Angular 2属性指令输入值未定义且未正确设置

Question

我有以下指令(TextElementDirective),它有4个输入变量colorHex,fontFamily,fontWeight,fontStyle.我想使用此指令设置元素的颜色和样式.

@Directive(
{
    selector: "[text-element-map]",
    // host: {
    //     '(mousemove)': "onMouseMove()"
    // }
}
)

export class TextElementDirective{
@Input() colorHex : string;
@Input() fontFamily : string;
@Input() fontWeight : string;
@Input() fontStyle : string;

constructor(private el: ElementRef){
    this.setElement();
}

setElement(){
    if(this.colorHex){
        this.el.nativeElement.style.color = this.colorHex;
    }
    if(this.fontFamily){
        this.el.nativeElement.style.fontFamily = this.fontFamily;
    }
    if(this.fontWeight){
        this.el.nativeElement.style.fontWeight = this.fontWeight;
    }
    if(this.fontStyle){
        this.el.nativeElement.style.fontStyle = this.fontStyle || "";
    }
}

onMouseMove(){
    this.setElement();
}
}

当我在另一个组件中使用此指令时,作为属性,它不会设置元素样式和颜色.即使单击该按钮,也不会设置元素值.

如果我在指令中使用主机(onmousemove),它可以正常工作.但我想在启动时设置值.

知道我错过了什么吗？

这是使用它的测试组件.

@Component({
template:
`
    <h3>Test</h3>
    <div>
        <span>text-element-map: </span>
        <span class="text-content" text-element-map [colorHex]="colorHex" 
             [fontFamily]="fontFamily" [fontWeight]="fontWeight" [fontStyle]="fontStyle">Change this text</span>

        <button (click)="setCurrentDesignElement()">Click</button>
    </div>
`,
directives:[TextElementDirective],
changeDetection: ChangeDetectionStrategy.Default
})
export class TestComponent{

@ViewChild(TextElementDirective)
private childTextElement: TextElementDirective;


colorHex: string = "#e2e2e2";
fontFamily: string = "Arial";
fontWeight: string = "normal";
fontStyle: string = "normal";

setCurrentDesignElement(){
    this.color = {
        hex: "#B4B4B4",
        id: 5745,
        name: "Athletic Heather"
    };

    this.font = {
        cssString: "Valera Round",
        weight: "normal",
        style: "italic"
        };

    this.colorHex = "#B4B4B4";
    this.fontFamily = "Valera Round";
    this.fontWeight = "normal";
    this.fontStyle = "italic";    

    //this.childTextElement.setElement();
}


}

Answer 1

Input()s在构造函数中不可用.它们由更改检测设置,并在组件实例化后运行更改检测.在更改检测更新输入后调用生命周期挂钩ngOnChanges(每次更新)和ngOnInit(在第一次ngOnChanges调用之后)

更改

constructor(private el: ElementRef){
    this.setElement();
}

至

constructor(private el: ElementRef) {};

ngOnInit() {
  this.setElement();
}

ngOnInit() 在输入初始化后调用.

代替

this.el.nativeElement.style.color = this.colorHex;

它最好用

@HostBinding('style.color')
@Input() colorHex : string;

@HostBinding('style.font-family')
@Input() fontFamily : string;

@HostBinding('style.font-weight')
@Input() fontWeight : string;

@HostBinding('style.font-style')
@Input() fontStyle : string;

实际上我没有尝试过添加@HostBinding()和@Input()在同一个领域,但我不明白为什么它不起作用.