# OrderingSystemDemo

**Repository Path**: xiongwg/ordering-system-demo

## Basic Information

- **Project Name**: OrderingSystemDemo
- **Description**: OrderingSystemDemo分布式点餐系统
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 1
- **Forks**: 0
- **Created**: 2021-10-26
- **Last Updated**: 2021-12-22

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# OrderingSystemDemo

## **#HarmonyOS技术训练营#第三期#基于分布式文件的点餐功能**

### 项目简介

基于分布式文件服务，实现多设备点餐功能。同一桌号，设备A点餐，设备B能实时看到，同理，设备B点餐，设备A也能实时更新。



### 实现效果

![](./screenshort/screen.gif)



### 实现过程解析

实现原理很简单，基于鸿蒙[分布式文件服务](https://developer.harmonyos.com/cn/docs/documentation/doc-guides/database-dfs-guidelines-0000000000030159)功能，对同一文件进行读写，同时为了达到及时更新的效果，这里简单的采用了Timer定时轮询去读取分布式文件。

步骤大致分为以下几步：

1、进入点餐页面，首先去读取该分布式文件，没有则创建文件

```java
public class DistributedDataManager {
    private static final String FILE_NAME = "orderInfo.txt";
    private final String filePath;


    public DistributedDataManager(Context context) {
        filePath = context.getDistributedDir() + File.separator + FILE_NAME;
        createFileIfNotExist();
    }
     private void createFileIfNotExist() {
        File file = new File(filePath);
        if (file.exists() && file.isFile()) {
            return;
        }
        writeDataToFile("[]");
    }

    private void writeDataToFile(String jsonData) {
        FileWriter fileWriter = null;
        try {
            File file = new File(filePath);
            if (file.exists() && file.isFile()) {
                file.delete();
            }
            fileWriter = new FileWriter(filePath, true);
            fileWriter.write(jsonData);
            fileWriter.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
  }   
```

2、提供查询和修改更新文件的方法

查询文件，获取文件内容，如果该桌号没有订单数据，则返回菜单列表

```java
private List<MenuInfo> getInfoFromDistributedFile() {
    List<MenuInfo> menuInfoList = new ArrayList<>();
    FileReader fileReader = null;
    try {
        fileReader = new FileReader(filePath);
        char[] buffer = new char[1024];
        StringBuilder str = new StringBuilder();
        int len;
        while ((len = fileReader.read(buffer)) != -1) {
            str.append(new String(buffer, 0, len));

        }
        System.out.print(str.toString());
        fileReader.close();

        menuInfoList = new Gson().fromJson(str.toString(), new TypeToken<List<MenuInfo>>() {
        }.getType());

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return menuInfoList;
}

public List<MenuInfo.OrderDetail> getOrderListByTableName(String tableName) {
    List<MenuInfo> menuInfoList = getInfoFromDistributedFile();
    if (tableName != null && !tableName.trim().isEmpty()) {
        for (MenuInfo menuInfo : menuInfoList) {
            if (menuInfo.getTableNumber().equals(tableName)) {
                return menuInfo.getList();
            }
        }
    }
    return MenuData.getMenuList();
}
```

更新分布式文件：

```java
private void writeDataToFile(String jsonData) {
    FileWriter fileWriter = null;
    try {
        File file = new File(filePath);
        if (file.exists() && file.isFile()) {
            file.delete();
        }
        fileWriter = new FileWriter(filePath, true);
        fileWriter.write(jsonData);
        fileWriter.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public void updateData(String tableName, List<MenuInfo.OrderDetail> details) {
    List<MenuInfo> menuInfoList = getInfoFromDistributedFile();

    boolean isExistTable = false;
    if (tableName != null && !tableName.trim().isEmpty()) {
        for (MenuInfo menuInfo : menuInfoList) {
            if (menuInfo.getTableNumber().equals(tableName)) {
                isExistTable = true;
                menuInfo.setList(details);
            }
        }
    }
    if (!isExistTable) {
        MenuInfo menuInfo = new MenuInfo();
        menuInfo.setTableNumber(tableName);
        menuInfo.setList(details);
        menuInfoList.add(menuInfo);
    }

    Gson gson = new Gson();
    String json = gson.toJson(menuInfoList);
    writeDataToFile(json);
}
```

3、定时去查询最新数据

```
Timer timer = new Timer();
timer.schedule(new TimerTask() {
    @Override
    public void run() {
        getUITaskDispatcher().asyncDispatch(new Runnable() {
            @Override
            public void run() {
                menuListProvider.setList(dataManager.getOrderListByTableName(tableNum));
            }
        });

    }
},0,500);
```

4、点击添加或删除按钮，更新分布式文件数据

```
menuListProvider.setListener(new MenuListProvider.IChangeListener() {
    @Override
    public void onChange() {
        dataManager.updateData(tableNum,menuListProvider.getData());
    }
});
```

至此，核心功能基本完成。

### 完整代码地址：

## **[OrderingSystemDemo](https://gitee.com/xiongwg/ordering-system-demo)**