首先请关注这个一步一步完成，然后你就得到了基础应用程序.

First, please follow this step by step to complete it, then you will get the base application.

二、添加发送Http到FCM服务器的按钮:

Second, add a button to send Http to the FCM server:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
  <TextView
      android:text=" "
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/msgText"
      android:textAppearance="?android:attr/textAppearanceMedium"
      android:padding="10dp" />
  <Button
    android:id="@+id/bt"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>
</LinearLayout>

在OnCreate中初始化按钮:

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);

    // Set our view from the "main" layout resource
    SetContentView(Resource.Layout.Main);
    msgText = FindViewById<TextView>(Resource.Id.msgText);
    IsPlayServicesAvailable();
    Button bt = FindViewById<Button>(Resource.Id.bt);
    bt.Click += Bt_Click;

}

这里我使用了两个类来生成 json 字符串，我使用的是 json.net:

Here I used two class to generate the json string, and I am using json.net:

class Mes
{
    public string to;
    public Noti notification;
    public Mes(string to,Noti notification){
        this.to = to;
        this.notification = notification;
    }
}
class Noti {
    public string title;
    public string text;
    public Noti(string body,string text) {
        this.title = body;
        this.text = body;
    }
}

点击事件(我使用的是okhttp3):

Click event(I am using okhttp3):

 private void Bt_Click(object sender, System.EventArgs e)
{

    Mes mes = new Mes("your token",
        new Noti("great","yes"));
    string json = JsonConvert.SerializeObject(mes);
    Log.Error("json",json);
    OkHttpClient client = new OkHttpClient();
    RequestBody body = RequestBody.Create(
    MediaType.Parse("application/json; charset=utf-8"),json);
    Request request = new Request.Builder()
        .Url("https://fcm.googleapis.com/fcm/send")// this is the base url which you can find it from  https://firebase.google.com/docs/cloud-messaging/http-server-ref?#params
        .Post(body)
        .AddHeader("Authorization", "your app key")// find it from this case https://***.com/questions/37337512/where-can-i-find-the-api-key-for-firebase-cloud-messaging
        .Build();

    // Synchronous blocking call

    client.NewCall(request).Enqueue(
        (call, response) => {
        // Response came back
        string body1 = response.Body().String();
        Log.Error("lv",body1);
        }, (call, exception) => {
            // There was an error
            Log.Error("lv", exception.Message);
        });
}

点击按钮后，你会收到一个通知(如果你已经完成了第一个链接)，而且你不需要发送通知，你可以使用数据做其他事情.

After clicking the button, you will get a notification(if you have done with the first link), also, you don't need send a notification, you can use the data to do other things.

将您的 MyFirebaseIIDService 更改为:

public class MyFirebaseIIDService : FirebaseInstanceIdService
{
    const string TAG = "MyFirebaseIIDService";
   public static string token;
    public override void OnTokenRefresh()
    {
         token = FirebaseInstanceId.Instance.Token;
        Log.Debug(TAG, "Refreshed token: " + token);
        SendRegistrationToServer(token);
    }
    void SendRegistrationToServer(string token)
    {
        // Add custom implementation, as needed.
    }
}

然后使用这个:

Mes mes = new Mes(MyFirebaseIIDService.token,new Noti("great","yes"));

更新 2:

    Request request = new Request.Builder()
        .Url("https://fcm.googleapis.com/fcm/send")
        .Post(body)
        .AddHeader("Authorization", "key=AAAAjPn9-TY:APA91bE-g4774KmFI72V1gWATmK8uta7N7NgcufoEgGgdidU9wyWBQ5YagCjP0WPBKrgILHZSVeb1I9vegYC-YfFHE2umWWcTzjo-t7W8ynDkwbB6qHY7JZExaxxvlI3VIg3d66sFZ40")
        .Build();

这是我的http请求，注意AddHeader方法，需要使用key=....

This is my http request, note that AddHeader method, you need use key=....