Android Weekly Notes #486

2021-11-09 本文已影响0人圣骑士wind

Android Weekly Issue #486

All About Opt-In Annotations

Kotlin中的opt-in机制.

有一些api直接使用, 会有警告, 加上这些标记表明自己是故意为之.

This can guarantee that there has been a conscious decision made about using the API on the use site.

本文示例了:

如何创建.
如何使用.
真实世界中的例子.

还有java, android, api verification.

Measure, measure, measure

如何测量Android的build time.

Jetpack Compose Side-Effects III— rememberUpdatedState

rememberUpdatedState保持一个更新的引用.

@Composable
fun Timer(
    buttonColour: String
) {
    val timerDuration = 5000L
    println("Composing timer with colour : $buttonColour")
    val buttonColorUpdated by rememberUpdatedState(newValue = buttonColour)
    LaunchedEffect(key1 = Unit, block = {
        startTimer(timerDuration) {
            println("Timer ended")
            println("[1] Last pressed button color is $buttonColour")
            println("[2] Last pressed button color is $buttonColorUpdated")
        }
    })
}

如果不用这个rememberUpdatedState, composable的参数变了, 但是launchedeffect不会重新进, 永远是第一次的值.