Angular TreeView Properties

The value of this option will be passed to the accesskey attribute of the HTML element that underlies the widget.

This option is used when the widget is displayed on a platform whose guidelines include the active state change for widgets.

This function is called at the beginning of the widget's lifetime and each time a user expands a node whose child nodes have not been loaded yet. It allows you to load the entire tree in portions: load root nodes first (when the function's parentNode parameter is null) and the child nodes of each expanded node later.

The following code shows how to use this function with a remote service:

$(function() {
    $("#treeViewContainer").dxTreeView({
        dataStructure: "plain",
        rootValue: 0, 
        createChildren: function (parentNode) {
            var d = $.Deferred();
            $.get("http://url/to/the/service", {
                    // Here, 0 is the "rootValue" option's value.
                    parentId: parentNode ? JSON.stringify(parentNode.key) : "0" 
                })
                .done(function (result) {
                    d.resolve(result);
                });
            return d.promise();
        }
    });
});

<dx-tree-view
    [rootValue]="0"
    dataStructure="plain"
    [createChildren]="createChildren">
</dx-tree-view>

import { ..., Inject } from "@angular/core";
import { HttpClient, HttpClientModule, HttpParams } from "@angular/common/http";
import "rxjs/add/operator/toPromise";
import { DxTreeViewModule } from "devextreme-angular";
// ...
export class AppComponent {
    constructor(@Inject(HttpClient) httpClient: HttpClient) { }
    createChildren = (parentNode) => {
        let params: HttpParams = new HttpParams()
            // Here, 0 is the "rootValue" option's value.
            .set("parentId", parentNode ? JSON.stringify(parentNode.key) : "0"); 
        return httpClient.get("http://url/to/the/service", {
                params: params
            })
            .toPromise();
    }
}
@NgModule({
    imports: [
        // ...
        DxTreeViewModule,
        HttpClientModule 
    ],
    // ...
})

View Demo

See Also

• Enhance Performance on Large Datasets
• TreeView - Use Plain Data

This option accepts one of the following.

• Array of objects
  A simple JavaScript array containing a collection of plain objects.

• URL
  The URL of a JSON file or service that returns JSON data.

• DataSource or its configuration object
  A DataSource is an object that provides a handy API for data processing. A DataSource is a stateful object, which means that it saves data processing settings and applies them each time data is loaded. All underlying data access logic of a DataSource is isolated in a Store. A Store provides an API for reading and modifying data. Unlike the DataSource, a Store is a stateless object.

If the data source is specified using the dataSource option, use the items option only for reading. Updating data items using the items option may cause unexpected results.

To display widget items, a default template can be used. This template is based on the data source fields that are listed in the Default Item Template section of the widget's API. Alternatively, you can implement a custom item template. For details, refer to the Customize Node Appearance topic.

See Also

• createChildren - allows you to load nodes manually.

If the option is set to "tree", the array should have a tree structure. This means that each item can contain the items field, which contains an array of nested items.

var treeViewData = [
    {
        id: 1,
        items: [
            { id: 11 },
            { id: 12 },
            { 
                id: 13,
                items: [
                    { id: 131 },
                    { id: 132 },
                    { id: 133 },
                ]
            },
        ]
    },
    { id: 2 }
];

View Demo

If the dataStructure option value is "plain", the array should have a plain structure. In this case, each array item should contain the parentId field, which specifies the key of the parent item.

var treeViewData = [
    { id: 1, parentId: 0 },
    { id: 11, parentId: 1 },
    { id: 12, parentId: 1 },
    { id: 13, parentId: 1 },
    { id: 131, parentId: 13 },
    { id: 132, parentId: 13 },
    { id: 133, parentId: 13 },
    { id: 2, parentId: 0 }
];

View Demo

Use the TreeViewDataStructure enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: Plain and Tree.

See Also

• TreeView - Use Hierarchical Data
• TreeView - Use Plain Data

View Demo

See Also

• Use Hierarchical Data
• Use Plain Data

See Also

• Expand and Collapse Nodes

This option accepts a value of one of the following types:

• Number
  The height in pixels.

• String
  A CSS-accepted measurement of height. For example, "55px", "80%", "auto", "inherit".

• Function
  A function returning either of the above. For example:

  JavaScript

  height: function() {
      return window.innerHeight / 1.5;
  }

You can use the dataSource option instead. Unlike the items option, the dataSource option can take on the DataSource configuration object as well as a simple array.

To display widget items, a default template can be used. This template is based on the data source fields that are listed in the Default Item Template section of the widget's API.

See Also

• Customize Node Appearance
• Custom Templates

See Also

• Specify data using dataSource option
• Specify data using items option

You cannot access widget elements in this function because it is executed before they are ready. Use the onContentReady function instead.

See Also

-Expand and Collapse Nodes - Events

See Also

• Expand and Collapse Nodes - Events

This function is executed under one of the following conditions:

• The selectByClick option is set to true;
• The showCheckBoxesMode option is not "none";
• One of the following methods is called: selectAll(), unselectAll(), selectItem(), unselectItem().

View Demo

See Also

• Select Nodes - Events

See Also

• onSelectionChanged
• Select Nodes

This function is executed under one of the following conditions:

• The selectByClick option is set to true;
• The showCheckBoxesMode option is not "none";
• One of the following methods is called: selectAll(), unselectAll(), selectItem(), unselectItem().

This option is used if the dataStructure option is set to "plain".

View Demo

When this option is set to true, the widget text flows from right to left, and the layout of elements is reversed. To switch the entire application/site to the right-to-left representation, assign true to the rtlEnabled field of the object passed to the DevExpress.config(config) method.

DevExpress.config({
    rtlEnabled: true
});

See Also

• Right-to-Left Support Demo: DataGrid | Navigation Widgets | Editors

Use the ScrollDirection enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: Vertical, Horizontal, and Both.

See the TextBox Configuration for options you can specify in this object.

View Demo

See Also

• TreeView - Searching

If you need to search several fields, assign an array of field names to this option.

searchExpr: ["firstName", "lastName"]

Use the CollectionSearchMode enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: Contains, StartsWith, and Equals.

See Also

• Search Nodes

See Also

• Select Nodes - User Interaction

Use the NavSelectionMode enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: Single and Multiple.

If this option is enabled, the widget selects (unselects) all child nodes if a user selects (unselects) the parent node.

The option accepts the following values.

• "none"
  The widget does not display check boxes.

• "normal"
  The widget displays a check box for each item.

• "selectAll"
  The widget displays a check box for each item and the "select all" check box at the top of the widget.

Use the TreeViewCheckBoxMode enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: None, Normal, and SelectAll.

View Demo

See Also

• Select Nodes - User Interaction

The value of this option will be passed to the tabindex attribute of the HTML element that underlies the widget.

If the option is set to true, the widget initially loads only root items. Child items are loaded when their parent is being expanded.

Use this option to improve the widget performance when working with a huge data source.

View Demo

See Also

• Enhance Performance on Large Datasets
• createChildren - allows you to load nodes manually.

This option accepts a value of one of the following types:

• Number
  The width in pixels.

• String
  A CSS-accepted measurement of width. For example, "55px", "80%", "auto", "inherit".

• Function
  A function returning either of the above. For example:

  JavaScript

  width: function() {
      return window.innerWidth / 1.5;
  }