我正在尝试在用户扩展节点时动态加载子级。
问题是当我填充children数组时，mat-tree没有显示子级。如果我使用简单的* ngFor显示相同的数据，则在children数组中添加了元素时，它将显示它们。
我在这里有一个有效的示例：stackblitz example 这是代码和html
ts
import {NestedTreeControl} from '@angular/cdk/tree';
import {Component} from '@angular/core';
import {MatTreeNestedDataSource} from '@angular/material/tree';
export class PropertyLevel {
constructor(
public code : string,
public hasSubLevels: boolean,
public subproperties : PropertyLevel[]
){}
}
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
name = 'Angular';
nestedTreeControl: NestedTreeControl<PropertyLevel>;
nestedDataSource: MatTreeNestedDataSource<PropertyLevel>;
constructor() {
this.nestedTreeControl = new NestedTreeControl<PropertyLevel>(this._getChildren);
this.nestedDataSource = new MatTreeNestedDataSource();
this.nestedDataSource.data = [
new PropertyLevel( '123', false, []),
new PropertyLevel( '345', true, [
new PropertyLevel( '345.a', false, null),
new PropertyLevel( '345.b', true, []),
]),
new PropertyLevel( '567', false,[]),
];
}
hasNestedChild = (_: number, nodeData: PropertyLevel) => nodeData.subproperties;
private _getChildren = (node: PropertyLevel) => node.subproperties;
expandToggle(node: PropertyLevel, isExpanded: boolean): void {
if (node.subproperties && node.subproperties.length == 0) {
if(node.code == '123') {
node.subproperties.push(new PropertyLevel('123.a', false, null))
}
else if(node.code == '567') {
node.subproperties.push(new PropertyLevel('567.a', false, null));
node.subproperties.push(new PropertyLevel('567.b', false, null));
node.subproperties.push(new PropertyLevel('567.c', false, null));
}
}
}
}
html
<mat-tree [dataSource]="nestedDataSource" [treeControl]="nestedTreeControl" class="example-tree">
<mat-tree-node *matTreeNodeDef="let node" matTreeNodeToggle>
<li class="mat-tree-node">
<button mat-icon-button disabled></button>
{{node.code}}
</li>
</mat-tree-node>
<mat-nested-tree-node *matTreeNodeDef="let node; when: hasNestedChild">
<li>
<div class="mat-tree-node">
<button mat-icon-button matTreeNodeToggle
(click)="expandToggle(node, nestedTreeControl.isExpanded(node))"
[attr.aria-label]="'toggle ' + node.filename">
<mat-icon class="mat-icon-rtl-mirror">
{{nestedTreeControl.isExpanded(node) ? 'expand_more' : 'chevron_right'}}
</mat-icon>
</button>
{{node.code}}
</div>
<ul [class.example-tree-invisible]="!nestedTreeControl.isExpanded(node)">
<ng-container matTreeNodeOutlet></ng-container>
</ul>
</li>
</mat-nested-tree-node>
</mat-tree>
<div>
<ul>
<li *ngFor="let node of nestedDataSource.data">
{{node.code}}<br />
<ul>
<li *ngFor="let subnode of node.subproperties">
{{subnode.code}}
</li>
</ul>
</li>
</ul>
</div>
答案 0 :(得分：0)
这个故事的寓意是（如果我错了，请纠正我）是在Angular vs Angularjs，或者至少是Material Tree中，开发人员必须提供更改事件，而不是自动对所有内容进行更改检测，这减少了很多幕后对象的创建，使Angular更快，更精简。
因此，解决方案是不为子代使用数组，而为BehaviorSubject，并向该类添加方法addChild。
我回到带有嵌套节点的树（https://material.angular.io/components/tree/examples）示例（https://stackblitz.com/angular/ngdvblkxajq），并调整FileNode类，并添加了addChild和addChildren方法
export class FileNode {
kids: FileNode[] = [];
children:BehaviorSubject<FileNode[]> = new BehaviorSubject<FileNode[]>(this.kids);
filename: string;
type: any;
addChild(node:FileNode):void {
this.kids.push(node);
this.children.next(this.kids);
}
addchildren(nodes:FileNode[]) {
this.kids = this.kids.concat(this.kids, nodes);
this.children.next(this.kids);
}
}
然后我更改了buildFileTree中设置子项的行，改为调用addChildren。 node.children = this.buildFileTree(value, level + 1)成为node.addchildren(this.buildFileTree(value, level + 1))
我还添加了一种方法，可以通过单击按钮来调用该方法，以将一个孩子添加到图片节点以进行测试。
addPictureFile():void {
var picNode = this.data.find((node) => node.filename == 'Pictures');
var newNode = new FileNode();
newNode.filename = 'foo';
newNode.type = 'gif';
picNode.addChild(newNode);
}
现在，“材料树”确实检测到我的孩子变化并进行了自我更新。 工作示例https://stackblitz.com/edit/angular-addchildtonestedtree
完整，更新的ts文件：
import {NestedTreeControl} from '@angular/cdk/tree';
import {Component, Injectable} from '@angular/core';
import {MatTreeNestedDataSource} from '@angular/material/tree';
import {BehaviorSubject} from 'rxjs';
/**
* Json node data with nested structure. Each node has a filename and a value or a list of children
*/
export class FileNode {
kids: FileNode[] = [];
children:BehaviorSubject<FileNode[]> = new BehaviorSubject<FileNode[]>(this.kids);
filename: string;
type: any;
addChild(node:FileNode):void {
this.kids.push(node);
this.children.next(this.kids);
}
addchildren(nodes:FileNode[]) {
this.kids = this.kids.concat(this.kids, nodes);
this.children.next(this.kids);
}
}
/**
* The Json tree data in string. The data could be parsed into Json object
*/
const TREE_DATA = JSON.stringify({
Applications: {
Calendar: 'app',
Chrome: 'app',
Webstorm: 'app'
},
Documents: {
angular: {
src: {
compiler: 'ts',
core: 'ts'
}
},
material2: {
src: {
button: 'ts',
checkbox: 'ts',
input: 'ts'
}
}
},
Downloads: {
October: 'pdf',
November: 'pdf',
Tutorial: 'html'
},
Pictures: {
'Photo Booth Library': {
Contents: 'dir',
Pictures: 'dir'
},
Sun: 'png',
Woods: 'jpg'
}
});
/**
* File database, it can build a tree structured Json object from string.
* Each node in Json object represents a file or a directory. For a file, it has filename and type.
* For a directory, it has filename and children (a list of files or directories).
* The input will be a json object string, and the output is a list of `FileNode` with nested
* structure.
*/
@Injectable()
export class FileDatabase {
dataChange = new BehaviorSubject<FileNode[]>([]);
get data(): FileNode[] { return this.dataChange.value; }
constructor() {
this.initialize();
}
initialize() {
// Parse the string to json object.
const dataObject = JSON.parse(TREE_DATA);
// Build the tree nodes from Json object. The result is a list of `FileNode` with nested
// file node as children.
const data = this.buildFileTree(dataObject, 0);
// Notify the change.
this.dataChange.next(data);
}
/**
* Build the file structure tree. The `value` is the Json object, or a sub-tree of a Json object.
* The return value is the list of `FileNode`.
*/
buildFileTree(obj: {[key: string]: any}, level: number): FileNode[] {
return Object.keys(obj).reduce<FileNode[]>((accumulator, key) => {
const value = obj[key];
const node = new FileNode();
node.filename = key;
if (value != null) {
if (typeof value === 'object') {
node.addchildren(this.buildFileTree(value, level + 1));
} else {
node.type = value;
}
}
return accumulator.concat(node);
}, []);
}
addPictureFile():void {
var picNode = this.data.find((node) => node.filename == 'Pictures');
var newNode = new FileNode();
newNode.filename = 'foo';
newNode.type = 'gif';
picNode.addChild(newNode);
}
}
/**
* @title Tree with nested nodes
*/
@Component({
selector: 'tree-nested-overview-example',
templateUrl: 'tree-nested-overview-example.html',
styleUrls: ['tree-nested-overview-example.css'],
providers: [FileDatabase]
})
export class TreeNestedOverviewExample {
nestedTreeControl: NestedTreeControl<FileNode>;
nestedDataSource: MatTreeNestedDataSource<FileNode>;
constructor(private database: FileDatabase) {
this.nestedTreeControl = new NestedTreeControl<FileNode>(this._getChildren);
this.nestedDataSource = new MatTreeNestedDataSource();
database.dataChange.subscribe(data => {
this.nestedDataSource.data = data;
}
);
}
hasNestedChild = (_: number, nodeData: FileNode) => !nodeData.type;
private _getChildren = (node: FileNode) => node.children;
}