1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
using System;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
namespace Xamarin.Forms.Platform.UWP
{
public class FormsCommandBar : CommandBar
{
// TODO Once 10.0.14393.0 is available (and we don't have to support lower versions), enable dynamic overflow: https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.controls.commandbar.isdynamicoverflowenabled.aspx
Windows.UI.Xaml.Controls.Button _moreButton;
public FormsCommandBar()
{
PrimaryCommands.VectorChanged += OnCommandsChanged;
SecondaryCommands.VectorChanged += OnCommandsChanged;
UpdateVisibility();
WatchForContentChanges();
}
protected override void OnApplyTemplate()
{
base.OnApplyTemplate();
_moreButton = GetTemplateChild("MoreButton") as Windows.UI.Xaml.Controls.Button;
}
void OnCommandsChanged(IObservableVector<ICommandBarElement> sender, IVectorChangedEventArgs args)
{
UpdateVisibility();
}
void UpdateVisibility()
{
var visibility = PrimaryCommands.Count + SecondaryCommands.Count > 0 ? Visibility.Visible : Visibility.Collapsed;
if (_moreButton != null)
{
// The "..." button should only be visible if we have commands to display
_moreButton.Visibility = visibility;
// There *is* an OverflowButtonVisibility property that does more or less the same thing,
// but it became available in 10.0.14393.0 and we have to support 10.0.10240
}
// If we have a title (or some other content) inside this command bar
// and that content is not collapsed
var frameworkElement = Content as FrameworkElement;
// Temporarily tie the visibility of the toolbar to the visibility of the Title
// to be consistent with the old style / other platforms
if (frameworkElement != null && frameworkElement.Visibility == Visibility.Collapsed)
{
Visibility = Visibility.Collapsed;
return;
}
if (frameworkElement != null && frameworkElement.Visibility != Visibility.Collapsed)
{
Visibility = Visibility.Visible;
}
else
{
// Otherwise, collapse it if there are no commands
Visibility = visibility;
}
}
void WatchForContentChanges()
{
// If the content of the command bar changes while it's collapsed, we need to
// react and update the visibility (e.g., if the bar is placed at the bottom and
// has no commands, then is moved to the top and now includes the title)
// There's no event on CommandBar when the content changes, so we'll bind our own
// dependency property to Content and update our visibility when it changes
var binding = new Windows.UI.Xaml.Data.Binding
{
Source = this,
Path = new PropertyPath(nameof(Content)),
Mode = Windows.UI.Xaml.Data.BindingMode.OneWay
};
BindingOperations.SetBinding(this, s_contentChangeWatcher, binding);
}
static readonly DependencyProperty s_contentChangeWatcher =
DependencyProperty.Register(
"ContentChangeWatcher",
typeof(object),
typeof(object),
new PropertyMetadata(null, ContentChanged));
static void ContentChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
(d as FormsCommandBar)?.UpdateVisibility();
}
}
}
|
