Issues have been identified with the collapse functionality of the Angular 6 Material Tree feature

Question

Issues have been identified with the collapse functionality of the Angular 6 Material Tree feature

Recently, I've been working on creating a tree structure to handle dynamic data using Angular material tree component. In order to achieve this, I referred to the code example mentioned below:

https://stackblitz.com/edit/material-tree-dynamic

However, I encountered an issue with the tree structure I developed, where the collapse functionality was not working as expected. I decided to copy the code from the above example and run it on my own machine. Here is the TypeScript file I used (the HTML code remained the same):

import {Component, Injectable} from '@angular/core';
import {FlatTreeControl} from '@angular/cdk/tree';
import {CollectionViewer, SelectionChange} from '@angular/cdk/collections';
import {BehaviorSubject} from 'rxjs/BehaviorSubject';
import {Observable} from 'rxjs/Observable';
import {merge} from 'rxjs/observable/merge';
import {map} from 'rxjs/operators/map';

// code continues...

Upon collapsing a root node that contains multiple levels of children, the resulting display can be seen here.

If anyone has insights into what might be causing this issue and how to resolve it, I would greatly appreciate the assistance.

typescript treeview angular-material angular6

Answer 1

Answer №1

Reason Behind the Behavior

The issue arises due to the implementation of the toggle function. When collapsing a node by calling toggleNode with the expand parameter set to false, the following line of code is executed:

this.data.splice(index + 1, children.length);

In the Flat Tree data structure used for the Material Tree, nodes are stored in a simple array along with their respective levels. The structure might resemble the following:

- Root (lvl: 1)
- Child1 (lvl: 2)
- Child2 (lvl: 2)
- Child1OfChild2 (lvl: 3)
- Child2OfChild2 (lvl: 3)
- Child3 (lvl: 2)

It is important to note that child elements are placed after their parent in the array when expanding a node. The issue arises when collapsing a node, especially if any of its children are expanded and have children of their own. This can be understood by revisiting the line of code mentioned previously.

Proposed Solution

To address this issue, I replaced the problematic line of code with the following logic:

const afterCollapsed: ArtifactNode[] = this.data.slice(index + 1, this.data.length);
let count = 0;
for (count; count < afterCollapsed.length; count++) {
    const tmpNode = afterCollapsed[count];
    if (tmpNode.level <= node.level){
        break;
    }
}
this.data.splice(index+1, count);

By utilizing the slice function and a for-loop, the revised logic accurately determines the number of elements to remove from the array when collapsing a node, ensuring that all appropriate child nodes are removed as well.

Answer 2

Reason Behind the Behavior

The issue arises due to the implementation of the toggle function. When collapsing a node by calling toggleNode with the expand parameter set to false, the following line of code is executed:

this.data.splice(index + 1, children.length);

In the Flat Tree data structure used for the Material Tree, nodes are stored in a simple array along with their respective levels. The structure might resemble the following:

- Root (lvl: 1)
- Child1 (lvl: 2)
- Child2 (lvl: 2)
- Child1OfChild2 (lvl: 3)
- Child2OfChild2 (lvl: 3)
- Child3 (lvl: 2)

It is important to note that child elements are placed after their parent in the array when expanding a node. The issue arises when collapsing a node, especially if any of its children are expanded and have children of their own. This can be understood by revisiting the line of code mentioned previously.

Proposed Solution

To address this issue, I replaced the problematic line of code with the following logic:

const afterCollapsed: ArtifactNode[] = this.data.slice(index + 1, this.data.length);
let count = 0;
for (count; count < afterCollapsed.length; count++) {
    const tmpNode = afterCollapsed[count];
    if (tmpNode.level <= node.level){
        break;
    }
}
this.data.splice(index+1, count);

By utilizing the slice function and a for-loop, the revised logic accurately determines the number of elements to remove from the array when collapsing a node, ensuring that all appropriate child nodes are removed as well.

Issues have been identified with the collapse functionality of the Angular 6 Material Tree feature

Answer №1

Similar questions

Two tags attached to four hypertext links

What causes the session storage to be accessed across various browser sessions?

Is there a way to modify the style when a different rarity is selected in Next.JS?

Is it possible for a React selector to retrieve a particular data type?

Currently trapped within the confines of a Next.js 13 application directory, grappling with the implementation of a

What is the best way to separate the user interface module from the logic in Angular2?

Is it possible that I am making a mistake when using the multi-mixin helper, which is causing an unexpected compiler error that I cannot

Divide a string using multiple delimiters just one time

Ionic user interface is not appearing on screen

Searching function in material-table does not work properly with pipe symbol

Numerous unspecified generic arguments

Using TypeScript with Angular-UI Modals

Unable to trigger click or keyup event

Retrieve information and transform it into a dynamic variable using Firebase

The application is having trouble accessing the property 'isXXXXX' because it is undefined

Receiving feedback from an http.post request and transferring it to the component.ts file in an Angular

Steps to link two mat-autocomplete components based on the input change of one another

Injecting services and retrieving data in Angular applications

Is there a way to obtain a unique response in TestCafe RequestMock?

Stock Chart that resembles the functionality of Google's popular line chart feature