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GridView doesn't scroll down to virtualized items

In my application, I need to select the newly created document(note) when I go back to library. After library item is selected, the Library must be scrolled to the selected item.
My library's OnLoaded method:
private async void OnLoaded(object sender, RoutedEventArgs e)
{
await this.ViewModel.InitializeAsync();
// CollectionViewSource of my GridView being filled
ViewModel.CollectionChanging = true;
GroupInfoCVS.Source = ViewModel.GroupsCollection;
ViewModel.CollectionChanging = false;
// Loading Last selected item - THIS CHANGES SELECTION
ViewModel.LoadLastSelection();
}
After I call the LoadLastSelection method, selection is changed successfuly (I've tested). This is the method that is called after that (in our GridView's extended control):
private void OnSelectionChanged(object sender, SelectionChangedEventArgs e)
{
this.SelectedItemsCount = this.SelectedItems.Count;
var newlySelectedItems = e.AddedItems;
if (newlySelectedItems.Any())
{
var item = newlySelectedItems.Last();
ScrollTo(item);
}
}
private void ScrollTo(object item)
{
UpdateLayout();
var itemUI = (FrameworkElement)this.ContainerFromItem(item);
if (itemUI != null)
{
_scrollViewer.UpdateLayout();
_scrollViewer.ChangeView(null, itemUI.ActualOffset.Y - itemUI.ActualHeight, null, false);
}
}
This also works for the most part. When itemUI is not null, the method scrolls successfully to the required item. The problems start when the items start to overflow the screen size. When items are completely hidden from the screen, they are virtualized. That means that ContainerFromItem returns null, so I can't take the offset properties. Keep in mind that this actually occurs before Library's OnLoaded method is finished.
Please, help me with some alternative to get such properties or other methods of scrolling, which will help me scroll successfully.
I've read a lot and tried using Dispatcher.RunAsync and ScrollIntoView methods, but I couldn't manage to produce any scrolling behavior. If you point me how to use them successfully, that would be a nice help too.
Here's what I've read (and tried):
ItemContainerGenerator.ContainerFromItem() returns null?
How to Know When a FrameworkElement Has Been Totally Rendered?
Is there a "All Children loaded" event in WPF
Let ListView scroll to selected item
Thanks in advance!
IMPORTANT: If you don't want to read all the conversation within the official answer, please read the solution in short here:
TemplatedControl's style had changed ScrollViewer's name from "ScrollViewer" to "LibraryScrollViewer" and that rendered ScrollIntoView method useless.

For GridView, the best way to achieve your needs is to call GridView.ScrollIntoView.
But you seem to have made similar attempts, and it does not to be successful, then the following points may help you:
1. Don't use GridView as a child element of ScrollViewer.
In your code, I see that you are calling the method of ScrollViewer.ChangeView to adjust the view scrolling, so it is speculated that you may put the GridView in the ScrollViewer, which is not recommended.
Because there is a ScrollViewer inside the GridView, and its ScrollIntoView method is to change the scroll area of the internal ScrollViewer. When there is a ScrollViewer outside, the ScrollViewer inside the GridView will lose the scrolling ability, thus making the ScrollIntoView method invalid.
2. Implement the Equals method of the data class.
If your data class is not a simple type (such as String, Int32, etc.), then implementing the Equals method of the data class will help the GridView to find the corresponding item.
Thanks.

WinForms : Dynamically add / remove AnchorStyles to / of control

I am currently working on a Editor, which lets the user design his own WinForm overlay, at least to a certain point.
Therefore I want the user to decide, which AnchorStyles the current selected Control should have. I would like it to be handled by checkboxes. Here's how I had it in mind:
As you can see, the user has currently selected a dynamically added Panel, called Grid. Handled by the CheckBoxes to the right, he should now be able to set the selected Controls AnchorStyles.
Here's my problem: I can't seem to find a usable solution, to dynamically add a specific AnchorStyle to the already existing ones, or the opposite, remove the AnchorStyle, but keep the other ones as they are.
I was trying to get it to work with...
SelectedControl.Anchor += AnchorStyles.Top;
which doesen't work at all. So i thought of this...
SelectedControl.Anchor = SelectedControl.Anchor | AnchorStyles.Top
which I imagine could work, but I haven't even tested it, since I wouldn't know how to remove ones unchecked AnchorStyle.
Building a gigantic if(){} else if(){}... doesen't seem to be a good Idea :)
I'm open for any ideas / solutions.
Thanks in advance!

Assuming you have four check box controls named top, bottom, left and right, you can handle CheckedChange event of them using a single method and set the anchor of the desired control based on the checked value of the controls. For example:
private void checkBox_CheckedChanged(object sender, EventArgs e)
{
var values = new[] { top.Checked, bottom.Checked, left.Checked, right.Checked };
byte[] data = new byte[1];
new BitArray(values).CopyTo(data, 0);
selectedControl.Anchor = (AnchorStyles)data[0];
}
Note: AnchorStyles is a flag enum having top=1, bottom=2, left=4 and right=8. Using above code I've mixed those flags to create the AnchorStyles and have assigned to the Anchor property of control.

UWP CustomRenderer for Checkbox: Pointer over Checkbox changes style?

I'm working with Xamarin.Forms and I made a CustomRenderer for Checkbox in UWP. When I set all the Checkboxes of my items in the ListView to true by clicking the button "Alle", the Checkboxes are displayed correctly with the check inside the box:
However, if I hover my mouse over the Checkboxes, they immediately change their appearence (the check disappears but it's still selected). In the following screenshot, I moved my cursor over the 3rd - 7th Checkboxes:
This is my overridden OnElementChanged method in the CustomRenderer:
protected override void OnElementChanged(ElementChangedEventArgs<EvaCheckbox> e)
{
base.OnElementChanged(e);
var model = e.NewElement;
if (model == null)
{
return;
}
nativeCheckbox = new CheckBox();
CheckboxPropertyChanged(model, null);
model.PropertyChanged += OnElementPropertyChanged;
nativeCheckbox.Checked += (object sender, Windows.UI.Xaml.RoutedEventArgs eargs) =>
{
model.IsChecked = (bool)nativeCheckbox.IsChecked;
};
nativeCheckbox.Unchecked += (object sender, Windows.UI.Xaml.RoutedEventArgs eargs) =>
{
model.IsChecked = (bool)nativeCheckbox.IsChecked;
};
SetNativeControl(nativeCheckbox);
}
I tried to override the PointerEntered event of nativeCheckbox. It works, for example if I set the model.IsChecked to true on this event, it will be set to true:
nativeCheckbox.PointerEntered += (s, args) =>
{
model.IsChecked = true;
};
But I don't know how to (if even at this place) prevent the checkbox from changing it's appearance when moving the cursor above the Checkbox. Just leaving the triggered event with empty code like this won't change anything about the described behaviour:
nativeCheckbox.PointerEntered += (s, args) => { };
How can I prevent the Checkbox from changing it's appearance when I move my cursor over it?
Update:
I've created a sample project for this issue. You can find the repository here: https://github.com/Zure1/CustomCheckbox
It has the exact same described behavior. In the following screenshot I pressed the button "All" on the bottom of the screen and then the checkboxes look like correct with a check inside of them:
After moving the mouse cursor over the bottom 3 checkboxes, their change their appearance:
Information: I'm debugging on my desktop (Windows 10). I don't know if this issue exists on WinPhone. Just in case you're wondering why my checkboxes are red: My system color in Windows is red.

This is a tricky one as I have been struggling with this issue for a while, I'll try my best to answer this.
TL;DR: It's caused by ViewCell.
The issue comes down to Xamarin Forms ListView and ViewCell.
I haven't been able to track down the cause yet for many months and the way I get around this issue is by refreshing the ListView every time a change happens forcing a redraw of the entire ListView which can really impact performance.
My educated guess on what the cause could be is the rendering code for the ViewCell is missing something.
As for your particular issue, I have created a CheckBoxCell which you can use to display a list of checkboxes with a title. I forked your project and made the changes.
This will display something similar to what you are trying to achieve and doesn't have rendering issues so will be a good starting point. You are able to customize this to display images and the like but you'll have to do that in the platform-specific layout code.
Please note that I have only created the code for UWP and that should be enough to get you going for the other platforms.
I hope this helps somewhat.

LayoutParams change only takes effect in fullscreen

im using Xamarin with MvvmCross.
Ive done a FragmentDialog with a recyclerView inside, the list is populated via bindings on xml file, so i have no adapter and i should keep it this way.
If im not wrong, theres no built in way to make the recyclerView take only the size needed for its content, this should not be a problem, but in this case i need the list to start from bottom...
So i did this (its a custom fullscreen dialog) :
MvxRecyclerView list = Dialog.FindViewById<MvxRecyclerView>(Resource.Id.recyclerview);
list.LayoutChange += List_LayoutChange;
Then in layoutChange
private void List_LayoutChange(object sender, View.LayoutChangeEventArgs e)
{
MvxRecyclerView list = Dialog.FindViewById<MvxRecyclerView>(Resource.Id.recyclerview);
int itemHeight = list.GetChildAt(0).Height;
if (itemHeight != 0)
{
ViewGroup.LayoutParams prms = list.LayoutParameters;
prms.Height = itemHeight * list.GetAdapter().ItemCount;
list.LayoutParameters = prms;
list.LayoutChange -= List_LayoutChange;
list.RequestLayout();
}
}
That was working fine, the list get exactly the height needed and the list looks like it starts from bottom.
Now the client tell me that he doesnt like the fullscreen dialog and wants the status bar, i think that should be easy, just to remove this line at the dialog creation right?
dialog.Window.AddFlags(WindowManagerFlags.Fullscreen);
But looks like its not that easy, when the dialog its not fullscreen the layoutParams change seems to have no effect, it just dont do nothing.
My method is being called and i get the right item height, it just dont change the recyclerview height.
Notice that setting fullscreen at creation and clearing the flag after the recyclerview params change works
So looks like it only works during fullscreen mode.
Can someone throw some light at this?
Thanks in advance.

As you said, RecyclerView was not aware of its size.
Since last update to the support lib, it is !
http://android-developers.blogspot.fr/2016/02/android-support-library-232.html
The RecyclerView widget provides an advanced and flexible base for creating lists and grids as well as supporting animations. This release brings an exciting new feature to the LayoutManager API: auto-measurement! This allows a RecyclerView to size itself based on the size of its contents. This means that previously unavailable scenarios, such as using WRAP_CONTENT for a dimension of the RecyclerView, are now possible. You’ll find all built in LayoutManagers now support auto-measurement.
I would suggest to wait for the Xamarin wrapped lib (there is already a beta https://www.nuget.org/packages/Xamarin.Android.Support.v4/23.2.0-beta1)

How to hide textboxes, labels and buttons C# WPF

I would like to hide several textboxes, a label and a button as soon as a button is clicked... however, for some reason, my code doesn't seem to cause this effect. Nothing appears to happen. I'm using WPF.
Here is my code:
private void doSomething_Click(object sender, RoutedEventArgs e)
{
Name.Visibility = Visibility.Hidden;
}
This code doesn't seem to work.. any ideas?

I believe Visibility.Collapsed is what you need and not Visibility.Hidden.
EDIT: Did you try follow up this code with UpdateLayout() method of parent element/component?

Your code seems to work fine, the "Signing in..." label appears after everything else disappear. I suggest you to just copy all your code from the .xaml.cs file and the .xaml file into a new project, but make sure you don't copy the first line"<Window x:Class="..." because it could generate an error if the class name isn't the same in the new project.
For the xaml code I suggest you not think the same as you design windows forms applications. WPF has the layout system, which re-orientates or re-sizes its elements when re-sizing the window. So you should not specify exact numbers in the margin property as if they where coordinates. Create a grid, create rows or columns for each element and then just set the horizontal or vertical alignment or margins. Think different than the old windows forms way.

I've run your code... and it's working great for me. I've not changed anything (except the variable names) so I guess it's a bug from VS.
As said nikolamm94 try to add this.UpdateLayout(); at the end of connect_Click it might help. I tried and it is still working fine. Or maybe create a new VS projet, it already worked for me a few times.
Sorry my answer is not the most helpful, I wanted to put a comment instead but I don't have enough reputation :/

Please refer: https://msdn.microsoft.com/en-us/library/ms748821(v=vs.85).aspx
Set to Visible: tb1.Visibility = System.Windows.Visibility.Visible;
Set to Hide: tb1.Visibility = System.Windows.Visibility.Hidden;

You can hide a textbox by going to properties->appearance->visibility, then setting it to "hidden"