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Image source not binding in xamarin form

My object has a property set elsewhere called:
ImageSrc = "icon.png"
In xaml file I am trying to bind to this:
<Image Source="{Binding ImageSrc}" />
In the ViewModel I am setting the property as such:
private string _imageSrc;
public string ImageSrc
{
get => this._imageSrc;
set
{
this._imageSrc = value;
this.RaisePropertyChanged(() => this.ImageSrc);
}
}
public override Task InitializeAsync(object _params)
{
ObjectParameters _objectParameters = (ObjectParameters)_params;
this.ImageSrc = _objectParameters.ImageSrc;
return Task.CompletedTask;
}
If I set this in class constructor:
this.ImageSrc = "icon.png";
it binds fine but not after calling:
public override Task InitializeAsync(object _params)
the property is set properly with the correct value of "icon.png" but the image does not show like when set in the class constructor. Any ideas appreciated.

I had to right click on Resources/drawable/icon.png then Add To Project and make sure Build Action: AndroidResource

Databinding with unnamed textboxes and listbox

I have been taught lately when using WPF and databinding it is good practice to not name any of the fields but only to associate them with the properties in the other classes. My problem right now is how do I add the data from 3 textboxes (the user enters), save the binded information to the model which then posts the account information into the listbox on the side. I need to add the data to my model. My code from main.xaml is below:
<ListBox ItemsSource="{Binding Path=Files}" SelectedItem="{BindingPath=CurrentItem}" />
<TextBox Text="{Binding Path=bankaccount}"/>
<TextBox Text="{Binding Path=accountnumber}"/>
<TextBox Text="{Binding Path=accounttype}"/>
<Button Content="Save Data To Listbox" Click="Save_Click"/>
Now I will show my FileModel class which holds all of my properties which will be from the textboxes
private short _BankAccount;
private long _AccountNumber;
private char _AccountType;
public short bankaccount{ get { return _BankAccount;} set {_BankAccount= value; Notify("bankaccount"); } }
public long accountnumber{ get { return _AccountNumber;} set {_AccountNumber= value; Notify("accountnumber"); } }
public char accounttype{ get { return _AccountType;} set{_AccountType= value; Notify("accounttype"); } }
I use a class called ProgramModel As my middle point between the Mainpage and my FileModel page and here is that code:
public class ProgramModel : INotifyPropertyChanged
{
public ObservableCollection<FileModel> Files { get; set; }
private FileModel _currentItem;
public FileModel CurrentItem { get { return _currentItem; } set { _currentItem = value; Notify("CurrentItem"); } }
public ProgramModel()
{
Files = new ObservableCollection<FileModel>();
}
And to finish it off I have my mainpage:
internal partial class MainWindow
{
public ProgramModel Model { get; set; }
private ViewSettings _viewSettings = new ViewSettings();
public MainWindow()
{
InitializeComponent();
this.DataContext = Model = new ProgramModel();
}
private void Save_Click(object sender, RoutedEventArgs e)
{
FileModel filemodel = new FileModel();
Model.Files.Add(new FileModel( filemodel.bankaccount, filemodel.accountnumber, filemodel.accounttype));
}
I feel like I am adding to the Files Collection incorrectly from the save button event. If you guys can help me out that would be great! All 3 textboxes and the listbox are on the Main page. Let me know if you have any questions. Also, this is a learning experience so let me know if I posted too much code or not enough. Thanks!

You read the values from a new FileModel instance instead of from what is bound to the view. Code should be this:
Model.Files.Add(new FileModel
(
Model.CurrentItem.bankaccount,
Model.CurrentItem.accountnumber,
Model.CurrentItem.accounttype
));
Make sure CurrentItem is actually initialized with an instance, don't see that in your code. Also, you could use a command here and have all the relevant logic in your bound view model without the need for the event.
Also, right now you bind the current item to the selected item in the ListBox, this will modify an existing instance instead. Not sure if this is intended. If you want those fields to be for input of new instances don't bind the ListBox to it.

I'm not going to answer your question directly because implementing proper data binding will take a bit of code to do so.
Using proper data binding, it is possible to have almost no code behind on your view.cs! (Specially if you start using frameworks)
Please take a look on A Simple MVVM Example for you to follow good practice.
By following this example, you will see that you can also use data binding on buttons and other controls.
Your View Model which is ProgramModel : INotifyPropertyChanged should handle all the work (data processing).
Your model should not handle the UI update notifications thus,
public short bankaccount{ get { return _BankAccount;} set {_BankAccount= value; Notify("bankaccount"); } }
will be moved to the ProgramModel (View Model).
Save_Click method will also be converted into an ICommand and be binded to the button in view like <Button Content="Save Data To Listbox" Command="{Binding SaveExec}"/>
The point is, if you are studying data binding, you should implement it right. Hope you understand...
In the end, it is possible for your Main.cs to only be..
internal partial class MainWindow
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new ProgramModel();
}
}

Just a small change and it should work . Change Your bindings as shown below for the TextBoxes.
<TextBox Text="{Binding Path=CurrentItem.bankaccount}"/>
<TextBox Text="{Binding Path=CurrentItem.accountnumber}"/>
<TextBox Text="{Binding Path=CurrentItem.accounttype}"/>

View Model not updating UI when inside constructor

I have a feeling that my view isn't being updated because the NotifyPropertyChanged event is firing prior to the UI being constructed but I don't know how to overcome this.
I am not really posting code for analysis because I know that the databindings work. They just fail during the construction of the page.
I am strictly posting it so you can get an idea of what I am talking about.
public Obj1 SelectedObj1
{
get { return _SelectedObj1; }
set { _SelectedObj1 = value; NotifyPropertyChanged("SelectedObj1"); }
}
public Obj2 SelectedObj2
{
get { return _SelectedObj2; }
set { _SelectedObj2= value; NotifyPropertyChanged("SelectedObj2"); }
}
public Obj3 SelectedObj3
{
get { return _SelectedObj3; }
set { _SelectedObj3 = value; NotifyPropertyChanged("SelectedObj3"); }
}
Inside my constructor
public constructor(){
BuildFakeData();
SelectedObj1 = observableCollection[0];
SelectedObj2 = SelectedObj1.obj2s.Count > 0 ? SelectedObj1.obj2s[0] : null;
SelectedObj3 = SelectedObj2.obj3s.Count > 0 ? SelectedObj2.obj3s[0] : null;
}
My question is, when you are doing MVVM, if you set bound properties in the constructor, say for a DataGrid selected Row, will it populate or is it failing because the XAML isn't built yet?
Here is where the datacontext is created in the view
<Window.Resources>
<vm:ViewModel x:Key="viewModel"/>
</Window.Resources>
<Grid
DataContext="{StaticResource viewModel}">
Here is where I am setting the selected item for the grid
<igWPF:XamDataGrid
ActiveDataItem="{Binding SelectedObj1}"
DataSource="{Binding observableCollection}"

If your view doesn’t exist yet when the view model is created, then of course, the view isn’t listening yet when your properties update. However, when the view is then created and the view model is assigned as its data context, then the view will automatically load the values from the view model (its data context).
So, INPC shoulnd’t be an issue there at all. You could create properties without INPC in your example and have it work (since the values are already set in the constructor).

Using MVVM instead of main window for the following code

I'm using the following code which is copy pasted from the main window which was working as expected ,
I have created View which is user control and put the code of the
code from the main window XAML
In the View model I put reference for the User model
In the user control I put the code for from the the main window which
is related to the event handlers for example the
DropText_PreviewDragEnter & listbox_SelectionChanged
Currently I have 2 issues in the User Control which Im not sure how to overcome...
1. Errors in the user control for all the occurrence of the ListBox (for example from listbox_SelectionChanged ystem.Windows.Controls.ListBox.SelectedItems.Count > 0 . the Selected items are marked at red with the following error
"cannot access non-static property SelectedItems item source in static context". ,not sure what is the reason since in the main window it was the same as static.
2. Since I have copied the code from the main window there is references to user object in the user controlwhich I believe is not acceptable in MVVM ,how should I change it ? for example
var mySelectedItem = System.Windows.Controls.ListBox.SelectedItem as User;
or
bool remove = _UsersList.Remove((User) System.Windows.Controls.ListBox.SelectedItem);
Here is the code.
I will appreciate your help !
The view model
public partial class ModelView : UserControl
{
private const string DRAG_SOURCE = "DragSource";
public ModelView()
{
InitializeComponent();
DataContext = new ModelView();
}
//Drag Over from text box to List box
private void ListBox_PreviewDrop(object sender, DragEventArgs e)
{
object dragSource = e.Data.GetData(DRAG_SOURCE);
if (dragSource != null && dragSource is TextBox)
{
(dragSource as TextBox).Text = String.Empty;
}
if (!String.IsNullOrEmpty(e.Data.GetData(DataFormats.StringFormat).ToString()) && dragSource is TextBox)
{
_UsersList.Add(new User {Name = e.Data.GetData(DataFormats.StringFormat).ToString()});
}
else
{
e.Handled = true;
}
}
}
}
The Xaml is
<TextBox x:Name="name1"
AcceptsReturn="True"
AllowDrop="True"
PreviewDragEnter="DropText_PreviewDragEnter"
PreviewDrop="DropText_PreviewDrop"
PreviewMouseDown="DropText_PreviewMouseDown"
HorizontalAlignment="Left" Height="20" Margin="360,70,0,0" TextWrapping="Wrap" Text=""
VerticalAlignment="Top" Width="70"/>
....
The model view
internal class ModelView
{
private ObservableCollection<User> _UsersList = new ObservableCollection<User>();
public ObservableCollection<User> UserList
{
get { return _UsersList; }
}
public void InitUsers()
{
_UsersList.Add(new User {Name = "fff"});
//Sort the User collection
ICollectionView usersView = CollectionViewSource.GetDefaultView(_UsersList);
usersView.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));
}
}

You already have two answers explaining why the first issue happend in the previous question. And follwoing points are what #Will said in comment as a mess in MVVM implementation that I can see in your codes :
UsersList in the model view is a Model as in Model-View-ViewModel.
And the model view it self is a ViewModel as in Model-View-ViewModel
Then what you call view model is actually a View in Model-View-ViewModel point of view. It inherits UserControl and UserControl is a view, no difference from Window or Page, etc. They're all View. And even if we agree to call it view model, then it violated MVVM principle everywhere, because view model shouldn't have reference to View/UI control object.
Not directly answering your question, but I hope you get a better prespective on MVVM pattern.

#phil correctly noted that you can't access the ListBox like this:
System.Windows.Controls.ListBox
What he failed to mention is that you shouldn't access a ListBox at all if you're using MVVM. Clearly you're not using MVVM now, but if you want to, then I would recommend that you read up on it so that you can get the full benefit from it. Just having a view and a view model does not mean that you're using MVVM.
In MVVM, we manipulate data, not UI controls. Therefore, you need to create a SelectedItem property in your view model and bind that to the ListBox.SelectedItem property and then you'll always have access to the item that is selected:
public User SelectedItem { get; set; } // Implement INotifyPropertyChanged here
...
<ListBox ItemsSource="{Binding YourCollection}" SelectedItem="{Binding SelectedItem}"/>
Now you can do something with the selected item like this:
string selectedItemName = SelectedItem.Name;

you have to access your listbox by
yourListBoxName.SelectedItems.Count > 0
you can't access it by
System.Windows.Controls.ListBox.SelectedItems.Count
same for
var mySelectedItem = System.Windows.Controls.ListBox.SelectedItem as User;
use the following instead
var mySelectedItem = yourListBoxName.SelectedItem as User;

Composite Binding to property and inner viewmodel property not firing

I've created a property "IsLoading" for my main view model. The idea is that a progressbar is displayed whenever this property is set to true. So far so good
The catch is, that I have a command, that calls another viewmodel (the code is there because it's a functionality from another page, but I want to be able to shortcut it as well from my main viewmodel)
So, I went ahead and modified the main property to something like this :
public const string IsLoadingPropertyName = "IsLoading";
private bool _isLoading;
public bool IsLoading
{
get
{
return _isLoading || ((ViewModelLocator)Application.Current.Resources["Locator"]).SettingsViewModel.IsLoading;
}
set
{
if (value != _isLoading)
{
_isLoading = value;
RaisePropertyChanged(IsLoadingPropertyName);
}
}
}
and the xaml
<shell:SystemTray.ProgressIndicator>
<shell:ProgressIndicator IsIndeterminate="true" IsVisible="{Binding Main.IsLoading, Source={StaticResource Locator}}" />
</shell:SystemTray.ProgressIndicator>
So, I'm saying that main view model is loading when there's something loading there, or if the settings view model is loading.
The problem is that the binding only works when setting the main view model's IsLoading property, it doesn't react when I set it in the inner IsLoading one. Both have the same property name "IsLoading". Shouldn't it be detected?
For example, in Main view model (just the execution of the command for simplicity) :
private void ExecuteRefreshCommand()
{
ViewModelLocator viewModelLocator = Application.Current.Resources["Locator"] as ViewModelLocator;
viewModelLocator.SettingsViewModel.GetCurrentLocationCommand.Execute(null);
}
and inside the settings view model :
public RelayCommand GetCurrentLocationCommand
{
get
{
Action getLocation = () =>
{
if (!NetworkInterface.GetIsNetworkAvailable())
{
return;
}
var watcher = new GeoCoordinateWatcher(GeoPositionAccuracy.Default);
watcher.PositionChanged += WatcherPositionChanged;
IsLoading = true; // settings view model "IsLoading" propertychanged raising property
watcher.Start();
};
return new RelayCommand(getLocation);
}
}

You're looking at the MainViewModel's isLoading property to determine whether to show the progressbar or not. Silverlight uses the NotifyPropertyChanged event to determine when it should reevaluate a certain property. When setting either the SettingsViewModel's IsLoading property- or the MainViewModel's property, you only raise the changedEvent for that ViewModel. You should raise the ChangedEvent for both.
A modified setter example could be (depending on the exposed methods)
set
{
if (value != _isLoading)
{
_isLoading = value;
RaisePropertyChanged(IsLoadingPropertyName);
((ViewModelLocator)Application.Current.Resources["Locator"]).SettingsViewModel.RaisePropertyChanged(IsLoadingPropertyName);
}
}
Note that many MVVM frameworks offer a functionality called Messaging which is ideal to do cross ViewModel communication without creating the strict dependency you created right now. Alternatively you can use a globally consumed IsLoading property.