Watch devices

The AdbDaemonWebUsbDeviceObserver class in @yume-chan/adb-daemon-webusb package wraps WebUSB API to monitor device changes.

Declaration

import { Event } from "@yume-chan/event";
import { DeviceObserver } from "@yume-chan/adb";
import { AdbDaemonWebUsbDevice } from "@yume-chan/adb-daemon-webusb";

export declare class AdbDaemonWebUsbDeviceObserver
  implements DeviceObserver<AdbDaemonWebUsbDevice>
{
  onDeviceAdd: Event<readonly AdbDaemonWebUsbDevice[], unknown>;
  onDeviceRemove: Event<readonly AdbDaemonWebUsbDevice[], unknown>;
  onListChange: Event<readonly AdbDaemonWebUsbDevice[], unknown>;

  current: readonly AdbDaemonWebUsbDevice[];

  stop(): void;
}

Create observer

There are two ways to create an AdbDaemonWebUsbDeviceObserver.

From AdbDaemonWebUsbDeviceManager

AdbDaemonWebUsbDeviceManager's trackDevices method creates an AdbDaemonWebUsbDeviceObserver using its USB handle and filters:

JavaScript

const observer = await Manager.trackDevices();
export {};

TypeScript

import {
  AdbDaemonWebUsbDeviceManager,
  AdbDaemonWebUsbDeviceObserver,
} from "@yume-chan/adb-daemon-webusb";

declare const Manager: AdbDaemonWebUsbDeviceManager;

const observer: AdbDaemonWebUsbDeviceObserver = await Manager.trackDevices();

Standalone usage

AdbDaemonWebUsbDeviceObserver.create method can also be used to create an AdbDaemonWebUsbDeviceObserver directly:

import { AdbDaemonWebUsbDeviceManager } from "@yume-chan/adb-daemon-webusb";

export declare class AdbDaemonWebUsbDeviceObserver {
  static create(
    usb: USB,
    options?: AdbDaemonWebUsbDeviceManager.RequestDeviceOptions,
  ): Promise<AdbDaemonWebUsbDeviceObserver>;

  // ...
}

import { AdbDaemonWebUsbDeviceObserver } from "@yume-chan/adb-daemon-webusb";

const observer = await AdbDaemonWebUsbDeviceObserver.create(navigator.usb);

Similar to AdbDaemonWebUsbDeviceManager#requestDevice and AdbDaemonWebUsbDeviceManager#getDevices, it accepts an optional options parameter to filter the list.

For example, to only receive events for a specific manufacturer and model:

import { AdbDaemonWebUsbDeviceObserver } from "@yume-chan/adb-daemon-webusb";

const observer = new AdbDaemonWebUsbDeviceObserver(navigator.usb, {
  filters: [
    {
      vendorId: 0x18d1,
      productId: 0x4ee2,
    },
  ],
});

When options is omitted, it defaults to only include devices that match the default ADB interface.

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 added devices, a new AdbDaemonWebUsbDevice instance will be created for each of them.

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 AdbDaemonWebUsbDeviceManager#getDevices is unnecessary.

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

onDeviceAdd and onDeviceRemove

When a device is added or connected, the onDeviceAdd event will fire with the list of new devices. It automatically creates AdbDaemonWebUsbDevice instances for them.

When a device is removed or disconnected, the onDeviceRemove event will fire with the list of removed devices. Calling AdbDaemonWebUsbDevice#connect method on disconnected devices will throw an error.

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

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

To remove an event listener, save and call the return value:

const removeListener = observer.onDeviceAdd((devices) => {
  // ...
});

removeListener();

Stop the observer

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