Angular Material 是一个基于 Angular 的 UI 组件库,提供了丰富的 UI 组件来帮助开发者快速构建现代化的 Web 应用程序。其中,mat-tree
组件用于展示层次结构的数据,类似于文件系统或组织结构。
mat-tree
组件允许你创建可展开和折叠的树形结构。它使用递归的方式来渲染树的节点,并且可以通过点击节点来展开或折叠子节点。
以下是一个简单的 Angular Material 树形结构的示例,展示了如何展开 firstLevel
树:
import { Component } from '@angular/core';
import { FlatTreeControl } from '@angular/cdk/tree';
import { MatTreeFlatDataSource, MatTreeFlattener } from '@angular/material/tree';
interface FoodNode {
name: string;
children?: FoodNode[];
}
const TREE_DATA: FoodNode[] = [
{
name: 'Fruit',
children: [{name: 'Apple'}, {name: 'Banana'}, {name: 'Fruit loops'}]
}, {
name: 'Vegetables',
children: [
{
name: 'Green',
children: [{name: 'Broccoli'}, {name: 'Brussels sprouts'}]
}, {
name: 'Orange',
children: [{name: 'Pumpkins'}, {name: 'Carrots'}]
},
]
},
];
interface ExampleFlatNode {
expandable: boolean;
name: string;
level: number;
}
@Component({
selector: 'app-tree',
templateUrl: './tree.component.html',
styleUrls: ['./tree.component.css']
})
export class TreeComponent {
private _transformer = (node: FoodNode, level: number) => {
return {
expandable: !!node.children && node.children.length > 0,
name: node.name,
level: level,
};
};
treeControl = new FlatTreeControl<ExampleFlatNode>(
node => node.level, node => node.expandable);
treeFlattener = new MatTreeFlattener(
this._transformer, node => node.level, node => node.expandable, node => node.children);
dataSource = new MatTreeFlatDataSource(this.treeControl, this.treeFlattener);
constructor() {
this.dataSource.data = TREE_DATA;
}
hasChild = (_: number, node: ExampleFlatNode) => node.expandable;
ngOnInit() {
// 展开 firstLevel 树
this.treeControl.expand(this.treeControl.dataNodes[0]);
}
}
在 HTML 模板中:
<mat-tree [dataSource]="dataSource" [treeControl]="treeControl">
<mat-tree-node *matTreeNodeDef="let node" matTreeNodeToggle>
{{node.name}}
</mat-tree-node>
<mat-nested-tree-node *matTreeNodeDef="let node; when: hasChild">
<div class="mat-tree-node" matTreeNodeToggle>
<button mat-icon-button disabled></button>
{{node.name}}
</div>
<div [class.hidden]="!treeControl.isExpanded(node)" role="group">
<ng-container matTreeNodeOutlet></ng-container>
</div>
</mat-nested-tree-node>
</mat-tree>
问题:树形结构无法展开。
原因:
treeControl
的初始化可能有问题。解决方法:
dataSource
正确地绑定了数据。treeControl
是否在组件初始化时正确创建。mat-tree
和相关指令使用正确。通过上述步骤,你应该能够成功地在 Angular Material 中展开 firstLevel
树。如果问题仍然存在,建议检查控制台是否有错误信息,并根据错误信息进行调试。
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