商品展示

本次程序是为了通过商品展示案例结合ListView和SQLite数据库来实现在界面上操作数据库。

需要的运行效果图如下图：



1.创建程序

“商品展示”程序对应的布局文件activity_main.xml代码如下：

<?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.example.administrator.a03lab7_4.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/ivGoods"
android:layout_width="match_parent"
android:layout_height="match_parent" />

</LinearLayout>

2.创建ListView Item布局

在res/layout目录下创建一个item.xml文件，具体代码如下：

<?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:gravity="left"
android:id="@+id/tvName"
android:textSize="20sp"
android:layout_weight="2" />
<TextView
android:text="商品金额"
android:gravity="left"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/tvAmount"
android:maxLines="1"
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.创建数据库

创建一个名为db的包，并在该包下定义一个DBHelper类继承自SQLiteOpenHelper，创建数据库的代码如下：

package com.example.administrator.a03lab7_4.db;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.
f210
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, "gooods.db", null, version);
}

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

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}
}

4.创建一个名为dao的包，并在该包下定义一个GoodsDao类，具体的代码如下：

package com.example.administrator.a03lab7_4.dao;

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

import com.example.administrator.a03lab7_4.db.DBHelper;
import com.example.administrator.a03lab7_4.entity.Goods;

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

/**
* 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;
}
}

5.创建一个名为entity的包，并在该包下定义一个GoodsAdapter类，具体的代码如下：

package com.example.administrator.a03lab7_4;

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.example.administrator.a03lab7_4.dao.GoodsDao;
import com.example.administrator.a03lab7_4.entity.Goods;

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

/**
* 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.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 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);
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;
}
}

6.编写界面交互代码（MainActivity）

数据库的操作完成之后需要界面与数据库进行交互，用于实现将数据库中的数据以ListView的形式展示在界面上，具体代码如下：

package com.example.administrator.a03lab7_4;

import android.content.SharedPreferences;
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.example.administrator.a03lab7_4.dao.GoodsDao;
import com.example.administrator.a03lab7_4.entity.Goods;

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.ivGoods);
goodsDao=new GoodsDao(this);
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();
}
}

最终的菜单列表如下图所示：



最终运行出错，找不到具体原因。