Blazor入门100天 : 自做一个支持长按事件的按钮组件

好长时间没继续写这个系列博客了, 不知道大家还记得我吗? 话不多说,直接开撸.

1. 新建 net8 blazor 工程 b19LongPressButton

至于用什么模式大家各取所需, 我创建的是ssr单工程, App.razor 里面改一下, 加入 @rendermode="RenderMode.InteractiveServer" 这句话, 默认使用ssr模式渲染.

<Routes @rendermode="RenderMode.InteractiveServer" />

2. Components\Pages 下新建组件 LongPressButton.razor

@inherits ComponentBase

<div @onclick="onClick" @oncontextmenu="onContextMenu" @ontouchstart="OnTouchStart" @ontouchend="OnTouchEnd">
    @ChildContent
</div>

@code {

    [Inject]
    private IJSRuntime? JS { get; set; }

    [Parameter]
    public RenderFragment? ChildContent { get; set; }

    bool IsEdit { get; set; } = false;

    private Task ValueChangedOnConfirm()
    {
        IsEdit = false;
        return Task.CompletedTask;
    }

    /// <summary>
    /// 获得/设置 启用长按
    /// </summary>
    [Parameter]
    public bool LongPress { get; set; } = true;

    /// <summary>
    /// 获得/设置 ContextMenu 菜单项回调委托
    /// </summary>
    [Parameter]
    public Func<MouseEventArgs, Task>? OnContextMenu { get; set; }

    /// <summary>
    /// 获得/设置 长按回调委托, 如果启用长按并且不是触摸设备,则回落到 Click 点击时触发
    /// </summary>
    [Parameter]
    public Func<MouseEventArgs, Task>? OnLongPress { get; set; }

    /// <summary>
    /// 获得/设置 Click 回调委托
    /// </summary>
    [Parameter]
    public Func<MouseEventArgs, Task>? OnClick { get; set; }

    /// <summary>
    /// 获得/设置 长按延时
    /// </summary>
    [Parameter]
    public int OnTouchTime { get; set; } = 500;

    /// <summary>
    /// ContextMenu 菜单项点击时触发
    /// </summary>
    /// <returns></returns>
    Task onContextMenu(MouseEventArgs args)
    {
        if (OnContextMenu != null)
        {
            return OnContextMenu.Invoke(args);
        }
        else
        {
            return Task.CompletedTask;
        }
    }

    /// <summary>
    /// 点击时触发
    /// </summary>
    /// <returns></returns>
    Task onClick(MouseEventArgs args)
    {
        if (OnClick != null)
        {
            return OnClick.Invoke(args);
        }
        else if (OnLongPress != null && !IsTouchDevice)
        {
            return OnLongPress.Invoke(args);
        }
        else
        {
            return Task.CompletedTask;
        }
    }

    /// <summary>
    /// 是否触摸设备
    /// </summary>
    private bool IsTouchDevice { get; set; }

    /// <summary>
    /// 是否触摸
    /// </summary>
    private bool TouchStart { get; set; }

    /// <summary>
    /// 触摸定时器工作指示
    /// </summary>
    private bool IsBusy { get; set; }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (firstRender)
        {
            IsTouchDevice = await JS!.InvokeAsync<bool>("eval", $"'ontouchstart' in document.documentElement");
        }
    }

    private async Task OnTouchStart(TouchEventArgs e)
    {
        if (!IsBusy)
        {
            IsBusy = true;
            TouchStart = true;

            // 延时保持 TouchStart 状态
            await Task.Delay(OnTouchTime);
            if (TouchStart)
            {
                var args = new MouseEventArgs()
                {
                    ClientX = e.Touches[0].ClientX,
                    ClientY = e.Touches[0].ClientY,
                    ScreenX = e.Touches[0].ScreenX,
                    ScreenY = e.Touches[0].ScreenY,
                    Type = "LongPress"
                };

                // 弹出关联菜单
                if (OnContextMenu != null)
                    await OnContextMenu(args);

                if (OnLongPress != null)
                    await OnLongPress(args);

                //延时防止重复激活菜单功能
                await Task.Delay(OnTouchTime);
            }
            IsBusy = false;
        }
    }

    private void OnTouchEnd()
    {
        TouchStart = false;
    }

}

3. 回到首页 Home.razor 添加组件测试

@page "/"

<PageTitle>Home</PageTitle>

 <LongPressButton OnLongPress="TaskOnLongPress" >
        <div style="width:200px;height:100px;background-color:gold;">
            <p>LongPressButton</p>
        </div>
</LongPressButton>

<p>@message</p>

@code {
    string message = "No long press";

    private Task TaskOnLongPress(MouseEventArgs e)
    {
        message = e.Type;
        StateHasChanged();
        return Task.CompletedTask;
    }
}

4. 测试

运行程序

普通浏览器模式, 不支持触摸,会自动会落到点击事件, 点击显示为 Click

F12打开开发者工具, 点击模拟手机/平板, 需要F5刷新页面重新读取是否为触摸设备, 点击无反应, 长按显示为