如何制作长按按键触发的键盘事件流？ （镖）

Question

如何创建一个在长按某个 html 元素中的键时触发的 KeyBoardEvent 流。

同样，我也对 Angular2 指令 (longpress) 感兴趣（想法相同）。

Answer 1

@Directive(
    selector: '[longpress]')
class LongPress {
  @Output() EventEmitter<KeyboardEvent> longpress =
      new EventEmitter<KeyboardEvent>();

  KeyboardEvent _startEvent;
  @Input() Duration longpressDelay = new Duration(seconds: 2);
  Timer timer;

  @HostListener("keydown", const [r"$event"])
  @HostListener("keyup", const [r"$event"])
  void keyEventHandler(KeyboardEvent event) {
    if (_startEvent == null ||
        _startEvent.type != event.type ||
        _startEvent.keyCode != event.keyCode) {
      if (timer != null) {
        timer.cancel();
      }
      _startEvent = event;

      if(event.type == 'keyup') {
        timer = new Timer(longpressDelay, () {
          longpress.add(_startEvent);
          timer = null;
        });
      }
    }
  }
}

并像使用它

<label for="input">Longpress: </label><input id="longpress" longpress (longpress)="longPressed($event)">

我还没有弄清楚如何让指令选择器与(...) 一起工作，所以这也可以：

<label for="input">Longpress: </label><input id="longpress" (longpress)="longPressed($event)">

事件处理 (preventDefault) 似乎还不能正常工作。 将此指令添加到 <input> 会中断输入中的写入。

一种解决方法是改为以这种方式订阅 keydown/keyup

LongPress(ElementRef elementRef) {
  (elementRef.nativeElement as Element).onKeyDown.listen(keyEventHandler);
  (elementRef.nativeElement as Element).onKeyUp.listen(keyEventHandler);
}

Answer 2

以下是打字稿版本，如果有人感兴趣：

import { Directive, EventEmitter, Output, Input, HostListener } from '@angular/core';

    @Directive({
        selector: '[longpress]'
    })
    export class LongPressDirective {

      @Output() longpress: EventEmitter<KeyboardEvent> = new EventEmitter(true);

      _startEvent: KeyboardEvent;
      @Input() longpressDelay: number = 1000;

      timer: any;

      @HostListener('keydown', ['$event'])
      @HostListener('keyup', ['$event'])
      keyEventHandler(event: KeyboardEvent) {
        if (this._startEvent == null ||
          this._startEvent.type != event.type ||
          this._startEvent.keyCode != event.keyCode) {

          //console.log(event.type, event);
          if (this.timer != null) {
            clearTimeout(this.timer);
          }

          this._startEvent = event;

          if(event.type == 'keydown') {
            this.timer = setTimeout(() => {
              console.log('longpress');
              this.longpress.emit(this._startEvent);
              clearTimeout(this.timer);
              this.timer = null;
            }, this.longpressDelay);
          }
        }
      }
    }