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1# 跨设备文件访问
2<!--Kit: Core File Kit-->
3<!--Subsystem: FileManagement-->
4<!--Owner: @wang_zhangjun; @zhuangzhuang-->
5<!--Designer: @wang_zhangjun; @zhuangzhuang; @renguang1116-->
6<!--Tester: @liuhonggang123; @yue-ye2; @juxiaopang-->
7<!--Adviser: @foryourself-->
8
9分布式文件系统为应用提供了跨设备文件访问的能力，开发者在两个设备上安装同一应用时，通过[基础文件接口](app-file-access.md)，可跨设备读写另一个设备上该应用[分布式目录](app-sandbox-directory.md#应用沙箱路径和真实物理路径的对应关系)（/data/storage/el2/distributedfiles/）下的文件。例如：多设备数据流转的场景，设备组网互联之后，设备A上的应用可访问设备B上的同应用分布式目录下的文件，当期望应用文件被其他设备访问时，只需将文件移动到分布式目录即可。
10
11## 开发步骤
12
131. 完成分布式组网。
14   将需要跨设备访问的两个设备登录同一账号，保证设备蓝牙和Wi-Fi功能开启，蓝牙无需互连，Wi-Fi无需接入同一个局域网。
15
162. 授权分布式数据同步权限。
17   分布式数据同步权限的授权方式为user_grant，因此需要调用requestPermissionsFromUser接口，以动态弹窗的方式向用户申请授权。示例中的context的获取方式请参见[获取UIAbility的上下文信息](../application-models/uiability-usage.md#获取uiability的上下文信息)。
18
19   ```ts
20   import { common, abilityAccessCtrl } from '@kit.AbilityKit';
21   import { BusinessError } from '@kit.BasicServicesKit';
22   // 请在组件内获取context，确保this.getUIContext().getHostContext()返回结果为UIAbilityContext
23   let context = this.getUIContext().getHostContext() as common.UIAbilityContext;
24   let atManager = abilityAccessCtrl.createAtManager();
25   try {
26     //以动态弹窗的方式向用户申请授权
27     atManager.requestPermissionsFromUser(context, ['ohos.permission.DISTRIBUTED_DATASYNC']).then((result) => {
28       console.info(`request permission result: ${JSON.stringify(result)}`);
29     }).catch((err: BusinessError) => {
30       console.error(`Failed to request permissions from user. Code: ${err.code}, message: ${err.message}`);
31     })
32   } catch (error) {
33     let err: BusinessError = error as BusinessError;
34     console.error(`Catch err. Failed to request permissions from user. Code: ${err.code}, message: ${err.message}`);
35   }
36   ```
37
383. 访问跨设备文件。
39   同一应用不同设备之间实现跨设备文件访问，只需要将对应的文件放在应用沙箱的分布式目录即可。
40
41   设备A上在分布式目录下创建测试文件，并写入内容。示例中的context的获取方式请参见[获取UIAbility的上下文信息](../application-models/uiability-usage.md#获取uiability的上下文信息)。
42
43   ```ts
44   import { fileIo as fs } from '@kit.CoreFileKit';
45   import { common } from '@kit.AbilityKit';
46   import { BusinessError } from '@kit.BasicServicesKit';
47
48   // 请在组件内获取context，确保this.getUIContext().getHostContext()返回结果为UIAbilityContext
49   let context = this.getUIContext().getHostContext() as common.UIAbilityContext;
50   let pathDir: string = context.distributedFilesDir;
51   // 获取分布式目录的文件路径
52   let filePath: string = pathDir + '/test.txt';
53
54   try {
55     // 在分布式目录下创建文件
56     let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
57     console.info('Succeeded in creating.');
58     // 向文件中写入内容
59     fs.writeSync(file.fd, 'content');
60     // 关闭文件
61     fs.closeSync(file.fd);
62   } catch (error) {
63     let err: BusinessError = error as BusinessError;
64     console.error(`Failed to openSync / writeSync / closeSync. Code: ${err.code}, message: ${err.message}`);
65   }
66   ```
67
68   设备B主动向设备A发起建链，建链成功后设备B可在分布式目录下读取测试文件。
69   > **说明：**
70   >
71   > 这里通过分布式设备管理的接口获取设备networkId，详见[设备管理接口](../reference/apis-distributedservice-kit/js-apis-distributedDeviceManager.md)。
72
73   ```ts
74   import { fileIo as fs } from '@kit.CoreFileKit';
75   import { common } from '@kit.AbilityKit';
76   import { BusinessError } from '@kit.BasicServicesKit';
77   import { buffer } from '@kit.ArkTS';
78   import { distributedDeviceManager } from '@kit.DistributedServiceKit';
79
80   // 通过分布式设备管理的接口获取设备A的networkId信息
81   let dmInstance = distributedDeviceManager.createDeviceManager("com.example.hap");
82   let deviceInfoList: Array<distributedDeviceManager.DeviceBasicInfo> = dmInstance.getAvailableDeviceListSync();
83   if (deviceInfoList && deviceInfoList.length > 0) {
84     console.info(`Success to get available device list`);
85     let networkId = deviceInfoList[0].networkId;
86     // 定义访问公共文件目录的回调
87     let listeners : fs.DfsListeners = {
88       onStatus: (networkId: string, status: number): void => {
89         console.info('Failed to access public directory');
90       }
91     };
92     // 开始跨设备文件访问
93     fs.connectDfs(networkId, listeners).then(() => {
94       console.info("Success to connect dfs");
95       // 请在组件内获取context，确保this.getUIContext().getHostContext()返回结果为UIAbilityContext
96       let context = this.getUIContext().getHostContext() as common.UIAbilityContext;
97       let pathDir: string = context.distributedFilesDir;
98       // 获取分布式目录的文件路径
99       let filePath: string = pathDir + '/test.txt';
100       try {
101         // 打开分布式目录下的文件
102         let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE);
103         // 定义接收读取数据的缓存
104         let arrayBuffer = new ArrayBuffer(4096);
105         // 读取文件的内容，返回值是读取到的字节个数
106         class Option {
107             public offset: number = 0;
108             public length: number = 0;
109         };
110         let option = new Option();
111         option.length = arrayBuffer.byteLength;
112         let num = fs.readSync(file.fd, arrayBuffer, option);
113         // 打印读取到的文件数据
114         let buf = buffer.from(arrayBuffer, 0, num);
115         console.info('read result: ' + buf.toString());
116         fs.closeSync(file);
117       } catch (error) {
118         let err: BusinessError = error as BusinessError;
119         console.error(`Failed to openSync / readSync. Code: ${err.code}, message: ${err.message}`);
120       }
121     }).catch((error: BusinessError) => {
122       let err: BusinessError = error as BusinessError;
123       console.error(`Failed to connect dfs. Code: ${err.code}, message: ${err.message}`);
124     });
125   }
126   ```
127
1283. B设备访问跨设备文件完成，断开链路。
129
130   ```ts
131   import { BusinessError } from '@kit.BasicServicesKit';
132   import { distributedDeviceManager } from '@kit.DistributedServiceKit';
133   import { fileIo as fs } from '@kit.CoreFileKit';
134
135   // 获取设备A的networkId
136   let dmInstance = distributedDeviceManager.createDeviceManager("com.example.hap");
137   let deviceInfoList: Array<distributedDeviceManager.DeviceBasicInfo> = dmInstance.getAvailableDeviceListSync();
138   if (deviceInfoList && deviceInfoList.length > 0) {
139     console.info(`Success to get available device list`);
140     let networkId = deviceInfoList[0].networkId;
141    // 关闭跨设备文件访问
142     fs.disconnectDfs(networkId).then(() => {
143       console.info("Success to disconnect dfs");
144     }).catch((err: BusinessError) => {
145       console.error(`Failed to disconnect dfs. Code: ${err.code}, message: ${err.message}`);
146     })
147   }
148   ```