Android 为什么我在 Jetpack Compose 中被警告可选修饰符参数应该具有默认值修饰符

发布于08月19日

我收到以下带有代码A的警告信息，为什么？

Optional Modifier parameter should have a default value of Modifier个

Code A个

@Composable
fun DisplayIcon(
    modifier: Modifier=Modifier.size(24.dp),
    icon: ImageVector,
    tint: Color = Color.Blue
) {
    Icon(icon, null, modifier = modifier, tint = tint)
}

推荐答案

这只是一种最佳做法.使用其他一些缺省值可能会导致奇怪的情况-假设您想要在一列中使用此组件中的两个:

Column {
    DisplayIcon()
    DisplayIcon()
}

一切都很好，但现在您想要对齐其中之一:

Column {
    DisplayIcon()
    DisplayIcon(modifier = Modifier.align(Alignment.End))
}

And suddenly, with no apparent reason, one has different size than the other. So you have to find out from DisplayIcon implementation what's going on, and then probably add .size(24.dp) to your aligned composable as well. But now you want to change the default size, and you have to do so on many different places...
Something like this might be better solution:

@Composable
fun DisplayIcon(
    modifier: Modifier = Modifier,
    icon: ImageVector,
    tint: Color = Color.Blue,
    size: Dp = 24.dp,
) {
    Icon(icon, null, modifier = modifier.size(size), tint = tint)
}