Added WiFi Communication to project

app/src/main/AndroidManifest.xml

@@ -2,6 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.example.greenwatch">
 
+    <uses-permission android:name="android.permission.INTERNET" />
+
     <application
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
@@ -9,9 +11,6 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.GreenWatch">
-        <activity
-            android:name=".ConnectionActivity"
-            android:exported="false" />
         <activity
             android:name=".VideodetectionAndAccelerometerActivity"
             android:exported="false" />

app/src/main/java/com/example/greenwatch/AccelerometerActivity.java

@@ -75,10 +75,10 @@ public class AccelerometerActivity extends AppCompatActivity implements SensorEv
             @Override
             public void onChanged(Boolean aBoolean) {
                 if (aBoolean) {
-                    mAccelerometerViewModel.setDevice(mAccelerometerViewModel.getLocalDeviceUUID(), mAccelerometerViewModel.getSystemTimeStamp(), mAccelerometerViewModel.getLocalDeviceUUID(), true, "Accelerometer", 10);
+                    mAccelerometerViewModel.setDevice(mAccelerometerViewModel.getLocalDeviceUUID(), mAccelerometerViewModel.getSystemTimeStamp(), true, "Accelerometer", 10);
                 }
                 else {
-                    mAccelerometerViewModel.setDevice(mAccelerometerViewModel.getLocalDeviceUUID(), mAccelerometerViewModel.getSystemTimeStamp(), mAccelerometerViewModel.getLocalDeviceUUID(), false, "Accelerometer", 0);
+                    mAccelerometerViewModel.setDevice(mAccelerometerViewModel.getLocalDeviceUUID(), mAccelerometerViewModel.getSystemTimeStamp(), false, "Accelerometer", 0);
                 }
 
             }

app/src/main/java/com/example/greenwatch/ConnectionActivity.java

@@ -1,27 +0,0 @@
-package com.example.greenwatch;
-
-import androidx.appcompat.app.AppCompatActivity;
-
-import android.os.Bundle;
-import android.view.View;
-import android.widget.Button;
-
-public class ConnectionActivity extends AppCompatActivity {
-
-    private Button backToMainActivity;
-
-    @Override
-    protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-        setContentView(R.layout.activity_connection);
-
-        backToMainActivity = (Button) findViewById(R.id.connectionBackToMainActivity);
-
-        backToMainActivity.setOnClickListener(new View.OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                finish();
-            }
-        });
-    }
-}

app/src/main/java/com/example/greenwatch/MainActivity.java

@@ -3,6 +3,8 @@ package com.example.greenwatch;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.lifecycle.Observer;
 import androidx.lifecycle.ViewModelProvider;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
 
 import android.content.Intent;
 import android.os.Bundle;
@@ -11,6 +13,7 @@ import android.widget.Button;
 import android.widget.TextView;
 import android.widget.Toast;
 
+import com.example.greenwatch.adapters.DeviceListAdapter;
 import com.example.greenwatch.models.Device;
 import com.example.greenwatch.viewmodels.MainActivityViewModel;
 
@@ -40,11 +43,19 @@ public class MainActivity extends AppCompatActivity {
         videodetectionAndAccelerometerButton = (Button) findViewById(R.id.videodetectionAndAccelerometerButton);
         connectionButton = (Button) findViewById(R.id.connectionButton);
 
+        RecyclerView recyclerView = findViewById(R.id.deviceListRecyclerView);
+        recyclerView.setLayoutManager(new LinearLayoutManager(this));
+        recyclerView.setHasFixedSize(true);
+
+        final DeviceListAdapter deviceListAdapter = new DeviceListAdapter();
+        recyclerView.setAdapter(deviceListAdapter);
+
         mMainActivityViewModel = new ViewModelProvider(this).get(MainActivityViewModel.class);
         mMainActivityViewModel.init();
         mMainActivityViewModel.getConnectedDeviceList().observe(this, new Observer<List<Device>>() {
             @Override
             public void onChanged(List<Device> devices) {
+                deviceListAdapter.setDevices(devices);
                 StringBuilder sb = new StringBuilder();
                 sb.append("Time Stamp: ");
                 sb.append(mMainActivityViewModel.getTimeStamp(mMainActivityViewModel.getLocalDeviceUUID()));
@@ -69,7 +80,7 @@ public class MainActivity extends AppCompatActivity {
             @Override
             public void onClick(View v) {
                 //openAudiodetectionActivity();
-                mMainActivityViewModel.setDevice(mMainActivityViewModel.getLocalDeviceUUID(), "10:51", "12345", false, "Audio", 10);
+                mMainActivityViewModel.setDevice(mMainActivityViewModel.getLocalDeviceUUID(), "10:51",  false, "Audio", 10);
             }
         });
         videodetectionButton.setOnClickListener(new View.OnClickListener() {
@@ -78,7 +89,7 @@ public class MainActivity extends AppCompatActivity {
                 //openVideodetectionActivity();
                 mMainActivityViewModel.setSensorType(mMainActivityViewModel.getLocalDeviceUUID(), "Video");
                 mMainActivityViewModel.setTimeStamp(mMainActivityViewModel.getLocalDeviceUUID(), "12:50");
-                mMainActivityViewModel.setDeviceID(mMainActivityViewModel.getLocalDeviceUUID(), mMainActivityViewModel.getLocalDeviceUUID());
+                mMainActivityViewModel.setDeviceID(mMainActivityViewModel.getLocalDeviceUUID(), "12345");
             }
         });
         accelerometerButton.setOnClickListener(new View.OnClickListener() {
@@ -127,12 +138,14 @@ public class MainActivity extends AppCompatActivity {
         startActivity(intent);
     }
     public void openVideodetectionAndAccelerometerActivity(){
-        Intent intent = new Intent(this, VideodetectionAndAccelerometerActivity.class);
-        startActivity(intent);
+        //Intent intent = new Intent(this, VideodetectionAndAccelerometerActivity.class);
+        //startActivity(intent);
+        mMainActivityViewModel.setDevice(mMainActivityViewModel.getLocalDeviceUUID(), "24:00",  false, "Video", 0);
     }
     public void openConnectionActivity(){
-        Intent intent = new Intent(this, ConnectionActivity.class);
-        startActivity(intent);
+        //Intent intent = new Intent(this, ConnectionActivity.class);
+        //startActivity(intent);
+        mMainActivityViewModel.setDevice(mMainActivityViewModel.getLocalDeviceUUID(), "10:51",  true, "Audio", 10);
     }
 
 }

app/src/main/java/com/example/greenwatch/adapters/DeviceListAdapter.java

@@ -0,0 +1,92 @@
+package com.example.greenwatch.adapters;
+
+import android.graphics.Color;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+
+import androidx.annotation.NonNull;
+import androidx.recyclerview.widget.RecyclerView;
+
+import com.example.greenwatch.R;
+import com.example.greenwatch.models.Device;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+public class DeviceListAdapter extends RecyclerView.Adapter<DeviceListAdapter.DeviceListHolder> {
+    private List<Device> devices = new ArrayList<>();
+
+
+    @NonNull
+    @Override
+    public DeviceListHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
+        View itemView = LayoutInflater.from(parent.getContext())
+                .inflate(R.layout.device_item, parent, false);
+        return new DeviceListHolder(itemView);
+    }
+
+    @Override
+    public void onBindViewHolder(@NonNull DeviceListHolder holder, int position) {
+        Device currentDevice = devices.get(position);
+        holder.textViewSensorType.setText(holder.itemView.getContext().getString(R.string.sensor_type_placeholder, currentDevice.getSensorType()));
+        holder.textViewDeviceID.setText(holder.itemView.getContext().getString(R.string.deviceID_placeholder, currentDevice.getDeviceID()));
+        holder.textViewTimeStamp.setText(holder.itemView.getContext().getString(R.string.sensor_time_stamp_placeholder, currentDevice.getTimeStamp()));
+        holder.textViewSensorMessage.setText(holder.itemView.getContext().getString(R.string.sensor_message_placeholder, currentDevice.getSensorMassage()));
+        holder.setDeviceSensorStatus(currentDevice);
+    }
+
+    @Override
+    public int getItemCount() {
+        return devices.size();
+    }
+
+    public void setDevices(List<Device> devices) {
+        this.devices = devices;
+        Collections.sort(this.devices, new Comparator<Device>() {
+
+            @Override
+            public int compare(Device device1, Device device2) {
+                if (device1.getSensorStatus() && !device2.getSensorStatus()) {
+                    return -1;
+                } else if (!device1.getSensorStatus() && device2.getSensorStatus()) {
+                    return 1;
+                } else {
+                    return 0;
+                }
+            }
+        });
+        notifyDataSetChanged();
+    }
+
+    class DeviceListHolder extends RecyclerView.ViewHolder {
+        private TextView textViewSensorType;
+        private TextView textViewSensorStatus;
+        private TextView textViewDeviceID;
+        private TextView textViewTimeStamp;
+        private TextView textViewSensorMessage;
+
+        public DeviceListHolder(View itemView) {
+            super(itemView);
+            textViewSensorType = (TextView) itemView.findViewById(R.id.tvDeviceSensorType);
+            textViewSensorStatus = (TextView) itemView.findViewById(R.id.tvDeviceSensorStatus);
+            textViewDeviceID = (TextView) itemView.findViewById(R.id.tvDeviceID);
+            textViewTimeStamp = (TextView) itemView.findViewById(R.id.tvDeviceTimeStamp);
+            textViewSensorMessage = (TextView) itemView.findViewById(R.id.tvDeviceSensorMassage);
+        }
+
+        public void setDeviceSensorStatus(Device device) {
+            if (device.getSensorStatus()) {
+                textViewSensorStatus.setText(itemView.getContext().getString(R.string.sensor_status_placeholder, "AN"));
+                itemView.setBackgroundColor(Color.RED);
+            }
+            else {
+                textViewSensorStatus.setText(itemView.getContext().getString(R.string.sensor_status_placeholder, "AUS"));
+                itemView.setBackgroundColor(Color.WHITE);
+            }
+        }
+    }
+}

app/src/main/java/com/example/greenwatch/communication/WiFiCommunication.java

@@ -0,0 +1,133 @@
+package com.example.greenwatch.communication;
+
+import com.example.greenwatch.repositories.DeviceRepository;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.Inet4Address;
+import java.net.InetAddress;
+import java.net.NetworkInterface;
+import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.util.Enumeration;
+
+public class WiFiCommunication {
+
+    private final InetAddress address;
+    private final DatagramSocket socket;
+    private final int port;
+    private String rxString;
+    private String sendMessage;
+    //private String sendMsg = "default";
+    private boolean isNewMessage;
+    volatile private boolean running;
+    private static WiFiCommunication wifiCommunicationInstance;
+    private DeviceRepository mDeviceRepository;
+
+    private WiFiCommunication() {
+        port = 1234;
+        try {
+            socket = new DatagramSocket(port);
+            socket.setBroadcast(true);
+            address = InetAddress.getByName("255.255.255.255");
+            running = true;
+            isNewMessage = false;
+            new ReceiveThread().start();
+            new SendThread().start();
+        } catch (SocketException | UnknownHostException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static synchronized WiFiCommunication getInstance() {
+        if (wifiCommunicationInstance == null){
+            wifiCommunicationInstance = new WiFiCommunication();
+        }
+        return wifiCommunicationInstance;
+    }
+
+    public void setDeviceRepository(DeviceRepository deviceRepository) {
+        this.mDeviceRepository = deviceRepository;
+    }
+
+    public void setNewMessage(String newMessage, boolean isNewMessage){
+        this.sendMessage = newMessage;
+        this.isNewMessage = isNewMessage;
+    }
+
+    public static String getLocalIpAddress() {
+        try {
+            for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
+                NetworkInterface networkInterface = (NetworkInterface) ((Enumeration<?>) en).nextElement();
+                for (Enumeration<InetAddress> addresses = networkInterface.getInetAddresses(); addresses.hasMoreElements();) {
+                    InetAddress inetAddress = addresses.nextElement();
+                    if (!inetAddress.isLoopbackAddress() && inetAddress instanceof Inet4Address) {
+                        return inetAddress.getHostAddress();
+                    }
+                }
+            }
+        } catch (SocketException ex) {
+            ex.printStackTrace();
+        }
+        return null;
+    }
+
+    public void stopCommunication() {
+        running = false;
+        socket.close();
+    }
+
+    private class SendThread extends Thread {
+        private int tmpCnt = 0;
+        @Override
+        public void run() {
+            try {
+                do {
+
+                    if(isNewMessage)
+                    {
+                        isNewMessage = false;
+                        //todo: adapt send String
+                        String txString = getLocalIpAddress() + " sends. #" + tmpCnt++ + sendMessage;
+                        byte[] txBuffer = txString.getBytes();
+
+                        DatagramPacket txPacket = new DatagramPacket(txBuffer, txBuffer.length, address, port);
+
+                        for(int i = 0; i < 20; i++) {
+                            socket.send(txPacket);
+                        }
+                    }
+                } while (running);
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    private class ReceiveThread extends Thread {
+        private String rxString = "";
+        private String previousRxString = "";
+        @Override
+        public void run() {
+            try {
+                do {
+                    byte[] rxBuffer = new byte[1024];
+                    DatagramPacket packet = new DatagramPacket(rxBuffer, rxBuffer.length);
+                    socket.receive(packet);
+                    rxString = new String(packet.getData(), 0, packet.getLength());
+
+                    if(!previousRxString.equals(rxString)){
+                        mDeviceRepository.getNewReceivedMessage(rxString);
+
+                    }
+                    previousRxString = rxString;
+
+                } while (running);
+            }
+            catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+}

app/src/main/java/com/example/greenwatch/repositories/DeviceRepository.java

@@ -4,6 +4,7 @@ package com.example.greenwatch.repositories;
 import androidx.lifecycle.MutableLiveData;
 
 import com.example.greenwatch.models.Device;
+import com.example.greenwatch.communication.WiFiCommunication;
 
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -12,21 +13,30 @@ import java.util.UUID;
 
 public class DeviceRepository {
 
-    private String delimiter = ", ";
-    private String deviceUUID;
+    private final String delimiter = ", ";
+    private final String SensorStatusKey = "An";
+    private String localDeviceUUID;
     private static DeviceRepository deviceRepositoryInstance;
+    private WiFiCommunication mWiFiCommunication;
     private MutableLiveData<List<Device>> deviceList = new MutableLiveData<>();
     private HashMap<String, Device> connectedDevicesList = new HashMap<>();
     private HashMap<String, String> deviceIDMapper = new HashMap<>();
 
+    private DeviceRepository() {
+        setLocalDeviceUUID();
+    }
+
     public static synchronized DeviceRepository getInstance() {
         if (deviceRepositoryInstance == null){
             deviceRepositoryInstance = new DeviceRepository();
-            deviceRepositoryInstance.setDeviceUUID();
         }
         return deviceRepositoryInstance;
     }
 
+    public void setWiFiCommunication(WiFiCommunication wiFiCommunication) {
+        this.mWiFiCommunication = wiFiCommunication;
+    }
+
     public MutableLiveData<List<Device>> getConnectedDeviceList() {
         setMutableLiveDataValue();
         return deviceList;
@@ -34,24 +44,12 @@ public class DeviceRepository {
 
     public void createNewDevice(String timeStamp, String deviceID, boolean sensorStatus, String sensorType, int sensorMassage){
         Device newDevice = new Device(timeStamp, deviceID, sensorStatus, sensorType, sensorMassage);
+        setDeviceIDMapper(deviceID);
         addToConnectedDeviceList(newDevice.getDeviceID(), newDevice);
         setMutableLiveDataValue();
     }
 
-    public void createNewRemoteDevice(String message) {
-        String[] messageString = messageStringSplitter(message);
-        String timeStamp = messageString[0];
-        String deviceID = messageString[1];
-        boolean sensorStatus = Boolean.valueOf(messageString[1]);
-        String sensorType = messageString[3];
-        int sensorMassage = Integer.valueOf(messageString[4]);
-
-        if(!connectedDevicesList.containsKey(deviceID)) {
-            createNewDevice(timeStamp, deviceID, sensorStatus, sensorType, sensorMassage);
-        }
-    }
-
-    public String messageStringBuilder(String deviceID) {
+    private String messageStringBuilder(String deviceID) {
         StringBuilder message = new StringBuilder();
         Device device = connectedDevicesList.get(deviceID);
         if(device != null) {
@@ -66,25 +64,33 @@ public class DeviceRepository {
                     .append(device.getSensorMassage());
             return message.toString();
         }
-        return message.toString();
+        else {
+            message.append("")
+                    .append(delimiter)
+                    .append("")
+                    .append(delimiter)
+                    .append("")
+                    .append(delimiter)
+                    .append("")
+                    .append(delimiter)
+                    .append("");
+            return message.toString();
+        }
     }
 
     public String getLocalDeviceUUID() {
-        return deviceUUID;
+        return localDeviceUUID;
     }
 
-    public void setDevice(String deviceID, String timeStamp, String newDeviceID, boolean sensorStatus, String sensorType, int sensorMassage) {
+    public void updateDevice(String deviceID, String timeStamp, boolean sensorStatus, String sensorType, int sensorMassage) {
         String checkedDeviceID = checkDeviceID(deviceID);
         Device device = connectedDevicesList.get(checkedDeviceID);
         if(device != null) {
             device.setTimeStamp(timeStamp);
-            device.setDeviceID(newDeviceID);
             device.setSensorStatus(sensorStatus);
             device.setSensorType(sensorType);
             device.setSensorMassage(sensorMassage);
-            setDeviceIDMapper(newDeviceID);
-            connectedDevicesList.remove(checkedDeviceID);
-            addToConnectedDeviceList(newDeviceID, device);
+            addToConnectedDeviceList(checkedDeviceID, device);
             setMutableLiveDataValue();
         }
     }
@@ -193,24 +199,51 @@ public class DeviceRepository {
 
     private void addToConnectedDeviceList(String key, Device device) {
         connectedDevicesList.put(key, device);
+        if (key.equals(checkDeviceID(localDeviceUUID))) {
+            mWiFiCommunication.setNewMessage(messageStringBuilder(device.getDeviceID()),true);
+        }
     }
 
     private String checkDeviceID(String deviceID) {
-        if(!deviceIDMapper.isEmpty() && deviceID.equals(deviceUUID)) {
+        if(!deviceIDMapper.isEmpty() && deviceID.equals(localDeviceUUID)) {
             return deviceIDMapper.get(deviceID);
         }
         return deviceID;
     }
 
     private void setDeviceIDMapper(String deviceID) {
-        deviceIDMapper.put(deviceUUID, deviceID);
+        deviceIDMapper.put(localDeviceUUID, deviceID);
     }
 
-    private void setDeviceUUID(){
-        this.deviceUUID = UUID.randomUUID().toString();
+    private void setLocalDeviceUUID(){
+        this.localDeviceUUID = UUID.randomUUID().toString();
     }
 
     private String[] messageStringSplitter(String message) {
         return message.split(delimiter);
     }
+
+    public void getNewReceivedMessage(String newMessage) {
+        String[] messageString = messageStringSplitter(newMessage);
+        String timeStamp = messageString[0];
+        String deviceID = messageString[1];
+        boolean sensorStatus = convertSensorStatus(messageString[2]);
+        String sensorType = messageString[3];
+        int sensorMassage = Integer.valueOf(messageString[4]);
+
+        if (deviceID.equals(checkDeviceID(localDeviceUUID))) {
+            return;
+        }
+
+        if(!connectedDevicesList.containsKey(deviceID)) {
+            createNewDevice(timeStamp, deviceID, sensorStatus, sensorType, sensorMassage);
+        }
+        else {
+            updateDevice(deviceID, timeStamp, sensorStatus, sensorType, sensorMassage);
+        }
+    }
+
+    private boolean convertSensorStatus(String status) {
+        return status.equals(SensorStatusKey);
+    }
 }

app/src/main/java/com/example/greenwatch/viewmodels/AccelerometerViewModel.java

@@ -93,8 +93,8 @@ public class AccelerometerViewModel extends ViewModel {
         return mDeviceList;
     }
 
-    public void setDevice(String deviceID, String timeStamp, String newDeviceID, boolean sensorStatus, String sensorType, int sensorMassage) {
-        mDeviceRepository.setDevice(deviceID, timeStamp,newDeviceID, sensorStatus, sensorType, sensorMassage);
+    public void setDevice(String deviceID, String timeStamp, boolean sensorStatus, String sensorType, int sensorMassage) {
+        mDeviceRepository.updateDevice(deviceID, timeStamp, sensorStatus, sensorType, sensorMassage);
     }
 
     public void setTimeStamp(String deviceID, String timeStamp) {

app/src/main/java/com/example/greenwatch/viewmodels/MainActivityViewModel.java

@@ -4,6 +4,7 @@ import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 import androidx.lifecycle.ViewModel;
 
+import com.example.greenwatch.communication.WiFiCommunication;
 import com.example.greenwatch.models.Device;
 import com.example.greenwatch.repositories.DeviceRepository;
 
@@ -14,12 +15,18 @@ public class MainActivityViewModel extends ViewModel {
     private MutableLiveData<List<Device>> mDeviceList;
     private DeviceRepository mDeviceRepository;
 
+
     public void init() {
+        WiFiCommunication mWiFiCommunication;
         if(mDeviceList != null) {
             return;
         }
+        //todo: check if WiFi instanz can be hold only by the repository
         mDeviceRepository = DeviceRepository.getInstance();
-        mDeviceRepository.createNewDevice("", mDeviceRepository.getLocalDeviceUUID(), false, "", 0);
+        mWiFiCommunication = WiFiCommunication.getInstance();
+        mDeviceRepository.setWiFiCommunication(mWiFiCommunication);
+        mWiFiCommunication.setDeviceRepository(mDeviceRepository);
+        mDeviceRepository.createNewDevice("", mDeviceRepository.getLocalDeviceUUID(), false, "No Sensor selected", 0);
         mDeviceList = mDeviceRepository.getConnectedDeviceList();
     }
 
@@ -27,8 +34,8 @@ public class MainActivityViewModel extends ViewModel {
         return mDeviceList;
     }
 
-    public void setDevice(String deviceID, String timeStamp, String newDeviceID, boolean sensorStatus, String sensorType, int sensorMassage) {
-        mDeviceRepository.setDevice(deviceID, timeStamp,newDeviceID, sensorStatus, sensorType, sensorMassage);
+    public void setDevice(String deviceID, String timeStamp, boolean sensorStatus, String sensorType, int sensorMassage) {
+        mDeviceRepository.updateDevice(deviceID, timeStamp, sensorStatus, sensorType, sensorMassage);
     }
 
     public void setTimeStamp(String deviceID, String timeStamp) {

app/src/main/res/layout/activity_connection.xml

@@ -1,25 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
-    xmlns:tools="http://schemas.android.com/tools"
-    android:layout_width="match_parent"
-    android:layout_height="match_parent"
-    android:orientation="vertical"
-    android:padding="10dp"
-    tools:context=".ConnectionActivity">
-
-    <TextView
-        android:id="@+id/tvConnectionStatusmessage"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:text="Connection Activity">
-    </TextView>
-
-    <Button
-        android:id="@+id/connectionBackToMainActivity"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:text="Back to MainActivity">
-    </Button>
-
-</LinearLayout>

app/src/main/res/layout/activity_main.xml

@@ -13,14 +13,22 @@
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:text="Hello World!"
-        android:layout_weight="1">
+        android:layout_weight="4">
     </TextView>
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/deviceListRecyclerView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:layout_weight="2"
+        tools:listitem="@layout/device_item">
+    </androidx.recyclerview.widget.RecyclerView>
     
     <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
-        android:layout_weight="1">
+        android:layout_weight="3">
 
         <Button
             android:id="@+id/audiodetectionButton"

app/src/main/res/layout/device_item.xml

@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:layout_marginEnd="8dp"
+    android:layout_marginStart="8dp"
+    android:layout_marginTop="8dp">
+    
+    <RelativeLayout
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:padding="8dp">
+        
+        <TextView
+            android:id="@+id/tvDeviceSensorStatus"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_alignParentEnd="true"
+            android:text="@string/sensor_status_placeholder"
+            android:textAppearance="@style/TextAppearance.AppCompat.Large">
+        </TextView>
+
+        <TextView
+            android:id="@+id/tvDeviceSensorType"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/sensor_type_placeholder"
+            android:textAppearance="@style/TextAppearance.AppCompat.Large"
+            android:maxLines="1"
+            android:layout_toStartOf="@id/tvDeviceSensorStatus"
+            android:layout_alignParentStart="true"
+            android:ellipsize="end">
+        </TextView>
+
+        <TextView
+            android:id="@+id/tvDeviceID"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_below="@id/tvDeviceSensorType"
+            android:text="@string/deviceID_placeholder">
+        </TextView>
+
+        <TextView
+            android:id="@+id/tvDeviceTimeStamp"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_below="@id/tvDeviceID"
+            android:text="@string/sensor_time_stamp_placeholder">
+        </TextView>
+
+        <TextView
+            android:id="@+id/tvDeviceSensorMassage"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_below="@id/tvDeviceTimeStamp"
+            android:text="@string/sensor_message_placeholder">
+        </TextView>
+
+    </RelativeLayout>
+
+</androidx.cardview.widget.CardView>

app/src/main/res/values/strings.xml

@@ -1,3 +1,8 @@
 <resources>
     <string name="app_name">GreenWatch</string>
+    <string name="sensor_type_placeholder">Sensortyp: %s</string>
+    <string name="sensor_status_placeholder">Sensorstatus: %s</string>
+    <string name="deviceID_placeholder">Sensor-ID: %s</string>
+    <string name="sensor_time_stamp_placeholder">Timestamp: %s</string>
+    <string name="sensor_message_placeholder">Sensormessage: %d</string>
 </resources>