1# 获取并使用公共目录
2
3## 通过 ArkTS 接口获取并访问公共目录
4
5目录环境能力接口（[ohos.file.environment](../reference/apis-core-file-kit/js-apis-file-environment.md)）提供获取公共目录路径的能力，支持三方应用在公共文件用户目录下进行文件访问操作。
6
7 **约束限制**
8 - 使用此方式，需确认设备具有以下系统能力：SystemCapability.FileManagement.File.Environment.FolderObtain，当前仅支持2in1设备。
9   ```ts
10   if (!canIUse('SystemCapability.FileManagement.File.Environment.FolderObtain')) {
11       console.error('this api is not supported on this device');
12       return;
13   }
14   ```
15 - 公共目录获取接口仅用于获取公共目录路径，不对公共目录访问权限进行校验。若需访问公共目录需申请对应的公共目录访问权限。三方应用需要访问公共目录时，需通过弹窗授权向用户申请授予 Download 目录权限、Documents 目录权限或 Desktop 目录权限，具体参考[访问控制-向用户申请授权](../security/AccessToken/request-user-authorization.md)。
16   <!--RP1-->
17   ```json
18   "requestPermissions" : [
19       "ohos.permission.READ_WRITE_DOWNLOAD_DIRECTORY",
20       "ohos.permission.READ_WRITE_DOCUMENTS_DIRECTORY",
21       "ohos.permission.READ_WRITE_DESKTOP_DIRECTORY",
22   ]
23   ```
24   <!--RP1End-->
25
26### 示例
27
281. 获取公共目录路径。
29
30   ```ts
31    import { BusinessError } from '@kit.BasicServicesKit';
32    import { Environment } from '@kit.CoreFileKit';
33
34    function getUserDirExample() {
35        try {
36            const downloadPath = Environment.getUserDownloadDir();
37            console.info(`success to getUserDownloadDir: ${downloadPath}`);
38            const documentsPath = Environment.getUserDocumentDir();
39            console.info(`success to getUserDocumentDir: ${documentsPath}`);
40        } catch (error) {
41            const err: BusinessError = error as BusinessError;
42            console.error(`failed to get user dir, because: ${JSON.stringify(err)}`);
43        }
44    }
45   ```
46
472. 以 Download 目录为例，访问 Download 目录下的文件。
48
49   ```ts
50    import { BusinessError } from '@kit.BasicServicesKit';
51    import { Environment } from '@kit.CoreFileKit';
52    import { fileIo as fs } from '@kit.CoreFileKit';
53    import { common } from '@kit.AbilityKit';
54
55    function readUserDownloadDirExample() {
56        // 检查是否具有 READ_WRITE_DOWNLOAD_DIRECTORY 权限，无权限则需要向用户申请授予权限。
57        try {
58            // 获取 Download 目录
59            const downloadPath = Environment.getUserDownloadDir();
60            console.info(`success to getUserDownloadDir: ${downloadPath}`);
61            const context = getContext() as common.UIAbilityContext;
62            const dirPath = context.filesDir;
63            console.info(`success to get filesDir: ${dirPath}`);
64            // 查看 Download 目录下的文件并拷贝到沙箱目录中
65            let fileList: string[] = fs.listFileSync(downloadPath);
66            fileList.forEach((file, index) => {
67                console.info(`${downloadPath} ${index}: ${file}`);
68                fs.copyFileSync(`${downloadPath}/${file}`, `${dirPath}/${file}`);
69            });
70            // 查看沙箱目录下对应的文件
71            fileList = fs.listFileSync(dirPath);
72            fileList.forEach((file, index) => {
73                console.info(`${dirPath} ${index}: ${file}`);
74            });
75        } catch (error) {
76            const err: BusinessError = error as BusinessError;
77            console.error(`Error code: ${err.code}, message: ${err.message}`);
78        }
79    }
80   ```
81
823. 以 Download 目录为例，保存文件到 Download 目录。
83
84   ```ts
85    import { BusinessError } from '@kit.BasicServicesKit';
86    import { Environment } from '@kit.CoreFileKit';
87    import { fileIo as fs } from '@kit.CoreFileKit';
88
89    function writeUserDownloadDirExample() {
90    // 检查是否具有 READ_WRITE_DOWNLOAD_DIRECTORY 权限，无权限则需要向用户申请授予权限。
91        try {
92            // 获取 Download 目录
93            const downloadPath = Environment.getUserDownloadDir();
94            console.info(`success to getUserDownloadDir: ${downloadPath}`);
95            // 保存 temp.txt 到 Download 目录下
96            const file = fs.openSync(`${downloadPath}/temp.txt`, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
97            fs.writeSync(file.fd, 'write a message');
98            fs.closeSync(file);
99        } catch (error) {
100            const err: BusinessError = error as BusinessError;
101            console.error(`Error code: ${err.code}, message: ${err.message}`);
102        }
103    }
104   ```
105
106
107
108## 通过 C/C++ 接口获取并使用公共目录
109
110除了通过 ArkTS 访问公共目录的方式，也可通过 C/C++ 接口进行目录访问，具体可以参考 [Environment](../reference/apis-core-file-kit/_environment.md)。
111
112 **约束限制**
113 - 使用此接口，需确认设备具有以下系统能力：SystemCapability.FileManagement.File.Environment.FolderObtain。
114 - 三方应用需要访问公共目录时，需通过弹窗授权向用户申请授予 Download 目录权限、Documents 目录权限或 Desktop 目录权限，具体参考[访问控制-向用户申请授权](../security/AccessToken/request-user-authorization.md)。
115
116### 接口说明
117
118接口的详细说明，请参考[API参考](../reference/apis-core-file-kit/_environment.md)
119
120| 接口名称                                                                 | 描述                           |
121| ------------------------------------------------------------------------ | ------------------------------ |
122| FileManagement_ErrCode OH_Environment_GetUserDownloadDir (char **result) | 获取用户Download目录沙箱路径。只支持2in1设备 |
123| FileManagement_ErrCode OH_Environment_GetUserDesktopDir (char **result)  | 获取用户Desktop目录沙箱路径。只支持2in1设备  |
124| FileManagement_ErrCode OH_Environment_GetUserDocumentDir (char **result) | 获取用户Document目录沙箱路径。只支持2in1设备 |
125
126### 开发步骤
127
128**在CMake脚本中链接动态库**
129
130CMakeLists.txt中添加以下lib。
131
132```txt
133target_link_libraries(sample PUBLIC libohenvironment.so libhilog_ndk.z.so)
134```
135
136**添加头文件**
137
138```c++
139#include <filemanagement/environment/oh_environment.h>
140#include <filemanagement/fileio/oh_fileio.h>
141#include <hilog/log.h>
142```
143
1441. 调用 OH_Environment_GetUserDownloadDir 接口获取用户 Download 目录沙箱路径，在接口中使用malloc申请的内存需要在使用完后释放因此需要free对应的内存。示例代码如下所示：
145
146    ```c++
147    void GetUserDownloadDirExample()
148    {
149        char *downloadPath = nullptr;
150        FileManagement_ErrCode ret = OH_Environment_GetUserDownloadDir(&downloadPath);
151        if (ret == 0) {
152            OH_LOG_INFO(LOG_APP, "Download Path=%{public}s", downloadPath);
153            free(downloadPath);
154        } else {
155            OH_LOG_ERROR(LOG_APP, "GetDownloadPath fail, error code is %{public}d", ret);
156        }
157    }
158    ```
159
1602. 调用 OH_Environment_GetUserDownloadDir 接口获取用户 Download 目录沙箱路径，并查看 Download 目录下的文件。示例代码如下所示：
161
162    ```c++
163    void ScanUserDownloadDirPathExample()
164    {
165        // 获取 download 路径
166        char *downloadPath = nullptr;
167        FileManagement_ErrCode ret = OH_Environment_GetUserDownloadDir(&downloadPath);
168        if (ret == 0) {
169            OH_LOG_INFO(LOG_APP, "Download Path=%{public}s", downloadPath);
170        } else {
171            OH_LOG_ERROR(LOG_APP, "GetDownloadPath fail, error code is %{public}d", ret);
172            return;
173        }
174        // 查看文件夹下的文件
175        struct dirent **namelist = {nullptr};
176        int num = scandir(downloadPath, &namelist, nullptr, nullptr);
177        if (num < 0) {
178            free(downloadPath);
179            OH_LOG_ERROR(LOG_APP, "Failed to scan dir");
180            return;
181        }
182        for (int i = 0; i < num; i++) {
183            OH_LOG_INFO(LOG_APP, "%{public}s", namelist[i]->d_name);
184        }
185        free(downloadPath);
186        free(namelist);
187    }
188    ```
189
1903. 调用 OH_Environment_GetUserDownloadDir 接口获取用户 Download 目录沙箱路径，并保存 temp.txt 到 Download 目录下。示例代码如下所示：
191
192    ```c++
193    void WriteUserDownloadDirPathExample()
194    {
195        // 获取 download 路径
196        char *downloadPath = nullptr;
197        FileManagement_ErrCode ret = OH_Environment_GetUserDownloadDir(&downloadPath);
198        if (ret == 0) {
199            OH_LOG_INFO(LOG_APP, "Download Path=%{public}s", downloadPath);
200        } else {
201            OH_LOG_ERROR(LOG_APP, "GetDownloadPath fail, error code is %{public}d", ret);
202            return;
203        }
204        // 保存文件到 download 目录下
205        std::string filePath = std::string(downloadPath) + "/temp.txt";
206        free(downloadPath);
207
208        std::ofstream outfile;
209        outfile.open(filePath.c_str());
210        if (!outfile) {
211            OH_LOG_ERROR(LOG_APP, "Failed to open file");
212            return;
213        }
214        std::string msg = "Write a message";
215        outfile.write(msg.c_str(), sizeof(msg));
216        outfile.close();
217    }
218    ```
219