Android的数据存储与访问：一个商品展示

最新推荐文章于 2024-01-30 18:11:39 发布

a1269916738

最新推荐文章于 2024-01-30 18:11:39 发布

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CC 4.0 BY-SA版权

本文链接：https://blog.youkuaiyun.com/a1269916738/article/details/71962944

本文介绍了一个简单的购物车应用开发过程，包括使用SQLite进行商品数据的增删改查操作，通过自定义适配器实现商品信息的动态更新，以及在Android平台上实现这些功能的具体代码。

本次任务要求：开发一个购物车，并将购物车里的商品以列表的形式展示，并对购物车中的商品进行增删改查操作。

建立主界面，分为main和item.xml的layout文件。

建立GoodsDao.Java用来实现增删改查方法。主要代码如下：

age 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;
    }
}1
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DBHelper.java 用来实现数据存入手机存储代码如下：

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();
}
}