商品展示

实验内容：

开发一个购物车，需要将购物车中的商品以列表的形式展示，并且还需要对购物车中的 商品进行增删改查操作。要实现这些功能就需要使用 ListView 和 SQLite 数据库。

运行效果图：

实现该案例的具体步骤如下：
1.创建程序
创建一个名为”ShopShowDemo”的应用程序，包名为”cn.edu.bzu.shopshowdemo”。设计用户交互界面，如图：

对应布局文件（activity_main.xml）如下：

  <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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"
    tools:context="cn.edu.bzu.shopshowdemo.MainActivity">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <EditText
            android:id="@+id/etName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:hint="商品名称"
            android:inputType="text"
            android:layout_weight="1"
            />
        <EditText
            android:id="@+id/etAmount"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:hint="金额"
            android:inputType="number"
            android:layout_weight="1"
            />
        <ImageView
            android:id="@+id/ivAdd"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="addGoods"
            android:src="@android:drawable/ic_input_add"
            />

    </LinearLayout>

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


</LinearLayout>

2.创建ListView Item布局
在res/layout目录下创建一个item.xml文件，编写如图所示界面：

对应布局文件（item.xml）如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:text="1"
        android:id="@+id/tvId"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:textSize="20sp" />

    <TextView
        android:text="商品名称"
        android:id="@+id/tvName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="left"
        android:layout_weight="2"
        android:textSize="20sp" />
    <TextView
        android:text="金额"
        android:id="@+id/tvAmount"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="left"
        android:layout_weight="2"
        android:textSize="20sp" />
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <ImageView
            android:id="@+id/ivUp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@android:drawable/arrow_up_float"
            />
    <ImageView
        android:id="@+id/ivDown"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@android:drawable/arrow_down_float"
        />

    </LinearLayout>
    <ImageView
        android:id="@+id/ivDelete"
        android:layout_width="25dp"
        android:layout_height="25dp"
        android:src="@android:drawable/ic_menu_delete"

        />
</LinearLayout>

3.创建数据库
在cn.edu.bzu.shopshowdemo包下创建一个名为db的包，并在该包下创建一个DBHelper类继承自SQLiteOpenHelper，创建数据库的代码如下：

package cn.edu.bzu.shopshowdemo.db;

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

/**
 * Created by LZJD on 2017/4/27.
 */

public class DBHelper extends SQLiteOpenHelper {
    public  static final String CREATE_GOODS="create table goods(_id integer primary key autoincrement,name varchar(20),amount integer)";

    public DBHelper(Context context,int version) {
        super(context,"goods.db",null,version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_GOODS);

    }

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

    }
}

4.创建实体类和适配器
在cn.edu.bzu.shopshowdemo包下创建一个名为entity的包，并在该包下创建一个Goods类，然后在cn.edu.bzu.shopshowdemo包下创建一个名为GoodsAdapter的适配器。

Goods类中的具体代码如下：

package cn.edu.bzu.shopshowdemo.entity;

/**
 * Created by Administrator on 2017/4/27.
 */

public class Goods {
    private Long id;
    private String name;
    private Integer amount;

    public Goods(Long id, String name, Integer amount) {
        this.id = id;
        this.name = name;
        this.amount = amount;
    }

    public Goods(String name, Integer amount) {
        this.name = name;
        this.amount = amount;
    }

    public String getName() {
        return name;
    }

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

    public Long getId() {
        return id;
    }

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

    public Integer getAmount() {
        return amount;
    }

    public void setAmount(Integer amount) {
        this.amount = amount;
    }

    @Override
    public String toString() {
        return "Goods{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", amount=" + amount +
                '}';
    }
}

GoodsAdapter适配器中的代码如下：

package cn.edu.bzu.shopshowdemo;

import android.content.Context;
import android.content.DialogInterface;
import android.support.annotation.NonNull;
import android.support.v7.app.AlertDialog;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

import cn.edu.bzu.shopshowdemo.dao.GoodsDao;
import cn.edu.bzu.shopshowdemo.entity.Goods;

/**
 * Created by Administrator on 2017/4/27.
 */

public class GoodsAdapter extends ArrayAdapter<Goods> {
    private int resourceId;
    private GoodsDao goodsDao;
    private List<Goods> goodsList;
    public GoodsAdapter(Context context, int resource, List<Goods> objects, GoodsDao goodsDao) {
        super(context, resource, objects);
        resourceId= resource;
        goodsList=objects;
        this.goodsDao=goodsDao;

    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final Goods goods=getItem(position);
        View view=null;
        ViewHolder viewHolder;

        if (convertView==null){
            view=LayoutInflater.from(getContext()).inflate(resourceId,null);
            viewHolder=new ViewHolder();
            viewHolder.tvId=(TextView)view.findViewById(R.id.tvId);
            viewHolder.tvName=(TextView)view.findViewById(R.id.tvName);
            viewHolder.tvAmount=(TextView)view.findViewById(R.id.tvAmount);
            viewHolder.ivUp=(ImageView)view.findViewById(R.id.ivUp);
            viewHolder.ivDown=(ImageView)view.findViewById(R.id.ivDown);
            viewHolder.ivDelete=(ImageView)view.findViewById(R.id.ivDelete);
            view.setTag(viewHolder);
        }else{
            view=convertView;
            viewHolder=(ViewHolder)view.getTag();

        }
        viewHolder.tvId.setText(goods.getId()+"");
        viewHolder.tvName.setText(goods.getName());
        viewHolder.tvAmount.setText(goods.getAmount()+"");
        viewHolder.ivDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                AlertDialog.Builder builder=new AlertDialog.Builder(getContext());
                builder.setTitle("你确定要删除吗？");
                builder.setPositiveButton("yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        goodsList.remove(goods);
                        goodsDao.delete(goods.getId());
                        notifyDataSetChanged();


                    }
                });
                builder.setNegativeButton("cancel",null);
                builder.show();
            }
        });
        viewHolder.ivUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                goods.setAmount(goods.getAmount()-1);
                goodsDao.update(goods);
                notifyDataSetChanged();
            }
        });

        return view;
    }
    class ViewHolder{
        TextView tvId;
        TextView tvName;

        TextView tvAmount;
        ImageView ivUp;
        ImageView ivDown;
        ImageView ivDelete;


    }
}

5.创建数据操作逻辑类
在cn.edu.bzu.shopshowdemo包下创建一个名为dao的包，并在该包下创建一个GoodsDao类用于操作数据，具体代码如下：

ackage cn.edu.bzu.shopshowdemo.dao;

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

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

import cn.edu.bzu.shopshowdemo.db.DBHelper;
import cn.edu.bzu.shopshowdemo.entity.Goods;

/**
 * Created by LZJD on 2017/4/27.
 */

public class GoodsDao {
    private DBHelper dbHelper;
    public GoodsDao(Context context){
        dbHelper=new DBHelper(context,1);
    }
    public void add(Goods goods){
        SQLiteDatabase sqLiteDatabase=dbHelper.getWritableDatabase();
        ContentValues values=new ContentValues();
        values.put("name",goods.getName());
        values.put("amount",goods.getAmount());
        long id=sqLiteDatabase.insert("goods",null,values);
        goods.setId(id);
        sqLiteDatabase.close();
    }
    public int delete(long id){
        SQLiteDatabase sqLiteDatabase=dbHelper.getWritableDatabase();
        int count=sqLiteDatabase.delete("goods","_id=?",new String[]{id+""});
        sqLiteDatabase.close();
        return count;
    }
    public int update(Goods goods){
        SQLiteDatabase sqLiteDatabase=dbHelper.getWritableDatabase();
        ContentValues values=new ContentValues();
        values.put("name",goods.getName());
        values.put("amount",goods.getAmount());
        sqLiteDatabase.insert("goods",null,values);
        sqLiteDatabase.close();
        int count=sqLiteDatabase.delete("goods","_id=?",new String[]{goods.getId()+""});
        return count;
    }
    public List<Goods> queryAll(){
        List<Goods> goodsList=new ArrayList<>();
        SQLiteDatabase sqLiteDatabase=dbHelper.getReadableDatabase();
        Cursor cursor=sqLiteDatabase.query("goods",null,null,null,null,null,"amount desc");
        while(cursor.moveToNext()){
            long id=cursor.getLong(cursor.getColumnIndex("_id"));
            String name=cursor.getString(cursor.getColumnIndex("name"));
            int amount=cursor.getInt(cursor.getColumnIndex("amount"));
            Goods goods=new Goods(id,name,amount);
            goodsList.add(goods);
        }
        cursor.close();
        sqLiteDatabase.close();
        return goodsList;
    }
}

6.编写界面交互代码（LoginActivity）

代码如下：

package cn.edu.bzu.shopshowdemo;

import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.appindexing.Thing;
import com.google.android.gms.common.api.GoogleApiClient;

import java.util.List;

import cn.edu.bzu.shopshowdemo.dao.GoodsDao;
import cn.edu.bzu.shopshowdemo.entity.Goods;

public class MainActivity extends AppCompatActivity {
    private EditText etName;
    private EditText etAmount;
    private ListView lvGoods;
    private GoodsAdapter goodsAdapter;
    private GoodsDao goodsDao;
    private List<Goods> goodsList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        etName = (EditText) findViewById(R.id.etName);
        etAmount = (EditText) findViewById(R.id.etAmount);
        lvGoods = (ListView) findViewById(R.id.lvGoods);
        goodsDao = new GoodsDao(this);
        goodsList = goodsDao.queryAll();
        goodsAdapter = new GoodsAdapter(this, R.layout.item, goodsList,goodsDao);
        lvGoods.setAdapter(goodsAdapter);
    }

    public void addGoods(View view) {
        String name = etName.getText().toString();
        String amount = etAmount.getText().toString();
        if(TextUtils.isEmpty(name)||TextUtils.isEmpty(amount))
            return;
        Goods goods = new Goods(name,Integer.parseInt(amount));
        goodsDao.add(goods);
        goodsList.add(goods);
        goodsAdapter.notifyDataSetChanged();
        etName.setText("");
        etAmount.setText("");
        Toast.makeText(this,"添加成功",Toast.LENGTH_LONG).show();

    }
}

7.运行程序展示商品
运行效果图如下：