Android example source code file (MessengerServiceActivities.java)

This example Android source code file (MessengerServiceActivities.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

activity, android, attached, binding, button, content, disconnected, incominghandler, message, messenger, messengerserviceactivities, onclicklistener, os, override, received, remoteexception, serviceconnection, ui, view, widget

The MessengerServiceActivities.java Android example source code

package com.example.android.apis.app;

import com.example.android.apis.R;
import com.example.android.apis.app.LocalServiceActivities.Binding;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MessengerServiceActivities {
    /**
     * Example of binding and unbinding to the remote service.
     * This demonstrates the implementation of a service which the client will
     * bind to, interacting with it through an aidl interface.</p>
     * 
     * <p>Note that this is implemented as an inner class only keep the sample
     * all together; typically this code would appear in some separate class.
     */
    public static class Binding extends Activity {

        /** Messenger for communicating with service. */
        Messenger mService = null;
        /** Flag indicating whether we have called bind on the service. */
        boolean mIsBound;
        /** Some text view we are using to show state information. */
        TextView mCallbackText;
        
        /**
         * Handler of incoming messages from service.
         */
        class IncomingHandler extends Handler {
            @Override
            public void handleMessage(Message msg) {
                switch (msg.what) {
                    case MessengerService.MSG_SET_VALUE:
                        mCallbackText.setText("Received from service: " + msg.arg1);
                        break;
                    default:
                        super.handleMessage(msg);
                }
            }
        }
        
        /**
         * Target we publish for clients to send messages to IncomingHandler.
         */
        final Messenger mMessenger = new Messenger(new IncomingHandler());
        
        /**
         * Class for interacting with the main interface of the service.
         */
        private ServiceConnection mConnection = new ServiceConnection() {
            public void onServiceConnected(ComponentName className,
                    IBinder service) {
                // This is called when the connection with the service has been
                // established, giving us the service object we can use to
                // interact with the service.  We are communicating with our
                // service through an IDL interface, so get a client-side
                // representation of that from the raw service object.
                mService = new Messenger(service);
                mCallbackText.setText("Attached.");

                // We want to monitor the service for as long as we are
                // connected to it.
                try {
                    Message msg = Message.obtain(null,
                            MessengerService.MSG_REGISTER_CLIENT);
                    msg.replyTo = mMessenger;
                    mService.send(msg);
                    
                    // Give it some value as an example.
                    msg = Message.obtain(null,
                            MessengerService.MSG_SET_VALUE, this.hashCode(), 0);
                    mService.send(msg);
                } catch (RemoteException e) {
                    // In this case the service has crashed before we could even
                    // do anything with it; we can count on soon being
                    // disconnected (and then reconnected if it can be restarted)
                    // so there is no need to do anything here.
                }
                
                // As part of the sample, tell the user what happened.
                Toast.makeText(Binding.this, R.string.remote_service_connected,
                        Toast.LENGTH_SHORT).show();
            }

            public void onServiceDisconnected(ComponentName className) {
                // This is called when the connection with the service has been
                // unexpectedly disconnected -- that is, its process crashed.
                mService = null;
                mCallbackText.setText("Disconnected.");

                // As part of the sample, tell the user what happened.
                Toast.makeText(Binding.this, R.string.remote_service_disconnected,
                        Toast.LENGTH_SHORT).show();
            }
        };
        
        void doBindService() {
            // Establish a connection with the service.  We use an explicit
            // class name because there is no reason to be able to let other
            // applications replace our component.
            bindService(new Intent(Binding.this, 
                    MessengerService.class), mConnection, Context.BIND_AUTO_CREATE);
            mIsBound = true;
            mCallbackText.setText("Binding.");
        }
        
        void doUnbindService() {
            if (mIsBound) {
                // If we have received the service, and hence registered with
                // it, then now is the time to unregister.
                if (mService != null) {
                    try {
                        Message msg = Message.obtain(null,
                                MessengerService.MSG_UNREGISTER_CLIENT);
                        msg.replyTo = mMessenger;
                        mService.send(msg);
                    } catch (RemoteException e) {
                        // There is nothing special we need to do if the service
                        // has crashed.
                    }
                }
                
                // Detach our existing connection.
                unbindService(mConnection);
                mIsBound = false;
                mCallbackText.setText("Unbinding.");
            }
        }

        
        /**
         * Standard initialization of this activity.  Set up the UI, then wait
         * for the user to poke it before doing anything.
         */
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            setContentView(R.layout.messenger_service_binding);

            // Watch for button clicks.
            Button button = (Button)findViewById(R.id.bind);
            button.setOnClickListener(mBindListener);
            button = (Button)findViewById(R.id.unbind);
            button.setOnClickListener(mUnbindListener);
            
            mCallbackText = (TextView)findViewById(R.id.callback);
            mCallbackText.setText("Not attached.");
        }

        private OnClickListener mBindListener = new OnClickListener() {
            public void onClick(View v) {
                doBindService();
            }
        };

        private OnClickListener mUnbindListener = new OnClickListener() {
            public void onClick(View v) {
                doUnbindService();
            }
        };
    }
}