Create a Static Custom Item for the Web Dashboard
- 7 minutes to read
Important
A custom item is an independent module called an extension. If you are not familiar with the basic concepts of extensions, please review the following topic before you continue: Extensions Overview.
This tutorial shows how to create a custom item that displays text and adds a custom property that allows you to change this static text in the UI.
You can download the ready-to-use projects based on the Create a custom item tutorials:
Prerequisites
A custom item script depends on the platform you use:
- Module script
- Client components (Angular, React, Vue) use imports and classes to define a custom item.
- Classic script
- A script for the ASP.NET Web Forms, ASP.NET MVC, ASP.NET Core, BLazor, and JavaScript controls encapsulates a custom item in the IIFE function expression.
Before you begin, create a Web Dashboard project for the required platform.
Create an External Script
In your project, create an external HelloWorldItem.js file, so you can reuse the created extension in other Web Dashboard applications.
Define a class that will be a custom item (HelloWorldItem).
import { CustomItemViewer, ResourceManager } from 'devexpress-dashboard/common'
import { CustomItem } from 'devexpress-dashboard/model'
class HelloWorldItem {
}
export default HelloWorldItem;
Warning
If you use the Classic script, place the code below inside the self-invoking function.
Define a Toolbox Icon
In the HelloWorldItem.js file, add a 24x24 SVG icon as a string variable:
var svgIcon = '<svg id="helloWorldItemIcon" viewBox="0 0 24 24"><path stroke="#42f48f" fill="#42f48f" d="M12 2 L2 22 L22 22 Z" /></svg>';
The icon will be used later to display the custom item in the Toolbox:
Specify the Custom Item’s Settings
Implement the ICustomItemMetaData interface to define this custom item’s settings:
- In the icon option, pass the SVG icon’s id (
helloWorldItemIcon). - In the title option, specify the text displayed in the dashboard item caption and as the Toolbox element’s tooltip (
Hello World Item).
Use the ICustomItemMetaData.customProperties and ICustomItemMetaData.optionsPanelSections properties to define a custom option that allows a user to change the custom dashboard item’s display text:
- Create the CustomPropertyMetadata object and define a string
customPropertyoption. Add the created option to the ICustomItemMetaData.customProperties collection. - Create the SectionOptions object that defines a new Custom Properties section in the dashboard item’s Options menu. The SectionOptions.items collection contains editors used to manage custom property values in the UI. Define dxTextBox as an editor. Add the created option to the ICustomItemMetaData.optionsPanelSections collection.
var helloWorldItemMetaData = {
customProperties: [{
ownerType: CustomItem,
propertyName: 'customProperty',
valueType: 'string',
defaultValue: 'Hello World!'
}],
optionsPanelSections: [{
title: 'Custom Properties',
items: [{
dataField: 'customProperty',
label: {
text: 'Item Text'
},
editorType: 'dxTextBox',
editorOptions: {
placeholder: "Enter text to display"
}
}]
}],
icon: 'helloWorldItemIcon',
title: 'Hello World Item'
};
Implement Custom Item Rendering
The CustomItemViewer class specifies visual representation of the custom item. Override the CustomItemViewer.renderContent method to display custom item content. Use the CustomItemViewer.getPropertyValue method to get the value of the created custom option and display this value in the viewer.
Note
Do not set IDs for DOM elements in the CustomItemViewer.renderContent method call. When the custom item is maximized, the renderContent method is called again and creates one more DOM element with the same ID. If you create an element inside this method, the element ID will not be unique on the page.
import { CustomItemViewer, ResourceManager } from 'devexpress-dashboard/common'
import { CustomItem } from 'devexpress-dashboard/model'
// ...
class HelloWorldItemViewer extends CustomItemViewer {
renderContent(element, changeExisting) {
element.innerText = this.getPropertyValue('customProperty');
};
}
Create an Extension
The ICustomItemExtension interface allows you to define a custom item as an extension.
- Use the ResourceManager.registerIcon static method to register the custom item’s icon.
- Pass the created metadata to the ICustomItemExtension.metaData property.
- Specify the IExtension.name property. This property defines the custom item name in the dashboard definition. If you want to display the same dashboard on the Desktop, make sure that the names of the custom item extensions on the Desktop and Web match.
- Call the ICustomItemExtension.createViewerItem method to implement the created custom item.
import { CustomItemViewer, ResourceManager } from 'devexpress-dashboard/common'
import { CustomItem } from 'devexpress-dashboard/model'
// ...
class HelloWorldItem {
constructor(dashboardControl) {
ResourceManager.registerIcon(svgIcon);
this.name = "helloWorldItem";
this.metaData = helloWorldItemMetaData;
}
createViewerItem(model, $element, content) {
return new HelloWorldItemViewer(model, $element, content);
}
}
export default HelloWorldItem;
The complete extension code:
// #region imports
import { CustomItemViewer, ResourceManager } from 'devexpress-dashboard/common'
import { CustomItem } from 'devexpress-dashboard/model'
// #endregion
// #region svgIcon
var svgIcon = '<svg id="helloWorldItemIcon" viewBox="0 0 24 24"><path stroke="#42f48f" fill="#42f48f" d="M12 2 L2 22 L22 22 Z" /></svg>';
// #endregion
// #region metadata
var helloWorldItemMetaData = {
customProperties: [{
ownerType: CustomItem,
propertyName: 'customProperty',
valueType: 'string',
defaultValue: 'Hello World!'
}],
optionsPanelSections: [{
title: 'Custom Properties',
items: [{
dataField: 'customProperty',
label: {
text: 'Item Text'
},
editorType: 'dxTextBox',
editorOptions: {
placeholder: "Enter text to display"
}
}]
}],
icon: 'helloWorldItemIcon',
title: 'Hello World Item'
};
// #endregion
// #region viewer
class HelloWorldItemViewer extends CustomItemViewer {
renderContent(element, changeExisting) {
element.innerText = this.getPropertyValue('customProperty');
};
}
// #endregion
// #region createItem
class HelloWorldItem {
constructor(dashboardControl) {
ResourceManager.registerIcon(svgIcon);
this.name = "helloWorldItem";
this.metaData = helloWorldItemMetaData;
}
createViewerItem(model, $element, content) {
return new HelloWorldItemViewer(model, $element, content);
}
}
export default HelloWorldItem;
// #endregion
Register the Custom Item Extension
Attach the created HelloWorldItem.js script file to the page containing the Web Dashboard code. The external script you created is now available in the application.
You need to register the extension before the control is rendered. Refer to the following topics for information on how to get access to the DashboardControl instance and customize it before any element in the Web Dashboard control has been rendered:
- Client-Side API Overview for ASP.NET Core Dashboard
- Client-Side API Overview for ASP.NET MVC Dashboard
- Client-Side API Overview for ASP.NET Web Forms Dashboard
- Manage Extensions in Angular
- Manage Extensions in React
- Manage Extensions in Vue
- Manage Extensions in the JavaScript Dashboard Control
- JavaScript Customization of Blazor Dashboard Component
Register the created extension in the DashboardControl.registerExtension method call:
function onBeforeRender(e) {
var dashboardControl = e.component;
dashboardControl.registerExtension(new DashboardPanelExtension(dashboardControl));
dashboardControl.registerExtension(new HelloWorldItem(dashboardControl));
// ...
}
Result
Run the project and click the Hello World Item Toolbox item to add the custom item to the dashboard:
This action adds the custom item with the predefined ‘Hello World!’ text on its surface. Open the item’s Options menu and go to the Custom Properties section to change the displayed text:
In the next lesson, you will learn how to create a custom item that is bound to data, and how to display data from a data source.