Added focus button for camera

WindowsPhone/BarcodeScanner/sources/BarcodeScanner/Scanner.xaml

@@ -36,6 +36,13 @@
                 </VideoBrush>
             </Rectangle.Fill>
         </Rectangle>
+        <Button Height="100" Width="100" x:Name="_focusButton"
+                Click="_focusButton_Click" Margin="368,656,12,44"
+                FontSize="18" Background="Black" Foreground="White">
+            <TextBlock Text="Focus"/>
+        </Button>
+        <Border Height="400" Width="240" BorderBrush="Green" BorderThickness="3">
+        </Border>
     </Grid>
  
 

WindowsPhone/BarcodeScanner/sources/BarcodeScanner/Scanner.xaml.cs

@@ -120,6 +120,7 @@ namespace BarcodeScanner
                 return false;
             }
             _timer.Stop();
+            _timer = null;
             _luminance = null;
             _reader = null;
             _photoCamera.Dispose();
@@ -127,5 +128,20 @@ namespace BarcodeScanner
 
             return true;
         }
+
+        private void _focusButton_Click(object sender, RoutedEventArgs e)
+        {
+            if (_photoCamera != null && _photoCamera.IsFocusSupported)
+            {
+                try
+                {
+                    _photoCamera.CancelFocus();
+                    _photoCamera.Focus();
+                }
+                catch
+                {
+                }
+            }
+        }
     }
 }