商品展示案例 （数据存储和访问

结果如下：

activity_main.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"

    xmlns:tools="http://schemas.android.com/tools"

    android:id="@+id/activity_main"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"

    android:layout_margin="8dp"

    tools:context="cn.edu.bzu.shopshow.MainActivity">

    <LinearLayout

        android:id="@+id/addLL"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal">

        

    <EditText

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:inputType="textPersonName"

        android:hint="商品名称"

        android:layout_weight="1"

        android:id="@+id/nameET" />

    <EditText

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:inputType="number"

        android:hint="金额"

        android:layout_weight="1"

        android:id="@+id/balanceET" />

        <ImageView

            android:onClick="add"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:src="@android:drawable/ic_input_add"

            android:id="@+id/addIV" />

</LinearLayout>

    <ListView

        android:id="@+id/accountLV"

        android:layout_width="match_parent"

        android:layout_height="match_parent" 

        android:layout_below="@+id/addLL">

    </ListView>

</LinearLayout>

item.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:orientation="horizontal"

    android:padding="10dp">

    <TextView

        android:text="13"

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:id="@+id/idTV"

        android:layout_weight="1" 

        android:textColor="#000000"

        android:textSize="20sp" />

    <TextView

        android:text="PQ"

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:id="@+id/nameTV"

        android:layout_weight="2"

        android:singleLine="true"

        android:textColor="#000000"

        android:textSize="20sp"/>

    <TextView

        android:text="12345"

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:id="@+id/balanceTV"

        android:layout_weight="2" 

        android:singleLine="true"

        android:textColor="#000000"

        android:textSize="20sp"/>

    

    <LinearLayout

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:orientation="vertical">

    <ImageView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        app:srcCompat="@android:drawable/arrow_up_float"

        android:id="@+id/upIV"

        android:layout_marginBottom="2dp" />

    <ImageView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        app:srcCompat="@android:drawable/arrow_down_float"

        android:id="@+id/downIV" />

        

    </LinearLayout>   

    

    <ImageView

            android:layout_width="25dp"

            android:layout_height="25dp"

            app:srcCompat="@android:drawable/ic_menu_delete"

            android:id="@+id/delectIV" />

    

</LinearLayout>

dao//MyHelper.java

package cn.edu.bzu.shopshow.dao;

import android.content.Context;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

import android.provider.Settings;

/**

 * Created by Administrator on 2017/4/28.

 */

public  class MyHelper extends SQLiteOpenHelper {

    public MyHelper(Context context) {

        super(context,"itcast.db",null,2);

    }

    @Override

    public void onCreate(SQLiteDatabase db) {

        System.out.println("onCreate");

        db.execSQL("CREATE TABLE account(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),balance INTEGER)");

    }

    @Override

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

        System.out.println("onUpgrade");

    }

}

Account.java

package cn.edu.bzu.shopshow.bean;

/**

 * Created by Administrator on 2017/5/2.

 */

public class Account {

    private long id;

    private String name;

    private int balance;

    public long getId() {

        return id;

    }

    public void setId(long id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public int getBalance() {

        return balance;

    }

    public void setBalance(int balance) {

        this.balance = balance;

    }

    public Account(long id, String name, int balance) {

        super();

        this.id = id;

        this.name = name;

        this.balance = balance;

    }

    public Account(String name, int balance) {

        super();

        this.name = name;

        this.balance = balance;

    }

    public Account(){

        super();

    }

    public String toString(){

        return "[序号:"+id+",商品名称:"+name+",余额:"+balance+"]";

    }

}

AccountDao.java

package cn.edu.bzu.shopshow.dao;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.renderscript.Sampler;

import java.util.ArrayList;
import java.util.List;

import cn.edu.bzu.shopshow.bean.Account;

/**
 * Created by Administrator on 2017/5/2.
 */

public class AccountDao {
    private MyHelper helper;
    public AccountDao(Context context){
        helper=new MyHelper(context);
    }
    public void insert(Account account){
        SQLiteDatabase db=helper.getWritableDatabase();
        ContentValues values=new ContentValues();
        values.put("name",account.getName());
        values.put("balance",account.getBalance());
        long id=db.insert("account",null,values);
        account.setId(id);
        db.close();
    }
    public int delete(long id){
        SQLiteDatabase db=helper.getWritableDatabase();
        int count=db.delete("account","_id=?",new String[] {id+""});
        db.close();
        return count;
    }
    public int update(Account account){
        SQLiteDatabase db=helper.getWritableDatabase();
        ContentValues values=new ContentValues();
        values.put("name",account.getName());
        values.put("balance",account.getBalance());
        int count=db.update("account",values,"_id=?",new String[]{account.getId()+""});
        db.close();
        return  count;
    }
    public List<Account> queryAll(){
        SQLiteDatabase db=helper.getReadableDatabase();
        Cursor c=db.query("account",null,null,null,null,null,"balance DESC");
        List<Account> list=new ArrayList<Account>();
        While(c.moveToNext()){
            long id=c.getLong()(c.getColumnIndex("_id"));
Stringname=c.getString(1);
int?balance=c.getInt(2);
list.add(new?Account(id,name,balance));

}
c.close();
db.close();
return?list;
}
}

package?cn.edu.bzu.productshow;??

import?android.app.Activity;??

import?android.app.AlertDialog.Builder;??

import?android.content.DialogInterface;??

import?android.os.Bundle;??

import?android.view.View;??

import?android.view.View.OnClickListener;??

import?android.view.ViewGroup;??

import?android.widget.AdapterView;??

import?android.widget.AdapterView.OnItemClickListener;??

import?android.widget.BaseAdapter;??

import?android.widget.EditText;??

import?android.widget.ImageView;??

import?android.widget.ListView;??

import?android.widget.TextView;??

import?android.widget.Toast;??

import?cn.edu.bzu.productshow.Bean.Account;??

??

import?java.util.List;??

import?java.util.Locale;??

??

import?cn.edu.bzu.productshow.Dao.AccountDao;??

??

public?class?MainActivity?extends?Activity?{??

//需要适配的数据集合??

????private?List<Account>?list;??

????//需要增删改查操作类??

????private?AccountDao?dao;??

????//输入姓名的edittext??

????private?EditText?nameET;??

????//输入金额的edittext??

????private?EditText?balanceET;??

????//适配器??

????private?MyAdapter?adapter;??

????//Listview??

????private?ListView?accountLV;??

????@Override??

????protected?void?onCreate(Bundle?savedInstanceState)?{??

????????super.onCreate(savedInstanceState);??

????????setContentView(R.layout.activity_main);??

????????//初始化控件??

????????initView();??

????????dao=new?AccountDao(this);??

????????//从数据库查询所有数据??

????????list=dao.queryAll();??

????????adapter=new?MyAdapter();??

????????accountLV.setAdapter(adapter);//给ListView添加适配器（自动把数据生成条目）??

????}??

????//初始化控件??

????private?void?initView()??

????{??

????????accountLV=(ListView)findViewById(R.id.accountLV);??

????????nameET=(EditText)?findViewById(R.id.nameET);??

????????balanceET=(EditText)findViewById(R.id.balanceET);??

????????//添加监听器，监听条目点击事件??

????????accountLV.setOnItemClickListener(new?MyOnItemClickListener());??

????}??

????//activity_main.xml对应的inageview的点击事件触发的方法??

????public?void?add(View?v)??

????{??

????????String?name=nameET.getText().toString().trim();??

????????String?balance=balanceET.getText().toString().trim();??

????????//三目运算balance.equals("")则等于0??

????????//如果balance不是空字符串，则进行强制类型转换??

????????Account?a=new?Account(name,?balance.equals("")?0:Integer.parseInt(balance));??

????????dao.insert(a);//插入数据库??

????????list.add(a);//插入集合??

????????adapter.notifyDataSetChanged();//刷新界面??

????????//选中最后一个??

????????accountLV.setSelection(accountLV.getCount()-1);??

????????nameET.setText("");??

????????balanceET.setText("");??

????}??

????//自定义一个适配器（把数据装到ListView的工具）??

????private?class?MyAdapter?extends?BaseAdapter{??

????????public?int?getCount(){???//获取条目总数??

????????????return?list.size();??

????????}??

????????public?Object?getItem(int?position)?//根据位置获取对象??

????????{??

????????????return??list.get(position);??

????????}??

????????public?long?getItemId(int?position)?//根据位置获取id??

????????{??

????????????return??position;??

????????}??

????????//获取一个条目视图??

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

????????{??

????????????//重用converView??

?????????????View?item=convertView!=null?convertView:View.inflate(getApplicationContext(),R.layout.item,null);??

????????????//获取该视图中的textview??

????????????TextView?idTV=(TextView)?item.findViewById(R.id.idTV);??

????????????TextView?nameTV=(TextView)?item.findViewById(R.id.nameTV);??

????????????TextView?balanceTV=(TextView)?item.findViewById(R.id.balanceTV);??

????????????//根据当前位置获取Account对象??

????????????final?Account?a=list.get(position);??

????????????//把Account对象中的数据放到textview中??

????????????idTV.setText(a.getId()+"");??

????????????nameTV.setText(a.getName());??

????????????balanceTV.setText(a.getBalance()+"");??

????????????ImageView?upTV=(ImageView)?item.findViewById(R.id.upIV);??

????????????ImageView?downTV=(ImageView)?item.findViewById(R.id.downIV);??

????????????ImageView?deleteTV=(ImageView)?item.findViewById(R.id.deleteIV);??

????????????//向上箭头的事件触发方法??

????????????upTV.setOnClickListener(new?View.OnClickListener()?{??

????????????????@Override??

????????????????public?void?onClick(View?v)?{??

????????????????????a.setBalance(a.getBalance()+1);??

????????????????????notifyDataSetChanged();??

????????????????????dao.update(a);??

????????????????}??

????????????});<pre?class="html"?name="code">???????????//向下箭头的事件触发方法??

????????????upTV.setOnClickListener(new?View.OnClickListener()?{??

????????????????@Override??

????????????????public?void?onClick(View?v)?{??

????????????????????a.setBalance(a.getBalance()-1);??

????????????????????notifyDataSetChanged();??

????????????????????dao.update(a);??

????????????????}??

????????????});

?deleteTV.setOnClickListener(new?View.OnClickListener()?{??

????????????????@Override??

????????????????public?void?onClick(View?v)?{??

????????????????????//删除数据之前首先弹出一个对话框??

????????????????????android.content.DialogInterface.OnClickListener?listener=??

????????????????????????????new?android.content.DialogInterface.OnClickListener(){??

????????????????????????????????public?void?onClick(DialogInterface?dialog,int?which){??

????????????????????????????????????list.remove(a);//从集合删除??

????????????????????????????????????dao.delete(a.getId());//从数据库删除??

????????????????????????????????????notifyDataSetChanged();//刷新界面??

????????????????????????????????}??

????????????????????????????};??

????????????????????//创建对话框??

?????????????????Builder?builder?=new?Builder(MainActivity.this);??

????????????????????builder.setTitle("确定要删除吗？");???????????//设置标题??

????????????????????//设置确定按钮的文本以及监听器??

????????????????????builder.setPositiveButton("确定",listener);??

????????????????????builder.setNegativeButton("取消",null);??

????????????????????builder.show();??

????????????????}??

????????????});??

????????????return?item;??

????????}??

????}??

????//Listview的item点击事件??

????private?class?MyOnItemClickListener?implements?OnItemClickListener{??

??

????????public?void?onItemClick(AdapterView<?>?parent,View?view,int?position,long?id)??

????????{??

????????????//获取点击位置上的数据??

???????????Account???a=(Account)?parent.getItemAtPosition(position);??

????????????Toast.makeText(getApplicationContext(),a.toString(),Toast.LENGTH_SHORT).show();??

????????}??

????}??

}??

不知怎么搞得复制过来都是问号，，，，