harmony 鸿蒙\@Extend Decorator: Extension of Built-in Components
\@Extend Decorator: Extension of Built-in Components
Apart from\@Styles used to extend styles, AkrUI also provides \@Extend, which allows you to add a new attribute feature to a built-in component.
NOTE
Since API version 9, this decorator is supported in ArkTS widgets.
Rules of Use
Syntax
@Extend(UIComponentName) function functionName { ... }
Rules of Use
Unlike \@Styles, \@Extend can be defined only globally, that is, outside a component declaration.
Unlike \@Styles, \@Extend can encapsulate private attributes and events of specified components and predefine \@Extend decorated methods of the same component.
// @Extend(Text) supports the private attribute fontColor of the <Text> component.
@Extend(Text) function fancy () {
.fontColor(Color.Red)
}
// superFancyText can call the predefined fancy method.
@Extend(Text) function superFancyText(size:number) {
.fontSize(size)
.fancy()
}
- Unlike \@Styles, \@Extend decorated methods support parameters. You can pass parameters when calling such methods. Regular TypeScript provisions for method parameters apply.
// xxx.ets
@Extend(Text) function fancy (fontSize: number) {
.fontColor(Color.Red)
.fontSize(fontSize)
}
@Entry
@Component
struct FancyUse {
build() {
Row({ space: 10 }) {
Text('Fancy')
.fancy(16)
Text('Fancy')
.fancy(24)
}
}
}
- A function can be passed as a parameter in an \@Extend decorated method to be used as the handler of the event.
@Extend(Text) function makeMeClick(onClick: () => void) {
.backgroundColor(Color.Blue)
.onClick(onClick)
}
@Entry
@Component
struct FancyUse {
@State label: string = 'Hello World';
onClickHandler() {
this.label = 'Hello ArkUI';
}
build() {
Row({ space: 10 }) {
Text(`${this.label}`)
.makeMeClick(this.onClickHandler)
}
}
}
- A state variable can be passed as a parameter in an \@Extend decorated method. When the state variable changes, the UI is updated and re-rendered.
@Extend(Text) function fancy (fontSize: number) {
.fontColor(Color.Red)
.fontSize(fontSize)
}
@Entry
@Component
struct FancyUse {
@State fontSizeValue: number = 20
build() {
Row({ space: 10 }) {
Text('Fancy')
.fancy(this.fontSizeValue)
.onClick(() => {
this.fontSizeValue = 30
})
}
}
}
Application Scenarios
The following example declares three <Text> components. The fontStyle, fontWeight, and backgroundColor styles are set for each <Text> component.
@Entry
@Component
struct FancyUse {
@State label: string = 'Hello World'
build() {
Row({ space: 10 }) {
Text(`${this.label}`)
.fontStyle(FontStyle.Italic)
.fontWeight(100)
.backgroundColor(Color.Blue)
Text(`${this.label}`)
.fontStyle(FontStyle.Italic)
.fontWeight(200)
.backgroundColor(Color.Pink)
Text(`${this.label}`)
.fontStyle(FontStyle.Italic)
.fontWeight(300)
.backgroundColor(Color.Orange)
}.margin('20%')
}
}
\@Extend combines and reuses styles. The following is an example:
@Extend(Text) function fancyText(weightValue: number, color: Color) {
.fontStyle(FontStyle.Italic)
.fontWeight(weightValue)
.backgroundColor(color)
}
With the use of \@Extend, the code readability is enhanced.
@Entry
@Component
struct FancyUse {
@State label: string = 'Hello World'
build() {
Row({ space: 10 }) {
Text(`${this.label}`)
.fancyText(100, Color.Blue)
Text(`${this.label}`)
.fancyText(200, Color.Pink)
Text(`${this.label}`)
.fancyText(300, Color.Orange)
}.margin('20%')
}
}
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