Sharing an Application File

An application can share its file with another application based on the file descriptor (FD) or uniform resource identifier (URI) of the file. However, if the FD of a shared file is closed, the file is no longer opened. Therefore, the FD-based file sharing is not recommended. This section describes how to share an application file based on its URI.

• You can use wantConstant.Flags to share a single application file in read or read/write mode based on its URI with another application. The target application can use open() of the ohos.file.fs module to open the URI and then perform read and/or write operations based on the permissions granted. OpenHarmony API version 9 supports only temporary authorization. The permission on the shared file is revoked once the target application exits.

• You can also use open() of the ohos.file.fs module to share a single application file with the specified permissions to another application based on the FD. After parsing the FD from Want, the target application can read and write the file by using read() and write() APIs of ohos.file.fs.

You can use the related APIs to share a file with another application or use shared application files.

Shareable Application Directories

File URI Specifications

The file URIs are in the following format:

file://<bundleName>/<path>

• file: indicates a file URI.

• bundleName: specifies the owner of the file.

• path: specifies the application sandbox path of the file.

Sharing a File with Another Application

Before sharing application files, you need to obtain the application file path.

1. Obtain the application sandbox path of the file and convert it into the file URI.

   import UIAbility from '@ohos.app.ability.UIAbility';
   import fileuri from '@ohos.file.fileuri';
   import window from '@ohos.window';
   
   export default class EntryAbility extends UIAbility {
     onWindowStageCreate(windowStage: window.WindowStage) {
       // Obtain the application sandbox path of the file.
       let pathInSandbox = this.context.filesDir + "/test.txt";
       // Convert the application sandbox path into a URI.
       let uri = fileuri.getUriFromPath(pathInSandbox);
       // The obtained URI is file://com.example.demo/data/storage/el2/base/files/test.txt.
     }
   }

1. Set the target application, with which you want to share the file, and grant permissions on the file. Use startAbility() to share the file with the target application. You need to pass in the obtained URI in uri of the want parameter, set the type of the file to share, set action to ohos.want.action.sendData, and set the granted permission on the file in flags. For details, see Want.

NOTE

The write permission granted includes the read permission.

   import fileuri from '@ohos.file.fileuri';
   import window from '@ohos.window';
   import wantConstant from '@ohos.app.ability.wantConstant';
   import UIAbility from '@ohos.app.ability.UIAbility';
   import Want from '@ohos.app.ability.Want';
   import { BusinessError } from '@ohos.base';
   
   export default class EntryAbility extends UIAbility {
     onWindowStageCreate(windowStage: window.WindowStage) {
       // Obtain the application sandbox path of the file.
       let filePath = this.context.filesDir + '/test.txt';
       // Convert the application sandbox path into a URI.
       let uri = fileuri.getUriFromPath(filePath);
       let want: Want  = {
         // Grant the read and write permissions on the shared file to the target application.
         flags: wantConstant.Flags.FLAG_AUTH_WRITE_URI_PERMISSION|wantConstant.Flags.FLAG_AUTH_READ_URI_PERMISSION,
         // Set the implicit startup rule for the application that shares the file.
         action: 'ohos.want.action.sendData',
         uri: uri,
         type: 'text/plain'
       }
       this.context.startAbility(want)
         .then(() => {
           console.info('Invoke getCurrentBundleStats succeeded.');
         })
         .catch((err: BusinessError) => {
           console.error(`Invoke startAbility failed, code is ${err.code}, message is ${err.message}`);
         });
     }
     // ...
   }

Figure 1 Example

Using Shared Files

In the module.json5 file of the application, which wants to use the shared file, set actions to ohos.want.action.sendData to allow the application to receive files shared by another application and set uris to the type of the URI to receive. In the following example, the application receives only .txt files with scheme of file.

{
  "module": {
    ...
    "abilities": [
      {
        ...
        "skills": [
          {
            ...
            "actions": [
              "ohos.want.action.sendData"
            ],
            "uris": [
              {
                "scheme": "file",
                "type": "text/plain"
              }
           ]
          }
        ]
      }
    ]
  }
}

After UIAbility of the application starts, the application obtains want information from onCreate() or onNewWant().

After obtaining the URI of the shared file from want, the application can call fs.open() to open the file, and then read and write the file after obtaining the related file object.

// xxx.ets
import fs from '@ohos.file.fs';
import Want from '@ohos.app.ability.Want';
import { BusinessError } from '@ohos.base';

function getShareFile() {
  try {
    let want: Want = ...; // Obtain the want sent from the application that shares the file.

    // Obtain the uri field from the want information.
    let uri = want.uri;
    if (uri == null||uri == undefined) {
      console.info('uri is invalid');
      return;
    }
    try {
      // Perform operations on the URI of the shared file as required. For example, open the URI to obtain the file object in read/write mode.
      let file = fs.openSync(uri, fs.OpenMode.READ_WRITE);
      console.info('open file successfully!');
    } catch (err) {
      let error: BusinessError = err as BusinessError;
      console.error(`Invoke openSync failed, code is ${error.code}, message is ${error.message}`);
    }
  } catch (error) {
    let err: BusinessError = error as BusinessError;
    console.error(`Invoke openSync failed, code is ${err.code}, message is ${err.message}`);
  }
}

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