商品展示案例

在实际开发中往往避免不了在界面上操作。在商品展示案例中我们可以在界面中对商品进行增、删、改、查。要实现这些功能需要使用ListView 和 SQLine数据库。

运行效果图：



1.创建程序：首先创建一个“商品展示”的应用。设计用户交互界面。

代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:orientation="vertical"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.aaa.myapplication.MainActivity"
>

<LinearLayout
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>

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

</LinearLayout>

创建数据库：DBHelper.xml

package cn.edu.bzu.test02.db;

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

public class DBHelper extends SQLiteOpenHelper {
private Context context;
public static final String DB_NAME = "GoodsStore.db";
public static final String CREATE_GOODS = "create table goods(id integer primary key autoincrement,name varchar(20),balance integer)";//商品名称列和金额列

public DBHelper(Context context) {
super(context, DB_NAME, null, 2);
}

@Override
public void onCreate(SQLiteDatabase db) {
System.out.println("create succeed");
db.execSQL(CREATE_GOODS);
}

@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
System.out.println("onUpgrade succeed");
}

}

Goods类：Goods.Java

public class Goods {
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 Goods(Long id, String name, Integer balance) {
super();
this.id=id;
this.balance = balance;
this.name = name;
}
public Goods(String name,Integer balance){
super();
this.name=name;
this.balance=balance;
}
public Goods(){
super();
}

public String toString() {
return "名称" + name + "价格" + balance;
}
}

GoodsDao.java，用于操作数据

package cn.edu.bzu.test02.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.edu.bzu.test02.bean.Goods;
import cn.edu.bzu.test02.db.DBHelper;

public class GoodsDao {
private DBHelper helper;

public GoodsDao(Context context) {
//创建Dao时，创建Helper
helper = new DBHelper(context);
}

public void insert(Goods goods) {
//获取数据库对象
SQLiteDatabase db = helper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", goods.getName());
values.put("balance", goods.getBalance());
long id = db.insert("goods", null, values);
goods.setId(id);
db.close();//关闭数据库
}
//根据id删除数据
public int detele(long id) {
SQLiteDatabase db = helper.getWritableDatabase();
int count = db.delete("goods", "id=?", new String[]{id + ""});
db.close();
return count;
}
//更新数据
public int update(Goods goods) {
SQLiteDatabase DB = helper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", goods.getName());
values.put("balance", goods.getBalance());
int count = DB.update("goods", values, "id=?", new String[]{goods.getId() + ""});
DB.close();
return count;
}
//查询所有数据倒序排列
public List<Goods> queryAll() {
SQLiteDatabase db = helper.getReadableDatabase();
Cursor curor = db.query("goods", null, null, null, null, null, "balance DESC");
List<Goods> list = new ArrayList<Goods>();
while (curor.moveToNext()) {
long id = curor.getLong(curor.getColumnIndex("id"));
String name = curor.getString(1);
int balance = curor.getInt(2);
list.add(new Goods(id, name, balance));
}
db.close();
curor.close();
return list;
}
}

界面交互：MainActivity.java

package cn.edu.bzu.test02;

import android.app.Activity;
import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import java.util.List;
import cn.edu.bzu.test02.bean.Goods;
import cn.edu.bzu.test02.dao.GoodsDao;

public class MainActivity extends Activity {
private ListView goodsLV;
private GoodsDao goodsdao;
private EditText nameET;
private EditText balanceET;
private MyAdapter adapter;
private List<Goods> list;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
goodsdao = new GoodsDao(this);
list = goodsdao.queryAll();
adapter = new MyAdapter();
goodsLV.setAdapter(adapter);
}
//初始化控件
private void initView() {
goodsLV = (ListView) findViewById(R.id.listView);
nameET = (EditText) findViewById(R.id.nameET);
balanceET = (EditText) findViewById(R.id.balanceET);
goodsLV.setOnItemClickListener(new MyOnItemClickListener());

}
//点击事件触发
public void add(View view) {
String name = nameET.getText().toString().trim();
String balance = balanceET.getText().toString().trim();
Goods goods = new Goods(name, balance.equals("") ? 0 : Integer.parseInt(balance));
goodsdao.insert(goods);
list.add(goods);
adapter.notifyDataSetChanged();
goodsLV.setSelection(goodsLV.getCount() - 1);
nameET.setText("");
balanceET.setText("");
}
/自定义一个适配器
private class MyAdapter extends BaseAdapter {

@Override
public int getCount() {
return list.size();
}

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

@Override
public long getItemId(int position) {
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
View item = convertView != null ? convertView : View.inflate(getApplicationContext(), R.layout.item, null);
TextView idTV = (TextView) item.findViewById(R.id.idTV);
TextView nameTV = (TextView) item.findViewById(R.id.nameTV);
TextView balanceTV = (TextView) item.findViewById(R.id.balanceTV);
final Goods g = list.get(position);
idTV.setText(g.getId() + "");
nameTV.setText(g.getName());
balanceTV.setText(g.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
upIV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
g.setBalance(g.getBalance() + 1);
notifyDataSetChanged();
goodsdao.update(g);
}
});
//向下箭头的点击事件
downIV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
g.setBalance(g.getBalance() - 1);
notifyDataSetChanged();
goodsdao.update(g);
}
});
//删除图片的点击事件
deleteIV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
android.content.DialogInterface.OnClickListener listener = new android.content.DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
list.remove(g);
goodsdao.detele(g.getId());
notifyDataSetChanged();
}
};
//创建对话框
AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle("确定要删除吗？");
builder.setPositiveButton("确定", listener);
builder.setNegativeButton("取消", null);
builder.show();
}
});
return item;
}
}
//ListView的点击事件
private class MyOnItemClickListener implements AdapterView.OnItemClickListener {

@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
Goods goods = (Goods) adapterView.getItemAtPosition(i);
Toast.makeText(getApplicationContext(), goods.toString(), Toast.LENGTH_SHORT).show();
}
}
}

2 、清单文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="cn.edu.bzu.test02">

<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

</manifest>