Android数据存储和访问-商品展示
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1:运行效果图:
2:首先建立一个ShopShowDemo的应用程序,将包名改为cn.bzu.edu.com。设计用户交互界面。ShopShoeDemo程序对应的布局文件如下所示:
activity_main.xml:
<?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="com.edu.bzu.cn.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="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" /></LinearLayout>
3:在res/layout目录下创建一个item.xml文件,该文件下有三个TextView,分别用于显示数据库中的某条数据的id,商品名称,金额。三个ImageView用于增加金额,减少金额,删除数据。
item.xml:
<?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:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/tvId" android:textSize="20sp" android:layout_weight="1" /> <TextView android:text="商品名称" android:layout_width="0dp" android:layout_height="wrap_content" android:maxLines="1" android:gravity="left" android:id="@+id/tvName" android:textSize="20sp" android:layout_weight="2" /> <TextView android:text="金额" android:gravity="left" android:layout_width="0dp" android:layout_height="wrap_content" android:id="@+id/tvAmount" 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>
4:在com.edu.bzu.cn.shopshowdemo下分别建三个包dao,db,entity,在dao包下建一个GoodsDao类,db包下建一个DBHelper类,entity包下建Goods类,GoodsAdapter类
GoodsDao:
package com.edu.bzu.cn.shopshowdemo.dao;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import com.edu.bzu.cn.shopshowdemo.db.DBHelper;import com.edu.bzu.cn.shopshowdemo.entity.Goods;import java.util.ArrayList;import java.util.List;/** * Created by Administrator on 2017/4/28. */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:
package com.edu.bzu.cn.shopshowdemo.db;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;/** * Created by Administrator on 2017/4/28. */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) { }}
Goods:
package com.edu.bzu.cn.shopshowdemo.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 public String toString() { return "Goods{" + "id=" + id + ", name='" + name + '\'' + ", amount=" + amount + '}'; }}
GoodsAdapter:
package com.edu.bzu.cn.shopshowdemo.entity;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 com.edu.bzu.cn.shopshowdemo.R;import com.edu.bzu.cn.shopshowdemo.dao.GoodsDao;import com.edu.bzu.cn.shopshowdemo.entity.Goods;import java.util.List;/** * Created by Administrator on 2017/4/28. */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(R.layout.item,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 v) { goods.setAmount(goods.getAmount()-1); goodsDao.update(goods); notifyDataSetChanged(); } }); viewHolder.ivDown.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 ivDown; ImageView ivDelete; }}
MainActivity:
package com.edu.bzu.cn.shopshowdemo;import android.content.SharedPreferences;import android.database.sqlite.SQLiteDatabase;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.edu.bzu.cn.shopshowdemo.dao.GoodsDao;import com.edu.bzu.cn.shopshowdemo.entity.Goods;import com.edu.bzu.cn.shopshowdemo.entity.GoodsAdapter;import java.util.List;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(); }}
5:首先添加三个商品:
继续添加一个如图:
点右边的小三角增删按钮,可实现对金额的增删:
删除操作:点右方的删除按钮,会出现“你确定要删除吗”的提示,点“YES”,就删除成功了
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