To create the screens displayed by your app, you define the classes that extend
the `Screen` class and implement its [`onGetTemplate`](https://developer.android.com/reference/androidx/car/app/Screen.md.txt#onGetTemplate()) method to return the
[`Template`](https://developer.android.com/reference/androidx/car/app/model/Template.md.txt) instance that represents the state of the UI to display in the
car screen.

This code snippet shows how to declare a `Screen` that uses a
[`PaneTemplate`](https://developer.android.com/reference/androidx/car/app/model/PaneTemplate.md.txt) template to display a "Hello world!" string:


```kotlin
class MyStartScreen(carContext: CarContext) : Screen(carContext) {
    override fun onGetTemplate(): Template {
        val row = Row.Builder().setTitle("Hello world!").build()
        val pane = Pane.Builder().addRow(row).build()
        val header = Header.Builder()
            .setStartHeaderAction(Action.APP_ICON)
            .build()
        return PaneTemplate.Builder(pane)
            .setHeader(header)
            .build()
    }
}
```

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