Using startAbility to Start a File Application

When to Use

You can call startAbility to search for an installed application that meets the requirements to open a specific file. For example, when a browser downloads a PDF file, this API can be called to select a file application to open the PDF file. You must set the file URI (specified by uri) and type (specified by type) and other fields in the request so that the system can identify the file to open. Then the system directly starts an application to open the file or displays a dialog box for users to select an application to open the file.

Figure 1 Example of opening a file

Key API Parameters

You can call startAbility to start an installed vertical application to open a file.

Table 1 Description of want in startAbility

Table 2 Description of parameters

Table 3 Description of flags

How to Develop

Procedure for the Caller Application

1. Import the required modules.

   // xxx.ets
   import { fileUri } from '@kit.CoreFileKit';
   import { UIAbility, Want, common, wantConstant } from '@kit.AbilityKit';
   import { BusinessError } from '@kit.BasicServicesKit';
   import { window } from '@kit.ArkUI';
   

2. Obtain the application file paths.

   // xxx.ets
   // Assume that the bundle name is com.example.demo.
   export default class EntryAbility extends UIAbility {
       onWindowStageCreate(windowStage: window.WindowStage) {
           // Obtain the application sandbox path of the file.
           let filePath = this.context.filesDir + '/test1.txt';
           // Convert the application sandbox path into a URI.
           let uri = fileUri.getUriFromPath(filePath);
           // The obtained URI is file://com.example.demo/data/storage/el2/base/files/test.txt.
       }
       // ...
   }
   

3. Construct request data.

   // xxx.ets
   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);
           // Construct the request data.
           let want: Want = {
           action: 'ohos.want.action.viewData', // Action of viewing data. The value is fixed at this value in the file opening scenario.
           uri: uri,
           type: 'general.plain-text', // Type of the file to open.
           // Grant the read and write permissions on the file to the target application.
           flags: wantConstant.Flags.FLAG_AUTH_WRITE_URI_PERMISSION|wantConstant.Flags.FLAG_AUTH_READ_URI_PERMISSION
           };
       }
       // ...
   }
   

4. Call the API to start the target application.

   // xxx.ets
   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);
           // Construct the request data.
           let want: Want = {
           action: 'ohos.want.action.viewData', // Action of viewing data. The value is fixed at this value in the file opening scenario.
           uri: uri,
           type: 'general.plain-text', // Type of the file to open.
           // Grant the read and write permissions on the file to the target application.
           flags: wantConstant.Flags.FLAG_AUTH_WRITE_URI_PERMISSION|wantConstant.Flags.FLAG_AUTH_READ_URI_PERMISSION
           };
           // Call startAbility.
           this.context.startAbility(want)
           .then(() => {
               console.info('Succeed to invoke startAbility.');
           })
           .catch((err: BusinessError) => {
               console.error(`Failed to invoke startAbility, code: ${err.code}, message: ${err.message}`);
           });
       }
       // ...
   }
   

Procedure for the Target Application

1. Declare the capability to open files.

   Applications that are able to open files must declare the file opening capability in the module.json5 file. The uris field indicates the type of the URIs, and the scheme field is fixed at file. The type field indicates the type of file that can be opened. For details, see UTDs (recommended) or MIME type. In the following example, the file type is .txt.

   {
   "module": {
       // ...
       "abilities": [
       {
           // ...
           "skills": [
           {
               "actions": [
               "ohos.want.action.viewData" // Mandatory. Declare the data processing capability.
               ],
               "uris": [
               {
                   // Declare the capability of opening local files whose URIs start with file://.
                   "scheme": "file", // Mandatory. Declare that the scheme type is file.
                   "type": "general.plain-text", // Mandatory. Specify the type of file that can be opened.
                   "linkFeature": "FileOpen" // Mandatory and case sensitive. Specify that the URI is used to open files.
               }
               // ...
               ]
               // ...
           }
           ]
       }
       ]
   }
   }
   

2. Process the file.

   After the target application is started and obtains the URI of the file to open from the want information, it opens the file and obtains the corresponding file object for reading and writing.

   // xxx.ets
   import fs from '@ohos.file.fs';
   import { Want, AbilityConstant } from '@kit.AbilityKit';
   import { BusinessError } from '@kit.BasicServicesKit';
   
   
   export default class EntryAbility extends UIAbility {
       onCreate(want: Want, launchParam: AbilityConstant.LaunchParam) {
           // 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 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('Succeed to open file.');
           } catch (err) {
               let error: BusinessError = err as BusinessError;
               console.error(`Failed to open file openSync, code: ${error.code}, message: ${error.message}`);
           }
       }
   }
   

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