商品展示案例

        此案例开发一个简单的购物车：

（1）需要将购物车中的商品以列表的形式展示

（2）并且还需要对购物车中的 商品进行增删改查操作。

（3）要实现这些功能就需要使用 ListView 和 SQLite 数据库。  



图7-1

1.添加商品，点击加号可以添加商品



图7-2

2.删除商品，可以删除商品，点击垃圾桶按钮，会出现一个确认对话框，点击确定，会将商品删除



图7-3

3修改商品，可以对商品数量进行修改，点击向上的箭头商品数量加1，点击向下的箭头商品数量减1



图7-4

4.点击列表，会出现商品的序号，名称，余额等信息

1.创建一个名为ProdectDisplay的程序名称

2.（1）在activity_main.xml文件中设计布局：

<?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="bzu.edu.cn.prodectdisply.MainActivity">

<LinearLayout
android:id="@+id/addLL"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<EditText
android:id="@+id/nameET"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:hint="商品名称"
android:inputType="textPersonName" />
<EditText
android:id="@+id/balanceET"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:hint="金额"
android:inputType="number" />
<ImageView
android:onClick="add"
android:id="@+id/addIV"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@android:drawable/ic_input_add" />

</LinearLayout[/b]>

<ListView
android:id="@+id/accountLV"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@id/addLL">
</ListView>
</LinearLayout>

（2）在layout下创建一个item.xml，编写一个ListViewItem的布局：

  

<?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"
android:orientation="horizontal"
android:padding="10dp">

<TextView
android:id="@+id/idTV"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="13"
android:textColor="#000000"
android:textSize="20sp" />

<TextView
android:id="@+id/nameTV"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="2"
android:text="PQ"
android:singleLine="true"
android:textColor="#000000"
android:textSize="20sp" />

<TextView
android:id="@+id/balanceTV"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="2"
android:text="12345"
android:singleLine="true"
android:textColor="#000000"
android:textSize="20sp" />

<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">

<ImageView
android:id="@+id/upIV"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="2dp"
android:src="@android:drawable/arrow_up_float" />
<ImageView
android:id="@+id/downIV"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@android:drawable/arrow_down_float" />
<ImageView
android:id="@+id/deleteIV"
android:layout_width="25dp"
android:layout_height="25dp"
android:src="@android:drawable/ic_menu_delete" />
</LinearLayout>
</LinearLayout>

3.(1)创建数据库，在包dao下创建一个MyHelper类，继承SQLiteOpenHelper：

package bzu.edu.cn.prodectdisply.dao;

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

/**
* Created by gxw on 2017/4/17.
*/

public class MyHelper extends SQLiteOpenHelper {

//由于父类没有无参的构造函数，所以父类必须指定调用父类哪个有参的构造函数

public  MyHelper(Context context){

super(context,"itcast.db",null,2);

}

@Override

public void onCreate(SQLiteDatabase db) {

System.out.println("onCreate");

db.execSQL("CREATE TABLE account(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),balance INTEGER)");

}

@Override

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

System.out.println("onUpgrade");

}

}

(2)在包dao下创建类AccountDao类，用于操作数据库：

package bzu.edu.cn.prodectdisply.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 bzu.edu.cn.prodectdisply.bean.Account;

/**
* Created by gxw on 2017/4/17.
*/

public class AccountDao {
private MyHelper helper;
public AccountDao(Context context){

//创建Dao时，创建Helper

helper=new MyHelper(context);
}
public void insert(Account account){

//获取数据库对象

SQLiteDatabase db=helper.getWritableDatabase();

//用来装载要插入的数据的Map<列名，列的值>

ContentValues values=new ContentValues();

values.put("name",account.getName());

values.put("balance",account.getBalance());

//向Account表插入数据values

long id=db.insert("account",null,values);

account.setId(id);//得到Id

db.close();//关闭数据库

}

//根据Id删除数据

public int delete(long id){

SQLiteDatabase db=helper.getWritableDatabase();

//按条件删除指定表中的数据，返回受影响的行数 

int count=db.delete("account","_id=?",new String[]{id+""});

db.close(); 

return count;   

}   

//更新数据

   public int update(Account account){

SQLiteDatabase db=helper.getWritableDatabase();

//要更改的数据 

   ContentValues values=new ContentValues();

   values.put("name",account.getName()); 

values.put("balance",account.getBalance());

//更新并得到行数

   int count=db.update("account",values,"_id=?",new String[]{account.getId()+""}); 

   db.close();

   return count;

}  

//查询所有数据倒叙排列

 public List<Account> queryAll(){

SQLiteDatabase db=helper.getWritableDatabase();

Cursor c=db.query("account",null,null,null,null,null,"balance DESC");   

List<Account> list=new ArrayList<>();

while(c.moveToNext()){ 

//可以根据列名获取索引  

long id=c.getLong(c.getColumnIndex("_id"));   

String name=c.getString(1);   

int balance=c.getInt(2);   

list.add(new Account(id,name,balance));

} 

c.close(); 

db.close(); 

return list;

}

}

4.创建一个bean包，用于存放JavaBean类，此包下创建一个Account类：

package bzu.edu.cn.prodectdisply.bean;

/**
* Created by gxw on 2017/4/17.
*/

public class Account {
private Long id;
private String name;
private Integer balance;

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 getBalance(){
return balance;
}
public void setBalance(Integer balance){
this.balance=balance;
}
public Account(Long id,String name,Integer balance){
super();
this.id=id;
this.name=name;
this.balance=balance;
}
public Account(String name,Integer balance){
super();
this.name=name;
this.balance=balance;
}
public Account(){
super();
}
public String toString(){
return "[序号："+id+",商品名称："+name+",余额："+balance+"]";
}
}

5.编写界面交互代码：

package bzu.edu.cn.prodectdisply;

import android.content.DialogInterface;
import android.net.Uri;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.app.NotificationCompat;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.appindexing.Thing;
import com.google.android.gms.common.api.GoogleApiClient;

import java.util.List;

import bzu.edu.cn.prodectdisply.bean.Account;
import bzu.edu.cn.prodectdisply.dao.AccountDao;

public class MainActivity extends AppCompatActivity {

//需要适配的数据集合

private List<Account> list;

//数据库增删改查操作类

private AccountDao dao;

//输入姓名的EditText

private EditText nameET;

//输入金额的EditText

private EditText balanceET;

//适配器

private MyAdapter adapter;

//ListView

private ListView accountLV;
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

 //初始化控件

initView();
dao = new AccountDao(this);

//从数据库查询出所有数据

list = dao.queryAll();
adapter = new MyAdapter();

//给ListView添加适配器（自动把数目生成条目）

accountLV.setAdapter(adapter);
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
}

//初始化控件

private void initView() {
accountLV = (ListView) findViewById(R.id.accountLV);
nameET = (EditText) findViewById(R.id.nameET);
balanceET = (EditText) findViewById(R.id.balanceET);

//添加监听器，监听条目点击事件

accountLV.setOnItemClickListener(new MyOnItemClickListener());
}

public void add(View v) {
String name = nameET.getText().toString().trim();
String balance = balanceET.getText().toString().trim();

 //三目运算balance.equals("")则等于0
//如果balance不是空字符串 则进行类型转换

Account a = new Account(name, balance.equals("") ? 0 : Integer.parseInt(balance));
dao.insert(a);//插入数据库

list.add(a);//插入集合

adapter.notifyDataSetChanged();//刷新界面

//选中最后一个

accountLV.setSelection(accountLV.getCount() - 1);
nameET.setText("");
balanceET.setText("");
}

/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
public Action getIndexApiAction() {
Thing object = new Thing.Builder().setName("Main Page") // TODO: Define a title for the content shown.
// TODO: Make sure this auto-generated URL is correct.
.setUrl(Uri.parse("http://[ENTER-YOUR-URL-HERE]"))
.build();
return new Action.Builder(Action.TYPE_VIEW)
.setObject(object)
.setActionStatus(Action.STATUS_TYPE_COMPLETED)
.build();
}

@Override
public void onStart() {
super.onStart();

// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client.connect();
AppIndex.AppIndexApi.start(client, getIndexApiAction());
}

@Override
public void onStop() {
super.onStop();

// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
AppIndex.AppIndexApi.end(client, getIndexApiAction());
client.disconnect();
}

//自定义一个适配器（把数据装到ListView的工具）

private class MyAdapter extends BaseAdapter {

//获取条目总数

public int getCount() {

return list.size();
}

//根据位置获取对象

public Object getItem(int position) {
return list.get(position);
}

//根据位置获取id

public long getItemId(int position) {

return position;
}

//获取一个条目视图

public View getView(int position, View convertView, ViewGroup parent) {

//重用convertView

View item = convertView != null ? convertView : View.inflate(getApplicationContext(), R.layout.item, null);

//获取视图中的TextView

TextView idTV = (TextView) item.findViewById(R.id.idTV);
TextView nameTV = (TextView) item.findViewById(R.id.nameTV);
TextView balanceTV = (TextView) item.findViewById(R.id.balanceTV);

//根据当前位置获取Account对象

final Account a = list.get(position);

//把Account对象中的数据放到TextView中

idTV.setText(a.getId() + "");
nameTV.setText(a.getName() + "");
balanceTV.setText(a.getBalance() + "");
ImageView upIV = (ImageView) item.findViewById(R.id.upIV);
ImageView downIV = (ImageView) item.findViewById(R.id.downIV);
ImageView deleteIV = (ImageView) item.findViewById(R.id.deleteIV);

//向上箭头的点击事件触发的方法

upIV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
a.setBalance(a.getBalance() + 1);
notifyDataSetChanged();
dao.update(a);
}
});

//向上箭头的点击事件触发的方法

downIV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
a.setBalance(a.getBalance() - 1);
notifyDataSetChanged();
dao.update(a);
}
});

//删除图片的点击事件触发的方法

deleteIV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {

//删除数据之前首先弹出一个对话框

android.content.DialogInterface.OnClickListener listener=new android.content.DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
list.remove(a);//从集合中删除
dao.delete(a.getId());//从数据库中删除
notifyDataSetChanged();//刷新界面
}
};

  //创建对话框

AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle("确定要删除吗？");//设置标题

  //设置确定按钮的文本以及监听器

builder.setPositiveButton("确定", listener);//设置取消按钮
builder.setNegativeButton("取消", null);
builder.show();//显示对话框
}
});
return item;
}
}

//ListView的Item点击事件

private class MyOnItemClickListener implements AdapterView.OnItemClickListener {
public void onItemClick(AdapterView<?> parent,View view,int position,long id){

//获取点击位置上的数据

Account a=(Account) parent.getItemAtPosition(position); Toast.makeText(getApplicationContext(),a.toString(),Toast.LENGTH_LONG).show();}}}

此上就是商品展示的案例