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WP7 Tip: Changing the background of a control based on the theme

Following a thread appeared on forum for the development in Microsoft Windows phone I will return an implementation of a converter that allows you to change the background of a control in XAML based on the active theme.

Getting Started "steal" the tip of the evil genius on the way to determine the active theme (link ) and convert it to VB.NET. In particular, we create a shared method (but should be a property shared well) in our application class App:

1. Public Shared Function GetCurrentTheme() As Theme
2.      Dim bgc = App.Current.Resources( "PhoneBackgroundColor" ).ToString()
3.      If bgc = "#FF000000" Then
4.          Return Theme .Dark
5. Else
6. Return Theme .
Light
7. End If End
8. Function

Theme enumeration is defined as follows:

1. Public Enum Theme
2. Dark
3. Light
4. End Enum

At this point we can create our conveter:

1. Imports System.Windows.Data
2. Imports System.Windows.Media
4. Public Class ThemeColorConverter
5. Implements IValueConverter
7. Private Function GetColorFromName( ByVal strColor As String ) As Color ?
8.          Dim retColor As Color ? = Nothing
9.          Try
10.              Dim propColor = GetType ( Colors ).GetProperty(strColor)
11.              If propColor IsNot Nothing Then
12.                  Dim value = propColor .GetValue( Nothing , Nothing )
13.                  If value IsNot Nothing Then
14.                     retColor = CType (value, Color )
15.                  End If
16.              End If
17.          Catch ex As Exception
18.             retColor = Nothing
19.          End Try
20.          Return retColor
21.      End Function
22.  
23.      Private Function GetColorFromRGB( ByVal strColor As String ) As Color ?
24.          Dim retColor As Color ? = Nothing
25.         strColor = strColor .Replace( "#" , "" )
26.          Dim a As Byte = 255
27.          Dim r As Byte = 255
28.          Dim g As Byte = 255
29.          Dim b As Byte = 255
30.          Dim start = 0
31.          If strColor .Length = 6 Or strColor .Length = 8 Then
32.              If strColor .Length = 8 Then
33.                 a = Byte .Parse( strColor .Substring(0, 2), System.Globalization. NumberStyles .HexNumber)
34.                 start = 2
35.              End If
36.             r = Byte .Parse( strColor .Substring(start, 2), System.Globalization. NumberStyles .HexNumber)
37.             g Bytes = . Parse ( strColor . Substring (start + 2, 2), System.Globalization. NumberStyles . HexNumber)
38. & # 160; b = Byte . Parse ( strColor . Substring (start + 4, 2) , System.Globalization. NumberStyles . HexNumber)
39. & # 160; retColor = Color .FromArgb(a, r, g, b)
40.          End If
41.          Return retColor
42.      End Function
43.  
44.      Private Function GetColor( ByVal strColor As String ) As Color
45.          Dim retColor As Color
46.  
47.          Dim tmpColor = GetColorFromName(strColor)
48.          If Not tmpColor .HasValue Then
49.             tmpColor = GetColorFromRGB(strColor)
50.              If tmpColor .HasValue Then
51.                 retColor = tmpColor .Value
52.              End If
53.          Else
54.             retColor = tmpColor .Value
55.          End If
56.  
57.          Return retColor
58.      End Function
59.  
60.      Public Function Convert( ByVal value As Object ,
61.                              ByVal targetType As System. Type ,
62.                              ByVal parameter As Object ,
63.                              ByVal culture As System.Globalization. CultureInfo ) As Object Implements System.Windows.Data. IValueConverter .Convert
64.          If value IsNot Nothing Then
65.              Dim brush As SolidColorBrush = Nothing
66. ,.. Dim values \u200b\u200b= value ToString () Split ( " If
67. App .GetCurrentTheme() = Theme .Light Then
68.                     brush = New SolidColorBrush (GetColor(values(0)))                  Else
69.                     brush = New SolidColorBrush
(GetColor(values(1)))
70.                  End
71. If              End
72. If              Return
brush
73.          Else
            
74. Return Nothing
75.          End
76. If      End
77. Function  
    
78. Public Function ConvertBack( ByVal
value
79. As
80. Object ,                                  ByVal targetType As System. Type ,
                                
81. ByVal parameter As Object ,
                                
82. ByVal culture As System.Globalization. CultureInfo ) As
83. Object Implements System.Windows.Data. IValueConverter .ConvertBack          Throw New NotImplementedException ()
    
84. End Function End
85. Class
86. La funzione GetColor ci consente di obtain a Color object from a string in the following formats AARRGGBB #, # RRGGBB or "color name" (as that may be one of the possible colors of the class Colors ).
The Convert method of our converter retrieves the argument value, which by convention should be a string with the following format:

light color theme can be used directly in binding within the XAML.

To do this you simply reference the appropriate namespace:

xmlns:

my = "clr-namespace: WP7ThemeBackground"

Insert the converter into the resources of 'application or page
1. \u0026lt; phone

:

PhoneApplicationPage.Resources

>

1. \u0026lt; my : ThemeColorConverter x :
2. Key = "TCC"> \u0026lt;/ my : ThemeColorConverter > \u0026lt;/ phone : PhoneApplicationPage.Resources >
3. And finally, put the drive in with the background binding of control desired: \u0026lt; Grid

x

:

Name = "LayoutRoot"

1. Background = "{Binding Converter = { StaticResource TCC} , Source = Red \u0026lt; phone : phone application page x

:

Class

= "WP7ThemeBackground.MainPage"

xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation"

1. ; xmlns: x = "http://schemas.microsoft.com/winfx/2006/xaml"
2. xmlns: phone = "clr-namespace: Microsoft.Phone.Controls; Microsoft.Phone assembly ="
3. ; xmlns:
4. shell = "clr-namespace: Microsoft.Phone.Shell; Microsoft.Phone assembly =" & # 160; xmlns:
5. d = "http://schemas.microsoft.com/expression/blend/2008"     xmlns :
6. mc ="http://schemas.openxmlformats.org/markup-compatibility/2006"     xmlns :
7. my ="clr-namespace:WP7ThemeBackground"     mc :
8. Ignorable ="d" d : DesignWidth
9. ="480" d : design height = "768"
10. FontFamily = "{ StaticResource phone FontFamily normal} " font size = "{ StaticResource phone font size normal} "
11. Foreground = "{ StaticResource PhoneForegroundBrush} "
   
12. SupportedOrientations ="Portrait" Orientation ="Portrait"     shell
13. : SystemTray.IsVisible ="True" >      <
14. phone : PhoneApplicationPage.Resources >
        
15. < my : ThemeColorConverter
16. x : Key ="TCC"></ my : ThemeColorConverter
17. >      </ phone : PhoneApplicationPage.Resources >      <!--LayoutRoot is the root grid where all page content is placed-->      <
18. Grid x : Name ="LayoutRoot" Background ="{
19. Binding Converter ={
20. StaticResource TCC} , Source =Red AA00FF00} "> \u0026lt; Grid. RowDefinitions > & # 160; \u0026lt; RowDefinition Height = "Auto" />
<
21. RowDefinition Height ="*"/>         
22. </ Grid.RowDefinitions >           
23. <!--TitlePanel contains the name of the application and page title--> \u0026lt; StackPanel
x
24. : Name = "title panel" Grid.Row
= "0"
Margin
26. = "12,17,0,28> & # 160;
27. \u0026lt; TextBlock x : Name = "application title" text = "My Application" Style = "{ StaticResource
phone text normal style}
28. "/> & # 160; \u0026lt; TextBlock x : name = "page title" text = "pagename" Margin = "9, -7,0,0"
Style = "{
29. StaticResource PhoneTextTitle1Style } "/> \u0026lt;/ StackPanel > \u0026lt;- content panel - place additional content here -> \u0026lt; Grid
x
30. : Name = "content panel" Grid.Row
= "1"
Margin
32. = "12,0,12,0"> \u0026lt;/
Grid>
33. \u0026lt;/ Grid> \u0026lt;/ phone: PhoneApplicationPage >
34. Tag on Technorati: IValueConverter ,
WP7
35. , binding , phone windows 7 , background , solidbrush , color, colors