Xamarin forms : UI freeze with this simple loop - xamarin.forms

Question

I have software that receives data from hardware using FTDI. Attached is a simulation code.
Xaml:
<StackLayout>
<ListView ItemsSource="{Binding Items}" IsVisible="True">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout Orientation="Horizontal">
<Label Text="{Binding Number}"></Label>
<Label Text="{Binding Id}"></Label>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
First attempt:
running the code, after a while I get around 2000 entries, and then it freezes the screen.
public class Data
{
public int Id { get; set; }
public int Number { get; set; }
}
public class MainViewModel
{
Thread _background;
int index = 0;
public MainViewModel()
{
Items = new ObservableCollection<Data>();
_background = new Thread(AddItems);
_background.Priority = ThreadPriority.AboveNormal;
_background.Start();
}
public void AddItems()
{
while (true)
{
List<Data> list = new List<Data>();
Random r = new Random();
for (int x = 1; x < 100; x++)
{
int value = r.Next();
Data d = new Data()
{
Id = index++,
Number = value
};
list.Add(d);
}
foreach (Data d in list)
{
Device.BeginInvokeOnMainThread(() =>
{
Items.Insert(0, d);
});
}
}
}
public ObservableCollection<Data> Items
{
get;
set;
}
}
}
Second attempt:
Single call to BeginInvokeOnMainThread
Better, I get a list that is updated every now and then, and the update becomes faster and faster?!
public class MainViewModel : INotifyPropertyChanged
{
Thread _background;
int index = 0;
public MainViewModel()
{
Items = new ObservableCollection<Data>();
_background = new Thread(AddItems);
_background.Priority = ThreadPriority.AboveNormal;
_background.Start();
}
protected void OnPropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propertyName));
}
public void AddItems()
{
while (true)
{
ObservableCollection<Data> list = new ObservableCollection<Data>();
Random r = new Random();
for (int x = 1; x < 100; x++)
{
int value = r.Next();
Data d = new Data()
{
Id = index++,
Number = value
};
list.Add(d);
}
var temp = new ObservableCollection<Data>(Items);
foreach (Data d in list)
{
temp.Insert(0, d);
}
Device.BeginInvokeOnMainThread(() =>
{
Items = temp;
});
}
}
private ObservableCollection<Data> _items;
public event PropertyChangedEventHandler PropertyChanged;
public ObservableCollection<Data> Items
{
get
{
return _items;
}
set
{
_items = value;
OnPropertyChanged(nameof(Items));
}
}
}
Third attempt
Added: Thread.Sleep(50);
Best, I can live with it...
public class MainViewModel : INotifyPropertyChanged
{
Thread _background;
int index = 0;
public MainViewModel()
{
Items = new ObservableCollection<Data>();
_background = new Thread(AddItems);
_background.Priority = ThreadPriority.AboveNormal;
_background.Start();
}
protected void OnPropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propertyName));
}
public void AddItems()
{
while (true)
{
ObservableCollection<Data> list = new ObservableCollection<Data>();
Random r = new Random();
for (int x = 1; x < 100; x++)
{
int value = r.Next();
Data d = new Data()
{
Id = index++,
Number = value
};
list.Add(d);
}
Thread.Sleep(50);
var temp = new ObservableCollection<Data>(Items);
foreach (Data d in list)
{
temp.Insert(0, d);
}
Device.BeginInvokeOnMainThread(() =>
{
Items = temp;
});
}
}
private ObservableCollection<Data> _items;
public event PropertyChangedEventHandler PropertyChanged;
public ObservableCollection<Data> Items
{
get
{
return _items;
}
set
{
_items = value;
OnPropertyChanged(nameof(Items));
}
}
}
I guess that the problem is with BeginInvokeOnMainThread, too much work is done on the UI thread...but why it is freezes?
Can anyone explain the behavior? Why adding Sleep solve the problem?
Thanks in advance