商品展示，SQLite数据库的使用

一，SQLite是轻量级数据库，

  1.优点为：占用资源少，运行时间快；

  2. 四个要素分别是:原子性，一致性，隔离性和持久性；

  3. 支持的五种数据类型：null、integer、real、text、和blob。

二。开发一个商品展示案例，将商品展示，并进行增、删、改、查操作。

具体步骤：

1、创建善品展示案例的布局文件（activity_main）；

mainActivity

 

 

<?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. shop.MainActivity">
    <LinearLayout
        android:id="@+id/addLL"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <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="商品金额"
            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"
        android:layout_below="@id/addLL"></ListView>

</LinearLayout>

2、创建Listview Item布局

<?xml version="1.0"encoding="utf-8"?>
<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="1"
        android:textSize="20sp"
        android:layout_weight="2"/>
    <TextView
        android:id="@+id/tvName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="商品名称"
        android:textSize="20sp"
        android:layout_weight="2"/><TextView
    android:id="@+id/tvNumber"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="商品数量"
    android:textSize="20sp"
    android:layout_weight="2"/>
    <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GoodsAdapter

package cn.edu.bzu.shopshowdemo;

import android.content.Context;
import android.support.annotation.NonNull;
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.entity.Goods;

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

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

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Goods goods=getItem(position);
        View view=null;
        ViewHolder viewHolder;
        if(convertView==null){
            view= LayoutInflater.from(getContext()).inflate(resounceId,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.setOnClickListner(new View.OnClickListener({
        @Override
        public void onClick(View v){
            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);
            bulider.show();

        }
        });
        viewHolder.ivUp.setOnClickListener(new View.OnClickListener({
        @Override
        public void onClick(View v){
            goods.setAmount(goods.getAmount()-1);
            goodsDao.updata(goods);
            notifyDataSetChanged();
        }
        });
        viewHolder.ivDown.setOnClickListener(new View.OnClickListener({
        @Override
        public void onClick(View v){
            goods.setAmount(goods.getAmount()+1);
            goodsDao.updata(goods);
            notifyDataSetChanged();
        }
        });
        return view;
    }
    class ViewHolder{
        TextView tvId;
        TextView tvName;
        TextView tvAmount;
        ImageView ivUp;
        ImageView ivDown;
        ImageView ivDelete;

    }
}

4、创建Goods

package cn.edu.bzu.shop.entity;

/**
 * Created by Administrator on 2017/4/28.
 */

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 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 Integer getAmount() {
        return amount;
    }

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

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

5、创建GoodsDao

package cn.edu.bzu.shop.dao;

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

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

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

/**
 * Created by Administrator on 2017/4/28.
 */

public class GoodsDao {
    private DBHelper dbHelper;
    public GoodsDao(Context context){
        dbHelper=newDBHelper(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());
        sqLiteDatabase.insert("goods",null,values);
        sqLiteDatabase.close();
    }
    public int delete(longid){
        SQLiteDatabase sqLiteDatabase=dbHelper.getWritableDatabase();
        int count=sqLiteDatabase.delete("goods","id-?",newString[]{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());
        int  count=sqLiteDatabase.update("goods",values,"id-?",newString[]{goods.getId()+""});
        sqLiteDatabase.close();
        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");
   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(name,amount);
       goodsList.add(goods);
   }
        cursor.close();

        sqLiteDatabase.close();
        return goodsList;
    }

}

6、创建DBhelper

package cn.edu.bzu.shop.db;

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

/**
 * Created by Administrator on 2017/4/28.
 */

public class DBHelperextends SQLiteOpenHelper {
    public  static  final StringCREATE_GOODS="create table goods(_id integer primary key autoincrement,name varchar(20),amount integer)";
    public DBHelper(Context context,  intversion) {
        super(context, "goods.db", null, version);
    }

    @Override
    public voidonCreate(SQLiteDatabase db) {
       db.execSQL(CREATE_GOODS);
    }

    @Override
    public voidonUpgrade(SQLiteDatabase db, intoldVersion, int newVersion) {

    }

7、创建MainActivity

package cn.edu.bzu.shopshowdemo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

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();

    }
}

注：此文中第一次起名为MainAcivity,第二次起名为Shop，图为第一次的截图，代码为第二次的。