bh006- Blazor hybrid / Maui 使用NFC快速教程

using BootstrapBlazor.Components;
using DH.NFC;
using Microsoft.AspNetCore.Components;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Text;

namespace bh006_NFC_tag.Pages;

public partial class Index : IAsyncDisposable
{
[Inject, NotNull] protected MessageService? MessageService { get; set; }

[NotNull]
protected Message? Message { get; set; }

[DisplayName("使标签为只读")]
bool ChkReadOnly { get; set; } = false;

protected override async Task OnAfterRenderAsync(bool firstRender)
{
    if (firstRender)
    {
        // 为了支持Mifare Classic 1K标签（读/写），必须将传统模式设置为true。
        CrossNFC.Legacy = false;

        if (CrossNFC.IsSupported)
        {
            if (!CrossNFC.Current.IsAvailable)
                await ShowAlert("NFC is not available");

            NfcIsEnabled = CrossNFC.Current.IsEnabled;
            if (!NfcIsEnabled)
                await ShowAlert("NFC is disabled");

            if (DeviceInfo.Platform == DevicePlatform.iOS)
                _isDeviceiOS = true;

            await AutoStartAsync().ConfigureAwait(false);
        }

    }
}

//连接外设
private async Task XamlPage()
{
    MauiProgram.OpenNFCXamlPage();
    //异步更新UI
    await InvokeAsync(StateHasChanged);
}

async ValueTask IAsyncDisposable.DisposeAsync()
{
    await StopListening();
}

public const string ALERT_TITLE = "NFC";
public const string MIME_TYPE = "application/com.densen.nfc";

NFCNdefTypeFormat _type;
bool _makeReadOnly = false;
bool _eventsAlreadySubscribed = false;
bool _isDeviceiOS = false;

//https://gitee.com/dengho/DH.Maui.FrameWork/blob/master/Demo/DH.NFCDemo/NfcPage.xaml.cs

/// <summary>
/// 跟踪Android设备是否仍在监听的属性，
/// 因此它可以向用户指示这一点。
/// </summary>
public bool DeviceIsListening 
{
    get => _deviceIsListening;
    set
    {
        _deviceIsListening = value;
        StateHasChanged();
    }
}
private bool _deviceIsListening;

private bool _nfcIsEnabled;
public bool NfcIsEnabled
{
    get => _nfcIsEnabled;
    set
    {
        _nfcIsEnabled = value;
        StateHasChanged();
    }
}

public bool NfcIsDisabled => !NfcIsEnabled;


/// <summary>
/// 自动开始收听
/// </summary>
/// <returns></returns>
async Task AutoStartAsync()
{
    // 在Android上阻止Java.Lang.IllegalStateException的一些延迟“仅当您的活动恢复时才能启用前台调度”
    await Task.Delay(500);
    await StartListeningIfNotiOS();
}

/// <summary>
/// 订阅NFC活动
/// </summary>
void SubscribeEvents()
{
    if (_eventsAlreadySubscribed)
        UnsubscribeEvents();

    _eventsAlreadySubscribed = true;

    CrossNFC.Current.OnMessageReceived += Current_OnMessageReceived;
    CrossNFC.Current.OnMessagePublished += Current_OnMessagePublished;
    CrossNFC.Current.OnTagDiscovered += Current_OnTagDiscovered;
    CrossNFC.Current.OnNfcStatusChanged += Current_OnNfcStatusChanged;
    CrossNFC.Current.OnTagListeningStatusChanged += Current_OnTagListeningStatusChanged;

    if (_isDeviceiOS)
        CrossNFC.Current.OniOSReadingSessionCancelled += Current_OniOSReadingSessionCancelled;
}

/// <summary>
/// 取消订阅NFC活动
/// </summary>
void UnsubscribeEvents()
{
    CrossNFC.Current.OnMessageReceived -= Current_OnMessageReceived;
    CrossNFC.Current.OnMessagePublished -= Current_OnMessagePublished;
    CrossNFC.Current.OnTagDiscovered -= Current_OnTagDiscovered;
    CrossNFC.Current.OnNfcStatusChanged -= Current_OnNfcStatusChanged;
    CrossNFC.Current.OnTagListeningStatusChanged -= Current_OnTagListeningStatusChanged;

    if (_isDeviceiOS)
        CrossNFC.Current.OniOSReadingSessionCancelled -= Current_OniOSReadingSessionCancelled;

    _eventsAlreadySubscribed = false;
}

/// <summary>
/// 侦听器状态更改时引发的事件
/// </summary>
/// <param name="isListening"></param>
void Current_OnTagListeningStatusChanged(bool isListening) => DeviceIsListening = isListening;

/// <summary>
/// NFC状态更改时引发的事件
/// </summary>
/// <param name="isEnabled">NFC status</param>
async void Current_OnNfcStatusChanged(bool isEnabled)
{
    NfcIsEnabled = isEnabled;
    await ShowAlert($"NFC has been {(isEnabled ? "enabled" : "disabled")}");
}

/// <summary>
/// 收到NDEF消息时引发的事件
/// </summary>
/// <param name="tagInfo">Received <see cref="ITagInfo"/></param>
async void Current_OnMessageReceived(ITagInfo tagInfo)
{
    if (tagInfo == null)
    {
        await ShowAlert("No tag found");
        return;
    }

    // 自定义序列号
    var identifier = tagInfo.Identifier;
    var serialNumber = NFCUtils.ByteArrayToHexString(identifier, ":");
    var title = !string.IsNullOrWhiteSpace(serialNumber) ? $"标签 [{serialNumber}]" : "标签信息";

    if (!tagInfo.IsSupported)
    {
        await ShowAlert("Unsupported tag (app)", title);
    }
    else if (tagInfo.IsEmpty)
    {
        await ShowAlert("Empty tag", title);
    }
    else
    {
        var first = tagInfo.Records[0];
        await ShowAlert(GetMessage(first), title);
    }
}

/// <summary>
/// Event raised when user cancelled NFC session on iOS 
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void Current_OniOSReadingSessionCancelled(object? sender, EventArgs e) => Debug("iOS NFC Session has been cancelled");

/// <summary>
/// 在标记上发布数据时引发的事件
/// </summary>
/// <param name="tagInfo">发布<see cref="ITagInfo"/></param>
async void Current_OnMessagePublished(ITagInfo tagInfo)
{
    try
    {
        ChkReadOnly = false;
        CrossNFC.Current.StopPublishing();
        if (tagInfo.IsEmpty)
            await ShowAlert("Formatting tag operation successful");
        else
            await ShowAlert("Writing tag operation successful");
    }
    catch (Exception ex)
    {
        await ShowAlert(ex.Message);
    }
}

/// <summary>
/// 发现NFC标签时引发的事件
/// </summary>
/// <param name="tagInfo"><see cref="ITagInfo"/>被发布</param>
/// <param name="format">设置标签格式</param>
async void Current_OnTagDiscovered(ITagInfo tagInfo, bool format)
{
    if (!CrossNFC.Current.IsWritingTagSupported)
    {
        await ShowAlert("此设备不支持写入标签");
        return;
    }

    try
    {
        NFCNdefRecord? record = null;
        switch (_type)
        {
            case NFCNdefTypeFormat.WellKnown:
                record = new NFCNdefRecord
                {
                    TypeFormat = NFCNdefTypeFormat.WellKnown,
                    MimeType = MIME_TYPE,
                    Payload = NFCUtils.EncodeToByteArray("DH.Maui.FrameWork是很棒的!"),
                    LanguageCode = "en"
                };
                break;
            case NFCNdefTypeFormat.Uri:
                record = new NFCNdefRecord
                {
                    TypeFormat = NFCNdefTypeFormat.Uri,
                    Payload = NFCUtils.EncodeToByteArray("https://gitee.com/dengho/DH.Maui.FrameWork")
                };
                break;
            case NFCNdefTypeFormat.Mime:
                record = new NFCNdefRecord
                {
                    TypeFormat = NFCNdefTypeFormat.Mime,
                    MimeType = MIME_TYPE,
                    Payload = NFCUtils.EncodeToByteArray("DH.Maui.FrameWork是很棒的!")
                };
                break;
            default:
                break;
        }

        if (!format && record == null)
            throw new Exception("记录不能为空.");

        tagInfo.Records = new[] { record };

        if (format)
            CrossNFC.Current.ClearMessage(tagInfo);
        else
        {
            CrossNFC.Current.PublishMessage(tagInfo, _makeReadOnly);
        }
    }
    catch (Exception ex)
    {
        await ShowAlert(ex.Message);
    }
}


/// <summary>
/// 当将引发<see cref="Current_OnTagDiscovered(ITagInfo, bool)"/>事件时，启动发布操作以写入文本标签
/// </summary>
async Task Button_Clicked_StartWriting() => await Publish(NFCNdefTypeFormat.WellKnown);

/// <summary>
/// 当将引发<see cref="Current_OnTagDiscovered(ITagInfo, bool)"/>事件时，启动发布操作以写入URI标签
/// </summary>
async Task Button_Clicked_StartWriting_Uri() => await Publish(NFCNdefTypeFormat.Uri);

/// <summary>
/// 当将引发<see cref="Current_OnTagDiscovered(ITagInfo, bool)"/>事件时，启动发布操作以写入自定义标签
/// </summary>
async Task Button_Clicked_StartWriting_Custom() => await Publish(NFCNdefTypeFormat.Mime);

/// <summary>
/// 当将引发<see cref="Current_OnTagDiscovered(ITagInfo, bool)"/>事件时，启动发布操作以格式化标签
/// </summary>
async Task Button_Clicked_FormatTag() => await Publish();

/// <summary>
/// 将数据发布到标签的任务
/// </summary>
/// <param name="type"><see cref="NFCNdefTypeFormat"/></param>
/// <returns>要执行的任务</returns>
async Task Publish(NFCNdefTypeFormat? type = null)
{
    await StartListeningIfNotiOS();
    try
    {
        _type = NFCNdefTypeFormat.Empty;
        if (ChkReadOnly)
        {
            //if (!await DisplayAlert("警告", "使标签为只读操作是永久性的，无法撤消。您确定要继续吗？", "是", "否"))
            //{
            //    ChkReadOnly = false;
            //    return;
            //}
            _makeReadOnly = true;
        }
        else
            _makeReadOnly = false;

        if (type.HasValue) _type = type.Value;
        CrossNFC.Current.StartPublishing(!type.HasValue);
    }
    catch (Exception ex)
    {
        await ShowAlert(ex.Message);
    }
}

/// <summary>
/// 返回NDEF记录中的标记信息
/// </summary>
/// <param name="record"><see cref="NFCNdefRecord"/></param>
/// <returns>标签信息</returns>
string GetMessage(NFCNdefRecord record)
{
    var message = $"消息: {record.Message}";
    message += Environment.NewLine;
    message += $"原始消息: {Encoding.UTF8.GetString(record.Payload)}";
    message += Environment.NewLine;
    message += $"类型: {record.TypeFormat}";

    if (!string.IsNullOrWhiteSpace(record.MimeType))
    {
        message += Environment.NewLine;
        message += $"Mime类型: {record.MimeType}";
    }

    return message;
}

/// <summary>
/// 在调试控制台中编写调试消息
/// </summary>
/// <param name="message">要显示的消息</param>
void Debug(string message) => System.Diagnostics.Debug.WriteLine(message);

/// <summary>
/// 显示消息
/// </summary>
/// <param name="message">要显示的消息</param>
/// <param name="title">消息标题</param>
/// <returns>要执行的任务</returns>
async Task ShowAlert(string message, string? title = null) =>
await MessageService.Show(new MessageOption()
{
    Content = message,
    Icon = "fa-solid fa-circle-info",
}, Message);

/// <summary>
/// 如果用户的设备平台不是iOS，则开始监听NFC标签的任务
/// </summary>
/// <returns>要执行的任务</returns>
async Task StartListeningIfNotiOS()
{
    if (_isDeviceiOS)
    {
        SubscribeEvents();
        return;
    }
    await BeginListening();
}

/// <summary>
/// 安全开始监听NFC标签的任务
/// </summary>
/// <returns>要执行的任务</returns>
async Task BeginListening()
{
    try
    {
        MainThread.BeginInvokeOnMainThread(() =>
        {
            SubscribeEvents();
            CrossNFC.Current.StartListening();
        });
    }
    catch (Exception ex)
    {
        await ShowAlert(ex.Message);
    }
}

/// <summary>
/// 安全停止监听NFC标签的任务
/// </summary>
/// <returns>要执行的任务</returns>
async Task StopListening()
{
    try
    {
        MainThread.BeginInvokeOnMainThread(async () =>
        {
            try
            {

                CrossNFC.Current.StopListening();
                UnsubscribeEvents();
            }
            catch (Exception ex)
            {
                await ShowAlert(ex.Message);
            }
        });
    }
    catch (Exception ex)
    {
        await ShowAlert(ex.Message);
    }
}

}

</details>

### 6. 添加 UI Pages/Index.razor

Index.razor

@page "/"

NFC

<Button OnClick="BeginListening"
        IsDisabled="NfcIsDisabled"
        Text="读取标签" />

<Button OnClick="StopListening"
        IsDisabled="NfcIsDisabled"
        Text="停止侦听器" />

<GroupBox Title="写入">

    @*<CheckBox TValue="bool" DisplayText="双向绑定" ShowLabel="true" @bind-value="@ChkReadOnly" IsDisabled="NfcIsDisabled" />*@

    <Button OnClick="Button_Clicked_StartWriting"
            IsDisabled="NfcIsDisabled"
            Text="标签写入文本" />

    <Button OnClick="Button_Clicked_StartWriting_Uri"
            IsDisabled="NfcIsDisabled"
            Text="标签写入网址" />

    <Button OnClick="Button_Clicked_StartWriting_Custom"
            IsDisabled="NfcIsDisabled"
            Text="标签写入自定义内容" />

</GroupBox>

<Button OnClick="Button_Clicked_FormatTag"
        IsDisabled="NfcIsDisabled"
        Text="标签清除" />

@if (DeviceIsListening)
{
    <p>监听NFC标签...</p>

}

@if (NfcIsDisabled)
{
    <p>NFC已禁用</p>

}

<div class="btn-group" role="group">
    <Button Text="NFC XAML" OnClick=XamlPage />
</div>

@Message

### 10. 运行

![](https://img2023.cnblogs.com/blog/1980213/202308/1980213-20230825190522368-1815785483.png)

![](https://img2023.cnblogs.com/blog/1980213/202308/1980213-20230825192352945-1151572992.gif)


### 11. 相关资料

如何远程调试 MAUI blazor / Blazor Hybrid
https://www.cnblogs.com/densen2014/p/16988516.html