@ohos.app.ability.childProcessManager (childProcessManager)

The childProcessManager module provides the child process management capability. Currently, it provides APIs to start a child process and is valid only for 2-in-1 devices and tablets.

The created child process does not support the UI or the calling of context-related APIs.

A maximum of 512 child processes can be started through this module (non-SELF_FORK mode) and ChildProcess.

NOTE

The initial APIs of this module are supported since API version 11. 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 { childProcessManager } from '@kit.AbilityKit';

StartMode

Enumerates the child process start modes.

System capability: SystemCapability.Ability.AbilityRuntime.Core

childProcessManager.startChildProcess

startChildProcess(srcEntry: string, startMode: StartMode): Promise<number>

Creates a child process and invokes the entrypoint method of the child process. This API uses a promise to return the result.

A PID is returned once the child process is created. However, this does not mean that the child process is started. It is started only when ChildProcess.onStart is successfully called. This API cannot be called by a child process to create its child process.

System capability: SystemCapability.Ability.AbilityRuntime.Core

Parameters

Return value

Error codes

For details about the error codes, see Universal Error Codes and Ability Error Codes.

Example

// Create the child process class DemoProcess.ets in src/main/ets/process of the entry module.
// entry/src/main/ets/process/DemoProcess.ets
import { ChildProcess } from '@kit.AbilityKit';

export default class DemoProcess extends ChildProcess {
  onStart() {
    console.log("DemoProcess OnStart() called");
  }
}

// Call childProcessManager.startChildProcess to start the child process.
// entry/src/main/ets/tool/Tool.ets
import { childProcessManager } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';
import DemoProcess from '../process/DemoProcess';

try {
  DemoProcess.toString(); // Call any API of the DemoProcess class to prevent the code from being directly optimized by the compiler because it is not being referenced.
  childProcessManager.startChildProcess("./ets/process/DemoProcess.ets", childProcessManager.StartMode.SELF_FORK)
    .then((data) => {
      console.log(`startChildProcess success, pid: ${data}`);
    }, (err: BusinessError) => {
      console.error(`startChildProcess error, errorCode: ${err.code}`);
    })
} catch (err) {
  console.error(`startChildProcess error, errorCode: ${(err as BusinessError).code}`);
}

childProcessManager.startChildProcess

startChildProcess(srcEntry: string, startMode: StartMode, callback: AsyncCallback<number>): void

Creates a child process and invokes the entrypoint method of the child process. This API uses an asynchronous callback to return the result.

A PID is returned once the child process is created. However, this does not mean that the child process is started. It is started only when ChildProcess.onStart is successfully called. This API cannot be called by a child process to create its child process.

System capability: SystemCapability.Ability.AbilityRuntime.Core

Parameters

Error codes

For details about the error codes, see Universal Error Codes and Ability Error Codes.

Example

// Create the child process class DemoProcess.ets in src/main/ets/process of the entry module.
// entry/src/main/ets/process/DemoProcess.ets
import { ChildProcess } from '@kit.AbilityKit';

export default class DemoProcess extends ChildProcess {
  onStart() {
    console.log("DemoProcess OnStart() called");
  }
}

// Call childProcessManager.startChildProcess to start the child process.
// entry/src/main/ets/tool/Tool.ets
import { childProcessManager } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';
import DemoProcess from '../process/DemoProcess';

try {
  DemoProcess.toString(); // Call any API of the DemoProcess class to prevent the code from being directly optimized by the compiler because it is not being referenced.
  childProcessManager.startChildProcess("./ets/process/DemoProcess.ets", childProcessManager.StartMode.SELF_FORK, (err, data) => {
    if (data) {
      console.log(`startChildProcess success, pid: ${data}`);
    } else {
      console.error(`startChildProcess error, errorCode: ${err.code}`);
    }
  });
} catch (err) {
  console.error(`startChildProcess error, errorCode: ${(err as BusinessError).code}`);
}

childProcessManager.startArkChildProcess¹²⁺

startArkChildProcess(srcEntry: string, args: ChildProcessArgs, options?: ChildProcessOptions): Promise<number>

Creates a child process and invokes the entrypoint method of the child process. This API uses a promise to return the result.

The child process does not inherit the resources of the parent process. A PID is returned once the child process is created. However, this does not mean that the child process is started. It is started only when ChildProcess.onStart is successfully called. This API cannot be called by a child process to create its child process.

The child process supports parameter transfer and asynchronous ArkTS API calls (except for some APIs that depend on application context). After ChildProcess.onStart is called, the child process will not be automatically destroyed. Instead, you must call process.abort to destroy the child process. After the main process is destroyed, the child processes are also destroyed.

System capability: SystemCapability.Ability.AbilityRuntime.Core

Parameters

Return value

Error codes

For details about the error codes, see Universal Error Codes and Ability Error Codes.

Example

Sample code for the child process:

// Create the child process class DemoProcess.ets in src/main/ets/process of module1.
// module1/src/main/ets/process/DemoProcess.ets
import { ChildProcess, ChildProcessArgs } from '@kit.AbilityKit';

export default class DemoProcess extends ChildProcess {

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

Sample code for the main process is provided below. For details about how to obtain the context in the example, see Obtaining the Context of UIAbility.

// Call childProcessManager.startArkChildProcess to start the child process.
// module1/src/main/ets/tool/Tool.ets
import { common, ChildProcessArgs, ChildProcessOptions, childProcessManager } from '@kit.AbilityKit';
import { fileIo } from '@kit.CoreFileKit';
import { BusinessError } from '@kit.BasicServicesKit';
import DemoProcess from '../process/DemoProcess';

@Entry
@Component
struct Index {
  build() {
    Row() {
      Column() {
        Text('Click')
          .fontSize(30)
          .fontWeight(FontWeight.Bold)
          .onClick(() => {
            try {
              DemoProcess.toString(); // Call any API of the DemoProcess class to prevent the code from being directly optimized by the compiler because it is not being referenced.
              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
                }
              };
              let options: ChildProcessOptions = {
                isolationMode: false
              };
              childProcessManager.startArkChildProcess("module1/./ets/process/DemoProcess.ets", args, options)
                .then((pid) => {
                  console.info(`startChildProcess success, pid: ${pid}`);
                })
                .catch((err: BusinessError) => {
                  console.error(`startChildProcess business error, errorCode: ${err.code}, errorMsg:${err.message}`);
                })
            } catch (err) {
              console.error(`startChildProcess error, errorCode: ${err.code}, errorMsg:${err.message}`);
            }
          });
      }
      .width('100%')
    }
    .height('100%')
  }
}

childProcessManager.startNativeChildProcess¹³⁺

startNativeChildProcess(entryPoint: string, args: ChildProcessArgs, options?: ChildProcessOptions): Promise<number>

Starts a native child process, loads the specified dynamic library file, and calls the entry function. This API uses a promise to return the result.

The child process does not inherit the resources of the parent process. A PID is returned once the child process is created. However, this does not mean that the entry function is successfully called, which depends on the execution result of the entry function of the child process. This API cannot be called by a child process to create its child process. It cannot be called to create a child process in an ArkTS basic runtime environment.

After the entry function is executed, the child process is automatically destroyed. After the main process is destroyed, the child processes are also destroyed.

System capability: SystemCapability.Ability.AbilityRuntime.Core

Parameters

Return value

Error codes

For details about the error codes, see Universal Error Codes and Ability Error Codes.

Example

Sample code for the child process is provided below. For details, see Native Child Process Development (C/C++) - Creating a Child Process That Supports Pass-by-Parameter.

#include <AbilityKit/native_child_process.h>

extern "C" {

/**
 * Entry function of a child process, which implements the service logic of the child process.
 * The function name can be customized and is specified when the main process calls the OH_Ability_StartNativeChildProcess method. In this example, the function name is Main.
 * After the function is returned, the child process exits.
 */
void Main(NativeChildProcess_Args args)
{
    // Obtain the input entryPrams.
    char *entryParams = args.entryParams;
    // Obtain the input FD list, corresponding to args.fds in ChildProcessArgs.
    NativeChildProcess_Fd *current = args.fdList.head;
    while (current != nullptr) {
        char *fdName = current->fdName;
        int32_t fd = current->fd;
        current = current->next;
        // Service logic
    }
}
} // extern "C"

Sample code for the main process is provided below. For details about how to obtain the context in the example, see Obtaining the Context of UIAbility.

// Main process:
// Call childProcessManager.startNativeChildProcess to start the child process.
import { common, ChildProcessArgs, ChildProcessOptions, childProcessManager } from '@kit.AbilityKit';
import { fileIo } from '@kit.CoreFileKit';
import { BusinessError } from '@kit.BasicServicesKit';

@Entry
@Component
struct Index {
  build() {
    Row() {
      Column() {
        Text('Click')
          .fontSize(30)
          .fontWeight(FontWeight.Bold)
          .onClick(() => {
            try {
              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
                }
              };
              let options: ChildProcessOptions = {
                isolationMode: false
              };
              childProcessManager.startNativeChildProcess("libentry.so:Main", args, options)
                .then((pid) => {
                  console.info(`startChildProcess success, pid: ${pid}`);
                })
                .catch((err: BusinessError) => {
                  console.error(`startChildProcess business error, errorCode: ${err.code}, errorMsg:${err.message}`);
                })
            } catch (err) {
              console.error(`startChildProcess error, errorCode: ${err.code}, errorMsg:${err.message}`);
            }
          });
      }
      .width('100%')
    }
    .height('100%')
  }
}

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