beginUpdate()
Postpones rendering that can negatively affect performance until the endUpdate() method is called.
The beginUpdate() and endUpdate() methods reduce the number of renders in cases where extra rendering can negatively affect performance.
See Also
defaultOptions(rule)
| Name | Type | Description |
|---|---|---|
| device | | |
Device parameters. |
| options |
Options to be applied. |
defaultOptions is a static method that the UI component class supports. The following code demonstrates how to specify default properties for all instances of the Chat UI component in an application executed on the desktop.
jQuery
DevExpress.ui.dxChat.defaultOptions({
device: { deviceType: "desktop" },
options: {
// Here go the Chat properties
}
});Angular
import Chat, { Properties } from "devextreme/ui/chat";
// ...
export class AppComponent {
constructor () {
Chat.defaultOptions<Properties>({
device: { deviceType: "desktop" },
options: {
// Here go the Chat properties
}
});
}
}Vue
<template>
<div>
<DxChat id="chat1" />
<DxChat id="chat2" />
</div>
</template>
<script>
import DxChat from "devextreme-vue/chat";
import Chat from "devextreme/ui/chat";
Chat.defaultOptions({
device: { deviceType: "desktop" },
options: {
// Here go the Chat properties
}
});
export default {
components: {
DxChat
}
}
</script>React
import dxChat from "devextreme/ui/chat";
import Chat from "devextreme-react/chat";
dxChat.defaultOptions({
device: { deviceType: "desktop" },
options: {
// Here go the Chat properties
}
});
export default function App() {
return (
<div>
<Chat id="chat1" />
<Chat id="chat2" />
</div>
)
}You can also set rules for multiple device types:
jQuery
const devicesConfig = [
{ deviceType: 'desktop' },
{ deviceType: 'tablet' },
{ deviceType: 'phone' },
];
devicesConfig.forEach(deviceConfig => {
DevExpress.ui.dxChat.defaultOptions({
device: deviceConfig,
options: {
// Here go the Chat properties
}
});
});Angular
import Chat, { Properties } from "devextreme/ui/chat";
// ...
export class AppComponent {
constructor () {
const devicesConfig = [
{ deviceType: 'desktop' },
{ deviceType: 'tablet' },
{ deviceType: 'phone' },
];
devicesConfig.forEach(deviceConfig => {
Chat.defaultOptions<Properties>({
device: deviceConfig,
options: {
// Here go the Chat properties
}
});
});
}
}Vue
<template>
<div>
<DxChat />
</div>
</template>
<script>
import DxChat from "devextreme-vue/chat";
import Chat from "devextreme/ui/chat";
const devicesConfig = [
{ deviceType: 'desktop' },
{ deviceType: 'tablet' },
{ deviceType: 'phone' },
];
devicesConfig.forEach(deviceConfig => {
Chat.defaultOptions({
device: deviceConfig,
options: {
// Here go the Chat properties
}
});
});
export default {
components: {
DxChat
}
}
</script>React
import dxChat from "devextreme/ui/chat";
import Chat from "devextreme-react/chat";
const devicesConfig = [
{ deviceType: 'desktop' },
{ deviceType: 'tablet' },
{ deviceType: 'phone' },
];
devicesConfig.forEach(deviceConfig => {
dxChat.defaultOptions({
device: deviceConfig,
options: {
// Here go the Chat properties
}
});
});
export default function App() {
return (
<div>
<Chat />
</div>
)
}dispose()
jQuery
After calling this method, remove the DOM element associated with the UI component:
$("#myChat").dxChat("dispose");
$("#myChat").remove();Angular
Use conditional rendering instead of this method:
<dx-chat ...
*ngIf="condition">
</dx-chat>Vue
Use conditional rendering instead of this method:
<template>
<DxChat ...
v-if="condition">
</DxChat>
</template>
<script>
import DxChat from 'devextreme-vue/chat';
export default {
components: {
DxChat
}
}
</script>React
Use conditional rendering instead of this method:
import React from 'react';
import Chat from 'devextreme-react/chat';
function DxChat(props) {
if (!props.shouldRender) {
return null;
}
return (
<Chat ... >
</Chat>
);
}
class App extends React.Component {
render() {
return (
<DxChat shouldRender="condition" />
);
}
}
export default App;endUpdate()
Refreshes the UI component after a call of the beginUpdate() method.
The beginUpdate() and endUpdate() methods reduce the number of renders in cases where extra rendering can negatively affect performance.
See Also
getDataSource()
Gets the DataSource instance.
See Also
getInstance(element)
getInstance is a static method that the UI component class supports. The following code demonstrates how to get the Chat instance found in an element with the myChat ID:
// Modular approach
import Chat from "devextreme/ui/chat";
...
let element = document.getElementById("myChat");
let instance = Chat.getInstance(element) as Chat;
// Non-modular approach
let element = document.getElementById("myChat");
let instance = DevExpress.ui.dxChat.getInstance(element);See Also
on(eventName, eventHandler)
Use this method to subscribe to one of the events listed in the Events section.
See Also
on(events)
Use this method to subscribe to several events with one method call. Available events are listed in the Events section.
See Also
registerKeyHandler(key, handler)
A handler. Accepts the keydown event as the argument. It is a EventObject or a jQuery.Event when you use jQuery.
The key argument accepts one of the following values:
- "backspace"
- "tab"
- "enter"
- "escape"
- "pageUp"
- "pageDown"
- "end"
- "home"
- "leftArrow"
- "upArrow"
- "rightArrow"
- "downArrow"
- "del"
- "space"
- "F"
- "A"
- "asterisk"
- "minus"
A custom handler for a key cancels the default handler for this key.
See Also
renderMessage(message)
jQuery
This method is the primary way to render a new message in jQuery:
$(() => {
const chat = $("#chat").dxChat({
onMessageEntered: (e) => {
e.component.renderMessage(e.message);
},
}).dxChat('instance');
});Angular
Vue
React
repaint()
Renders the component again without reloading data. Use the method to update the component's markup and appearance dynamically.
The repaint() method re-initializes the component with new settings, resetting its state and history.
See Also
- reload() in DataSource | List
- refresh() in DataGrid | TreeList
If you have technical questions, please create a support ticket in the DevExpress Support Center.