Question

我正在实现角度/材质树组件，并且遇到一些问题。保存对树的更改后，我正在重置支持树的数据（有效），但是应用程序变得异常缓慢，扩展节点可能需要8秒钟。

让这更奇怪的是，实际上操纵数据源的代码在其他地方运行，例如向树中添加新的子级-我们希望更新UI，这不会造成问题。只有在保存时，应用程序才会变慢。

save(): void {
    const trees = this.flattenedTree.filter(node => this.isRootNode(node));

    this.serviceThatHasNoSideEffects.save(trees)
        .then(result => {
            this.tree = result;
            this.flattenedTree = this.getFlattenedTree();
            this.refreshTree();
        });
}

private refreshTree() {
    const data: any[] = this.flattenedTree
        .filter(x => this.isRootNode(x))
        .filter(x => x.children.length > 0 || x.id === this.focusId);

    this.nestedDataSource.data = null;
    this.nestedDataSource.data = data;

    const focusNode = this.getNode(this.focusId);
    this.nestedTreeControl.expand(focusNode);
}

private addChild(parentNode: any, childNode: any) {
    if (!this.getNode(parentNode)) {
        this.flattenedTree.push(parentNode);
    }

    if (!this.getNode(childNode)) {
        this.flattenedTree.push(childNode);
    }

    parentNode.children.push(childNode);

    this.refreshTree();
    this.nestedTreeControl.expand(parentNode);
}

编辑：

更改刷新树以创建全新的数据源可解决缓慢的问题（内存泄漏？），但不会在UI中添加未显示的子对象。尽管孩子在展平的树上，但是应该显示。

private refreshTree() {
    const data: any[] = this.flattenedTree
        .filter(x => this.isRootNode(x))
        .filter(x => x.children.length > 0 || x.id === this.focusId);

        this.nestedDataSource = new MatTreeNestedDataSource<theTreeType>();
    this.nestedDataSource.data = data;

    const focusNode = this.getNode(this.focusId);
    this.nestedTreeControl.expand(focusNode);
}

编辑：这是支持它的html。很标准。

       <mat-tree-node *matTreeNodeDef="let node" matTreeNodeToggle>
            <li class="mat-tree-node">
                <button mat-icon-button disabled></button>
                {{node.uniqueName}}
            </li>
        </mat-tree-node>

        <!--when has nested child-->
        <mat-nested-tree-node *matTreeNodeDef="let node; when: hasNestedChild">
            <li>
                <div class="mat-tree-node">
                    <button mat-icon-button matTreeNodeToggle>
                        <mat-icon>
                            {{nestedTreeControl.isExpanded(node) ? 'expand_more' : 'chevron_right'}}
                        </mat-icon>
                    </button>
                    {{node.uniqueName}}
                </div>
                <ul [class.invisible]="!nestedTreeControl.isExpanded(node)">
                    <ng-container matTreeNodeOutlet></ng-container>
                </ul>
            </li>
        </mat-nested-tree-node>
    </mat-tree>

Answer 1

尽管公认的答案似乎可以提高速度，但最终为我做到的解决方案（在Angular 8中）是：

https://stackoverflow.com/a/59655114/134120

从官方示例中更改该行：

<ul [class.example-tree-invisible]="!treeControl.isExpanded(node)">

对此：

<ul *ngIf="treeControl.isExpanded(node)">

以使折叠的子树根本不会加载到DOM中。

Answer 2

我花了几个小时才开始工作，但这是我所做的更改：

// cdk tree that mat tree is based on has a bug causing children to not be rendered in the UI without first setting the data to null
this.nestedDataSource.data = null;
// mat-tree has some sort of memory leak issue when not instantiating a new MatTreeNestedDataSource which causes the app to become very slow
this.nestedDataSource = new MatTreeNestedDataSource<LocationHierarchyNodeDataModel>();
this.nestedDataSource.data = data;

我在这里发现的展示儿童的问题：https://github.com/angular/material2/issues/11381

在更改支持垫树的数据后，为什么我的角度应用程序会变得非常慢？

2 个答案: