开源鸿蒙 Basic Concepts

2022-08-09
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Basic Concepts

The TypeScript-based declarative development paradigm provides a wide array of basic components, which can be combined and extended in a declarative manner to describe the UI of an application. It also provides basic data binding and event processing mechanisms to help you implement the application interaction logic.

HelloWorld Example

// An example of displaying Hello World. After you click the button, Hello UI is displayed.
@Entry
@Component
struct Hello {
    @State myText: string = 'World'
    build() {
        Column() {
            Text('Hello')
                .fontSize(30)
            Text(this.myText)
                .fontSize(32)
            Divider()
            Button() {
                Text('Click me')
                .fontColor(Color.Red)
            }.onClick(() =&gt; {
                this.myText = 'UI'
            })
            .width(500)
            .height(200)
        }
    }
}

Basic Concepts

The preceding sample code shows the structure of a simple page. It involves the following basic concepts:

Decorator: a special kind of declaration that can be applied to classes, structures, methods, and variables. In the sample code, @Entry, @Component, and @State are decorators.
Custom component: a reusable UI unit, which can be combined with other components. In the sample code, struct Hello decorated by @Component is a custom component.
UI description: declaratively describes the UI structure. In the sample code, the block of code in the build() method provides the UI description.
Built-in component: the default basic or layout component preset in the framework. You can directly invoke these components, such as <Column>, <Text>, <Divider>, and <Button> components in the sample code.
Attribute method: a method used to configure component attributes, such as fontSize(), width(), height(), and color().
Event method: a method used to add the component response logic to an event. In the sample code, the onClick method is added for the Button component for defining the click response logic.