Angular4 @HostBinding @HostListener

host属性

@Component({

selector: 'jhi-project',

templateUrl: './project.html',

styleUrls: [],

host: { '(window:keydown)': 'keyboardInput($event)' }    //绑定事件和方法

})

export class JhiProjectComponent {

keyboardInput(event) {

if (event.keyCode == 65 && event.ctrlKey) {

// ctrl + a

....

}

}

}

@HostListener

HostListener是属性装饰器，用来为宿主元素添加事件监听。

定义：

// HostListenerDecorator的定义
export interface HostListenerDecorator {
    (eventName: string, args?: string[]): any;
    new (eventName: string, args?: string[]): any;
}

应用：

// counting.directive.ts
import { Directive, HostListener } from '@angular/core';

@Directive({
    selector: 'button[counting]'
})
class CountClicks {
    numberOfClicks = ;

    @HostListener('click', ['$event.target'])
    onClick(btn: HTMLElement) {
        console.log('button', btn, 'number of clicks:', this.numberOfClicks++);
    }
}

app.component.ts

import { Component} from '@angular/core';

@Component({
  selector: 'exe-app',
  styles: [`
    button {
      background: blue;
      color: white;
      border: 1px solid #eee;
    }
  `],
  template: `
    <button counting>增加点击次数</button>
  `
})
export class AppComponent {}

以上代码运行结果：

此外，还可以监听宿主元素外，其他对象产生的事件，如windown或document对象。

highlight.directive.ts

import { Directive, HostListener, ElementRef, Renderer } from '@angular/core';

@Directive({
    selector: '[exeHighlight]'
})
export class ExeHighlight {
    constructor(private el: ElementRef, private renderer: Renderer) { }

    @HostListener('document:click', ['$event'])
    onClick(btn: Event) {
        if (this.el.nativeElement.contains(event.target)) {
            this.highlight('yellow');
        } else {
            this.highlight(null);
        }
    }

    highlight(color: string) {
        this.renderer.setElementStyle(this.el.nativeElement, 'backgroundColor', color);
    }
}

import {HostListener} from '@angular/core';

@HostListener('window:keydown', ['$event'])
onKeyDown(event: KeyboardEvent) {
  ...
}

app.component.ts

import { Component} from '@angular/core';

@Component({
  selector: 'exe-app',
  template: `
    <h4 exeHighlight>点击该区域，元素会被高亮。点击其它区域，元素会取消高亮</h4>
  `
})
export class AppComponent {}

也可以在指定的metadata信息中，设定宿主元素的事件监听信息，示例：

counting.directive.ts

import { Directive } from '@angular/core';

@Directive({
    selector: 'button[counting]',
    host: {
      '(click)': 'onClick($event.target)'
    }
})
export class CountClicks {
    numberOfClicks = ;

    onClick(btn: HTMLElement) {
        console.log('button', btn, 'number of clicks:', this.numberOfClicks++);
    }
}

@HostBinding

HostBinding 是属性装饰器，用来动态设置宿主元素的属性值。

定义：

export interface HostBindingDecorator {
    (hostPropertyName?: string): any;
    new (hostPropertyName?: string): any;
}

应用：

@HostBindings('attr.foo') foo = 'bar'

button-press.directive.ts

import { Directive, HostBinding, HostListener } from '@angular/core';

@Directive({
    selector: '[exeButtonPress]'
})
export class ExeButtonPress {
    @HostBinding('attr.role') role = 'button';
    @HostBinding('class.pressed') isPressed: boolean;

    @HostListener('mousedown') hasPressed() {
        this.isPressed = true;
    }
    @HostListener('mouseup') hasReleased() {
        this.isPressed = false;
    }
}

app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'exe-app',
  styles: [`
    button {
      background: blue;
      color: white;
      border: 1px solid #eee;
    }
    button.pressed {
      background: red;
    }
  `],
  template: `
    <button exeButtonPress>按下按钮</button>
  `
})
export class AppComponent { }

我们也可以在指令的 metadata 信息中，设定宿主元素的属性绑定信息，具体示例如下：

button-press.directive.ts

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

@Directive({
    selector: '[exeButtonPress]',
    host: {
      'role': 'button',
      '[class.pressed]': 'isPressed'
    }
})
export class ExeButtonPress {
    isPressed: boolean;

    @HostListener('mousedown') hasPressed() {
        this.isPressed = true;
    }
    @HostListener('mouseup') hasReleased() {
        this.isPressed = false;
    }
}