Develop Reference

MVVM with dynamic the Michrochart-NugetPackage doesn't work

I want to add a dynamic micro chart to my application but it doesn't work. After a call from a method a value gets added and it makes a completely new micro chart for my chart to have the new values, but the change isn't visible in the app. So the old Values stayed and there is no new one. Thanks for helping me.
WeightList = new List<float>();
WeightList.Add(0);
WeightList.Add((float)74.3);
entries = new ChartEntry[30];
SyncArray();
private void SyncArray()
{
if (WeightList.Count != entries.Length)
{
entries = new ChartEntry[WeightList.Count];
}
for (int i = 0; i <= WeightList.Count - 1; i++)
{
if (i == WeightList.Count - 1 || i == 0)
{
entries[i] = new ChartEntry(WeightList[i]) { Label = "" + i, ValueLabel = "" + WeightList[i] };
}
else
{
entries[i] = new ChartEntry(WeightList[i]) { Label = "" + i };
}
}
chart = new LineChart() { Entries = entries, BackgroundColor = SKColors.Transparent };
Chart = chart;
}
public LineChart Chart
{
get => chart;
set => SetProperty(ref chart, value);
}
public float Weight
{
get => weight;
set
{
weight = value;
WeightList.Add(weight);
SyncArray();
}
}

Credits: #Jason
What to change:
private void SyncArray()
{
if (WeightList.Count != entries.Length)
{
entries = new ChartEntry[WeightList.Count];
}
for (int i = 0; i <= WeightList.Count - 1; i++)
{
if (i == WeightList.Count - 1 || i == 0)
{
entries[i] = new ChartEntry(WeightList[i]) { Label = "" + i, ValueLabel = "" + WeightList[i] };
}
else
{
entries[i] = new ChartEntry(WeightList[i]) { Label = "" + i };
}
}
Chart = new LineChart() { Entries = entries, BackgroundColor = SKColors.Transparent };
}

Place patterns on polyline in iOS using Xamarin.forms.maps

Im using xamarin.forms.maps and successfully getting the polyline but I want to get some patterns on it as here and not able to achieve it.
Can anyone please help me in solving this issue and my code is as below :
formsMap.DrawPolyLine = () =>
{
if (nativeMaps == null)
{
nativeMaps = Control as MKMapView;
}
nativeMaps.OverlayRenderer = GetOverlayRenderer;
CLLocationCoordinate2D[] coords = new CLLocationCoordinate2D[IOSMapViewModel.DeviceTrackData.Count];
int index = 0;
foreach (var position in IOSMapViewModel.DeviceTrackData)
{
coords[index] = new CLLocationCoordinate2D(position.Latitude, position.Longitude);
index++;
}
routeOverlay = MKGeodesicPolyline.FromCoordinates(coords);
if (nativeMap.Overlays != null)
nativeMaps.RemoveOverlays(nativeMap.Overlays);
IMKOverlay overlay = routeOverlay;
nativeMaps.AddOverlay(routeOverlay, MKOverlayLevel.AboveLabels);
};
nativeMap.GetViewForAnnotation = GetViewForAnnotation;
nativeMap.CalloutAccessoryControlTapped += OnCalloutAccessoryControlTapped;
}
}
MKOverlayRenderer GetOverlayRenderer(MKMapView mapView, IMKOverlay overlayWrapper)
{
if (polylineRenderer == null && !Equals(overlayWrapper, null))
{
var overlay = Runtime.GetNSObject(overlayWrapper.Handle) as IMKOverlay;
Foundation.NSNumber[] dashValues = { 3, 6 };
polylineRenderer = new MKPolylineRenderer(overlay as MKGeodesicPolyline)
{
FillColor = UIColor.Orange,
StrokeColor = UIColor.Orange,
LineWidth = 3,
Alpha = 1f,
LineDashPattern = dashValues
};
//polylineRenderer.CreatePath();
}
return polylineRenderer;
}

Delete annotations from the map

How could i delete annotations from the map after chosing the new one ?
So let's say i have chosen pin on the X and Y coordinates and would like to move this pin to another place without adding the new one.
Also simply map.RemoveAnnotations(); does not work.
Here is a code which depends on it:
map = new MKMapView(new CGRect(0, 74 + point * 13, UIScreen.MainScreen.Bounds.Width, (UIScreen.MainScreen.Bounds.Height - (74 + point * 20))));
map.UserInteractionEnabled = true;
map.ZoomEnabled = true;
map.ScrollEnabled = true;
map.MapType = MKMapType.Standard;
map.ShowsUserLocation = true;
var longTap = new UILongPressGestureRecognizer() { };
longTap.AddTarget(() => AddPin(longTap, slider.Value));
longTap.MinimumPressDuration = 2.0;
map.AddGestureRecognizer(longTap);
map.GetViewForAnnotation += (mapView, annotation) =>
{
anView = new MKAnnotationView(annotation, Resources.kClusterAnnotationId);
anView.ClipsToBounds = true;
anView.CanShowCallout = false;
anView.Image = UIImage.FromFile("Icons/customMapPin.png");
return anView;
};
private void AddPin(UILongPressGestureRecognizer longTap, float value)
{
if (ifPointExist == false)
{
ifPointExist = true;
touchPoint = longTap.LocationInView(map);
pinMapCords = this.map.ConvertPoint(touchPoint, map);
CLLocation loc = new CLLocation(pinMapCords.Latitude, pinMapCords.Longitude);
map.AddAnnotations(new MKPointAnnotation()
{
Coordinate = new CLLocationCoordinate2D(pinMapCords.Latitude, pinMapCords.Longitude)
});
CLGeocoder geocoder = new CLGeocoder();
geocoder.ReverseGeocodeLocation(loc, (CLPlacemark[] placemarks, NSError error) =>
{
str = placemarks[0].AddressDictionary;
str.ToString();
});
AddCircle(value);
MKCoordinateSpan span = new MKCoordinateSpan(0.10, 0.10);
var coords = new CLLocationCoordinate2D(pinMapCords.Latitude, pinMapCords.Longitude);
map.Region = new MKCoordinateRegion(coords, span);
ifPointExist = false;
}
}
Thanks in advance

Java.Lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification (xamarin.forms)

I have bound one list from web service. First time only 5 items are loaded and then when user scroll the list view other 5 items are loaded. Every thing is working fine but I am facing issue in one scenario.
First time when List is bound (don't do scrolling) and if immediately I clicked on some list item then "ItemTepped" event is fired and page should be navigated to other page but problem is it showing me error as below image.
I have put Active indicator for loading.
This code is in xamarin.forms (Portable library). This is not xamarin.Android project.
public partial class NewsGalleryListPage : ContentPage
{
int totalItems = 0;
decimal MaxIndex = 0;
int index = 0;
List<Newslist> NewsList;
public NewsGalleryListPage()
{
InitializeComponent();
NewsGalleryLists.ItemTapped += NewsGalleryLists_ItemTapped;
NewsGalleryLists.ItemAppearing += NewsGalleryLists_ItemAppearing1;
loadingIndicator.IsVisible = true;
loading.IsRunning = true;
loading.IsVisible = true;
CallWebServiceForNewsGalleryList(index);
}
private void NewsGalleryLists_ItemAppearing1(object sender, ItemVisibilityEventArgs e)
{
try
{
if (totalItems != 0)
{
MaxIndex = Math.Ceiling(((decimal)totalItems) / 5);
if (index < MaxIndex)
{
if (NewsList != null && e.Item != null && e.Item == NewsList[NewsList.Count - 1])
{
index++;
if (index != MaxIndex)
{
loadingIndicator.IsVisible = true;
loading.IsVisible = true;
loading.IsRunning = true;
CallWebServiceForNewsGalleryList(index);
}
}
}
}
}
catch(Exception ex)
{
}
}
private void NewsGalleryLists_ItemTapped(object sender, ItemTappedEventArgs e)
{
var selectedNewsGalleryListItem = sender as Xamarin.Forms.ListView;
var obj = selectedNewsGalleryListItem.SelectedItem as CMO.ServicesClasses.Newslist;
Navigation.PushAsync(new CMO.Gallery.NewsGalleryDetail(obj));
}
public async void CallWebServiceForNewsGalleryList(int index)
{
try
{
string lang = "en";
if (Application.Current.Properties.ContainsKey("Language"))
{
lang = Application.Current.Properties["Language"] as string;
// do something with i
}
List<KeyValuePair<string, string>> values = new List<KeyValuePair<string, string>>();
values.Add(new KeyValuePair<string, string>("lang",lang));
values.Add(new KeyValuePair<string, string>("title", ""));
values.Add(new KeyValuePair<string, string>("index", Convert.ToString(index)));
values.Add(new KeyValuePair<string, string>("limit", "5"));
var response = await GeneralClass.GetResponse<CMO.ServicesClasses.RootObjectNewsGalleryList>("http://14.141.36.212/maharastracmo/api/getnewslist", values);
if (response != null)
{
if (NewsList == null || index==0)
{
NewsList = new List<Newslist>();
}
for(int i = 0; i < response.newslist.Count; i++)
{
var ObjectNewslist = new Newslist();
ObjectNewslist.page_id = response.newslist[i].page_id;
ObjectNewslist.title = response.newslist[i].title;
ObjectNewslist.date = response.newslist[i].date;
ObjectNewslist.news_photo = response.newslist[i].news_photo;
ObjectNewslist.content = response.newslist[i].content;
NewsList.Add(ObjectNewslist);
}
totalItems = response.total_results;
NewsGalleryLists.RowHeight = 100;
var x = NewsGalleryLists.RowHeight;
this.Title = AppResources.LNewsGallery;
NewsGalleryLists.ItemsSource = NewsList;
}
}
catch (WebException exception)
{
}
loading.IsVisible = false;
loading.IsRunning = false;
loadingIndicator.IsVisible = false;
}
}
I have gone through following link
https://forums.xamarin.com/discussion/23124/proper-way-to-update-the-tableviews-sections-content
https://forums.xamarin.com/discussion/21994/threading-in-xamarin-forms
I have tried
Xamarin.Forms.Device.BeginInvokeOnMainThread (() =>
{});
Task.Run(() => { });
I don't know how to handle thread in xamarin forms as beginner level.

It usually happens when you use TemplateSelector, but creating a new one for each row. Create one instance of TemplateSelector and use it.

How to check if checkbox is selected?

I have little issue with checkbox added programmatically. I don't know how to check which checkbox are selected, when I hit "Send Button".
layout.RemoveAllViewsInLayout();
CheckBox _Options = new CheckBox(Activity);
ScrollView _Scroll = new ScrollView(Activity);
_Scroll.LayoutParameters = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WrapContent, ViewGroup.LayoutParams.WrapContent);
LinearLayout _LScroll = new LinearLayout(Activity);
_LScroll.LayoutParameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WrapContent, ViewGroup.LayoutParams.WrapContent);
_LScroll.Orientation = Orientation.Vertical;
_LScroll.SetGravity(GravityFlags.CenterHorizontal);
//_Scroll.AddView(_LScroll);
Button _Send = new Button(Activity);
_Send.Text = "Wyślij";
_Send.LayoutParameters = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MatchParent, ViewGroup.LayoutParams.WrapContent);
for (int i = 0; i < _Item.options.Length; i++)
{
_Options.Text = _Item.options[i];
_Options.Id = i;
_Options.LayoutParameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MatchParent, ViewGroup.LayoutParams.WrapContent);
_LScroll.AddView(_Options);
}
_Send.Click += delegate
{
_MultiAnswer._QuestionId = _Item.id;
for(int i = 0; i < _Item.options.Length; i++)
{
if (_Options.Selected == true)
{
_MultiAnswer._AnwserOptionIds.SetValue(i + 1, i);
}
}
output = JsonConvert.SerializeObject(_MultiAnswer);
SendJson(_Url, DataCache._Login, output);
SetLayout(layout, btn);
};
_Scroll.AddView(_LScroll);
layout.AddView(_Scroll);
layout.AddView(_Send);
I'll try to work on ID of checkbox, but I really don't know how to do it. I was thinking on method, which give me code which create checkbox, but still don't know how to check if checkbox is selected.

I understand that you've many checkbox controls. So add them to a list as follows:
List<Checkbox> checkboxes = new List<Checkbox>
{
chk1, chk2, chk3
};
When you want to know which ones are checked, you'll do this:
IEnumerable<Checkbox> checkedCheckboxes = checkboxes.Where(chk => chk.Checked);

This is a quick and dirty sample on how to generate dynamic cheboxes and retreive their state :
public class MainActivity : Activity
{
public class MyItem
{
public string[] options { get; set; }
public int id { get; set; }
}
public class MyMultiAnswer
{
public int _QuestionId { get; set; }
}
private List<CheckBox> _chkList = new List<CheckBox>();
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
var _Item = new MyItem() { options =new string [] { "aaa", "bbb", "ccc" }, id=0 };
var _MultiAnswer = new MyMultiAnswer() { _QuestionId = 0 };
ScrollView _Scroll = new ScrollView(this);
_Scroll.LayoutParameters = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WrapContent, ViewGroup.LayoutParams.WrapContent);
LinearLayout _LScroll = new LinearLayout(this);
_LScroll.LayoutParameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WrapContent, ViewGroup.LayoutParams.WrapContent);
_LScroll.Orientation = Orientation.Vertical;
_LScroll.SetGravity(GravityFlags.CenterHorizontal);
TextView txView = new TextView(this);
//_Scroll.AddView(_LScroll);
Button _Send = new Button(this);
_Send.Text = "test";
_Send.LayoutParameters = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MatchParent, ViewGroup.LayoutParams.WrapContent);
for (int i = 0; i < _Item.options.Length; i++)
{
CheckBox _Options = new CheckBox(this);
_chkList.Add(_Options);
_Options.Text = _Item.options[i];
_Options.Id = i;
_Options.LayoutParameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MatchParent, ViewGroup.LayoutParams.WrapContent);
_LScroll.AddView(_Options);
}
_Send.Click += delegate
{
_MultiAnswer._QuestionId = _Item.id;
string strChkIds = "";
foreach (var chk in _chkList.Where(c => c.Checked))
{
//_MultiAnswer._AnwserOptionIds.SetValue(_Options.Id + 1, _Options.Id);
//do something
strChkIds += " - " + chk.Id;
}
// or
for (int i = 0; i < _Item.options.Length; i++)
{
if (_chkList[i].Checked == true)
{
//_MultiAnswer._AnwserOptionIds.SetValue(i + 1, i);
//do something
}
}
//output = JsonConvert.SerializeObject(_MultiAnswer);
//SendJson(_Url, DataCache._Login, output);
//SetLayout(layout, btn);
txView.Text = "selected ids " + strChkIds;
};
_Scroll.AddView(_LScroll);
_LScroll.AddView(_Send);
_LScroll.AddView(txView);
// Set our view from the "main" layout resource
SetContentView(_Scroll);
}
}
This is a sample about how you can achieve this in a minimum effort.