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java – Send message from wearable to phone and then immediately reply

Posted by: admin May 14, 2020 Leave a comment

Questions:

I’ve been battling with the Android Wear Message API all day today and have finally accepted I need some help with this.

My app is very straightforward. The Mobile portion consists of a MainActivity (which does nothing but display “Hello world” and a Service which extends WearableListenerService. The Wear portion is just a MainActivity with a single Button, and implements MessageApi.MessageListener.

The idea is simple: press the Button on the Wear device which sends a message to the Mobile. When the Mobile receives the message, it displays a Toast with the sender’s message path (e.g. /mobile). Immediately after doing this, the Mobile should send a message back to the Wear device using my reply() method. All I want to do then is Log this message.

I can achieve the first part perfectly fine. When the Button is pressed, the Mobile pops up a Toast saying “/mobile”. The reply, however, seems to just get lost in the aether; no errors, but no message either.

Can someone please help me understand what I’m doing wrong? I have pasted my files below.

This is the tutorial I am following. Cheers!

Wear: MainActivity.java

package org.thecosmicfrog.toastdroidmessageapitutorial;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.support.wearable.view.WatchViewStub;
import android.util.Log;
import android.view.View;

import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.wearable.MessageApi;
import com.google.android.gms.wearable.MessageEvent;
import com.google.android.gms.wearable.Node;
import com.google.android.gms.wearable.NodeApi;
import com.google.android.gms.wearable.Wearable;

import java.util.List;
import java.util.concurrent.TimeUnit;

public class MainActivity extends Activity implements MessageApi.MessageListener {

    private final String LOG_TAG = MainActivity.class.getSimpleName();

    private static final long CONNECTION_TIME_OUT_MS = 100;
    private static final String MOBILE_PATH = "/mobile";

    private GoogleApiClient googleApiClient;
    private String nodeId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initGoogleApiClient();

        final WatchViewStub stub = (WatchViewStub) findViewById(R.id.watch_view_stub);
        stub.setOnLayoutInflatedListener(new WatchViewStub.OnLayoutInflatedListener() {
            @Override
            public void onLayoutInflated(WatchViewStub stub) {
                initWidgets();
            }
        });
    }

    private void initGoogleApiClient() {
        googleApiClient = getGoogleApiClient(this);
        retrieveDeviceNode();
    }

    private GoogleApiClient getGoogleApiClient(Context context) {
        return new GoogleApiClient.Builder(context)
                .addApi(Wearable.API)
                .build();
    }

    private void retrieveDeviceNode() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                if (googleApiClient != null && !(googleApiClient.isConnected() || googleApiClient.isConnecting()))
                    googleApiClient.blockingConnect(CONNECTION_TIME_OUT_MS, TimeUnit.MILLISECONDS);

                NodeApi.GetConnectedNodesResult result =
                        Wearable.NodeApi.getConnectedNodes(googleApiClient).await();

                List<Node> nodes = result.getNodes();

                if (nodes.size() > 0)
                    nodeId = nodes.get(0).getId();

                Log.v(LOG_TAG, "Node ID of phone: " + nodeId);

                googleApiClient.disconnect();
            }
        }).start();
    }

    private void initWidgets() {
        findViewById(R.id.button_toast).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                sendToast();
            }
        });
    }

    private void sendToast() {
        if (nodeId != null) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    if (googleApiClient != null && !(googleApiClient.isConnected() || googleApiClient.isConnecting()))
                        googleApiClient.blockingConnect(CONNECTION_TIME_OUT_MS, TimeUnit.MILLISECONDS);

                    Wearable.MessageApi.sendMessage(googleApiClient, nodeId, MOBILE_PATH, null).await();
                    googleApiClient.disconnect();
                }
            }).start();
        }
    }

    @Override
    public void onMessageReceived(MessageEvent messageEvent) {
        Log.v(LOG_TAG, "In onMessageReceived()");

        if (messageEvent.getPath().equals("/wear")) {
            Log.v(LOG_TAG, "Success!");
        }
    }
}

Mobile: ListenerService.java

package org.thecosmicfrog.toastdroidmessageapitutorial;

import android.util.Log;
import android.widget.Toast;

import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.wearable.MessageEvent;
import com.google.android.gms.wearable.Wearable;
import com.google.android.gms.wearable.WearableListenerService;

import java.util.concurrent.TimeUnit;

public class ListenerService extends WearableListenerService {

    private final String LOG_TAG = ListenerService.class.getSimpleName();

    private static GoogleApiClient googleApiClient;

    private static final long CONNECTION_TIME_OUT_MS = 100;
    private static final String WEAR_PATH = "/wear";
    private String nodeId;

    @Override
    public void onMessageReceived(MessageEvent messageEvent) {
        if (messageEvent.getPath().equals("/mobile")) {
            nodeId = messageEvent.getSourceNodeId();
            Log.v(LOG_TAG, "Node ID of watch: " + nodeId);
            showToast(messageEvent.getPath());

            reply(WEAR_PATH);
        }
    }

    private void showToast(String message) {
        Toast.makeText(this, message, Toast.LENGTH_LONG).show();
    }

    private void reply(final String path) {
        googleApiClient = new GoogleApiClient.Builder(getApplicationContext())
                .addApi(Wearable.API)
                .build();

        Log.v(LOG_TAG, "In reply()");
        Log.v(LOG_TAG, "Path: " + path);

        if (googleApiClient != null && !(googleApiClient.isConnected() || googleApiClient.isConnecting()))
            googleApiClient.blockingConnect(CONNECTION_TIME_OUT_MS, TimeUnit.MILLISECONDS);

        Wearable.MessageApi.sendMessage(googleApiClient, nodeId, path, null).await();
        googleApiClient.disconnect();
    }
}

The Mobile MainActivity is pretty trivial so I’ve left it out for clarity.

How to&Answers:

You never call MessageApi.addListener() in your Wear activity so your MessageListener is never registered to receive messages. You should also call MessageApi.removeListener() when your activity is being destroyed.

Note: both methods require a connected GoogleApiClient. It may make logic easier if you leave a GoogleApiClient open throughout the duration of your activity rather than try connecting/removeListener()/disconnect in your onDestroy().