I am a student learning xamarin forms, I am trying to create a basic chat app in this I want to know how to get position of current item in listview that's user watching. When a new message received i want to know if user is at bottom or not if at bottom focus the new and if not at the bottom then just add not by adding focus to it.
you get the selected item from the Xamarin.Forms.ListView.SelectedItem property of your ListView.
If your ListView.ItemSource is of a type that allows using IndexOf you can now do something like
int position = (yourlistview.ItemSource as ObservableCollection<your type>).IndexOf(yourlistview.SelectedItem)
Update:
ok I think i understood what you want.
In most cases more than one item is currently shown when using a listview. So their exists not a single index
but i think you just want to know if the last item of the list is visible/the user has scrolled to the end?
If so ListView has an ItemAppearing event. I use it for example to load more data from an websource if the user scrolled through the first 100 items.
You could do something like this
listview.ItemAppearing += listviewItemAppearing;
listview.ItemDisappearing += listviewItemDisappearing;
bool m_scrolledToEnd;
private void listviewItemDisappearing(object sender, ItemVisibilityEventArgs e)
{
if(e.Item == yourlastiem)
m_scrolledToEnd = false;
}
private void listviewItemAppearing(object sender, ItemVisibilityEventArgs e)
{
if(e.Item == yourlastiem)
m_scrolledToEnd = true;
}
if you realy need to know if a specific index is shown you could create a List<int> m_idxlist;
and in the appearing event add the index of the item to the list
and in the disappearing event remove the index of the item from the list.
Then you will have a list where all indexes of the items currently shown are stored.
From the Documentation
ListView supports selection of one item at a time. Selection is on by
default. When a user taps an item, two events are fired: ItemTapped
and ItemSelected. Note that tapping the same item twice will not fire
multiple ItemSelected events, but will fire multiple ItemTapped
events. Also note that ItemSelected will be called if an item is
deselected.
To detect selecting an item, you can add a method, onSelection:
void OnSelection (object sender, SelectedItemChangedEventArgs e)
{
if (e.SelectedItem == null) {
return; //ItemSelected is called on deselection, which results in SelectedItem being set to null
}
DisplayAlert ("Item Selected", e.SelectedItem.ToString (), "Ok");
//((ListView)sender).SelectedItem = null; //uncomment line if you want to disable the visual selection state.
}
To disable selection just set the selectedItem to null:
SelectionDemoList.ItemSelected += (sender, e) => {
((ListView)sender).SelectedItem = null;
};
Related
I have two views of WPF (Vista1.xaml and Vista2.xaml), and they are part of a MainWindow.xaml.
In the Vista1.xaml i have a listview, where the user selects some items by clicking and the Vista2.xaml has a button.
I want that when the user clicks on the button of Vista2.xaml, get the items that the user previously selected in the listview of Vista1.xaml.
I have class in the Vista1.xaml.cs ListViewItem_PreviewMouseLeftButtonDown method that captures the user selects the item in the listview.
the code is as follows
private void ListViewItem_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
var item = sender as ListViewItem;
if (item != null && item.IsSelected)
{
...
}
}
I appreciate your help
Add a public property to you MainPage that contains the data you want to pass between Vista1 and Vista2. Then, in your event handler of Vista1, set the property and on the button click of Vista2 read the property.
I've got a form that contains a listview which pulls in ticket info from a database. The database objects are all abstracted into a class library. There is a tabpage below the listview which displays various details of the tickets.
My problem is that I've implemented a search at the top of this form which isn't updating that tabpage, only the listview gets updated. After typing in keywords the listview refreshes properly and any items that dont' contain the keywords are removed until the text from the search box is cleared. But I can't get the tabpage to exhibit the same behavior. The tabpage still always contains all tickets.
For example, if I were to search for something where only 1 ticket was returned in the listview and say that ticket was the 10th ticket on record; the tabpage would show me details for the very first ticket. How can I get the tabpage to exhibit the same behavior as my listview after a search is made?
The tabpage currently gets filled with this function:
private void FillTicket()
{
try
{
if (listView1.SelectedIndices.Count > 0)
{
CTicket thistkt = comp.Tickets[listView1.SelectedIndices[0]];
dedit1.DocumentHTML = thistkt.LineItems.GetCombinedProblem();
dedit2.DocumentHTML = thistkt.LineItems.GetCombinedResolution();
lvAssignmentHistory.Items.Clear();
foreach (CInc_AssignmentHistory a in thistkt.AssignmentHistory)
{
ListViewItem itm = new ListViewItem();
itm.Text = a.pAsgn_Datetime.ToString();
itm.SubItems.Add(a.pAsgn_Group_fr);
itm.SubItems.Add(a.pAsgn_from);
itm.SubItems.Add(a.pAsgn_Group_to);
itm.SubItems.Add(a.pAsgn_to);
itm.SubItems.Add(a.pChanged_By);
lvAssignmentHistory.Items.Add(itm);
}
when this is called:
private void listView1_SelectedIndexChanged(object sender, System.EventArgs e)
{
//FillTicket();
if (txtBox_TicketSearch.Text != "")
{
FillTicketNothing();
}
else
{
FillTicket();
}
It seems to me you only update the tab page if the user selects different items in your ListView.
If your listView1_SelectedIndexChanged method is only a handler for the ListView.SelectedIndexChanged event, it is only called when the selection in listView1 changes, not when it's content is changed (without changing selection).
So you should call FillTicket when you changed the content of listView1.Items after your search.
Also, your FillTicket method only updates the tabpage if there are selected items in your ListView:
if (listView1.SelectedIndices.Count > 0)
I don't know if there is an else-branch for that if. If not, there will nothing change on your tab page if no items were selected. You may want to use listView1.Items.Count.
Okay, so I have four listBox controls. I want to select the same index on all four listBox when one item is clicked on any of them. To be mentioned, I do change the index sometimes in the program. I tryed using a method listSelectChange (int index) and adding for each listBox an event for selectIndexChange, but it would activate the event even if the select is made by the program and not by user-control.
Please don't use classes, just a brute method would be fine!
You can unsubscribe from selectedIndexChanged before you update the ListBox and re-subscribe to it immediately after that. It's a common practice.
Since you gave no code example I'm doing some guessing here.
// Enumerable of all the synchronized list boxes
IEnumerable<ListBox> mListBoxes = ...
...
public void OnSelectedIndexChanged(object sender, EventArgs e) {
var currentListBox = (ListBox)sender;
// Do this for every listbox that isn't the one that was just updated
foreach(var listBox in mListBoxes.Where(lb => lb != currentListBox)) {
listBox.SelectedIndexChanged -= OnSelectedIndexChanged;
listBox.SelectedIndex = currentListBox.SelectedIndex;
listBox.SelectedIndexChanged += OnSelectedIndexChanged;
}
}
I have a pretty basic Datagrid XAML bound to a CollectionViewSource.
<DataGrid ItemsSource="{Binding Source={StaticResource EditingItemsCollectionViewSource}}"/>
And the Collection View Source is bound to an observable collection of very basic items with 3 numerical values. C# obviously.
I want to be able to add a new row (add a new item) at the bottom of this datagrid by pressing Tab on the keyboard when I am in the last cell of the last row.
Is this possible?
One possible solution is to programmatically set the property:
dataGrid.AllowUserToAddRows = true;
in order to implement "Add Row" functionality (provided that it was originally set to false, thus the new row was invisible). As per your task definition, it could be triggered by Tab key press (with any additional condition you may add):
private void dataGrid_PreviewKeyDown(object sender, KeyEventArgs e)
{
try
{
if (e.Key == Key.Tab)
{
e.Handled = true;
// your code
}
}
catch{}
}
You may also want to set some default values for newly created row item by adding event handling procedure:
dataGrid.InitializingNewItem += new InitializingNewItemEventHandler(dataGrid_InitNewItem);
private void dataGrid_InitNewItem(object sender, InitializingNewItemEventArgs e)
{
// your code
}
Other sample implementations of adding row to WPF DataGrid could be found here: Wpf DataGrid Add new row
Also, pertinent to your description, you can add the item to the underlying ObservableCollection, so it will automatically appear in the DataGrid.
Hope this will help. Best regards,
i have 2 listBoxes in a window, one next to the other, with buttons to copy items from one listBox to the other.
when an item from the first listBox is selected the copy button gets enabled, and remove button gets disabled. when i choose an item for the second listBox the copy button gets disabled, and remove button gets enabled.
when you select an item in one of the listBoxes the buttons change with no problem, after the listBox lost focus and you choose the same item that was selected the buttons dont change back.
i understand the problem is that the event of selected item changed will not fire, beacuse the selected item did not change.
setting the selected item to null when the listBox loses focus was not usefull beacuse i need the selcted item. i need to find a way to reselect the selected item when the listBox gains focus, or just fire the even of selected item changed. any suggestions?
You can try the ListBox.LostFocus Event and set the SelectedItem Property to null.
private void ListBox_LostFocus(object sender, RoutedEventArgs e)
{
((ListBox)sender).SelectedItem = null;
}
Use the ListBox.GotFocus event check if there is a SelectedItem, store the index, remove the SelectedItem and use the stored index to reset the SelectedItem. Something like this
private void ListBox_GotFocus(object sender, RoutedEventArgs e)
{
ListBox lb = (ListBox)sender;
if(lb.SelectedItem != null )
{
int index = lb.SelectedIndex;
lb.SelectedItem = null;
lb.SelectedIndex = index;
}
}