Xamarin.Forms Working with ListView from existing List of objects

Question

I am using Xamarin.Forms and I am trying to create a ListView from c# List of my model, this is what I have tried...I created this view

<ListView x:Name="lst">
             <ListView.ItemTemplate>
                 <DataTemplate>
                     <TextCell Text="{Binding Email}" />
                 </DataTemplate>
             </ListView.ItemTemplate>
         </ListView>

and I tried to set the ItemSource like so:

List<UserClass> users = new List<UserClass>();

            users = webService.getScannedLog();

            BindingContext = this;
            lst.ItemsSource = users;

but when I do this, I get this error:

Object reference not set to an instance of an object

What am I doing wrong?

I would be curious to know what do you think about my second post/answer to your question (also, if any of those answers solved your problem, please do not forget to mark it as THE ANSWER, so that that is reflected in the feed) — deczaloth
– deczaloth, Commented Oct 27, 2019 at 22:17

deczaloth · Accepted Answer · 2019-10-25 19:33:43Z

1

You have to set the binding for ItemsSource:

<ListView x:Name="lst"
          ItemsSource="{Binding .}">
             <ListView.ItemTemplate>
                 <DataTemplate>
                     <TextCell Text="{Binding Email}" />
                 </DataTemplate>
             </ListView.ItemTemplate>
         </ListView>

And in the code behind:

List<UserClass> users = new List<UserClass>();

            users = webService.getScannedLog();

            BindingContext = users;

Note that ItemsSource binding was set in XAML.

edited Oct 25, 2019 at 19:33

answered Oct 25, 2019 at 19:31

deczaloth

7,5854 gold badges31 silver badges64 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

user979331 Over a year ago

How will it know to use the user List?

deczaloth Over a year ago

I edited my answer. If you still have doubts, please let me know.

deczaloth Over a year ago

My pleasure! Please do not forget to set this post as Answer ;)

Jason Over a year ago

there is no reason you can't set ItemsSource directly in code

deczaloth Over a year ago

@Jason, no one said "you can't set ItemsSource directly in code". I just used my own style and pointed that out in my post by telling user979331 to "Note that ItemsSource binding was set in XAML".

|

deczaloth · Accepted Answer · 2019-10-25 20:26:47Z

Motivated by the comment of @Jason on my first answer to this post i got curious to know if he was right when he said:

there is no reason you can't set ItemsSource directly in code

and after a bit of research i found out that as he pointed out, the code in my answer was doing fundamentally the same as the code of the OP. But... how did then my answer help OP to solve the problem?

Well, the only way i can get the exception

Object reference not set to an instance of an object

using the code in the original post is if the c# code posted is called before InitializeComponent() is called, that is, if the code behind looks like:

public MainPage()
{

    List<UserClass> users = new List<UserClass>();

    users = webService.getScannedLog();

    BindingContext = this;
    lst.ItemsSource = users;

    InitializeComponent();

}

in which case lst is being called before it is even created by InitializeComponent(). In that case, my answer solved the issue by removing lst reference and setting ItemsSource directly in XAML.

If that is the case, at all, then i would like to say that to solve the issue it is enough to move the setting of ItemsSource after the call to InitializeComponent(), in which case the code would look something like:

public MainPage()
{

    InitializeComponent();    

    List<UserClass> users = new List<UserClass>();

    users = webService.getScannedLog();

    BindingContext = this;
    lst.ItemsSource = users;

}

@user979331, please let me know if this is the case.

Collectives™ on Stack Overflow

Xamarin.Forms Working with ListView from existing List of objects

2 Answers 2

7 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

7 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related