harmony 鸿蒙@ohos.app.ability.ChildProcessArgs

2025-06-12
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@ohos.app.ability.ChildProcessArgs

The ChildProcessArgs module describes the parameters transferred to the child process. When starting a child process through childProcessManager, you can transfer parameters to the child process through ChildProcessArgs.

NOTE

The initial APIs of this module are supported since API version 12. Newly added APIs will be marked with a superscript to indicate their earliest API version.

The APIs of this module can be used only in the stage model.

Modules to Import

import { ChildProcessArgs } from '@kit.AbilityKit';

Properties

System capability: SystemCapability.Ability.AbilityRuntime.Core

Name	Type	Mandatory	Description
entryParams	string	No	Custom parameters to be transparently transmit to the child process. The parameters can be obtained through args.entryParams in ChildProcess.onStart. The maximum data volume supported by entryParams is 150 KB.
fds	Record	No	File Descriptor (FD) handles, which are used for communication between the main process and child process. They are passed to the child process in the form of key-value pairs, where key is a custom string and value is a DF handle. The FD handles can be obtained through args.fds in ChildProcess.onStart. NOTE - fds supports a maximum of 16 groups. In each group, key contains a maximum of 20 characters. - The ID of a handle passed to the child process may change, but the handle always points to the same file.

Example

For details about how to obtain the context in the example, see Obtaining the Context of UIAbility.

// In the main process:
import { common, ChildProcessArgs, childProcessManager } from '@kit.AbilityKit';
import { fileIo } from '@kit.CoreFileKit';

@Entry
@Component
struct Index {
  build() {
    Row() {
      Column() {
        Text('Click')
          .fontSize(30)
          .fontWeight(FontWeight.Bold)
          .onClick(() => {
            let context = this.getUIContext().getHostContext() as common.UIAbilityContext;
            let path = context.filesDir + "/test.txt";
            let file = fileIo.openSync(path, fileIo.OpenMode.READ_ONLY|fileIo.OpenMode.CREATE);
            let args: ChildProcessArgs = {
              entryParams: "testParam",
              fds: {
                "key1": file.fd
              }
            };
            childProcessManager.startArkChildProcess("entry/./ets/process/DemoProcess.ets", args);
          });
      }
      .width('100%')
    }
    .height('100%')
  }
}

// In the child process:
import { ChildProcess, ChildProcessArgs } from '@kit.AbilityKit';

export default class DemoProcess extends ChildProcess {

  onStart(args?: ChildProcessArgs) {
    let entryParams = args?.entryParams;
    let fd = args?.fds?.key1;
    // ..
  }
}