这两天用 Blazor.Server 写了个小工具，算是对 Blazor 的入门吧。
用到了组件库：Bootstrap.Blazor 。这个库存， 总体来说， 很棒。
使用过程中， 发现了一个BUG，bool? 类型的数据，DisplayText 显示不出来, 用于修改时， bool? 类型的数据， 也读取不到真实的值。
bool? 的DisplayText 读取不到
另外， AutoFill / AutoComplete 两个组件的设计，脱离了真实的使用场景。自动完成的数据源， 一般都是建立在海量的数据基础之上（比如从 ES 中实时获取查询结果）。但是这两个组件却使用的是本地数据源，这显然是不可能的。
做为 AutoComplete 的升级 （AutoComplete 的数据源只能是 IEnumerable<string>）， AutoFill (数据源是IEnumerable<TValue>) 要求 TValue 必须是实现ISelectedItem， 这个设计可以说很不合理， 太麻烦。
为了解决上面两个问题， 我复制 了 AutoFill 的源码，写了这个 RemoteSourceAutoFill
RemoteSourceAutoFill.razor
@typeparam TValue
@inherits BootstrapInput<TValue>
@if (IsShowLabel)
{
<label class="form-label" required="@Required" for="@Id">@DisplayText</label>
}
<div class="@ClassString" @ref="RemoteSourceAutoFillElement">
<input @attributes="AdditionalAttributes" class="@ClassName" autocomplete="off" type="text" placeholder="@PlaceHolder" @bind-value="@Query" @bind-value:event="oninput" @onblur="OnBlur" @onkeyup="OnKeyUp" @ref="FocusElement" />
<i class="fa fa-fw fa-spinner fa-spin"></i>
<div class="select-dropdown">
<ul class="dropdown-list">
@if (items != null && items.Any())
{
foreach (var item in items)
{
<li class="dropdown-item" @onmousedown="e => OnClickItem(item)">
@if (Template != null)
{
@Template(item)
}
else
{
<div>@this.GetDisplayText(item)</div>
}
</li>
}
}
else
{
<li class="dropdown-item">@NoDataTip</li>
}
</ul>
</div>
</div>
<CascadingValue Value="this" IsFixed="true">
@ChildContent
</CascadingValue>
RemoteSourceAutoFill.razor.cs
/// <summary>
/// 支持远程数据源的自动完成
/// </summary>
/// <typeparam name="TValue"></typeparam>
public partial class RemoteSourceAutoFill<TValue> /*where TValue : ISelectedItem*/
{
private bool _isLoading;
private bool _isShown;
private string _lastFilterText;
/// <summary>
/// 获得 组件样式
/// </summary>
protected virtual string ClassString => CssBuilder.Default("auto-complete")
.AddClass("is-loading", _isLoading)
.AddClass("is-complete", _isShown)
.Build();
/// <summary>
///
/// </summary>
private IEnumerable<TValue> items;
/// <summary>
/// 获得/设置 无匹配数据时显示提示信息 默认提示"无匹配数据"
/// </summary>
[Parameter]
[NotNull]
public string NoDataTip { get; set; }
/// <summary>
/// 获得/设置 候选项模板
/// </summary>
[Parameter]
public RenderFragment<TValue> Template { get; set; }
/// <summary>
/// 获得/设置 选项改变回调方法 默认 null
/// </summary>
[Parameter]
public Func<TValue, Task> OnSelectedItemChanged { get; set; }
/// <summary>
/// 文本框内容改变时, 触发的数据查询
/// </summary>
[Parameter]
public Func<string, Task<IEnumerable<TValue>>> Search { get; set; }
/// <summary>
/// 获取显示值
/// </summary>
[Parameter]
[NotNull]
public Func<TValue, string> GetDisplayText { get; set; }
/// <summary>
/// 查询的字符串, 文本框的值
/// </summary>
[Parameter]
public string Query { get; set; }
/// <summary>
///
/// </summary>
[Parameter]
public string QueryChanged { get; set; }
/// <summary>
///
/// </summary>
[Inject]
[NotNull]
private IStringLocalizer<AutoComplete> Localizer { get; set; }
/// <summary>
///
/// </summary>
private TValue ActiveSelectedItem { get; set; }
/// <summary>
///
/// </summary>
protected ElementReference RemoteSourceAutoFillElement { get; set; }
/// <summary>
///
/// </summary>
protected int? CurrentItemIndex { get; set; }
/// <summary>
/// OnInitialized 方法
/// </summary>
protected override void OnInitialized()
{
base.OnInitialized();
NoDataTip ??= Localizer[nameof(NoDataTip)];
PlaceHolder ??= Localizer[nameof(PlaceHolder)];
items ??= Enumerable.Empty<TValue>();
}
/// <summary>
/// firstRender
/// </summary>
/// <param name="firstRender"></param>
/// <returns></returns>
protected override async Task OnAfterRenderAsync(bool firstRender)
{
await base.OnAfterRenderAsync(firstRender);
if (CurrentItemIndex.HasValue)
{
await InvokeVoidAsync(JSRuntime, RemoteSourceAutoFillElement, "bb_autoScrollItem", CurrentItemIndex.Value);
}
}
/// <summary>
/// 调用 JSInvoke 方法
/// </summary>
/// <param name="jsRuntime">IJSRuntime 实例</param>
/// <param name="el">Element 实例或者组件 Id</param>
/// <param name="func">Javascript 方法</param>
/// <param name="args">Javascript 参数</param>
public static ValueTask InvokeVoidAsync(IJSRuntime jsRuntime, object el = null, string func = null, params object[] args)
{
var paras = new List<object>();
if (el != null) paras.Add(el);
if (args != null) paras.AddRange(args);
try
{
var _ = jsRuntime.InvokeVoidAsync($"$.{func}", paras.ToArray()).ConfigureAwait(false);
}
catch (TaskCanceledException) { }
return ValueTask.CompletedTask;
}
/// <summary>
/// OnBlur 方法
/// </summary>
protected async Task OnBlur()
{
_isShown = false;
if (OnSelectedItemChanged != null && ActiveSelectedItem != null)
{
await OnSelectedItemChanged(ActiveSelectedItem);
ActiveSelectedItem = default;
}
}
/// <summary>
/// 鼠标点击候选项时回调此方法
/// </summary>
protected virtual async Task OnClickItem(TValue val)
{
CurrentValue = val;
this.Query = val != null ? this.GetDisplayText(val) : "";
ActiveSelectedItem = default;
if (OnSelectedItemChanged != null)
{
await OnSelectedItemChanged(val);
}
}
/// <summary>
/// 获得/设置 是否跳过 Enter 按键处理 默认 false
/// </summary>
protected bool SkipEnter { get; set; }
/// <summary>
/// 获得/设置 是否跳过 Esc 按键处理 默认 false
/// </summary>
protected bool SkipEsc { get; set; }
/// <summary>
/// OnKeyUp 方法
/// </summary>
/// <param name="args"></param>
/// <returns></returns>
protected virtual async Task OnKeyUp(KeyboardEventArgs args)
{
if (!_isLoading && _lastFilterText != this.Query)
{
_isLoading = true;
_lastFilterText = this.Query;
this.items = await this.Search(this.Query);
_isLoading = false;
}
var source = this.items?.ToList() ?? new List<TValue>();
if (source.Any())
{
_isShown = true;
// 键盘向上选择
if (_isShown && args.Key == "ArrowUp")
{
var index = 0;
if (ActiveSelectedItem != null)
{
index = source.IndexOf(ActiveSelectedItem) - 1;
if (index < 0)
{
index = source.Count - 1;
}
}
ActiveSelectedItem = source[index];
CurrentItemIndex = index;
}
else if (_isShown && args.Key == "ArrowDown")
{
var index = 0;
if (ActiveSelectedItem != null)
{
index = source.IndexOf(ActiveSelectedItem) + 1;
if (index > source.Count - 1)
{
index = 0;
}
}
ActiveSelectedItem = source[index];
CurrentItemIndex = index;
}
else if (args.Key == "Escape")
{
await OnBlur();
if (!SkipEsc && OnEscAsync != null)
{
await OnEscAsync(Value);
}
}
else if (args.Key == "Enter")
{
if (ActiveSelectedItem == null)
{
ActiveSelectedItem = source.FirstOrDefault();
}
if (ActiveSelectedItem != null)
{
this.Query = this.GetDisplayText(ActiveSelectedItem);
}
await OnBlur();
if (!SkipEnter && OnEnterAsync != null)
{
await OnEnterAsync(Value);
}
}
if (this.ActiveSelectedItem != null)
this.CurrentValue = this.ActiveSelectedItem;
}
}
/// <summary>
///
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
protected override string FormatValueAsString(TValue value) => this.GetDisplayText(value);
///// <summary>
/////
///// </summary>
///// <param name="value"></param>
///// <param name="result"></param>
///// <param name="validationErrorMessage"></param>
///// <returns></returns>
//protected override bool TryParseValueFromString(string value, [MaybeNullWhen(false)] out TValue result, out string? validationErrorMessage)
//{
// //CurrentValue.Text = value;
// result = CurrentValue;
// validationErrorMessage = null;
// return true;
//}
}
使用：
<GroupBox Title="查询">
<Row ItemsPerRow="ItemsPerRow.Three" RowType="RowType.Inline">
<RemoteSourceAutoFill TValue="CNB.ES.Models.B2CCity"
@bind-Value="city"
Search="SearchCity"
GetDisplayText="GetCityDisplayText"
DisplayText="城市"
ShowLabel="true" />
@*Query="@Data?.JegoHotelDetail?.CityCode"*@
<BootstrapInput @bind-Value="hotelQuery" DisplayText="酒店关键字" ShowLabel="true" />
<Button Text="查找" OnClick="SearchHotel" />
</Row>
</GroupBox>
private async Task<IEnumerable<B2CCity>> SearchCity(string txt)
{
var rst = await cityFinder.QueryAsync(new ES.Conds.B2CCityFindCondition()
{
Str = txt,
Page = 0,
PageSize = 10,
});
return rst?.Result;
}
private string GetCityDisplayText(B2CCity city)
{
return city.NameCnLong;
}
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