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I have a collectionview with many items. I have implemented a search which will find an item by a person's name and then scroll to that person.
Now it gets weird. Certain seachs cause the scrollto to work and the item is scrolled to the top. But other values find the item and use same code to scrollto and the collectionview goes into a up and down motion (does not scroll a full item) and the only thing the UI will handle is a close on the Title bar.
The code that is being used to scroll is the following :
public void SearchForPlayer(string value)
{
bool found = false;
int idx = 0;
foreach (PlayerYearStats s in displayScorers)
{
if (s.fullName.ToLower().Contains(value.ToLower()))
{
theCollView.ScrollTo(idx, position: ScrollToPosition.Start);
found = true;
break;
}
idx++;
}
if (found)
HideKeyBoard();
}
Shown above is using the index of the item to scroll but using s to scrollto the item has the same problem. Commenting out the HideKeyBoard also does not change the execution. I can see no difference (other than the data which is not used except to search for the item) between items that work and ones that don't.
I also have a Scrolled event defined for the CollectionView and after the code above this event keeps on getting called. On a breakpoint there is no call stack so I have no idea what is causing the scroll to keep on going. The definition of the CollectionView is :
<CollectionView
Grid.Row="2"
Grid.Column="1"
x:Name="scorersCV"
ItemsSource="{Binding displayScorers}"
ItemTemplate="{StaticResource scorersTemplate}"
HorizontalScrollBarVisibility="Always"
Scrolled="collScroll">
Also tried with the HorizontalScrollBarVisibility deleted and no change. Using 17.7.7 as 17.8.3 does not create Release builds so I had to go back to previous version.
Not sure if this is any help but the name is defined as follows for the CollectionView
<Label
Grid.Column="0"
Text="{Binding fullName}"
HorizontalOptions="End"
FontAttributes="Bold"
FontSize="10"
TextDecorations="Underline" Margin="0,0,5,0"
TextColor="Red">
<Label.GestureRecognizers>
<TapGestureRecognizer
NumberOfTapsRequired="1"
Tapped="playerTapped"></TapGestureRecognizer>
</Label.GestureRecognizers>
</Label>
As you can see it has a TextColor and Textdecorations. In the CollectionView some of the names show the underline but others don't. The Tap works with both. I did do a test try a search on a name with the underline vs one without but to the scroll search that makes no difference. The other thing to note is it is the same behaviour for the same name.
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Which platform is not working when running code?
Where did you execute SearchForPlayer in the SearchButtonPressed event or the SearchCommand? It is recommended that you use SearchForPlayer in the `SearchButtonPressed 'When you click the searchbutton, then Collectionview will execute scroll event. Meanwhile, please make sure the last item appears on the screen. If the last item appeared and you searched for the last items that appeared on the screen) this scroll event will not be executed.
On a breakpoint there is no call stack so I have no idea what is causing the scroll to keep on going.
Based on your description, it is more likely a VS issue. You can add Console.WriteLine("ScrollEvent executed"); in the ScollEvent, if you can see the message in the Output window but the breakpoint is still no call stack, please report this issue in VS (Click the Help tab-> Send feedback-> Report a Problem).
In the CollectionView some of the names show the underline but others don't.
Does this issue appear in the release mode or the debug mode?
Ok so I added a string to the code to capture all the scrolling events and the scrollto that starts them off.
When I search for a name that has no problem the scroll events are logged as follows:
Scroll player index = 219
Scroll vertical = 4363.636363636364 horizontal = 0
Scroll vertical = 892 horizontal = 0
Notice the first scroll which appears to scroll to the bottom and then scrolls to the actual item and there is no more scroll action.
When I search for a name that has problems the scroll logs are:
Scroll player index = 120
Scroll vertical = -4363.636363636364 horizontal = 0
Scroll vertical = 4363.636363636364 horizontal = 0
Scroll vertical = -4363.636363636364 horizontal = 0
Scroll vertical = 4363.636363636364 horizontal = 0
Scroll vertical = -4363.636363636364 horizontal = 0
Now this seems to indicate a major problem in the ScrollTo method as it seems that keeps scrolling but the VerticalDelta shows at first a negative and then scolls to bottom and then continues this. When this happens I have to kill the app as it has gone into a non responsive loop.
Platform is Android emulator V33.
The following is the XAML for UI for the search. Notice that the search method is called from a TapGestureRecognizer for view pleasure but did try a test with a button and that made no difference.
<HorizontalStackLayout
IsVisible="true"
Grid.Column="1">
<Label
Text="Find - "></Label>
<Entry
x:Name="theEntry"
Text="{Binding findText}"></Entry>
<Image
Source="search.jpg"
WidthRequest="24"
HeightRequest="24">
<Image.GestureRecognizers>
<TapGestureRecognizer
NumberOfTapsRequired="1"
Tapped="searchTapped"></TapGestureRecognizer>
</Image.GestureRecognizers>
</Image>
</HorizontalStackLayout>
Another thing to ponder. I changed the processing such that instead of using a name I input a numeric which is the item index. When I did that I found that if I scrolled to item 25 then 50 then 75 and then 120 there was no problem.
But if I use 120 as first search then it goes into the loop and logs are :
Scroll vertical = 0 horizontal = 0
Scroll player index = 120
Scroll vertical = 4363.636363636364 horizontal = 0
Scroll vertical = -4363.636363636364 horizontal = 0
Scroll vertical = 4363.636363636364 horizontal = 0
Scroll vertical = -4363.636363636364 horizontal = 0
Scroll vertical = 4363.636363636364 horizontal = 0
It seems that a long scrollto is not good for Maui.
It seems that the number of items in the CollectionView make ScrollTo work not so good. The other problem is a Maui problem. I was using a Take(xxx) to limit the items and was changing that value to see where Maui breaks. The problem with that was that 2 executions do not execute the same. This is a major problem in debugging Maui. Add this to the "not responding" problem and Maui debugging is simply horrible.
In debugging you will often want to stop (breakpoint) and check using Watch values. Way too often when you do this VS/Maui/Emulator start doing the "not responding" thing and its a reboot to fix this as just closing the emulator does nothing,
And even more. So I tried by enclosing the CollectionView with a ScrollView. Well when I click the label that normally takes me to the list of scorers it doesn't. And it locks the app. I guess Maui is telling that a search is above it's pay grade.
So using a ScrollView with a CollectionView just causes Maui to do its thing. (At this point I have no non rude words to describe it). Add the ScrollView and problem, take it away and the other problem with scrolling.
Just for giggles I changed the ScrollView to a Grid and oh there is the list again. So definitely ScrollView and CollectionView do not work well together
And still more. When I have only 120 items I do a search and it doesn't go nuts. What it doesn't do is scroll the item into view, it scrolls to the end of the CollectionView. And I thought it couldn't get worse, silly me
Ok so I found the problem. If you do not set the animate option on the ScrollTo to false then the scrolling gets into a loop with more than 150 items. Change it to false and the item pops up and that is it.
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I was never able to get ScrollTo on Windows to work.
Works on iOS, Windows, forget it, tried just about everything.