Fix SLAM controller, use PUB instead of PAIR sockets for zmq updater.

app/src/main/java/com/example/carcontroller/SLAM/SlamController.java

@@ -1,12 +1,12 @@
 package com.example.carcontroller.SLAM;
 
-import androidx.appcompat.app.AppCompatActivity;
-import androidx.preference.PreferenceManager;
-
 import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.widget.SeekBar;
 
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.preference.PreferenceManager;
+
 import com.example.carcontroller.PiLoader;
 import com.example.carcontroller.R;
 
@@ -75,21 +75,28 @@ public class SlamController extends AppCompatActivity implements SeekBar.OnSeekB
             grpcController = new PiLoader(prefs.getString("host", "10.0.0.53"), Integer.parseInt(prefs.getString("port", "50051")));
         }
         // Should call the equivalent of the load method either here or in the loader.
+        // Test without the grpc for steering.
         grpcController.start();
+        if (slamView != null) {
             slamView.resume();
         }
+    }
 
     @Override
     protected void onPause() {
         super.onPause();
         grpcController.stop();
+        if (slamView != null) {
             slamView.stop();
         }
+    }
 
     @Override
     protected void onStop() {
         super.onStop();
         grpcController.stop();
+        if (slamView != null) {
             slamView.stop();
         }
+    }
 }

app/src/main/java/com/example/carcontroller/SLAM/SlamView.java

@@ -12,9 +12,16 @@ import android.view.SurfaceView;
 
 import androidx.preference.PreferenceManager;
 
+import com.example.carcontroller.Empty;
+import com.example.carcontroller.SlamControlGrpc;
+import com.example.carcontroller.SlamDetails;
 import com.example.carcontroller.SlamLocation;
 import com.google.protobuf.ByteString;
 
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import io.grpc.stub.StreamObserver;
+
 public class SlamView extends SurfaceView implements SlamUpdater.MapChangedListener {
 
     private SlamUpdater slam;
@@ -23,6 +30,10 @@ public class SlamView extends SurfaceView implements SlamUpdater.MapChangedListe
     private int width;
     private SurfaceHolder surfaceHolder;
     private Paint paint;
+    private SlamControlGrpc.SlamControlStub stub;
+    private ManagedChannel channel;
+    private int mapSizePixels;
+    private int mapSizeMeters;
 
     public SlamView(Context context) {
         super(context);
@@ -46,21 +57,45 @@ public class SlamView extends SurfaceView implements SlamUpdater.MapChangedListe
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
         String host = prefs.getString("host", "10.0.0.53");
         String port = prefs.getString("zmqPort", "5050");
+        String gRPCPort = prefs.getString("port", "50051");
+        mapSizePixels = Integer.parseInt(prefs.getString("MAPSIZEPIXELS", "540"));
+        mapSizeMeters = Integer.parseInt(prefs.getString("MAPSIZEMETRES", "10"));
         slam = new ZmqSlamUpdater(host, port);
         slam.addMapChangedListener(this);
         surfaceHolder = getHolder();
         paint = new Paint();
         paint.setColor(Color.BLUE);
+        mapThread = new Thread(slam);
+        channel = ManagedChannelBuilder.forAddress(host, Integer.parseInt(gRPCPort)).usePlaintext().build();
+        stub = SlamControlGrpc.newStub(channel);
+
     }
 
     /**
      * Called by MainActivity.onResume() to start a thread.
      */
     public void resume() {
-        mapThread = new Thread(slam);
+        StreamObserver<Empty> response = new StreamObserver<Empty>() {
+            @Override
+            public void onNext(Empty value) {
                 mapThread.start();
             }
 
+            @Override
+            public void onError(Throwable t) {
+                // TODO: close the activity,
+                System.out.println(t.getMessage());
+            }
+
+            @Override
+            public void onCompleted() {
+                // Don't care.
+            }
+        };
+        // use async grpc method, ZMQ doesn't need to connect straight away.
+        stub.startMapStreaming(SlamDetails.newBuilder().setMapSizePixels(mapSizePixels).setMapSizeMeters(mapSizeMeters).build(), response);
+    }
+
     public void stop() {
         // Use grpc to tell the loader to stop. Interrupt the loader thread as well.
         slam.stop();

app/src/main/java/com/example/carcontroller/SLAM/ZmqSlamUpdater.java

@@ -35,14 +35,11 @@ public class ZmqSlamUpdater extends SlamUpdater {
 
     @Override
     public void run() {
-        // Should send a gRPC message to start listening...
-
-
         running = true;
         // Receive map from zmq and update appropriately.
-        try (ZMQ.Socket socket = context.createSocket(SocketType.PAIR)) {
+        try (ZMQ.Socket socket = context.createSocket(SocketType.SUB)) {
             socket.connect("tcp://" + host + ":" + port);
-            socket.send("Hi");
+            socket.subscribe("slam_map");
             while (running) {
                 byte[] map = socket.recv();
                 fireMapChanged(SlamScan.parseFrom(map));

app/src/main/proto/SlamController.proto

@@ -9,6 +9,7 @@ import "empty.proto";
 message SlamDetails {
     int32 map_size_pixels = 1;
     int32 map_size_meters = 2;
+    int32 port = 3;
 }
 
 message SlamRow{