Angular Konva 层叠顺序教程

要在 Angular 中控制图形层叠顺序，请更新用于渲染图形的数据数组顺序。

本示例展示以下操作：

1. 创建一个包含随机位置和颜色的圆形图形数组
2. 处理拖动事件以更新图形的视觉顺序
3. 通过操作数组顺序保持正确的层叠顺序
4. 通过 Angular state 驱动渲染，而不是以命令式方式调用 zIndex()

操作说明：尝试拖动圆形。开始拖动时，它会自动移到层叠顶部。此示例通过操作数据中的圆形数组实现该效果，而不是手动更改 zIndex。

import { Component, OnInit } from '@angular/core';
import { StageConfig } from 'konva/lib/Stage';
import { CircleConfig } from 'konva/lib/shapes/Circle';

import {
  CoreShapeComponent,
  StageComponent,
} from 'ng2-konva';

@Component({
  selector: 'app-root',
  standalone: true,
  template: `
    <ko-stage [config]="configStage">
      <ko-layer>
        @for (item of items; track trackById($index, item)) {
          <ko-circle
            [config]="item"
            (dragstart)="handleDragstart($event.event)"
            (dragend)="handleDragend()"
          ></ko-circle>
        }
      </ko-layer>
    </ko-stage>
  `,
  imports: [StageComponent, CoreShapeComponent],
})
export default class App implements OnInit {
  public configStage: StageConfig = {
    width: window.innerWidth,
    height: window.innerHeight,
  };
  
  public items: CircleConfig[] = [];
  private dragItemId: string | null = null;

  ngOnInit() {
    this.generateItems();
  }

  private generateItems(): void {
    const newItems: CircleConfig[] = [];
    for (let i = 0; i < 10; i++) {
      newItems.push({
        x: Math.random() * this.configStage.width!,
        y: Math.random() * this.configStage.height!,
        radius: 50,
        id: "node-" + i,
        fill: this.getRandomColor(),
        draggable: true
      });
    }
    this.items = newItems;
  }

  private getRandomColor(): string {
    const colors = ['#FF6B6B', '#4ECDC4', '#45B7D1', '#96CEB4', '#FFEAA7', '#DDA0DD', '#98D8C8', '#F7DC6F', '#BB8FCE', '#85C1E9'];
    return colors[Math.floor(Math.random() * colors.length)];
  }

  public handleDragstart(event: any): void {
    this.dragItemId = event.target.id();
    const item = this.items.find(i => i.id === this.dragItemId);
    if (item) {
      this.items = [
        ...this.items.filter((i) => i.id !== this.dragItemId),
        item
      ];
    }
  }

  public handleDragend(): void {
    this.dragItemId = null;
  }

  public trackById(index: number, item: CircleConfig): string {
    return item.id as string;
  }
}