不一致的标题栏高度返回

Question

Long story short, I tried to run this particular code

CoreApplicationViewTitleBar coreTitleBar = CoreApplication.GetCurrentView().TitleBar;
coreTitleBar.ExtendViewIntoTitleBar = true;
dragarea.Height = coreTitleBar.Height;
HamBut.Margin = new Thickness(0, dragarea.Height, 0, 0);
Window.Current.SetTitleBar(dragarea);

When I run it on the first time, coreTitleBar.Height returns 32. But, when I tried to re-run it, It returns 0.

Is this supposed to be a bug, or am I doing it wrong?

Currently using Visual Studio 2017 RC.

Answer 1

It depends on when the code is run, and yes UWP isn't very consistent about it.

What the docs don't explicitly mention is that you need to subscribe to the coreTitleBar.LayoutMetricsChanged event and then update the height in the callback. This will account for situations where the size of the title bar changed for some reason.

coreTitleBar.LayoutMetricsChanged += delegate
{
  dragarea.Height = coreTitleBar.Height;
  HamBut.Margin = new Thickness(0, dragarea.Height, 0, 0);
};

And it also eliminates the "but it's zero sometimes" problem.