harmony 鸿蒙Input Device Development

2023-02-03
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Input Device Development

When to Use

Input device management provides functions such as listening for device hot swap events and querying the keyboard type of a specified device. For example, as a user enters text, the input method determines whether to launch the virtual keyboard based on whether a physical keyboard is currently inserted. Your application can determine whether a physical keyboard is inserted by listening to device hot swap events.

Modules to Import

import inputDevice from '@ohos.multimodalInput.inputDevice';

Available APIs

The following table lists the common APIs for input device management. For details about the APIs, see ohos.multimodalInput.inputDevice.

Instance	API	Description
inputDevice	function getDeviceList(): Promise<Array<number>>;	Obtains the list of input devices.
inputDevice	function getKeyboardType(deviceId: number): Promise<KeyboardType>;	Obtains the keyboard type of the input device.
inputDevice	function on(type: “change”, listener: Callback<DeviceListener>): void;	Enables listening for device hot swap events.
inputDevice	function off(type: “change”, listener?: Callback<DeviceListener>): void;	Disables listening for device hot swap events.

Virtual Keyboard Detection

When a user enters text, the input method determines whether to launch the virtual keyboard based on whether a physical keyboard is currently inserted. Your application can determine whether a physical keyboard is inserted by listening to device hot swap events.

How to Develop

Call the getDeviceList API to obtain the list of connected input devices. Call the getKeyboardType API to traverse all connected devices to check whether a physical keyboard exists. If a physical keyboard exists, mark the physical keyboard as connected. This step ensures that your application detects all inserted input devices before listening for device hot swap events.
Call the on API to listen for device hot swap events. If a physical keyboard is inserted, mark the physical keyboard as connected. If a physical keyboard is removed, mark the physical keyboard as disconnected.

import inputDevice from '@ohos.multimodalInput.inputDevice';

let isPhysicalKeyboardExist = true;
try {
  // 1. Obtain the list of input devices and check whether a physical keyboard is connected.
  inputDevice.getDeviceList().then(data => {
    for (let i = 0; i < data.length; ++i) {
      inputDevice.getKeyboardType(data[i]).then(type => {
        if (type === inputDevice.KeyboardType.ALPHABETIC_KEYBOARD) {
          // The physical keyboard is connected.
          isPhysicalKeyboardExist = true;
        }
      });
    }
  });
  // 2. Listen for device hot swap events.
  inputDevice.on("change", (data) => {
    console.log(`Device event info: ${JSON.stringify(data)}`);
    inputDevice.getKeyboardType(data.deviceId).then((type) => {
      console.log("The keyboard type is: " + type);
      if (type === inputDevice.KeyboardType.ALPHABETIC_KEYBOARD && data.type == 'add') {
        // The physical keyboard is inserted.
        isPhysicalKeyboardExist = true;
      } else if (type == inputDevice.KeyboardType.ALPHABETIC_KEYBOARD && data.type == 'remove') {
        // The physical keyboard is removed.
        isPhysicalKeyboardExist = false;
      }
    });
  });
} catch (error) {
  console.log(`Execute failed, error: ${JSON.stringify(error, [`code`, `message`])}`);
}