android ListView_显示数据库数据

时间：2023-03-08 20:35:58

xml

<?xml version="1.0"?>

-<LinearLayout tools:context=".MainActivity" android:orientation="vertical" android:paddingTop="@dimen/activity_vertical_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingBottom="@dimen/activity_vertical_margin" android:layout_height="match_parent" android:layout_width="match_parent" xmlns:tools="http://schemas.android.com/tools" xmlns:android="http://schemas.android.com/apk/res/android">

<Button android:id="@+id/bt_add" android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/add"/>

<Button android:id="@+id/bt_del" android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/del"/>

<Button android:id="@+id/bt_update" android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/update"/>

<Button android:id="@+id/bt_query" android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/query"/>

<ListView android:id="@+id/lv_databases" android:layout_height="match_parent" android:layout_width="fill_parent"/>

</LinearLayout>

数据库按钮设计

java

package com.itheima.crud;

import java.util.ArrayList;

import android.app.Activity;

import android.content.Context;

import android.database.sqlite.SQLiteDatabase;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.ListView;

import android.widget.Toast;

import com.itheima.crud2_listview.R;

import com.itheima.crud.adapter.QueryAdapter;

import com.itheima.crud.bean.InfoBean;

import com.itheima.crud.dao.InfoDao;

public class MainActivity extends Activity implements OnClickListener {

    private Context mContext;

    private ListView lv_databases;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        mContext = this;

        //创建一个帮助类对象

        MySqliteOpenHelper mySqliteOpenHelper = new MySqliteOpenHelper(mContext);

        //调用getReadableDatabase方法,来初始化数据库的创建

        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

        //找到相应控件

        findViewById(R.id.bt_add).setOnClickListener(this);

        findViewById(R.id.bt_del).setOnClickListener(this);

        findViewById(R.id.bt_update).setOnClickListener(this);

        findViewById(R.id.bt_query).setOnClickListener(this);

        //找到listview

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

    }

    @Override

    public void onClick(View v) {

        InfoDao infoDao = new InfoDao(mContext);//创建一个dao对象做增删改查

        switch (v.getId()) {

        case R.id.bt_add:

            InfoBean bean = new InfoBean();

            bean.name = "张三";

            bean.phone ="110";

            boolean result = infoDao.add(bean);

            if(result){

                Toast.makeText(mContext, "添加成功", 0).show();

            }else{

                Toast.makeText(mContext, "添加失败", 0).show();

            }

            break;

        case R.id.bt_del:

            int del = infoDao.del("张三");

            Toast.makeText(mContext, "成功删除"+del+"行", 0).show();

            break;

        case R.id.bt_update:

            InfoBean bean2 = new InfoBean();

            bean2.name = "张三";

            bean2.phone ="119";

            int update = infoDao.update(bean2);

            Toast.makeText(mContext, "成功修改"+update+"行", 0).show();

            break;

        case R.id.bt_query:

            //获取查询的数据

            ArrayList<InfoBean> arrayList = infoDao.query("张三");

            //封装adapter

            QueryAdapter queryAdapter = new QueryAdapter(mContext,arrayList);

            //将adapter设置给listview

            lv_databases.setAdapter(queryAdapter);

            break;

        default:

            break;

        }

    }

}

MainActivity

package com.itheima.crud;

import android.content.Context;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteDatabase.CursorFactory;

import android.database.sqlite.SQLiteOpenHelper;

public class MySqliteOpenHelper extends SQLiteOpenHelper {

    public MySqliteOpenHelper(Context context) {

        //context :上下文   ， name：数据库文件的名称    factory：用来创建cursor对象，默认为null

        //version:数据库的版本号，从1开始，如果发生改变，onUpgrade方法将会调用,4.0之后只能升不能将

        super(context, "info.db", null,1);

    }

    //oncreate方法是数据库第一次创建的时候会被调用;  特别适合做表结构的初始化,需要执行sql语句；SQLiteDatabase db可以用来执行sql语句

    @Override

    public void onCreate(SQLiteDatabase db) {

        //通过SQLiteDatabase执行一个创建表的sql语句

        db.execSQL("create table info (_id integer primary key autoincrement,name varchar(20),phone varchar(11))");

    }

    //onUpgrade数据库版本号发生改变时才会执行； 特别适合做表结构的修改

    @Override

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

        //添加一个phone字段

//        db.execSQL("alter table info add phone varchar(11)");

    }

}

MySqliteOpenHelper

package com.itheima.crud.dao;

import java.util.ArrayList;

import android.content.ContentValues;

import android.content.Context;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import com.itheima.crud.MySqliteOpenHelper;

import com.itheima.crud.bean.InfoBean;

public class InfoDao {

    private MySqliteOpenHelper mySqliteOpenHelper;

    public InfoDao(Context context){

        //创建一个帮助类对象

        mySqliteOpenHelper = new MySqliteOpenHelper(context);

    }

    public boolean add(InfoBean bean){

        //执行sql语句需要sqliteDatabase对象

        //调用getReadableDatabase方法,来初始化数据库的创建

        SQLiteDatabase     db = mySqliteOpenHelper.getReadableDatabase();

        ContentValues values = new ContentValues();//是用map封装的对象，用来存放值

        values.put("name", bean.name);

        values.put("phone", bean.phone);

        //table: 表名 , nullColumnHack：可以为空，标示添加一个空行, values:数据一行的值 , 返回值：代表添加这个新行的Id ，-1代表添加失败

        long result = db.insert("info", null, values);//底层是在拼装sql语句

        //关闭数据库对象

        db.close();

        if(result != -1){//-1代表添加失败

            return true;

        }else{

            return false;

        }

    }

    public int del(String name){

        //执行sql语句需要sqliteDatabase对象

        //调用getReadableDatabase方法,来初始化数据库的创建

        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

        //table ：表名, whereClause: 删除条件, whereArgs：条件的占位符的参数 ; 返回值：成功删除多少行

        int result = db.delete("info", "name = ?", new String[]{name});

        //关闭数据库对象

        db.close();

        return result;

    }

    public int update(InfoBean bean){

        //执行sql语句需要sqliteDatabase对象

        //调用getReadableDatabase方法,来初始化数据库的创建

        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

        ContentValues values = new ContentValues();//是用map封装的对象，用来存放值

        values.put("phone", bean.phone);

        //table:表名, values：更新的值, whereClause:更新的条件, whereArgs：更新条件的占位符的值,返回值：成功修改多少行

        int result = db.update("info", values, "name = ?", new String[]{bean.name});

        //关闭数据库对象

        db.close();

        return result;

    }

    public ArrayList<InfoBean> query(String name){

        ArrayList<InfoBean> list = new ArrayList<InfoBean>();

        //执行sql语句需要sqliteDatabase对象

        //调用getReadableDatabase方法,来初始化数据库的创建

        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

        //table:表名, columns：查询的列名,如果null代表查询所有列； selection:查询条件, selectionArgs：条件占位符的参数值,

        //groupBy:按什么字段分组, having:分组的条件, orderBy:按什么字段排序

        Cursor cursor = db.query("info", new String[]{"_id","name","phone"}, "name = ?", new String[]{name}, null, null, "_id asc");

        //解析Cursor中的数据

        if(cursor != null && cursor.getCount() >0){//判断cursor中是否存在数据

            //循环遍历结果集，获取每一行的内容

            while(cursor.moveToNext()){//条件，游标能否定位到下一行

                InfoBean bean = new InfoBean();

                //获取数据

                bean. id = cursor.getInt(0)+"";

                bean. name = cursor.getString(1);

                bean. phone = cursor.getString(2);

                list.add(bean);

            }

            cursor.close();//关闭结果集

        }

        //关闭数据库对象

        db.close();

        return list;

    }

}

包 dao

package com.itheima.crud.bean;

public class InfoBean {

    public String id;

    public  String name;

    public String phone;

}

包 bean

package com.itheima.crud.adapter;

import java.util.ArrayList;

import com.itheima.crud.bean.InfoBean;

import com.itheima.crud2_listview.R;

import android.content.Context;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.TextView;

public class QueryAdapter  extends BaseAdapter{

    private Context mContext;

    private ArrayList<InfoBean> arrayList;

    public QueryAdapter(Context mContext, ArrayList<InfoBean> arrayList) {

        this.mContext = mContext;

        this.arrayList = arrayList;

    }

    @Override

    public int getCount() {

        return arrayList.size();

    }

    @Override

    public Object getItem(int position) {

        return arrayList.get(position);

    }

    @Override

    public long getItemId(int position) {

        return position;

    }

    @Override

    public View getView(int position, View convertView, ViewGroup parent) {

        //复用convertView

        View view = null;

        if(convertView != null){

            view = convertView;

        }else {

            view =  View.inflate(mContext, R.layout.item_database_layout, null);

        }

        //找到控件

        TextView item_tv_id = (TextView) view.findViewById(R.id.item_tv_id);

        TextView item_tv_name = (TextView) view.findViewById(R.id.item_tv_name);

        TextView item_tv_phone = (TextView) view.findViewById(R.id.item_tv_phone);

        //找到内容

        InfoBean infoBean = arrayList.get(position);

        //设置内容

        item_tv_id.setText(infoBean.id);

        item_tv_name.setText(infoBean.name);

        item_tv_phone.setText(infoBean.phone);

        return view;

    }

}

包 adapter

新闻会了，这个就会了

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