appBarContrastColor function
计算反差色
Implementation
Color appBarContrastColor(BuildContext context) {
final appBarColor = Theme.of(context).appBarTheme.backgroundColor;
// 计算导航栏颜色的亮度
final appBarBrightness = appBarColor!.computeLuminance() > 0.5
? Brightness.light
: Brightness.dark;
return appBarBrightness == Brightness.light ? Colors.black : Colors.white;
}