Watch devices

Google ADB Server has a hidden command to notify the client about device added and removed, so you don't need to poll the device list.

import type { MaybePromiseLike } from "@yume-chan/async";
import type { Event } from "@yume-chan/event";

export interface DeviceObserver<T> {
  onDeviceAdd: Event<readonly T[]>;
  onDeviceRemove: Event<readonly T[]>;
  onListChange: Event<readonly T[]>;
  current: readonly T[];
  stop(): MaybePromiseLike<void>;
}

export declare class AdbServerClient {
  trackDevices(): Promise<AdbServerDeviceObserver>;
}

export namespace AdbServerClient {
  export interface DeviceObserver extends DeviceObserverBase<Device> {
    onError: Event<Error>;
  }
}

Equivalent ADB command

There is no equivalent ADB command.

Create an observer

The AdbServerClient#trackDevices method creates an AdbServerDeviceObserver:

JavaScript

const observer = await client.trackDevices();

TypeScript

import { AdbServerClient } from "@yume-chan/adb";

declare const client: AdbServerClient;

const observer = await client.trackDevices();

onError

The onError event is fired when an error occurs, like the connection to Google ADB Server is lost.

observer.onError((error) => {
  console.error(error);
});

current

current is an immutable array containing all currently connected devices. It will be populated upon creation. When the list changes, a new array will be created and returned from current.

for (const device of observer.current) {
  console.log(device.serial);
}

onListChange

When device list changes, the onListChange event will also fire with the new array.

onListChange is a sticky event, meaning newly attached event listeners will be invoked immediately with latest value.

This means, if you don't care about individual add or remove events, only listening to onListChange event is enough, reading current or calling AdbServerClient#getDevices is unnecessary.

observer.onListChange((devices) => {
  console.log(devices === observer.current); // true
});

onDeviceAdd and onDeviceRemove

The onDeviceAdd and onDeviceRemove events are fired when a device is added or removed. The event argument is an array of AdbServerClient.Device objects that have changed.

observer.onDeviceAdd((devices) => {
  for (const device of devices) {
    console.log(device.serial);
  }
});

observer.onDeviceRemove((devices) => {
  for (const device of devices) {
    console.log(device.serial);
  }
});

Stop the observer

The stop method removes all the event listeners and releases all the resources. The device observer instance is no longer usable after calling stop.