Carousel.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Input;
using System.Windows.Markup;
using System.Windows.Threading;
using HandyControl.Data;
using HandyControl.Interactivity;
using HandyControl.Tools;

namespace HandyControl.Controls
{
    /// <summary>
    ///     轮播控件
    /// </summary>
    [DefaultProperty("Items")]
    [ContentProperty("Items")]
    [TemplatePart(Name = ElementPanelPage, Type = typeof(Panel))]
    public class Carousel : SimpleItemsControl, IDisposable
    {
        #region Constants

        private const string ElementPanelPage = "PART_PanelPage";

        #endregion Constants

        #region Data

        private bool _isDisposed;

        private Panel _panelPage;

        private bool _appliedTemplate;

        private int _pageIndex = -1;

        private RadioButton _selectedButton;

        private DispatcherTimer _updateTimer;

        private readonly List<double> _widthList = new();

        private readonly Dictionary<object, CarouselItem> _entryDic = new();

        private bool _isRefresh;

        private IEnumerable _itemsSourceInternal;

        #endregion Data

        public override void OnApplyTemplate()
        {
            _appliedTemplate = false;

            _panelPage?.RemoveHandler(ButtonBase.ClickEvent, new RoutedEventHandler(ButtonPages_OnClick));

            base.OnApplyTemplate();

            _panelPage = GetTemplateChild(ElementPanelPage) as Panel;

            if (!CheckNull()) return;

            _panelPage.AddHandler(ButtonBase.ClickEvent, new RoutedEventHandler(ButtonPages_OnClick));
            _appliedTemplate = true;
            Update();
        }

        private void Update()
        {
            TimerSwitch(AutoRun);
            UpdatePageButtons(_pageIndex);
        }

        private bool CheckNull() => _panelPage != null;

        public static readonly DependencyProperty AutoRunProperty = DependencyProperty.Register(
            "AutoRun", typeof(bool), typeof(Carousel), new PropertyMetadata(ValueBoxes.FalseBox, (o, args) =>
            {
                var ctl = (Carousel) o;
                ctl.TimerSwitch((bool) args.NewValue);
            }));

        public static readonly DependencyProperty IntervalProperty = DependencyProperty.Register(
            "Interval", typeof(TimeSpan), typeof(Carousel), new PropertyMetadata(TimeSpan.FromSeconds(2)));

        public static readonly DependencyProperty ExtendWidthProperty = DependencyProperty.Register(
            "ExtendWidth", typeof(double), typeof(Carousel), new PropertyMetadata(ValueBoxes.Double0Box));

        public double ExtendWidth
        {
            get => (double) GetValue(ExtendWidthProperty);
            set => SetValue(ExtendWidthProperty, value);
        }

        public static readonly DependencyProperty IsCenterProperty = DependencyProperty.Register(
            "IsCenter", typeof(bool), typeof(Carousel), new PropertyMetadata(ValueBoxes.FalseBox));

        public bool IsCenter
        {
            get => (bool) GetValue(IsCenterProperty);
            set => SetValue(IsCenterProperty, ValueBoxes.BooleanBox(value));
        }

        public static readonly DependencyProperty PageButtonStyleProperty = DependencyProperty.Register(
            "PageButtonStyle", typeof(Style), typeof(Carousel), new PropertyMetadata(default(Style)));

        public Style PageButtonStyle
        {
            get => (Style) GetValue(PageButtonStyleProperty);
            set => SetValue(PageButtonStyleProperty, value);
        }

        public Carousel()
        {
            CommandBindings.Add(new CommandBinding(ControlCommands.Prev, ButtonPrev_OnClick));
            CommandBindings.Add(new CommandBinding(ControlCommands.Next, ButtonNext_OnClick));
            CommandBindings.Add(new CommandBinding(ControlCommands.Selected, ButtonPages_OnClick));

            Loaded += (s, e) => UpdatePageButtons();
            IsVisibleChanged += Carousel_IsVisibleChanged;
        }

        ~Carousel() => Dispose();

        public void Dispose()
        {
            if (_isDisposed) return;

            IsVisibleChanged -= Carousel_IsVisibleChanged;
            _updateTimer?.Stop();
            _isDisposed = true;

            GC.SuppressFinalize(this);
        }

        private void Carousel_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            if (_updateTimer == null) return;

            if (IsVisible)
            {
                _updateTimer.Tick += UpdateTimer_Tick;
                _updateTimer.Start();
            }
            else
            {
                _updateTimer.Stop();
                _updateTimer.Tick -= UpdateTimer_Tick;
            }
        }

        /// <summary>
        ///     是否自动跳转
        /// </summary>
        public bool AutoRun
        {
            get => (bool) GetValue(AutoRunProperty);
            set => SetValue(AutoRunProperty, ValueBoxes.BooleanBox(value));
        }

        /// <summary>
        ///     跳转时间间隔
        /// </summary>
        public TimeSpan Interval
        {
            get => (TimeSpan) GetValue(IntervalProperty);
            set => SetValue(IntervalProperty, value);
        }

        /// <summary>
        ///     页码
        /// </summary>
        public int PageIndex
        {
            get => _pageIndex;
            set
            {
                if (Items.Count == 0) return;
                if (_pageIndex == value) return;
                if (value < 0)
                    _pageIndex = Items.Count - 1;
                else if (value >= Items.Count)
                    _pageIndex = 0;
                else
                    _pageIndex = value;
                UpdatePageButtons(_pageIndex);
            }
        }

        /// <summary>
        ///     计时器开关
        /// </summary>
        private void TimerSwitch(bool run)
        {
            if (!_appliedTemplate) return;

            if (_updateTimer != null)
            {
                _updateTimer.Tick -= UpdateTimer_Tick;
                _updateTimer.Stop();
                _updateTimer = null;
            }

            if (!run) return;
            _updateTimer = new DispatcherTimer
            {
                Interval = Interval
            };
            _updateTimer.Tick += UpdateTimer_Tick;
            _updateTimer.Start();
        }

        private void UpdateTimer_Tick(object sender, EventArgs e)
        {
            if (IsMouseOver) return;
            PageIndex++;
        }

        /// <summary>
        ///     更新页按钮
        /// </summary>
        public void UpdatePageButtons(int index = -1)
        {
            if (!CheckNull()) return;
            if (!_appliedTemplate) return;

            var count = Items.Count;
            _widthList.Clear();
            _widthList.Add(0);
            var width = .0;
            foreach (FrameworkElement item in ItemsHost.Children)
            {
                item.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
                width += item.DesiredSize.Width;
                _widthList.Add(width);
            }

            ItemsHost.Width = _widthList.Last() + ExtendWidth;
            _panelPage.Children.Clear();
            for (var i = 0; i < count; i++)
            {
                _panelPage.Children.Add(new RadioButton
                {
                    Style = PageButtonStyle
                });
            }

            if (index == -1 && count > 0) index = 0;
            if (index >= 0 && index < count)
            {
                if (_panelPage.Children[index] is RadioButton button)
                {
                    button.IsChecked = true;
                    button.RaiseEvent(new RoutedEventArgs(ButtonBase.ClickEvent, button));
                    UpdateItemsPosition();
                }
            }
        }

        /// <summary>
        ///     更新项的位置
        /// </summary>
        private void UpdateItemsPosition()
        {
            if (!CheckNull() || !_appliedTemplate || Items.Count == 0)
            {
                return;
            }

            if (PageIndex == -1)
            {
                PageIndex = 0;
            }

            if (!IsCenter)
            {
                ItemsHost.BeginAnimation(MarginProperty,
                    AnimationHelper.CreateAnimation(new Thickness(-_widthList[PageIndex], 0, 0, 0)));
            }
            else
            {
                var ctl = (FrameworkElement) ItemsHost.Children[PageIndex];
                var ctlWidth = ctl.DesiredSize.Width;
                ItemsHost.BeginAnimation(MarginProperty,
                    AnimationHelper.CreateAnimation(
                        new Thickness(-_widthList[PageIndex] + (ActualWidth - ctlWidth) / 2, 0, 0, 0)));
            }
        }

        protected override void OnRenderSizeChanged(SizeChangedInfo sizeInfo)
        {
            base.OnRenderSizeChanged(sizeInfo);
            UpdateItemsPosition();
        }

        private void ButtonPages_OnClick(object sender, RoutedEventArgs e)
        {
            if (!CheckNull()) return;

            _selectedButton = e.OriginalSource as RadioButton;

            var index = _panelPage.Children.IndexOf(_selectedButton);
            if (index != -1)
            {
                PageIndex = index;
            }
        }

        private void ButtonPrev_OnClick(object sender, RoutedEventArgs e) => PageIndex--;

        private void ButtonNext_OnClick(object sender, RoutedEventArgs e) => PageIndex++;

        protected override DependencyObject GetContainerForItemOverride() => new CarouselItem();

        protected override bool IsItemItsOwnContainerOverride(object item) => item is CarouselItem;

        private void ClearItems()
        {
            ItemsHost?.Children.Clear();
            _entryDic.Clear();
        }

        private void RemoveItem(object item)
        {
            if (_entryDic.TryGetValue(item, out var entry))
            {
                ItemsHost.Children.Remove(entry);
                Items.Remove(item);
                _entryDic.Remove(item);
            }
        }

        protected override void Refresh()
        {
            if (ItemsHost == null) return;

            _entryDic.Clear();
            _isRefresh = true;

            foreach (var item in Items)
            {
                AddItem(item);
            }

            _isRefresh = false;
        }

        private void AddItem(object item) => InsertItem(_entryDic.Count, item);

        private void InsertItem(int index, object item)
        {
            if (ItemsHost == null)
            {
                Items.Insert(index, item);
                _entryDic.Add(item, null);
            }
            else
            {
                DependencyObject container;
                if (IsItemItsOwnContainerOverride(item))
                {
                    container = item as DependencyObject;
                }
                else
                {
                    container = GetContainerForItemOverride();
                    PrepareContainerForItemOverride(container, item);
                }

                if (container is CarouselItem element)
                {
                    element.Style = ItemContainerStyle;
                    _entryDic[item] = element;
                    ItemsHost.Children.Insert(index, element);

                    if (IsLoaded && !_isRefresh && _itemsSourceInternal != null)
                    {
                        Items.Insert(index, item);
                    }
                }
            }
        }

        protected override void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
        {
            if (_itemsSourceInternal != null)
            {
                if (_itemsSourceInternal is INotifyCollectionChanged s)
                {
                    s.CollectionChanged -= InternalCollectionChanged;
                }

                Items.Clear();
                ClearItems();
            }
            _itemsSourceInternal = newValue;
            if (_itemsSourceInternal != null)
            {
                if (_itemsSourceInternal is INotifyCollectionChanged s)
                {
                    s.CollectionChanged += InternalCollectionChanged;
                }
                foreach (var item in _itemsSourceInternal)
                {
                    AddItem(item);
                }
            }
        }

        private void InternalCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (ItemsHost == null) return;

            if (e.Action == NotifyCollectionChangedAction.Reset)
            {
                if (_entryDic.Count == 0) return;
                ClearItems();
                Items.Clear();
                return;
            }

            if (e.OldItems != null)
            {
                foreach (var item in e.OldItems)
                {
                    RemoveItem(item);
                }
            }
            if (e.NewItems != null)
            {
                var count = 0;
                foreach (var item in e.NewItems)
                {
                    var index = e.NewStartingIndex + count++;
                    InsertItem(index, item);
                }
            }
        }

        protected override void OnItemsChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (_itemsSourceInternal != null) return;

            InternalCollectionChanged(sender, e);
        }

        protected override void OnItemTemplateChanged(DependencyPropertyChangedEventArgs e)
        {

        }

        protected override void OnItemContainerStyleChanged(DependencyPropertyChangedEventArgs e)
        {

        }
    }
}