例
            clist.set_id(cursor.getString(cursor.getColumnIndex("_id")));
            clist.setTitle(cursor.getString(cursor.getColumnIndex("Title")));
            clist.setDate(cursor.getString(cursor.getColumnIndex("Date")));
            clist.setMoney(cursor.getString(cursor.getColumnIndex("Money")));
            list.add(clist);
        }
        //绑定适配器
        listView.setAdapter(new ListAdapter(this,list));
        db.close();
    }




    private void initView() {
       helper=new DBHelper(MainActivity.this);
       listView = findViewById(R.id.list_view);
       Add=findViewById(R.id.add);
}

    //事件：添加
public void addAccount(View view){//跳转
    Intent intent=new Intent(MainActivity.this,new_cost.class);
    startActivityForResult(intent,1);
}

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode==1&&resultCode==1)
        {
            this.initData();
        }
    }
}