angular - 根据提供的json动态生成多个 Canvas 区域

Question

我正在使用 angular2 和 html5 Canvas 。基于提供的 json，我想创建多个带有 Canvas 区域的 div。

这就是如何用 Canvas 区域生成我的 div(HTML 代码)

<div class="masterpage" *ngFor="let x of masterPages" draggable [dragScope]="'masterpage'" [dragData]="x">
    <canvas #myCanvas width="105" height="149" style="background:lightgray;"></canvas>
</div>

.ts代码

ngAfterViewInit() {
    let canvas = this.myCanvas.nativeElement;
    this.context = canvas.getContext("2d");
    this.tick(this.masterPages);
}

tick(masterPages) {
    var ctx = this.context;
    ctx.clearRect(0, 0, 150, 150);
    for (let j = 0; j < this.masterPages[this.count].areas.length; j++) {
        ctx.fillStyle = this.masterPages[this.count].areas[j].type;
        ctx.fillRect(masterPages[this.count].areas[j].x / 2, masterPages[this.count].areas[j].y / 2, masterPages[this.count].areas[j].width / 2, masterPages[this.count].areas[j].height / 2);
    }
    this.count = this.count + 1;
}

下面是我的json

masterPages = [{
        areas: [
            {
                type: "FlowArea",
                width: "183.0",
                x: "12.0",
                y: "40.0",
                id: "FAR.1",
                height: "237.0"
            },
            {
                type: "StaticArea",
                width: "210.0",
                x: "0.0",
                y: "7.0",
                id: "SAR.2",
                height: "25.0"
            },
            {
                type: "StaticArea",
                width: "210.0",
                x: "0.0",
                y: "282.0",
                id: "SAR.1",
                height: "15.0"
            },
            {
                type: "StaticArea",
                width: "2.0",
                x: "6.0",
                y: "26.0",
                id: "SAR.3",
                height: "256.0"
            }
        ]
    },
    {
        areas: [
            {
                type: "FlowArea",
                width: "183.0",
                x: "12.0",
                y: "13.25",
                id: "FAR.1",
                height: "265.0"
            },
            {
                type: "StaticArea",
                width: "210.0",
                x: "0.0",
                y: "282.0",
                id: "SAR.1",
                height: "15.0"
            }
        ]
    }
    ];

根据 json，两个 Canvas 都应该有一些形状，但在我的例子中，第二个 Canvas 是空的

Answer 1

尝试使用@ViewChildren 而不是@ViewChild 并使用

遍历每个 Canvas

let canvas = this.myCanvas.toArray()[i].nativeElement;

那么谁将有权访问动态创建的每个 Canvas 区域。