Develop Reference

How can you store a Control in a class and reuse it in a binding?

I am trying to reuse NumberBoxes for a GridView because having the NumberBoxes embedded directly in the GridView data template causes undesirable behavior, while reusing them does not. The problem is that I keep getting exceptions. They say "No installed components were detected" on the following line (templateRoot.FindName("NumberBox") as GridViewItem).Content = item.NumberBox; in this context
/// <summary>
/// The callback for updating a container in the GridView named CardGridView.
/// </summary>
/// <param name="sender"></param>
/// <param name="args"></param>
private void UpdateGridViewContainer(ListViewBase sender, ContainerContentChangingEventArgs args)
{
if (args.Phase == 1)
{
Grid templateRoot = args.ItemContainer.ContentTemplateRoot as Grid;
CardItem item = args.Item as CardItem;
(templateRoot.FindName("NumberBox") as GridViewItem).Content = item.NumberBox;
TypedEventHandler<NumberBox, NumberBoxValueChangedEventArgs> handler =
(box, args) =>
{
if (!double.IsNaN(args.NewValue))
{
_viewModel.ChangeCount(args, item);
}
};
item.SetHandler(handler);
}
}
The exception is thrown when the Page that contains the GridView is left and renavigated to. I have tried nulling out the NumberBoxes when the page is left, but that did not work. Well, it appeared to before the issue cropped up again.
This is the code that nulls out the NumberBoxes
/// <summary>
/// Creates new NumberBoxes for when this Page is loaded again.
/// </summary>
private void ResetNumberBoxes()
{
foreach (CardItem card in CardGridView.Items.Cast<CardItem>())
{
card.ResetNumberBox();
}
CardGridView.ItemsSource = null;
CardGridView.Items.Clear();
}
ResetNumberBox is just setting the NumberBox to null and assigning a new one.
The exception details
System.Runtime.InteropServices.COMException
HResult=0x800F1000
Message=No installed components were detected. (0x800F1000)
Source=WinRT.Runtime
StackTrace:
at WinRT.ExceptionHelpers.<ThrowExceptionForHR>g__Throw|20_0(Int32 hr)
at ABI.Microsoft.UI.Xaml.Controls.IContentControlMethods.set_Content(IObjectReference _obj, Object value)
An update. I have removed the GridViewItem control from the DataTemplate and tried doing the following with the same result
CardItem item = args.Item as CardItem;
Grid.SetColumn(item.NumberBox, 1);
item.NumberBox.HorizontalAlignment = HorizontalAlignment.Center;
item.NumberBox.VerticalAlignment = VerticalAlignment.Center;
(templateRoot.FindName("GridViewTemplate") as Grid).Children.Add(item.NumberBox);
I also examined a heap dump right before the line that throws, and there was only one instance of the Grid, and the NumberBox had a parent of null.

Animate (smoothly) ScrollViewer programmatically

Is there a way to smoothly animate a ScrollViewers vertical offset in Windows Phone 8.1 Runtime?
I have tried using the ScrollViewer.ChangeView() method and the change of vertical offset is not animated no matter if I set the disableAnimation parameter to true or false.
For example: myScrollViewer.ChangeView(null, myScrollViewer.VerticalOffset + p, null, false);
The offset is changed without animation.
I also tried using a vertical offset mediator:
/// <summary>
/// Mediator that forwards Offset property changes on to a ScrollViewer
/// instance to enable the animation of Horizontal/VerticalOffset.
/// </summary>
public sealed class ScrollViewerOffsetMediator : FrameworkElement
{
/// <summary>
/// ScrollViewer instance to forward Offset changes on to.
/// </summary>
public ScrollViewer ScrollViewer
{
get { return (ScrollViewer)GetValue(ScrollViewerProperty); }
set { SetValue(ScrollViewerProperty, value); }
}
public static readonly DependencyProperty ScrollViewerProperty =
DependencyProperty.Register("ScrollViewer",
typeof(ScrollViewer),
typeof(ScrollViewerOffsetMediator),
new PropertyMetadata(null, OnScrollViewerChanged));
private static void OnScrollViewerChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
var mediator = (ScrollViewerOffsetMediator)o;
var scrollViewer = (ScrollViewer)(e.NewValue);
if (null != scrollViewer)
{
scrollViewer.ScrollToVerticalOffset(mediator.VerticalOffset);
}
}
/// <summary>
/// VerticalOffset property to forward to the ScrollViewer.
/// </summary>
public double VerticalOffset
{
get { return (double)GetValue(VerticalOffsetProperty); }
set { SetValue(VerticalOffsetProperty, value); }
}
public static readonly DependencyProperty VerticalOffsetProperty =
DependencyProperty.Register("VerticalOffset",
typeof(double),
typeof(ScrollViewerOffsetMediator),
new PropertyMetadata(0.0, OnVerticalOffsetChanged));
public static void OnVerticalOffsetChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
var mediator = (ScrollViewerOffsetMediator)o;
if (null != mediator.ScrollViewer)
{
mediator.ScrollViewer.ScrollToVerticalOffset((double)(e.NewValue));
}
}
/// <summary>
/// Multiplier for ScrollableHeight property to forward to the ScrollViewer.
/// </summary>
/// <remarks>
/// 0.0 means "scrolled to top"; 1.0 means "scrolled to bottom".
/// </remarks>
public double ScrollableHeightMultiplier
{
get { return (double)GetValue(ScrollableHeightMultiplierProperty); }
set { SetValue(ScrollableHeightMultiplierProperty, value); }
}
public static readonly DependencyProperty ScrollableHeightMultiplierProperty =
DependencyProperty.Register("ScrollableHeightMultiplier",
typeof(double),
typeof(ScrollViewerOffsetMediator),
new PropertyMetadata(0.0, OnScrollableHeightMultiplierChanged));
public static void OnScrollableHeightMultiplierChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
var mediator = (ScrollViewerOffsetMediator)o;
var scrollViewer = mediator.ScrollViewer;
if (null != scrollViewer)
{
scrollViewer.ScrollToVerticalOffset((double)(e.NewValue) * scrollViewer.ScrollableHeight);
}
}
}
and I can animate the VerticalOffset property with DoubleAnimation:
Storyboard sb = new Storyboard();
DoubleAnimation da = new DoubleAnimation();
da.EnableDependentAnimation = true;
da.From = Mediator.ScrollViewer.VerticalOffset;
da.To = da.From + p;
da.Duration = new Duration(TimeSpan.FromMilliseconds(300));
da.EasingFunction = new ExponentialEase() { EasingMode = EasingMode.EaseOut };
Storyboard.SetTarget(da, Mediator);
Storyboard.SetTargetProperty(da, "(Mediator.VerticalOffset)");
sb.Children.Add(da);
sb.Begin();
Mediator is declared in XAML.
But this animation is not smooth on my device (Lumia 930).

You should stick with ChangeView for scrolling animations regardless of whether data virtualization is on or not.
Without seeing your code where the ChangeView doesn't work, it's a bit hard to guess what's really going on but there are a couple of things that you can try.
First approach is to add a Task.Delay(1) before calling ChangeView, just to give the OS some time to finish off other concurrent UI tasks.
await Task.Delay(1);
scrollViewer.ChangeView(null, scrollViewer.ScrollableHeight, null, false);
The second approach is a bit more complex. What I've noticed is that, when you have many complex items in the ListView, the scrolling animation from the first item to the last (from the ChangeView method) isn't very smooth at all.
This is because the ListView first needs to realize/render many items along the way due to data virtualization and then does the animated scrolling. Not very efficient IMHO.
What I came up with is this - First, use a non-animated ListView.ScrollIntoView to scroll to the last item just to get it realized. Then, call ChangeView to move the offset up to a size of the ActualHeight * 2 of the ListView with animation disabled (you can change it to whatever size you want based on your app's scrolling experience). Finally, call ChangeView again to scroll back to the end, with animation this time. Doing this will give a much better scrolling experience 'cause the scrolling distance is just the ActualHeight of the ListView.
Keep in mind that when the item you want to scroll to is already realized on the UI, you don't want to do anything above. You simply just calculate the distance between this item and the top of the ScrollViewer and call ChangeView to scroll to it.
I already wrapped the logic above in this answer's Update 2 section (thanks to this question I realized my initial answer doesn't work when virtualization is on :p). Let me know how you go.

I think that question has already been answered here:
Animated (Smooth) scrolling on ScrollViewer
There is also the WinRT XAML Toolki, which provides "a way to scroll a ScrollViewer to specified offset with animation":
http://winrtxamltoolkit.codeplex.com/

With ScrollToVerticalOffset deprecated/obsolete in newer builds of Windows 10 (leaving the ScrollViewOffSetMediator extension control no longer working), and the new ChangeView method not actually providing smooth or controllable animation, a new solution is needed. Please see my answer here which allows one to smoothly animate and zoom the ScrollViewer and its contents to any desired position, regardless of where the application's end user has the scrollbars initially positioned:
How to scroll to element in UWP

I believe this article is what you're looking for and it seems the method he used is working for you.
Quick Way:
Add offset dependency parameter manually to scrollviewer.
Duplicate your scrollviewer
Use an animator.

How to disallow interaction on a view behind uipopovercontroller

I have a UIPopoverController that I am using and I have two buttons each displays a popup when clicked. However, I do not want the popup to be displayed at the same time - meaning I do not want the user to be able to press the one button and while the popup is displayed be able to press the other button. It seems like I have tried everything - disabling the user interaction on the buttons, hiding the view behind the pop up, using passthrough views for the pop and more. None of it works! The disabling of the user interaction seems to work for the most part but then stops disallowing the user to interact with the button and causes the application to crash...
popupView.PassthroughViews = new UIView[]{this.View.Superview, this.View, this.Gray}; //gray is another view that sits under the view that calls the popup
this.View.UserInteractionEnabled = false;
this.PositiveMeterBtn.UserInteractionEnabled = false;
this.View.Hidden = true;
My UIPopoverController is declared at the class level and I have even done code like this:
if(popupView != null)
return;
I still get multiple popups. I am using mono touch/xamarin - is this a bug with xamarin or an ios issue? Am I handling this in the correct manner?

I haven't worked with Xamarin before, but what's worked for me in native Objective-C is
[controller setModalInPopover:YES];
where controller is the view controller displayed within the popover.
From the UIViewController class reference:
#property(nonatomic, readwrite, getter=isModalInPopover) BOOL modalInPopover
The default value of this property is NO. Setting it to YES causes an owning popover controller to disallow interactions outside this view controller while it is displayed.

You can either make the popover modal but if it doesn't contain content that is meant to be modal, you shouldn't block the user.
Usually the better option is to make two helper methods and place them for instance in your app delegate. The methods take care that an existing popover is dismissed if another one is to be shown. This way you will have a maximum of on UIPopoverController and don't have to worry about dismissal.
/// <summary>
/// Shows a popover.
/// </summary>
/// <param name='controllerToShow'>the controller to show in the popover</param>
/// <param name='showFromRect'>the rectangle to present the popover from. Not used if showFromItem is specified.</param>
/// <param name='showInView'>the view the popover is hosted in</param>
/// <param name='showFromItem'>the bar button item the popover gets presented from.</param>
/// <param name='popoverContentSize'>the content size of the popover</param>
/// <param name='animated'>If set to <c>true</c>, animated the popover</param>
/// <param name='arrowDirection'>the allowed arrow directions</param>
/// <param name='onDismiss'>callback if the popover gets dismissed. Careful that the object that owns the callback doesn't outlive the popover controller to prevent uncollectable memory.</param>
public static void ShowPopover(UIViewController controllerToShow, RectangleF showFromRect, UIView showInView, UIBarButtonItem showFromItem, SizeF popoverContentSize, bool animated = true, UIPopoverArrowDirection arrowDirection = UIPopoverArrowDirection.Any, EventHandler onDismiss = null)
{
if(AppDelegateBase.popoverController != null)
{
AppDelegateBase.DismissPopover(false);
}
if(showFromItem == null && showFromRect.IsEmpty)
{
// Nothing to attach the popover to.
return;
}
popoverController = new UIPopoverController(controllerToShow);
if(!popoverContentSize.IsEmpty)
{
popoverController.SetPopoverContentSize(popoverContentSize, false);
}
if(onDismiss != null)
{
popoverController.DidDismiss += onDismiss;
}
// Send a notification that a popover will be presented.
NSNotificationCenter.DefaultCenter.PostNotificationName("WillPresentPopover", popoverController);
if(showFromItem != null)
{
popoverController.PresentFromBarButtonItem(showFromItem, arrowDirection, animated);
}
else
{
popoverController.PresentFromRect(showFromRect, showInView, arrowDirection, animated );
}
}
/// <summary>
/// Dismisses the popover presented using ShowPopover().
/// </summary>
/// <param name='animated'>If set to <c>true</c>, animates the dismissal</param>
public static void DismissPopover(bool animated = false)
{
if(popoverController != null)
{
popoverController.Dismiss(animated);
}
AppDelegateBase.popoverController = null;
}
private static UIPopoverController popoverController;

One thing you might try is using the method
-(BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender
And in that method check if one of your popover view controller's is on screen.
if (popupView.view.window) {
return NO;
} else {
return YES;
}

Change background of the thumb of Trackbar

Is any way to change the background of the thumb of Trackbar? I use C# winform.
Only the background of the Trackbar can be changed, so how can I change or set something in the thumb?
Any answer appreciated.

I saw the project:
http://www.codeproject.com/Articles/7974/A-variation-on-the-default-TrackBar
And add the Picture of it to let user choose:
/// <summary>
/// Set Image of Trackbar's thumb
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
[Description("Set the picture of the thumb")]
[Category("Image")]
public Image Picture
{
set
{
myPic = value;
}
get { return myPic; }
}
And use TextureBrush to let the picture People shoose be an ImageBrush:
TextureBrush newBrush = new TextureBrush(myPic);
if (myPic != null)
{
g.FillRegion(newBrush, new Region(PaintPath));
newBrush.Dispose();
}
else
{
g.FillRegion(bgBrush, new Region(PaintPath));
bgBrush.Dispose();
}
There is only one problem that the imagebrush is tile style,
if I let it not a tile style, it may resolve my questrion.

How to localize DatePicker and TimePicker in WP8

I am attempting to localize the DatePicker and TimePicker associated with the toolkit on WP7, but I am unsure of how to access the Header and the application bar texts. I have not been able to find any links showing methods of accomplishing these tasks. Are there any useful links or does someone have the source of how this many be accomplished?

Easiest method to download Source and Samples of the latest version of the Toolkit (Nov 2011) which has by default localization for DatePicker and TimePicker.
Add the it as project reference to your solution.
If you have the Toolkit version prior to Nov 2011,
Again add it as Project Reference in your Solution
In side the project tookit in your solution. Add the necessary resx files. You can see there is a default Resources.resx file which has the English text for date pickers. Add the necessary resx files for other languages.

It's very simple: Parameter - Language. Xaml code:
<toolkit:DatePicker Language="ru-RU" Margin="-12, 0" Value="{Binding BirthDate, Mode=TwoWay}" />

Another alternative without modifying the XAML source is to modify the "HeaderTitle" TextBlock once the page loads.
/// <summary>
/// Called from app.xaml.cs if the user navigates to the DatePickerPage
/// </summary>
/// <param name="page">The page.</param>
public static void DatePickerHook(PhoneApplicationPage page)
{
// Somehow modify the text on the top of the page...
LoopThroughControls(page, (ui => {
var tb = ui as TextBlock;
if (tb != null && tb.Name == "HeaderTitle")
{
tb.Text = "<<Local Translation>>";
}
}));
}
/// <summary>
/// Applies an action to every element on a page
/// </summary>
/// <param name="parent">The parent.</param>
/// <param name="modifier">The modifier.</param>
private static void LoopThroughControls(UIElement parent, Action<UIElement> modifier)
{
int count = VisualTreeHelper.GetChildrenCount(parent);
if (count > 0)
{
for (int i = 0; i < count; i++)
{
UIElement child = (UIElement)VisualTreeHelper.GetChild(parent, i);
modifier(child);
LoopThroughControls(child, modifier);
}
}
return;
}
Here's the link to the blog post that describes the modifications to app.xaml.cs also: http://blog.dotnetframework.org/2015/11/09/localise-datepicker-in-wp8-silverlighttoolkit-using-hooks/