Android 模拟器的 Xamarin 按钮单击事件失败

Question

I'm having trouble making Button clicks work using Xamarin Forms for Android. My code is just the blank template with a Button and a Click handler added. I'm using Visual Studio 2019 Enterprise. The iOS and UWP projects are present, but disabled.

I've updated all NuGet packages and Android SDKs and Tools to the latest (Xamarin.Forms v4.4.0.991477). I've tried Android 9.0 API 28 and 6.0 API 23.

A breakpoint set in OnButtonClicked is never hit. MainPage itself seems to load fine; no obvious errors or layout problems. No Exceptions are thrown.

I tried downloading a sample project with similar code and running it unmodified -- same problem.

It's acting as though the mouse click / tap on the emulator is being ignored.

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             Title="Home"
             x:Class="Sched.MainPage">
    <ContentPage.Content>
        <StackLayout>
            <Button Text="Button" Clicked="OnButtonClicked" />
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

using System;
using System.ComponentModel;
using Xamarin.Forms;

namespace Sched
{
    [DesignTimeVisible(false)]
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
        }

        async void OnButtonClicked(object sender, EventArgs e)
        {
            var taskPage = new TaskPage();
            await this.Navigation.PushAsync(taskPage);
        }
    }
}

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             Title="Task"
             x:Class="Sched.TaskPage">
    <ContentPage.Content>
        <StackLayout>
            <Label Text="Welcome to Xamarin.Forms!"
                VerticalOptions="CenterAndExpand" 
                HorizontalOptions="CenterAndExpand" />
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

Answer 1

Problem solved.

The code is fine. The issue was that my primary monitor is 3840 x 2160 px and is normally configured for 150% scaling, using Windows Display Settings. If I set it to 100% scaling, the problem goes away. Equivalently, if I drag the Android emulator window to my secondary monitor, which has 100% scaling, that also works.

Another side-effect of 150% scaling is that it causes the emulator to render as a large solid black box, with the Android screen in the upper-left. With 100% scaling, the black box goes away, leaving only the Android screen.