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TextView value of the list view items shuffle while scrolling in customized list-view

I am using a customized list view in my application. I have list of items to be displayed. For each cell I need to show the "Title of the Item", "Description of the Item", and "Count".
The data is displayed correctly when list is launched for the first time. When I scroll the list the count of each cell item shuffle with each other, whereas the title and description is displayed correctly only count gets shuffle when scrolled.
adapter class code for GetView()
public override View GetView(int position, View convertView, ViewGroup parent)
{
var item = tableItems[position];
ViewHolder holder;
View view = convertView;
LayoutInflater layoutInflator = LayoutInflater.From(mContext);
if(view==null)
{
view = layoutInflator.Inflate(Resource.Layout.list_cell, null);
holder=new ViewHolder();
holder.mTvTitleName = view.FindViewById<TextView>(Resource.Id.tv_title);
holder.mTvDescriptionName = view.FindViewById<TextView>(Resource.Id.tv_description);
holder.mTvCount = view.FindViewById<LinearLayout>(Resource.Id.tv_Count);
view.Tag=holder
}
else
{
holder = (ViewHolder)view.Tag;
}
return view;
}
I gone through the similar links :
Text values are changed in customized listview when scroll the listview in android?
It is suggested to use final keyword. But in C# there is no final keyword instead there is const but const variable require to be initialised with certain value.
Can anyone suggest the correct approach to do this in xamarin.android.

How to get GTKSharp TreeView widget to display expanders?

So I am creating a treeview selector with C#/GTKSharp. I have the basic tree view selector functionality working: The data is loaded into my model and I can click on a node to collapse/expand.
The part I can't work out is how to tell the cell renderer to display the collapse/expand toggle button. In the examples it appears as a triangle that points right or down depending on whether the node is opened or collapsed. I just have a blank space that works as expected as I click but shows nothing.
One possibility is that I have a white on white text issue but I doubt it as my labels show up fine and I have not done any formatting yet.
I tried adding code for ShowExpanders but that was already true.
TreeView = new Gtk.TreeView();
// We add the event handlers (i.e. the control part) to the tree
TreeView.RowActivated += SelectorActivated; //On double click
TreeView.Selection.Changed += SelectorSelected; // On select (single click)
// Raise a context menu here??
// Connect to the ButtonPressEvent
// Raise a popup button
// Create columns [View]
Gtk.TreeViewColumn TreeViewColumTitle = new Gtk.TreeViewColumn();
TreeViewColumTitle.Title = "Profile";
Gtk.CellRendererText NameCellTitle = new Gtk.CellRendererText();
TreeViewColumTitle.PackStart(NameCellTitle, true);
TreeViewColumTitle.SetCellDataFunc(NameCellTitle, new Gtk.TreeCellDataFunc(RenderTitle));
NameCellTitle.Mode = CellRendererMode.Activatable;
// Populate the model
// Note that we could dispense with this step if we generated an ITreeModel
// interface in the Object class.
BindModel(Model);
// Attach everything to the pane
TreeView.Model = GTKModel;
TreeView.AppendColumn(TreeViewColumTitle);
TreeView.ShowExpanders = true;
TreeView.ExpanderColumn.Visible = true;
...
private void BindModel(Model Model) {
GTKModel = new Gtk.TreeStore(typeof(Object));
foreach (Object Object in Model.Selector) {
var BindingData = new BindingDataGTK(this, Object);
BindingData.Iter = GTKModel.AppendValues(Object);
Object.BindingData = BindingData;
BindChildren(GTKModel, BindingData);
}
}
private void BindChildren(TreeStore TreeStore, BindingDataGTK ObjectBinding) {
foreach (var Child in ObjectBinding.Object) {
var BindingData = new BindingDataGTK(this, Child);
BindingData.Iter = TreeStore.AppendValues(ObjectBinding.Iter, Child);
Child.BindingData = BindingData;
BindChildren(TreeStore, BindingData);
}
}
private void RenderTitle(Gtk.TreeViewColumn Column, Gtk.CellRenderer Cell,
Gtk.ITreeModel GTKModel, Gtk.TreeIter Iter) {
Object Object = (Object)GTKModel.GetValue(Iter, 0);
(Cell as Gtk.CellRendererText).Text = Object.Title;
Console.WriteLine("Render {0}", Object.Title);
}

So far as I know this is pretty much an automatic feature, I don't think anything special is needed to make it happen (I've certainly never needed to). You might want to try using a TreeIter to construct your tree instead?
E.g. assuming you already have a TreeView on your form with 0 (zero) columns in it called "treeview" and a list of "MyObject"s called "myListOfObjects"...
treeview.AppendColumn ("Some Title", new CellRendererText(), "text", 0);
Gtk.TreeStore _ts = new TreeStore (typeof(string));
foreach (IMyObject _mo in myListOfObjects) {
Gtk.TreeIter _it = _ts.AppendValues (_mo.SomeText);
RecurseInto (_ts, _it, _mo);
}
treeview.Model = _ts;
...
void RescureInto(Gtk.TreeStore ts, Gtk.TreeIter it, IMyObject mo)
{
foreach (IMyObject _child_mo in mo.Children) {
Gtk.TreeIter _it = ts.AppendValues (it, _child_mo.SomeText);
RecurseInto (ts, _it, _child_mo);
}
}
In theory this should work fine.

Dynamically adding rows to ASP.NET repeater in reaction to event

I am trying to create ASP.NET server control (pure code, without ascx template - because control must be completly contained in .dll and it must not rely on external .ascx files), and I have a problem with dynamically adding items to repeater.
I want to add item to repeater in reaction to SelectedIndexChanged event, but when i do second DataBind() in that event, i lose data from ViewModel (for example, textboxes contains default data instead of text entered by user).
Simplified version of my code (in large portion borrowed from MS composite control example - http://msdn.microsoft.com/en-us/library/3257x3ea%28v=vs.100%29.aspx):
[ToolboxData("<{0}:FilterControl runat=server />")]
public class FilterControl : CompositeControl, IPostBackDataHandler
{
private List<FilteringProperty> elements = new List<FilteringProperty>();
private DropDownList filteringElementsDropDownList;
private Repeater usedFiltersRepeater;
[Bindable(true), DefaultValue(null), Description("Active filters")]
public List<FilteringProperty> UsedElements
{
get
{
EnsureChildControls();
if (ViewState["UsedElements"] == null)
{
ViewState["UsedElements"] = new List<FilteringProperty>();
}
return (List<FilteringProperty>)ViewState["UsedElements"];
}
set
{
EnsureChildControls();
ViewState["UsedElements"] = value;
}
}
protected override void RecreateChildControls()
{
EnsureChildControls();
}
protected override void CreateChildControls()
{
Controls.Clear();
filteringElementsDropDownList = new DropDownList { AutoPostBack = true };
usedFiltersRepeater = new Repeater();
foreach (var element in elements)
{
filteringElementsDropDownList.Items.Add(new ListItem(element.DisplayName));
}
filteringElementsDropDownList.SelectedIndexChanged += (sender, e) =>
{
string selectedText = filteringElementsDropDownList.SelectedValue;
FilteringProperty condition = elements.First(x => x.DisplayName == selectedText);
var toRemove = filteringElementsDropDownList.Items.Cast<ListItem>().FirstOrDefault(x => x.Text == condition.DisplayName);
if (toRemove != null)
{
filteringElementsDropDownList.Items.Remove(toRemove);
}
UsedElements.Add(condition);
// ======> A <========
};
usedFiltersRepeater.ItemDataBound += (sender, args) =>
{
FilteringProperty dataItem = (FilteringProperty)args.Item.DataItem;
Control template = args.Item.Controls[0];
TextBox control = (TextBox)template.FindControl("conditionControl");
control.Text = dataItem.DisplayName;
// ======> C <========
};
usedFiltersRepeater.ItemTemplate = // item template
usedFiltersRepeater.DataSource = UsedElements;
usedFiltersRepeater.DataBind();
// ======> B <========
Controls.Add(filteringElementsDropDownList);
Controls.Add(usedFiltersRepeater);
}
}
I marked important portions of code with (A), (B) and (C)
The problem is, (A) is executed after DataBinding (B and C), so changes in UsedElements are not visible until next postback.
It is possible to add usedFiltersRepeater.DataBind(); after (A), but than all controls are recreated without data from viewstate (i.e empty)
Is there a way to dynamically change repeater after databinding, such that data of contained controls is preserved?
Tl;dr - i have a DropDownList and I want to add editable items to Repeater on SelectedIndexChanged (without losing viewstate).

I finally solved my problem.
My solution is rather dirty, but it seems to work fine.
Instead of simple databinding:
I get state from all controls in repeater and save it in temporary variable (state for each control includes everything, such as selected index for dropdownlists) using my function GetState()
modify this state in any way i want
restore full state using my function SetState()
For example:
FilterState state = GetState();
state.Conditions.Add(new ConditionState { Item = condition });
SetState(state);

C# inline sorting ObservableCollection does not update Data Binding

I have a ViewModel which contains an ObservableCollection<CustomKeyGroup<CustomItem>> property bound to a control in a View and the problem is that I want to sort this collection by a property in CustomKeyGroup<T>, without setting the ObservableCollection<...> object property (i.e. sort the collection inline):
public class MainViewModel : ViewModelBase {
... // data service etc code
private ObservableCollection<CustomKeyGroup<CustomItem>> _items = new ObservableCollection<CustomKeyGroup<CustomItem>>();
public ObservableCollection<CustomKeyGroup<CustomItem>> Items
{
get
{
return _items;
}
set
{
_items = value;
RaisePropertyChanged("Items");
}
}
public void Sort(string _orderBy = null, bool _descending = true) {
if (string.IsNullOrEmpty(_orderBy) || this.Items.Count == 0) {
return;
}
var test = this.Items.ToList();
// bubble sort
try {
for (int i = test.Count - 1; i >= 0; i--) {
for (int j = 1; j <= i; j++) {
CustomKeyGroup<CustomItem> o1 = test[j - 1];
CustomKeyGroup<CustomItem> o2 = test[j];
bool move = false;
var order = typeof(CustomKeyGroup<CustomItem>).GetProperty(orderBy);
var t = order.GetValue(o1);
var t2 = order.GetValue(o2);
// sort comparisons depending on property
if (_descending) { // ascending
if (t.GetType() == typeof(int)) { // descending and int property
if ((int)t < (int)t2) {
move = true;
}
} else { // descending and string property
if (t.ToString().CompareTo(t2.ToString()) > 0) {
move = true;
}
}
} else { // ascending
if (t.GetType() == typeof(int)) { // ascending and int property
if ((int)t > (int)t2) {
move = true;
}
} else { // ascending and string property
if (t.ToString().CompareTo(t2.ToString()) < 0) {
move = true;
}
}
}
// swap elements
if (move) {
//this.Items.Move(j - 1, j); // "inline"
test[j] = o1;
test[j - 1] = o2;
}
}
}
// set property to raise property changed event
this.Items = new ObservableCollection<CustomKeyGroup<CustomItem>>(test);
} catch (Exception) {
Debug.WriteLine("Sorting error");
}
//RaisePropertyChanged("Items"); // "inline sort" raise property changed to update Data binding
Debug.WriteLine("Sorted complete");
}
... // get data from service, etc.
From the code above, the attempted inline sorts are commented out (as they do not update the control that databinds to it), and the manual setting of Items are left in (works, but if you scroll down the control and sort, it will take you back to the top - undesirable!).
Anyone have any idea how I can update the view/control using an inline sort option? I've also tried manually raising the RaisePropertyChanged event (specified in ObservableObject using the MVVMLight Toolkit) to no avail.
Note: Setting a breakpoint at the end of the try-catch reveals that the ObservableCollection<...> is indeed sorted, but the changes just do not reflect in the View! Even weirder is that the control (LongListSelector) has a JumpList bound to another property of CustomKeyGroup<T> and it successfully updates instantly!! If I tap on any of these items in the JumpList, the View correctly updates itself, revealing the sorted items... I then thought of setting the DataContext of the View after sorting, but that also does not solve the issue.
Thanks.

Adding my own answer here.
So following the comments from the original post, #piofusco points out that a View does not update when an ObservableCollection has only been sorted. Even manually changing the collection (hence, raising NotifyPropertyChanged or NotifyCollectionChanged) does not update it.
Searching around a little more, I decided I could make use of CollectionViewSource, which would do my sorting for me - without changing the collection itself (hence allowing the control to retain its current scroll position). To get it working, basically, add a new property to the ViewModel of type CollectionViewSource, add a SortDescription, set its Source and bind directly to that property (instead of the original ObservableCollection:
In ViewModel:
private CollectionViewSource _sortedCollection = new CollectionViewSource();
public CollectionViewSource SortedCollection {
get {
_sortedCollection.Source = this.Items; // Set source to our original ObservableCollection
return _sortedCollection;
}
set {
if (value != _sortedCollection) {
_sortedCollection = value;
RaiseNotifyPropertyChanged("SortedCollection"); // MVVMLight ObservableObject
}
}
}
View XAML (note the binding to Property.View):
<ListBox ItemsSource="{Binding SortedCollection.View}" ... />
And in your View code-behind, if you have a Sort button:
ViewModel _vm = this.DataContext as ViewModel;
viewModel.SortedCollection.SortDescriptions.Clear(); // Clear all
viewModel.SortedCollection.SortDescriptions.Add(new SortDescription("PropertyName", ListSortDirection.Descending)); // Sort descending by "PropertyName"
And boom! Your sorted collection should update instantly in the View! Even better is that it retains our ObservableCollection functionality in that any updates to objects in the ObservableCollection will raise the NotifyPropertyChanged or NotifyCollectionChanged handlers, thereby updating the View (allowing for both sorting and updating of objects while retaining current scroll positions)!
Note: For those out there using a LongListSelector control, I wasn't able to get it to work, and with a little more internet-digging with I came across this post, which, discusses why LLS cannot bind to a CollectionViewSource.View without some modifications. So I ended up using a ListBox control instead. You can read about some of the differences here. For my task though, the ListBox will suffice.

Drop Item into Specific Index in ListView in WPF C#

I have a list of files in a ListView in WPF. Users can drag files onto the list view, and right now they are just appended to the end of the list. Is it possible to insert the file into the ListView right where the user dropped it?

WPF isn't really designed to be used that way. While you can brute force add ListViewItem's directly to the ListView, the way it's really supposed to work is that you have a collection of some kind (ObservableCollection<FileInfo> would work well) and bind the ListView's ItemsSource property to that collection.
Then the answer is simple. Instead of the Add method, you use the Insert method of the collection which takes an index.
As for finding which ListViewItem the mouse event occurred over, you could use the VisualTreeHelper.HitTest method.

From my point of view it is little tricky when I used the templated item. I have fight with it little bit. I am sharing my usecase which works with DraggableListBox. But I suppose the same solution works with ListBox control.
As the first I created the dependency object extension which is able to provide me ListItem element:
public static class WpfDomHelper
{
public static T FindParent<T>(this DependencyObject child) where T : DependencyObject
{
DependencyObject parentObject = VisualTreeHelper.GetParent(child);
if (parentObject == null) return null;
T parent = parentObject as T;
if (parent != null)
return parent;
else
return FindParent<T>(parentObject);
}
}
Then I implemented Drop logic which inserts(adds) item according specific Drop Y position of destination ListBoxItems:
private void Grid_Drop(object sender, DragEventArgs e)
{
int dropIndex = -1; // default position directong to add() call
// checking drop destination position
Point pt = e.GetPosition((UIElement)sender);
HitTestResult result = VisualTreeHelper.HitTest(this, pt);
if (result != null && result.VisualHit != null)
{
// checking the object behin the drop position (Item type depend)
var theOne = result.VisualHit.FindParent<Microsoft.TeamFoundation.Controls.WPF.DraggableListBoxItem>();
// identifiing the position according bound view model (context of item)
if (theOne != null)
{
//identifing the position of drop within the item
var itemCenterPosY = theOne.ActualHeight / 2;
var dropPosInItemPos = e.GetPosition(theOne);
// geting the index
var itemIndex = tasksListBox.Items.IndexOf(theOne.Content);
// decission if insert before or below
if (dropPosInItemPos.Y > itemCenterPosY)
{ // when drag is gropped in second half the item is inserted bellow
itemIndex = itemIndex + 1;
}
dropIndex = itemIndex;
}
}
.... here create the item .....
if (dropIndex < 0)
ViewModel.Items.Add(item);
else
ViewModel.Items.Insert(dropIndex, item);
e.Handled = true;
}
So this solution works with my template DraggableListBoxView, I suppose the same solution must work with standard ListBoxView. Good Luck

You can do this. It takes a bit of work, but it can be done. There are a couple demos out there, here is one on CodeProject. This particular one is by the wpf master known as Josh Smith. It's probably not exactly what you are looking for, but it should be pretty darn close.