Android-数据存储与访问：商品展示

本次关于Android数据存储与访问的实验要求是：开发一个购物车，需要将购物车里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。
运行效果图如图所示：完成增删改查功能

建立主界面，分为main和item.xml的layout文件，具体界面为–

建立GoodsDao.java用来实现增删改查方法

package cn.bzu.edu.shopshow.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.bzu.edu.shopshow.entity.Goods;
import cn.bzu.edu.shopshow.db.DBHelper;
/**
 * Created by Administrator 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());
        int count=sqLiteDatabase.update("goods",values,"_id=?",new String[]{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 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;
    }
}

DBHelper.java 用来实现数据存入手机存储

package cn.bzu.edu.shopshow.db;

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

/**
 * Created by Administrator 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) {

    }
}

封装一个商品类对应的适配器GoodsAdapter.java

package cn.bzu.edu.shopshow;

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.bzu.edu.shopshow.dao.GoodsDao;
import cn.bzu.edu.shopshow.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 goodsDao) {
        super(context, resource, objects);
        resounceId=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(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.ivDowm=(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 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("cancle",null);
                builder.show();
            }
        });
        viewHolder.ivUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                goods.setAmount(goods.getAmount()-1);
                goodsDao.update(goods);
                notifyDataSetChanged();
            }
        });
        viewHolder.ivDowm.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                goods.setAmount(goods.getAmount()+1);
                goodsDao.update(goods);
                notifyDataSetChanged();
            }
        });

        return view;
    }

    class ViewHolder{
        TextView tvId;
        TextView tvName;
        TextView tvAmount;
        ImageView ivUp;
        ImageView ivDowm;
        ImageView ivDelete;
    }
}

MainActivity

package cn.bzu.edu.shopshow;

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 java.util.List;

import cn.bzu.edu.shopshow.dao.GoodsDao;
import cn.bzu.edu.shopshow.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);
        lvGoods=(ListView)findViewById(R.id.lvGoods);
        etName=(EditText) findViewById(R.id.etName);
        etAmount=(EditText) findViewById(R.id.etAmount);
        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();
    }
}

这样就完成了任务.