Creating a nested tree structure within a dropdown menu using Angular Material

Question

Creating a nested tree structure within a dropdown menu using Angular Material

Looking for guidance on implementing a tree view within a dropdown menu. The dropdown values will be retrieved from a REST API call in JSON format, with the potential of having multiple levels of child elements.

I also need to add an auto-suggestion feature that filters both parent and child elements.

 VehicleList = [
      {
        parent: "audi",
        child: [{
          type: 'G-audiA',
          subchild: [{
              id: 1,
              name: 'type audi A1'
          }, {
              id: 2,
              name: 'type audi A2'
          }]
        }, {
          type: 'G-audiB',
          subchild: [{
              id: 1,
              name: 'type audi B1'
          }, {
              id: 2,
              name: 'type audi B2'
          }]
        }]
      }, {
        parent: "bmw",
        child: [{
          type: 'G-bmwA',
          subchild: [{
              id: 1,
              name: 'type bmw A1'
          }, {
              id: 2,
              name: 'type bmw A2'
          }]
        }, {
          type: 'G-bmwB',
          subchild: [{
              id: 1,
              name: 'type bmw B1'
          }, {
              id: 2,
              name: 'type bmw B2'
          }]
        }]
  }]

Any assistance would be greatly appreciated!

javascript angular typescript angular-material

Answer 1

Answer №1

After exploring the first example provided in the Angular Material Tree documentation, I successfully created a dropdown with a nested tree structure like this:

https://i.sstatic.net/rGTmB.png

To display the tree effectively, I added a disabled/empty option which served as a label. The tree structure was borrowed from the examples without any modifications, allowing flexibility for adjusting the node structure based on personal requirements.

To showcase the selected items within the dropdown label, you can implement a method that returns the selected items as a string. Utilizing the SelectionModel object's selected property makes it possible to retrieve all selected nodes efficiently.

/** Checklist selection */
checklistSelection = new SelectionModel<TodoItemFlatNode>(
    true /* multiple */
);

To retrieve the selected items from the tree:

return this.checklistSelection.selected.map(s => s.item).join(",");

https://i.sstatic.net/rlXcZ.png

If you need assistance with filtering, refer to this resource. I hope this proves helpful!

Stackblitz

Edit: Selecting a child will automatically select its parent and include it in the SelectionModel even if not all children are selected. To alter this behavior, you can comment out the descendantsPartiallySelected function. This adjustment prevents parents from being added to the SelectionModel unless all children are selected.

Answer 2

After exploring the first example provided in the Angular Material Tree documentation, I successfully created a dropdown with a nested tree structure like this:

https://i.sstatic.net/rGTmB.png

To display the tree effectively, I added a disabled/empty option which served as a label. The tree structure was borrowed from the examples without any modifications, allowing flexibility for adjusting the node structure based on personal requirements.

To showcase the selected items within the dropdown label, you can implement a method that returns the selected items as a string. Utilizing the SelectionModel object's selected property makes it possible to retrieve all selected nodes efficiently.

/** Checklist selection */
checklistSelection = new SelectionModel<TodoItemFlatNode>(
    true /* multiple */
);

To retrieve the selected items from the tree:

return this.checklistSelection.selected.map(s => s.item).join(",");

https://i.sstatic.net/rlXcZ.png

If you need assistance with filtering, refer to this resource. I hope this proves helpful!

Stackblitz

Edit: Selecting a child will automatically select its parent and include it in the SelectionModel even if not all children are selected. To alter this behavior, you can comment out the descendantsPartiallySelected function. This adjustment prevents parents from being added to the SelectionModel unless all children are selected.

Creating a nested tree structure within a dropdown menu using Angular Material

Answer №1

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