Pass object in click/tapped event handler in Xamarin Forms

Question

Here is my job class:

public class Job
{
        public string Id{ get; set;}
        public string Name{ get; set;}
}

And here is my ListView:

public class JobListePage:ContentPage
    {
        // Members
        private ListView lstView;

        // Constructor    
        public JobListePage ()
        {
            // Set members
            lstView = new ListView ();

            // Create job objects
            Job[] jobs = {new Job(){Id="1", Name="Benny"}, new Job(){Id="2", Name="Lukas"}};

            // Fill listview with job objects
            lstView.ItemsSource = jobs;

            // HOW CAN I PASS THE TAPPED OBJECT HERE???
            lstView.ItemTapped += async (o, e) => {
                await DisplayAlert("Tapped",  "HERE I WANT TO SHOW THE ID", "OK");
                ((ListView)o).SelectedItem = null; // de-select the row
            };

            ....

Now how can I pass the tapped "job-object" to the event?

You can see that I show a message to the user. And in there it should stand the ID of the tapped object.

You can just use the object inside a lambda. It will create a closure which will save the reference to it. — JustSomeGuy, Mar 11 '15 at 11:35
And the title is misleading, it's not an event, but rather event handler. — JustSomeGuy, Mar 11 '15 at 11:36

score 12 · Accepted Answer · answered Mar 11 '15 at 11:46

12

try:

        lstView.ItemTapped += async (o, e) => {
            var myList= (ListView)o;
            var myJob = (myList.SelectedItem as Job);
            await DisplayAlert("Tapped",  myJob.Id, "OK");
            myList.SelectedItem = null; // de-select the row
        };

answered Mar 11 '15 at 11:46

JKennedy

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It works!!!!!! What am I missing here? Does the sender contain the job object? And what are you doing? A cast? Can you reference me to an article, that explains it? Thanks a lot! – arnie Mar 11 '15 at 12:49
this is a combination of different things. an `EventHandler` sends an `object (o)` and `eventargs (e)` in your case the sender `o` is a `ListView` therefore you must cast the object to a `ListView` to access it's properties. The property we need in this case is the `SelectedItem` property which is a `Job` and again we cast this (although I'm not sure we need to) and then access the `Job's` propertie `Id` [this is an article explaining this (Boxing and Unboxing)](https://msdn.microsoft.com/en-gb/library/yz2be5wk.aspx) If this answer has helped you please mark it as the correct answer – JKennedy Mar 11 '15 at 13:02
perfect explanation! no more to say here – arnie Mar 11 '15 at 13:06
@user1 You just saved me a ton of headaches. Thank you! – Derek Foulk Jun 20 '17 at 19:31

Rohit Vipin Mathews · Answer 2 · 2016-08-02T10:32:18.560

6

The following page explains exactly what you are looking for: Selecting an Item in a ListView

listView.ItemSelected += async (sender, e) => 
{
    await DisplayAlert("Tapped!", (e.SelectedItem as Job).Id + " was tapped.", "OK");
};

If you want to navigate to a detail page passing arguments then use the following:

listView.ItemSelected += async (sender, e) => 
{       
      var jobPage = new JobPage(e.SelectedItem as Job); // new page shows correct data          
      await Navigation.PushAsync(jobPage);
};

edited Aug 02 '16 at 10:32

answered Mar 17 '15 at 06:52

Rohit Vipin Mathews

11,629
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@arnie very happy to help – Rohit Vipin Mathews Mar 17 '15 at 13:48

Pass object in click/tapped event handler in Xamarin Forms

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