Steven Kirk
6 years ago
committed by
GitHub
GitHub
10 changed files with 302 additions and 37 deletions
@ -0,0 +1,29 @@ |
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using Avalonia.Controls.Templates; |
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namespace Avalonia.Controls |
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{ |
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public abstract class ElementFactory : IElementFactory |
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{ |
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bool IDataTemplate.SupportsRecycling => false; |
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public IControl Build(object data) |
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{ |
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return GetElementCore(new ElementFactoryGetArgs { Data = data }); |
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} |
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public IControl GetElement(ElementFactoryGetArgs args) |
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{ |
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return GetElementCore(args); |
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} |
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public bool Match(object data) => true; |
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public void RecycleElement(ElementFactoryRecycleArgs args) |
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{ |
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RecycleElementCore(args); |
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} |
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protected abstract IControl GetElementCore(ElementFactoryGetArgs args); |
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protected abstract void RecycleElementCore(ElementFactoryRecycleArgs args); |
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} |
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} |
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@ -0,0 +1,66 @@ |
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using Avalonia.Controls.Templates; |
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namespace Avalonia.Controls |
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{ |
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/// <summary>
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/// Represents the optional arguments to use when calling an implementation of the
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/// <see cref="IElementFactory"/>'s <see cref="IElementFactory.GetElement"/> method.
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/// </summary>
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public class ElementFactoryGetArgs |
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{ |
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/// <summary>
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/// Gets or sets the data item for which an appropriate element tree should be realized
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/// when calling <see cref="IElementFactory.GetElement"/>.
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/// </summary>
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public object Data { get; set; } |
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/// <summary>
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/// Gets or sets the <see cref="IControl"/> that is expected to be the parent of the
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/// realized element from <see cref="IElementFactory.GetElement"/>.
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/// </summary>
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public IControl Parent { get; set; } |
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/// <summary>
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/// Gets or sets the index of the item that should be realized.
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/// </summary>
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public int Index { get; set; } |
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} |
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/// <summary>
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/// Represents the optional arguments to use when calling an implementation of the
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/// <see cref="IElementFactory"/>'s <see cref="IElementFactory.GetElement"/> method.
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/// </summary>
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public class ElementFactoryRecycleArgs |
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{ |
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/// <summary>
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/// Gets or sets the <see cref="IControl"/> to recycle when calling
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/// <see cref="IElementFactory.RecycleElement"/>.
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/// </summary>
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public IControl Element { get; set; } |
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/// <summary>
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/// Gets or sets the <see cref="IControl"/> that is expected to be the parent of the
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/// realized element from <see cref="IElementFactory.GetElement"/>.
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/// </summary>
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public IControl Parent { get; set; } |
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} |
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/// <summary>
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/// A data template that supports creating and recyling elements for an <see cref="ItemsRepeater"/>.
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/// </summary>
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public interface IElementFactory : IDataTemplate |
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{ |
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/// <summary>
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/// Gets an <see cref="IControl"/>.
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/// </summary>
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/// <param name="args">The element args.</param>
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public IControl GetElement(ElementFactoryGetArgs args); |
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/// <summary>
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/// Recycles an <see cref="IControl"/> that was previously retrieved using
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/// <see cref="GetElement"/>.
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/// </summary>
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/// <param name="args">The recycle args.</param>
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public void RecycleElement(ElementFactoryRecycleArgs args); |
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} |
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} |
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@ -0,0 +1,119 @@ |
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using System; |
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using System.Collections.Generic; |
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using System.Linq; |
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using Avalonia.Controls.Templates; |
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#nullable enable |
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namespace Avalonia.Controls |
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{ |
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public class SelectTemplateEventArgs : EventArgs |
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{ |
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public string? TemplateKey { get; set; } |
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public object? DataContext { get; internal set; } |
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public IControl? Owner { get; internal set; } |
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} |
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public class RecyclingElementFactory : ElementFactory |
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{ |
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private RecyclePool? _recyclePool; |
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private IDictionary<string, IDataTemplate>? _templates; |
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private SelectTemplateEventArgs? _args; |
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public RecyclingElementFactory() |
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{ |
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Templates = new Dictionary<string, IDataTemplate>(); |
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} |
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public RecyclePool RecyclePool |
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{ |
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get => _recyclePool ??= new RecyclePool(); |
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set => _recyclePool = value ?? throw new ArgumentNullException(nameof(value)); |
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} |
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public IDictionary<string, IDataTemplate> Templates |
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{ |
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get => _templates ??= new Dictionary<string, IDataTemplate>(); |
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set => _templates = value ?? throw new ArgumentNullException(nameof(value)); |
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} |
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public event EventHandler<SelectTemplateEventArgs>? SelectTemplateKey; |
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protected override IControl GetElementCore(ElementFactoryGetArgs args) |
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{ |
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if (_templates == null || _templates.Count == 0) |
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{ |
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throw new InvalidOperationException("Templates cannot be empty."); |
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} |
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var templateKey = Templates.Count == 1 ? |
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Templates.First().Key : |
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OnSelectTemplateKeyCore(args.Data, args.Parent); |
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if (string.IsNullOrEmpty(templateKey)) |
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{ |
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// Note: We could allow null/whitespace, which would work as long as
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// the recycle pool is not shared. in order to make this work in all cases
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// currently we validate that a valid template key is provided.
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throw new InvalidOperationException("Template key cannot be null or empty."); |
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} |
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// Get an element from the Recycle Pool or create one
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var element = RecyclePool.TryGetElement(templateKey, args.Parent); |
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if (element is null) |
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{ |
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// No need to call HasKey if there is only one template.
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if (Templates.Count > 1 && !Templates.ContainsKey(templateKey)) |
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{ |
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var message = $"No templates of key '{templateKey}' were found in the templates collection."; |
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throw new InvalidOperationException(message); |
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} |
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var dataTemplate = Templates[templateKey]; |
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element = dataTemplate.Build(args.Data); |
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// Associate ReuseKey with element
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RecyclePool.SetReuseKey(element, templateKey); |
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} |
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return element; |
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} |
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protected override void RecycleElementCore(ElementFactoryRecycleArgs args) |
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{ |
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var element = args.Element; |
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var key = RecyclePool.GetReuseKey(element); |
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RecyclePool.PutElement(element, key, args.Parent); |
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} |
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protected virtual string OnSelectTemplateKeyCore(object dataContext, IControl owner) |
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{ |
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if (SelectTemplateKey is object) |
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{ |
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_args ??= new SelectTemplateEventArgs(); |
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_args.TemplateKey = null; |
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_args.DataContext = dataContext; |
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_args.Owner = owner; |
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try |
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{ |
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SelectTemplateKey(this, _args); |
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} |
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finally |
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{ |
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_args.DataContext = null; |
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_args.Owner = null; |
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} |
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} |
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if (string.IsNullOrEmpty(_args?.TemplateKey)) |
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{ |
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throw new InvalidOperationException( |
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"Please provide a valid template identifier in the handler for the SelectTemplateKey event."); |
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} |
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return _args!.TemplateKey!; |
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} |
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} |
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} |
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