Adding Data to a Picker's Items Collection

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last updated: 2017-04

The Picker view is a control for selecting a text item from a list of data. This article explains how to populate a Picker with data by adding it to the Items collection, and how to respond to item selection by the user.

Populating a Picker with Data

Prior to Xamarin.Forms 2.3.4, the process for populating a Picker with data was to add the data to be displayed to the read-only Items collection, which is of type IList<string>. Each item in the collection must be of type string. Items can be added in XAML by initializing the Items property with a list of x:String items:

<Picker Title="Select a monkey">
  <Picker.Items>
    <x:String>Baboon</x:String>
    <x:String>Capuchin Monkey</x:String>
    <x:String>Blue Monkey</x:String>
    <x:String>Squirrel Monkey</x:String>
    <x:String>Golden Lion Tamarin</x:String>
    <x:String>Howler Monkey</x:String>
    <x:String>Japanese Macaque</x:String>
  </Picker.Items>
</Picker>

The equivalent C# code is shown below:

var picker = new Picker { Title = "Select a monkey" };
picker.Items.Add("Baboon");
picker.Items.Add("Capuchin Monkey");
picker.Items.Add("Blue Monkey");
picker.Items.Add("Squirrel Monkey");
picker.Items.Add("Golden Lion Tamarin");
picker.Items.Add("Howler Monkey");
picker.Items.Add("Japanese Macaque");

In addition to adding data using the Items.Add method, data can also be inserted into the collection by using the Items.Insert method.

Responding to Item Selection

A Picker supports selection of one item at a time. When a user selects an item, the SelectedIndexChanged event fires, and the SelectedIndex property is updated to an integer representing the index of the selected item in the list. The SelectedIndex property is a zero-based number indicating the item that the user selected. If no item is selected, which is the case when the Picker is first created and initialized, SelectedIndex will be -1.

ℹ️

Item selection behavior in a Picker can be customized on iOS with a platform-specific. For more information, see Controlling Picker Item Selection.

The following code example shows the OnPickerSelectedIndexChanged event handler method, which is executed when the SelectedIndexChanged event fires:

void OnPickerSelectedIndexChanged(object sender, EventArgs e)
{
  var picker = (Picker)sender;
  int selectedIndex = picker.SelectedIndex;

  if (selectedIndex != -1)
  {
    monkeyNameLabel.Text = picker.Items[selectedIndex];
  }
}

This method obtains the SelectedIndex property value, and uses the value to retrieve the selected item from the Items collection. Because each item in the Items collection is a string, they can be displayed by a Label without requiring a cast.

ℹ️

A Picker can be initialized to display a specific item by setting the SelectedIndex property. However, the SelectedIndex property must be set after initializing the Items collection.

Summary

The Picker view is a control for selecting a text item from a list of data. This article explained how to populate a Picker with data by adding it to the Items collection, and how to respond to item selection by the user. This was the process for using a Picker prior to Xamarin.Forms 2.3.4.

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