ErdbebenSender/src/main/java/com/example/erdbebensender/MessageSender.java

package com.example.erdbebensender;

import android.content.Context;
import android.nfc.Tag;
import android.util.Log;
import com.android.volley.*;
import com.android.volley.toolbox.*;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;


public class MessageSender {

    private static final String FCM_API = "https://fcm.googleapis.com/fcm/send";
    private static final String TOPIC = "erdbeben";
    private static final String SERVER_KEY = "AAAA2pVhMk4:APA91bHeiZGBd0BZi-RqnlCqnMkD7ICFW7SKzft-j1RIm16LX4M0Jez8AUQOoGgKYhHsVDD1kDxfKnul9Xbcjwo6QDAnPNLqOnk3XViVI5HjxgL8mpyzDLZXFharMIaqPANqBiMs5Gm2";

    private static final String TAG = "ErdbebenMessage";


    public void sendMessage(ErdbebenParameter erdbebenParameter) throws IOException, JSONException {
        URL url = new URL(FCM_API);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        try {
            Log.i(TAG, "Init HTTP Request");
            con.setRequestMethod("POST");
            con.setRequestProperty("Content-Type", "application/json");
            //con.setRequestProperty("Accept", "application/json");
            con.setRequestProperty("Authorization", "key=" + SERVER_KEY);
            con.setDoOutput(true);
            //con.setChunkedStreamingMode(0);
            Log.i(TAG, "---Fehlerstelle kommt----");
            OutputStream out = new BufferedOutputStream(con.getOutputStream());
            Log.i(TAG, "---Fehler behoben---");
            out.write("Test".getBytes(),0, "Test".getBytes().length);
            out.flush();
            out.close();

            Log.i(TAG, "Request Erfolgreich gesendet");

            try (BufferedReader br = new BufferedReader(
                    new InputStreamReader(con.getInputStream(), "utf-8"))) {
                StringBuilder response = new StringBuilder();
                String responseLine = null;
                while ((responseLine = br.readLine()) != null) {
                    response.append(responseLine.trim());
                }
                Log.i(TAG, "Response erhalten: ");
            }

        } catch (Exception e) {
            throw e;
        }
        finally {
            con.disconnect();
        }
    }

    private JSONObject generateJson(ErdbebenParameter erdbebenParameter) throws JSONException {
        Log.i(TAG, "Erstelle JSON");
        JSONObject json = new JSONObject();
        JSONObject data = new JSONObject();
        JSONObject notification = new JSONObject();

        notification.put("title", "Erdbeben");
        notification.put("body", "Neues Erdbebeben aufgetretten");
        data.put("sender", erdbebenParameter.getSender());
        data.put("x", erdbebenParameter.getX());
        data.put("y", erdbebenParameter.getY());
        data.put("v", erdbebenParameter.getV());

        json.put("to", "/topics/" + TOPIC);
        json.put("notification", notification);
        json.put("data", data);

        return json;
    }
}