修改 TextBox 上下文菜单/MenuFlyout

Question

I tried to modify TextBox context menu/MenuFlyout using this code but it doesn't work (the additional menu Items don't appear and myFlyout always null ) (UWP/C#)

        private void Menu_Opening(object sender, object e)
        {
            MenuFlyout myFlyout = sender as MenuFlyout;
            if (myFlyout != null && myFlyout.Target == TextBox)
            {
                MenuFlyoutSubItem searchWith = new MenuFlyoutSubItem();
                searchWith.Icon = new SymbolIcon(Symbol.Find);
                searchWith.Text = "Search With";
                MenuFlyoutItem googles = new MenuFlyoutItem();
                googles.Text = "Google";
                googles.Click += Googles_Click;
                searchWith.Items.Add(googles);
                MenuFlyoutItem bings = new MenuFlyoutItem();
                bings.Text = "Bing";
                bings.Click += Bings_Click;
                searchWith.Items.Add(bings);
                myFlyout.Items.Add(searchWith);
            }
        }

        private async void Googles_Click(object sender, RoutedEventArgs e)
        {
            if (TextBox.SelectedText != null)
            {
                var uri= new Uri(@"https://google.com/search?q=" + TextBox.SelectedText);
                var success = await Launcher.LaunchUriAsync(uri);
            }
        }

        private async void Bings_Click(object sender, RoutedEventArgs e)
        {
            if (TextBox.SelectedText != null)
            {
                var uri = new Uri(@"https://bing.com/search?q=" + TextBox.SelectedText);
                var success = await Launcher.LaunchUriAsync(uri);
            }
        }

        private void TextBox_Loaded(object sender, RoutedEventArgs e)
        {
            TextBox.SelectionFlyout.Opening += Menu_Opening;
            TextBox.ContextFlyout.Opening += Menu_Opening;
        }

        private void TextBox_Unloaded(object sender, RoutedEventArgs e)
        {
            TextBox.SelectionFlyout.Opening -= Menu_Opening;
            TextBox.ContextFlyout.Opening -= Menu_Opening;
        }

<TextBox x:Name="TextBox" Loaded="TextBox_Loaded" Unloaded="TextBox_Unloaded"/>                        

Answer 1

The problem is that you have not give MenuFlyout instance to SelectionFlyout or ContextFlyout . Please refer the following code to add MenuFlyout .

<TextBox x:Name="TextBox" Loaded="TextBox_Loaded" Unloaded="TextBox_Unloaded">
    <TextBox.ContextFlyout>
        <MenuFlyout>
        </MenuFlyout>
    </TextBox.ContextFlyout>
</TextBox>

Update

The default type of SelectionFlyout is TextCommandBarFlyout , and it could not convert to MenuFlyout , if you don't want to replace the default one. you could add TextCommandBarFlyout like the following,

private void Menu_Opening(object sender, object e)
{
    TextCommandBarFlyout myFlyout = sender as TextCommandBarFlyout;

    if (myFlyout != null && myFlyout.Target == TextBox)
    {
        AppBarButton searchCommandBar = new AppBarButton() { Icon = new SymbolIcon(Symbol.Find), Label = "Search With" };
        searchCommandBar.Click += SearchCommandBar_Click;
        myFlyout.PrimaryCommands.Add(searchCommandBar);

    }
}

private void SearchCommandBar_Click(object sender, RoutedEventArgs e)
{

}