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Xamarin.Android ListView Parts and Functionality

  • Artikkeli

A ListView consists of the following parts:

  • Rows – The visible representation of the data in the list.

  • Adapter – A non-visual class that binds the data source to the list view.

  • Fast Scrolling – A handle that lets the user scroll the length of the list.

  • Section Index – A user interface element that floats over the scrolling rows to indicate where in the list the current rows are located.

These screenshots use a basic ListView control to show how Fast Scrolling and Section Index are rendered:

Screenshots of apps using Plain old rows, fast scrolling, and section index

The elements that make up a ListView are described in more detail below:

Rows

Each row has its own View. The view can be either one of the built-in views defined in Android.Resources, or a custom view. Each row can use the same view layout or they can all be different. There are examples in this document of using built-in layouts and others explaining how to define custom layouts.

Adapter

The ListView control requires an Adapter to supply the formatted View for each row. Android has built-in Adapters and Views that can be used, or custom classes can be created.

Fast Scrolling

When a ListView contains many rows of data fast-scrolling can be enabled to help the user navigate to any part of the list. The fast-scrolling 'scroll bar' can be optionally enabled (and customized in API level 11 and higher).

Section Index

While scrolling through long lists, the optional section index provides the user with feedback on what part of the list they are currently viewing. It is only appropriate on long lists, typically in conjunction with fast scrolling.

Classes Overview

The primary classes used to display ListViews are shown here:

UML diagram illustrating relationships between ListView and associated classes

The purpose of each class is described below:

  • ListView – user interface element that displays a scrollable collection of rows. On phones it usually uses up the entire screen (in which case, the ListActivity class can be used) or it could be part of a larger layout on phones or tablet devices.

  • View – a View in Android can be any user interface element, but in the context of a ListView it requires a View to be supplied for each row.

  • BaseAdapter – Base class for Adapter implementations to bind a ListView to a data source.

  • ArrayAdapter – Built-in Adapter class that binds an array of strings to a ListView for display. The generic ArrayAdapter<T> does the same for other types.

  • CursorAdapter – Use CursorAdapter or SimpleCursorAdapter to display data based on an SQLite query.

This document contains simple examples that use an ArrayAdapter as well as more complex examples that require custom implementations of BaseAdapter or CursorAdapter.