Column.comparison

Description

The comparison to use when using ColumnSortingMode.Default. Compares two items by their index in the source.

The following example creates a MultiColumnListView that can be sorted with the default algorithm:

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using UnityEditor;
using UnityEngine;
using UnityEngine.UIElements;
using Debug = UnityEngine.Debug;

namespace MultiColumnViewExample
{
    public class FileExplorerWindow : EditorWindow
    {
        MultiColumnListView m_ListView;
        List<FileInfoWrapper> m_Source = new List<FileInfoWrapper>();
        StringBuilder m_StringBuilder = new StringBuilder();

        [MenuItem("MultiColumnView Examples/File Explorer (List)")]
        public static void ShowExample()
        {
            var wnd = GetWindow<FileExplorerWindow>();
            wnd.titleContent = new GUIContent("File Explorer");
        }

        public void CreateGUI()
        {
            // Here we're setting up a 3-column list view to display information on all files in the project.
            // Each column will be sorted using the `comparison` callback.
            // Use CTRL/CMD + click on a column header to sort multiple columns.
            // Use Shift + click on a column header to remove sorting.
            m_ListView = new MultiColumnListView(new Columns()
            {
                new Column()
                {
                    name = "filename", title = "Name", minWidth = 600,
                    bindCell = (ve, row) => ((Label)ve).text = m_Source[row].fullFileName,
                    comparison = (a, b) => m_Source[a].fullFileName.CompareTo(m_Source[b].fullFileName),
                },
                new Column()
                {
                    name = "type", title = "Type", minWidth = 60,
                    bindCell = (ve, row) => ((Label)ve).text = m_Source[row].type,
                    comparison = (a, b) => m_Source[a].type.CompareTo(m_Source[b].type),
                },
                new Column()
                {
                    name = "size", title = "Size", minWidth = 60,
                    bindCell = (ve, row) => ((Label)ve).text = m_Source[row].displaySize,
                    comparison = (a, b) => m_Source[a].sizeLong.CompareTo(m_Source[b].sizeLong),
                }
            });

            // This causes the list view to take all the space available.
            m_ListView.style.flexGrow = 1;

            // Setting the sortingMode to Default enables Unity's sorting algorithm, which will use the Columns' comparison callbacks.
            m_ListView.sortingMode = ColumnSortingMode.Default;

            // Use all the files in the project as the source.
            foreach (var file in Directory.EnumerateFiles(Application.dataPath, "*.*", SearchOption.AllDirectories))
            {
                m_Source.Add(new FileInfoWrapper(new FileInfo(file)));
            }

            m_ListView.itemsSource = m_Source;

            // The columnSortingChanged and sortedColumns property can be used to know when the ordering changes.
            // This is the callback to use if you want to implement a custom sorting algorithm, when using ColumnSortingMode.Custom.
            m_ListView.columnSortingChanged += () =>
            {
                m_StringBuilder.Clear();
                foreach (var s in m_ListView.sortedColumns)
                {
                    m_StringBuilder.Append($"Sorted {s.columnName} in {s.direction} order.");
                }

                Debug.Log(m_StringBuilder.ToString());
            };

            rootVisualElement.Add(m_ListView);
        }
    }

    public class FileInfoWrapper
    {
        static readonly string[] k_SizeSuffixes = { "B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };

        static string GetBytesReadable(long fileSizeInBytes)
        {
            if (fileSizeInBytes == 0)
                return "0" + k_SizeSuffixes[0];

            var magnitude = (int)Math.Log(fileSizeInBytes, 1024);
            var adjustedSize = fileSizeInBytes / (1L << (magnitude * 10));

            return $"{adjustedSize:n1} {k_SizeSuffixes[magnitude]}";
        }

        public FileInfoWrapper(FileInfo fileInfo)
        {
            fullFileName = fileInfo.FullName;
            type = fileInfo.Extension.Substring(1).ToUpper();
            displaySize = GetBytesReadable(fileInfo.Length);
            sizeLong = fileInfo.Length;
        }

        public readonly string fullFileName;
        public readonly string type;
        public readonly string displaySize;
        public readonly long sizeLong; // It is faster to compare long than strings.
    }
}