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.