I looked up on the internet, but couldn't find an example covering my scenario. What I am trying to do is:
1) To start and bind to a service as soon as my activity starts (done)
2) The service then binds itself to another service looking for a user
input from a connected device, and saves a string a string to a variable (done)
3) I would like to send back this string to the activity, so I can check what it
is and based on it to make a network call.
Now number 3) is my challenge. I managed to do it with a Timer that runs for one second and then checks the value written in the service, but somehow this doesn't seem to be the right way and I think that there might be a more mature solution. However, I can't seem to figure it out.
I've taken the code from the documentation and only added the timer. It is just one service in this example that just generates a random number (this will normally be replaced by my second service).
This is the code for the service:
public class LocalService extends Service {
private final IBinder mBinder = new LocalBinder();
private final Random mGenerator = new Random();
public class LocalBinder extends Binder {
LocalService getService() {
return LocalService.this;
}
}
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}
public int getRandomNumber() {
return mGenerator.nextInt(100);
}
}
And this is the code in my activity:
public class MainActivity extends AppCompatActivity {
LocalService mService;
boolean mBound = false;
Timer timer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
timer = new Timer();
}
#Override
protected void onStart() {
super.onStart();
Intent intent = new Intent(this, LocalService.class);
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
timer.schedule(new MyTimerTask(new Handler(), this), 1000, 1000); // run on every second
}
#Override
protected void onStop() {
super.onStop();
if (mBound) {
unbindService(mConnection);
mBound = false;
}
timer.cancel();
timer.purge();
}
private class MyTimerTask extends TimerTask {
Handler handler;
MainActivity ref;
public MyTimerTask(Handler handler, MainActivity ref) {
super();
this.handler = handler;
this.ref = ref;
}
#Override
public void run() {
handler.post(new Runnable() {
#Override
public void run() {
if (mBound) {
int num = ref.mService.getRandomNumber();
// just as an example, raise a toast to see if it works
// but otherwise the value will be handled
Toast.makeText(ref, "number: " + num, Toast.LENGTH_SHORT).show();
}
}
});
}
}
private ServiceConnection mConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className,
IBinder service) {
LocalService.LocalBinder binder = (LocalService.LocalBinder) service;
mService = binder.getService();
mBound = true;
}
#Override
public void onServiceDisconnected(ComponentName arg0) {
mBound = false;
}
};
}
My question is: is this a good approach (it works) or is it bad and what's the alternative?
You can use LocalBroadcastManager to send broadcasts from your Service to your Activity. For example, in your Service declare:
public static final String BROADCAST_INTENT = "broadcast_intent";
public static final String BROADCAST_VALUE = "broadcast_value";
private LocalBroadcastManager broadcastManager;
public void onCreate() {
super.onCreate();
broadcastManager = LocalBroadcastManager.getInstance(this);
}
Now whenever you want to send a String to your Activity you can do so like this:
private void sendBroadcast(String value) {
Intent intent = new Intent(BROADCAST_INTENT);
intent.putExtra(BROADCAST_VALUE, value);
broadcastManager.sendBroadcast(intent);
}
In your Activity declare a BroadcastReceiver:
private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
handleIntent(intent);
}
};
Register the receiver when you bind to your Service:
IntentFilter broadcastIntentFilter = new IntentFilter();
broadcastIntentFilter.addAction(StreamService.BROADCAST_INTENT);
LocalBroadcastManager.getInstance(context).registerReceiver((broadcastReceiver), broadcastIntentFilter);
And unregister where you unbind from your Service:
LocalBroadcastManager.getInstance(context).unregisterReceiver(broadcastReceiver);
Now when your service sends the broadcast you can handle it in your Activity:
private void handleIntent(Intent intent) {
if (intent.getAction().equals(StreamService.BROADCAST_INTENT)) {
String value = intent.getStringExtra(StreamService.BROADCAST_VALUE, "default");
}
}
I would like to send back this string to the activity, so I can check what it is and based on it to make a network call.
Use LocalBroadcastManager, greenrobot's EventBus, Square's Otto, or some other in-process event bus implementation. Raise an event when you have changed data. Have the activity register with the bus to find out about the event. Have the activity use the changed data when the change occurs.
is this a good approach
No.
Related
Hi in project I'm using service for chat communication using SignalR. Chat communication is working fine but when the app goes to background the service got stopped I need to run the services fully till my app get deleted
Here is me service code
public class SignalRService extends Service {
private HubConnection mHubConnection;
private HubProxy mHubProxy;
private Handler mHandler; // to display Toast message
private final IBinder mBinder = new LocalBinder(); // Binder given to clients
public SignalRService() {
}
#Override
public void onCreate() {
super.onCreate();
mHandler = new Handler(Looper.getMainLooper());
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
int result = super.onStartCommand(intent, flags, startId);
startSignalR();
return result;
}
#Override
public void onDestroy() {
Log.i("onDestroy","onDestroy");
mHubConnection.stop();
super.onDestroy();
}
#Override
public IBinder onBind(Intent intent) {
// Return the communication channel to the service.
startSignalR();
return mBinder;
}
/**
* Class used for the client Binder. Because we know this service always
* runs in the same process as its clients, we don't need to deal with IPC.
*/
public class LocalBinder extends Binder {
public SignalRService getService() {
// Return this instance of SignalRService so clients can call public methods
return SignalRService.this;
}
}
/**
* method for clients (activities)
*/
public void sendMessage(String message) {
String SERVER_METHOD_SEND = "Send";
mHubProxy.invoke(SERVER_METHOD_SEND, message);
}
/**
* method for clients (activities)
*/
public void sendMessage_To(String receiverName, String message) {
String SERVER_METHOD_SEND_TO = "SendChatMessage";
mHubProxy.invoke(SERVER_METHOD_SEND_TO, receiverName, message);
}
private void startSignalR() {
Platform.loadPlatformComponent(new AndroidPlatformComponent());
Credentials credentials = new Credentials() {
#Override
public void prepareRequest(Request request) {
request.addHeader("User-Name", "BNK");
}
};
String serverUrl = "http://10.10.10.180/signalr/hubs";
mHubConnection = new HubConnection(serverUrl);
mHubConnection.setCredentials(credentials);
String SERVER_HUB_CHAT = "ChatHub";
mHubProxy = mHubConnection.createHubProxy(SERVER_HUB_CHAT);
ClientTransport clientTransport = new ServerSentEventsTransport(mHubConnection.getLogger());
SignalRFuture<Void> signalRFuture = mHubConnection.start(clientTransport);
try {
signalRFuture.get();
} catch (InterruptedException | ExecutionException e) {
Log.e("SimpleSignalR", e.toString());
return;
}
sendMessage("Hello from BNK!");
String CLIENT_METHOD_BROADAST_MESSAGE = "broadcastMessage";
mHubProxy.on(CLIENT_METHOD_BROADAST_MESSAGE,
new SubscriptionHandler1<CustomMessage>() {
#Override
public void run(final CustomMessage msg) {
final String finalMsg = msg.UserName + " says " + msg.Message;
// display Toast message
mHandler.post(new Runnable() {
#Override
public void run() {
Log.i("message","message: "+finalMsg);
Toast.makeText(getApplicationContext(), finalMsg, Toast.LENGTH_SHORT).show();
}
});
}
}
, CustomMessage.class);
}}
And here is the activity code
public class MainActivity extends AppCompatActivity {
private final Context mContext = this;
private SignalRService mService;
private boolean mBound = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent intent = new Intent();
intent.setClass(mContext, SignalRService.class);
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
}
#Override
protected void onStop() {
// Unbind from the service
Log.i("onStop","onStop");
if (mBound) {
unbindService(mConnection);
mBound = false;
}
super.onStop();
}
public void sendMessage(View view) {
if (mBound) {
// Call a method from the SignalRService.
// However, if this call were something that might hang, then this request should
// occur in a separate thread to avoid slowing down the activity performance.
EditText editText = (EditText) findViewById(R.id.edit_message);
EditText editText_Receiver = (EditText) findViewById(R.id.edit_receiver);
if (editText != null && editText.getText().length() > 0) {
String receiver = editText_Receiver.getText().toString();
String message = editText.getText().toString();
mService.sendMessage_To(receiver, message);
mService.sendMessage(message);
}
}
}
/**
* Defines callbacks for service binding, passed to bindService()
*/
private final ServiceConnection mConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className,
IBinder service) {
// We've bound to SignalRService, cast the IBinder and get SignalRService instance
SignalRService.LocalBinder binder = (SignalRService.LocalBinder) service;
mService = binder.getService();
mBound = true;
}
#Override
public void onServiceDisconnected(ComponentName arg0) {
Log.i("onServiceDisconnected","onServiceDisconnected");
mBound = false;
}
};}
My manifest code for service
<service
android:name=".SignalRService"
android:enabled="true"
android:exported="true" >
</service>
Plese help me on this
If you bind the service with any component the system will automatically destroy the service if no other client is bound with it.
If you want to run a service independently then you have to start a service rather than bind. But you can't communicate with a service if you start it with startService()
For more details you can see the documentation here
You can BOTH start AND bind the service.
In this way, even if multiple components bind to the service at once, then ALL of them unbind, the service will NOT be destroyed. Refer to A service can essentially take two forms: Bound
your service can work both ways: it can be started (to run indefinitely) and also allow binding. It's simply a matter of whether you implement a couple callback methods: onStartCommand() to allow components to start it and onBind() to allow binding.
// onBind method just return the IBinder, to allow clients to get service.
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}
// onStartCommand just return START_STICKY to let system to
// try to re-create the service if the servcie's process is killed.
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
return START_STICKY;
}
// and make startSignalR public to allow client to call this method.
public void startSignalR() {
}
In your clients, no need to keep a boolean mBound.
Just bind service when onCreate, unbind service when onDestroy. DO NOT unbind when onStop. Since onStop may called many times, for example dialog popup will invoke onStop, but your activity is still on foreground, this will cause your service destroyed.
Refer to my answer for question: Pass Service From one Activity to Another for sample code.
I have seen many posts in SO regarding this but could not get the exact and most easy way to call an activity method from service class. Is broadcast receiver only the option? No easy way out ? I just need to call the following method in Activity class after the media player is prepared in Service class .
Activity class:
public void updateProgress() {
// set Progress bar values
songProgressBar.setProgress(0);
songProgressBar.setMax(100);
// Updating progress bar
updateProgressBar();
}
Service class:
#Override
public IBinder onBind(Intent intent) {
Log.d(this.getClass().getName(), "BIND");
return musicBind;
}
#Override
public boolean onUnbind(Intent intent) {
return false;
}
#Override
public void onPrepared(MediaPlayer mp) {
try {
mp.start();
} catch (IllegalStateException e) {
e.printStackTrace();
}
// updateProgress();// Need to call the Activity method here
}
Define an interface your Service will use to communicate events:
public interface ServiceCallbacks {
void doSomething();
}
Write your Service class. Your Activity will bind to this service, so follow the sample shown here. In addition, we will add a method to set the ServiceCallbacks.
public class MyService extends Service {
// Binder given to clients
private final IBinder binder = new LocalBinder();
// Registered callbacks
private ServiceCallbacks serviceCallbacks;
// Class used for the client Binder.
public class LocalBinder extends Binder {
MyService getService() {
// Return this instance of MyService so clients can call public methods
return MyService.this;
}
}
#Override
public IBinder onBind(Intent intent) {
return binder;
}
public void setCallbacks(ServiceCallbacks callbacks) {
serviceCallbacks = callbacks;
}
}
Write your Activity class following the same guide, but also make it implement your ServiceCallbacks interface. When you bind/unbind from the Service, you will register/unregister it by calling setCallbacks on the Service.
public class MyActivity extends Activity implements ServiceCallbacks {
private MyService myService;
private boolean bound = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(...);
}
#Override
protected void onStart() {
super.onStart();
// bind to Service
Intent intent = new Intent(this, MyService.class);
bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);
}
#Override
protected void onStop() {
super.onStop();
// Unbind from service
if (bound) {
myService.setCallbacks(null); // unregister
unbindService(serviceConnection);
bound = false;
}
}
/** Callbacks for service binding, passed to bindService() */
private ServiceConnection serviceConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className, IBinder service) {
// cast the IBinder and get MyService instance
LocalBinder binder = (LocalBinder) service;
myService = binder.getService();
bound = true;
myService.setCallbacks(MyActivity.this); // register
}
#Override
public void onServiceDisconnected(ComponentName arg0) {
bound = false;
}
};
/* Defined by ServiceCallbacks interface */
#Override
public void doSomething() {
...
}
}
Now when your service wants to communicate back to the activity, just call one of the interface methods from earlier. Inside your service:
if (serviceCallbacks != null) {
serviceCallbacks.doSomething();
}
Use Broadcast receiver with service for updating your view from the service class.
For example:
In my activity class
public class ServiceDemoActivity extends Activity {
Intent intent;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final TextView notification = (TextView) findViewById(R.id.notification);
if (CheckIfServiceIsRunning()) {
} else {
startService(new Intent(this, MyService.class));
}
}
private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
updateDate(intent);
}
};
private void updateDate(Intent intent) {
String time = intent.getStringExtra("time");
Toast.makeText(getApplicationContext(), "Yea!!! Service called", Toast.LENGTH_SHORT).show();
TextView date = (TextView) findViewById(R.id.date);
date.setText(time);
}
#Override
public void onResume() {
super.onResume();
registerReceiver(broadcastReceiver, new IntentFilter(
MyService.BROADCAST_ACTION));
}
}
And in my service class I am calling my update ui after a few interval of time which updates my UI.
public class MyService extends Service {
public static final String
BROADCAST_ACTION = "com.mukesh.service";
private final Handler handler = new Handler();
#Override
public void onCreate() {
intent = new Intent(BROADCAST_ACTION);
}
#Override
public void onDestroy() {
stopService(intent);
}
#Override
public void onStart(Intent intent, int startid) {
int i = 0;
while (i <= 2) {
if (i > 1) {
i++;
this.onDestroy();
} else {
counter = i;
i++;
handler.removeCallbacks(sendUpdatesToUI);
handler.postDelayed(sendUpdatesToUI, 1 * 1000); // 1 sec
}
}
}
private Runnable sendUpdatesToUI = new Runnable() {
public void run() {
DisplayLoggingInfo();
handler.postDelayed(this, 7 * 1000); // 7 sec
}
};
private void DisplayLoggingInfo() {
intent.putExtra("time", new Date().toLocaleString());
intent.putExtra("counter", String.valueOf(counter));
sendBroadcast(intent);
stopService(intent);
}
}
For complete code check this link
I created a general class called Delegate (it's not a special name, you can name it John) and passed MainActivity class into it as a static field. Then I can access it from the service since its global now. I am not sure if it is cost-effective but it solved the problem for me simple.
My service:
package com.some.package;
import com.google.firebase.iid.FirebaseInstanceId;
import com.google.firebase.iid.FirebaseInstanceIdService;
public class FirebaseInstanceIDService extends FirebaseInstanceIdService {
#Override
public void onTokenRefresh() {
String token = FirebaseInstanceId.getInstance().getToken();
Delegate.theMainActivity.onDeviceTokenChange(token);
}
}
Delegate class:
package com.some.package;
public class Delegate {
static MainActivity theMainActivity;
}
What I did in MainActivity:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Delegate.theMainActivity = this;
//rest of the code...
}
public void onDeviceTokenChange(String token){
Log.e("updated token:", token);
}
You can't call your sevices method direcly from your activity or vise versa. There are 3 ways to communicate with a service; using broadcasters and receivers, using Messenger or binding to the service. For further information look at http://developer.android.com/guide/components/bound-services.html
You can call from your service
getContentResolver().notifyChange(uri, null);
and in your activity you set up a
getContentResolver().registerContentObserver(uri, false, new ContentObserver(getHandler())
{
public void onChange(boolean selfChange)
{
updateProgress()
}
};
the onChange method will ba called on the UI thread
You can call a method of activity from service by implementing your own listener like this
https://stackoverflow.com/a/18585247/5361964
You might consider running your activity method in runOnUiThread like this:
// method will be called from service
override fun callback(activity: Activity, result: String) {
runOnUiThread{
Toast.makeText(activity, result, Toast.LENGTH_LONG).show()
}
}
I would prefer to use some very easy and cleaner solution provided by
EventBus
I am trying to make my own MusicPlayer for android. Where i came to a problem is running some things in background. Main activity manages GUI and up to now all the songs are playing. I wanted to separate GUI and music playing classes. I want to put music managing part in Service and leave other things as they are now.
My problem is that i can't organize communication between Activity and Service as lot of communication is happening between them including moving objects in both directions. I tried many techniques that I searched here on Stack Overflow but every time I had problems. I need Service to be able to send objects to Activity and vice versa. When I add widget i also want it to be able to communicate with Service.
Any tips are appreciated, if you need source code place comment bellow but now in this transition it became chaotic.
Is there any more advanced tutorial on this than calling one method that returns random number from service? :P
EDIT: Possible solution is to use RoboGuice library and move objects with injection
I have implemented communication between Activity and Service using Bind and Callbacks interface.
For sending data to the service I used Binder which retruns the Service instace to the Activity, and then the Activity can access public methods in the Service.
To send data back to the Activity from the Service, I used Callbacks interface like you are using when you want to communicate between Fragment and Activity.
Here is some code samples for each:
The following example shows Activity and Service bidirectional relationship:
The Activity has 2 buttons:
The first button will start and stop the service.
The second button will start a timer which runs in the service.
The service will update the Activity through callback with the timer progress.
My Activity:
//Activity implements the Callbacks interface which defined in the Service
public class MainActivity extends ActionBarActivity implements MyService.Callbacks{
ToggleButton toggleButton;
ToggleButton tbStartTask;
TextView tvServiceState;
TextView tvServiceOutput;
Intent serviceIntent;
MyService myService;
int seconds;
int minutes;
int hours;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
serviceIntent = new Intent(MainActivity.this, MyService.class);
setViewsWidgets();
}
private void setViewsWidgets() {
toggleButton = (ToggleButton)findViewById(R.id.toggleButton);
toggleButton.setOnClickListener(btListener);
tbStartTask = (ToggleButton)findViewById(R.id.tbStartServiceTask);
tbStartTask.setOnClickListener(btListener);
tvServiceState = (TextView)findViewById(R.id.tvServiceState);
tvServiceOutput = (TextView)findViewById(R.id.tvServiceOutput);
}
private ServiceConnection mConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className,
IBinder service) {
Toast.makeText(MainActivity.this, "onServiceConnected called", Toast.LENGTH_SHORT).show();
// We've binded to LocalService, cast the IBinder and get LocalService instance
MyService.LocalBinder binder = (MyService.LocalBinder) service;
myService = binder.getServiceInstance(); //Get instance of your service!
myService.registerClient(MainActivity.this); //Activity register in the service as client for callabcks!
tvServiceState.setText("Connected to service...");
tbStartTask.setEnabled(true);
}
#Override
public void onServiceDisconnected(ComponentName arg0) {
Toast.makeText(MainActivity.this, "onServiceDisconnected called", Toast.LENGTH_SHORT).show();
tvServiceState.setText("Service disconnected");
tbStartTask.setEnabled(false);
}
};
View.OnClickListener btListener = new View.OnClickListener() {
#Override
public void onClick(View v) {
if(v == toggleButton){
if(toggleButton.isChecked()){
startService(serviceIntent); //Starting the service
bindService(serviceIntent, mConnection, Context.BIND_AUTO_CREATE); //Binding to the service!
Toast.makeText(MainActivity.this, "Button checked", Toast.LENGTH_SHORT).show();
}else{
unbindService(mConnection);
stopService(serviceIntent);
Toast.makeText(MainActivity.this, "Button unchecked", Toast.LENGTH_SHORT).show();
tvServiceState.setText("Service disconnected");
tbStartTask.setEnabled(false);
}
}
if(v == tbStartTask){
if(tbStartTask.isChecked()){
myService.startCounter();
}else{
myService.stopCounter();
}
}
}
};
#Override
public void updateClient(long millis) {
seconds = (int) (millis / 1000) % 60 ;
minutes = (int) ((millis / (1000*60)) % 60);
hours = (int) ((millis / (1000*60*60)) % 24);
tvServiceOutput.setText((hours>0 ? String.format("%d:", hours) : "") + ((this.minutes<10 && this.hours > 0)? "0" + String.format("%d:", minutes) : String.format("%d:", minutes)) + (this.seconds<10 ? "0" + this.seconds: this.seconds));
}
}
And here is the service:
public class MyService extends Service {
NotificationManager notificationManager;
NotificationCompat.Builder mBuilder;
Callbacks activity;
private long startTime = 0;
private long millis = 0;
private final IBinder mBinder = new LocalBinder();
Handler handler = new Handler();
Runnable serviceRunnable = new Runnable() {
#Override
public void run() {
millis = System.currentTimeMillis() - startTime;
activity.updateClient(millis); //Update Activity (client) by the implementd callback
handler.postDelayed(this, 1000);
}
};
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
//Do what you need in onStartCommand when service has been started
return START_NOT_STICKY;
}
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}
//returns the instance of the service
public class LocalBinder extends Binder{
public MyService getServiceInstance(){
return MyService.this;
}
}
//Here Activity register to the service as Callbacks client
public void registerClient(Activity activity){
this.activity = (Callbacks)activity;
}
public void startCounter(){
startTime = System.currentTimeMillis();
handler.postDelayed(serviceRunnable, 0);
Toast.makeText(getApplicationContext(), "Counter started", Toast.LENGTH_SHORT).show();
}
public void stopCounter(){
handler.removeCallbacks(serviceRunnable);
}
//callbacks interface for communication with service clients!
public interface Callbacks{
public void updateClient(long data);
}
}
Update: July 10 2016
IMO I think using BroadcastReceiver for custom events is better way
as the Messengers mentioned don't handle activity recreation on device
rotation as well as possible memory leaks.
You may create custom BroadCast Receiver for events in the activity, Then you may also use Messengers.
In your Activity
create a MessageHandler class as
public static class MessageHandler extends Handler {
#Override
public void handleMessage(Message message) {
int state = message.arg1;
switch (state) {
case HIDE:
progressBar.setVisibility(View.GONE);
break;
case SHOW:
progressBar.setVisibility(View.VISIBLE);
break;
}
}
}
Now you can have it's instance as
public static Handler messageHandler = new MessageHandler();
Start your Service with this Handler object as an extra data as
Intent startService = new Intent(context, SERVICE.class)
startService.putExtra("MESSENGER", new Messenger(messageHandler));
context.startService(startService);
In your Service you receive this object from the intent and initialize the Messenger variable in Service as
private Messenger messageHandler;
Bundle extras = intent.getExtras();
messageHandler = (Messenger) extras.get("MESSENGER");
sendMessage(ProgressBarState.SHOW);
And then write a method sendMessage to send messages to activity.
public void sendMessage(ProgressBarState state) {
Message message = Message.obtain();
switch (state) {
case SHOW :
message.arg1 = Home.SHOW;
break;
case HIDE :
message.arg1 = Home.HIDE;
break;
}
try {
messageHandler.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}
}
The sample code above shows and hides a ProgressBar in Activity as messages are received from Service.
Intents are good solution for communication between Activitiy and Service.
A fast solution for receive intents in your service is subclassing IntentService class. It handles asynchronous requests expressed as Intents using a queue and worker thread.
For communication from service to Activity you can broadcast the intent but instead of using normal sendBroadcast() from Context, a more efficent way is to use LocalBroadcastManager from support library.
Example service.
public class MyIntentService extends IntentService {
private static final String ACTION_FOO = "com.myapp.action.FOO";
private static final String EXTRA_PARAM_A = "com.myapp.extra.PARAM_A";
public static final String BROADCAST_ACTION_BAZ = "com.myapp.broadcast_action.FOO";
public static final String EXTRA_PARAM_B = "com.myapp.extra.PARAM_B";
// called by activity to communicate to service
public static void startActionFoo(Context context, String param1) {
Intent intent = new Intent(context, MyIntentService.class);
intent.setAction(ACTION_FOO);
intent.putExtra(EXTRA_PARAM1, param1);
context.startService(intent);
}
public MyIntentService() {
super("MyIntentService");
}
#Override
protected void onHandleIntent(Intent intent) {
if (intent != null) {
final String action = intent.getAction();
if (ACTION_FOO.equals(action)) {
final String param1 = intent.getStringExtra(EXTRA_PARAM_A);
// do something
}
}
}
// called to send data to Activity
public static void broadcastActionBaz(String param) {
Intent intent = new Intent(BROADCAST_ACTION_BAZ);
intent.putExtra(EXTRA_PARAM_B, param);
LocalBroadcastManager bm = LocalBroadcastManager.getInstance(this);
bm.sendBroadcast(intent);
}
}
Example Activity
public class MainActivity extends ActionBarActivity {
// handler for received data from service
private final BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals(MyIntentService.BROADCAST_ACTION_BAZ)) {
final String param = intent.getStringExtra(EXTRA_PARAM_B);
// do something
}
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
IntentFilter filter = new IntentFilter();
filter.addAction(MyIntentService.BROADCAST_ACTION_BAZ);
LocalBroadcastManager bm = LocalBroadcastManager.getInstance(this);
bm.registerReceiver(mBroadcastReceiver, filter);
}
#Override
protected void onDestroy() {
LocalBroadcastManager bm = LocalBroadcastManager.getInstance(this);
bm.unregisterReceiver(mBroadcastReceiver);
super.onDestroy();
}
// send data to MyService
protected void communicateToService(String parameter) {
MyIntentService.startActionFoo(this, parameter);
}
}
I think there is a problem with the correct answer. I have not enough reputation to comment on it.
Right in the answer:
Activity call bindService() to get pointer to Service is ok. Because service context is maintained when connection is maintained.
wrong in the answer:
service pointer to Activity class to call back is bad way. Activity instance maybe not null during Activity context is being Release => exception here.
solution for the wrong in the answer:
service send intent to Activity. and Activity receiver intent via BroadcastReceiver.
Note:
in this case, Service and Activity in the same Process, you should use LocalBroadcastManager to send intent. It make performance and security better
This is a simple example of communication between activity and service
Activity
MyReceiver myReceiver; //my global var receiver
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layourAwesomexD);
registerReceiver();
}
//When the activity resume, the receiver is going to register...
#Override
protected void onResume() {
super.onResume();
checkStatusService(); // verficarStatusServicio(); <- name change
registerReceiver();
}
//when the activity stop, the receiver is going to unregister...
#Override
protected void onStop() {
unregisterReceiver(myReceiver); //unregister my receiver...
super.onStop();
}
//function to register receiver :3
private void registerReceiver(){
//Register BroadcastReceiver
//to receive event from our service
myReceiver = new MyReceiver();
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(MyService.SENDMESAGGE);
registerReceiver(myReceiver, intentFilter);
}
// class of receiver, the magic is here...
private class MyReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context arg0, Intent arg1) {
//verify if the extra var exist
System.out.println(arg1.hasExtra("message")); // true or false
//another example...
System.out.println(arg1.getExtras().containsKey("message")); // true or false
//if var exist only print or do some stuff
if (arg1.hasExtra("message")) {
//do what you want to
System.out.println(arg1.getStringExtra("message"));
}
}
}
public void checkStatusService(){
if(MyService.serviceStatus!=null){
if(MyService.serviceStatus == true){
//do something
//textview.text("Service is running");
}else{
//do something
//textview.text("Service is not running");
}
}
}
Service
public class MyService extends Service {
final static String SENDMESAGGE = "passMessage";
public static Boolean serviceStatus = false;
#Override
public void onCreate() {
super.onCreate();
serviceStatus=true;
}
#Nullable
#Override
public IBinder onBind(Intent intent) {return null;}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
//you service etc...
passMessageToActivity("hello my friend this an example of send a string...");
return START_STICKY;
}
#Override
public void onDestroy() {
super.onDestroy();
passMessageToActivity("The service is finished, This is going to be more cooler than the heart of your ex...");
System.out.println("onDestroy");
serviceStatus=false;
}
private void passMessageToActivity(String message){
Intent intent = new Intent();
intent.setAction(SENDMESAGGE);
intent.putExtra("message",message);
sendBroadcast(intent);
}
}
if we don't unregister BroadcastReceiver we will have an error, you need to unregister when the activity go onPause, onStop, onDestroy...
if you don't register BroadcastReceiver when you back to activity, it will not listen anything from the service... the service will send information to BroadcastReceiver but it will not receive anything because it isn't registered.
When you create more than one service, the following services are going to begin in onStartCommand.
You can pass information to service with intent and you get it in onStartCommand
Difference about return in onStartCommand: Difference between START_STICKY and START_REDELIVER_INTENT? and check the official website of google: Services
The best way in this case is to communicate by doing broadcasting from your service for different actions and receiving it in your activity. You can create a custom broadcast and send some codes defining specific events like complete, change, prepare etc...
Most easy and efficient way will be using EventBus from GreenRobot.
Use simple 3 steps:
1 Define events
public static class MessageEvent { /* Additional fields if needed */ }
2 Prepare subscribers: Declare and annotate your subscribing method, optionally specify a thread mode:
#Subscribe(threadMode = ThreadMode.MAIN)
public void onMessageEvent(MessageEvent event) {/* Do something */};
Register and unregister your subscriber. For example on Android, activities and fragments should usually register according to their life cycle:
#Override
public void onStart() {
super.onStart();
EventBus.getDefault().register(this);
}
#Override
public void onStop() {
super.onStop();
EventBus.getDefault().unregister(this);
}
3 Post events:
EventBus.getDefault().post(new MessageEvent());
Very easy yet powerful way is to use EventBus you can add it to your gradle build and enjoy the easy publisher/subscriber pattern .
I need to implement such a procedure:
Start a background service
Update the service with parameters (from UI - user input)
After activity ended the service should keep on running and preform requests to HTTP server every minute. in this stage i still need the parameters I updated in the second stage - I send them to the server.
The service should store the server last response and compere each with the last. if there is a change, notify the user.
Finally, when the activity starts again, the service should update UI with latest the server response.
What I tried:
BroadcastReciver - The problem is after onRecive ended all the arguments which aren't declared as final will wipe out, as well as I didn't found a way to update the Intent being sent automatically every minute.
Service - Using startService() - The problem is when the activity ended the service like stops and starts , flushing all it's arguments. and once again I didn't figured out how to update the arguments after the service is already started.
So how to handle such a situation?
Thanks.
It sounds like what you need to do is to be able to "bind" to your service. What I have posted below is a simple template of how to do that. For your purposes you will need to store variables in your Service class and create getters so that when you re-launch your activity you can get the most up to date variables. Also - please note that I start and stop the Service example below in onResume and onPause. You will no doubt want to do this differently.
//Activity
//Bind to Service Example
public class ExampleActivity extends Activity implements OnClickListener {
// UI
private Button binderButton;
// service
private MyService myService;
private Intent serviceIntent;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_layout);
// binder button
binderButton = (Button) findViewById(R.id.button1);
binderButton.setOnClickListener(this);
binderButton.setText("start");
serviceIntent = new Intent(this, MyService.class);
}
private ServiceConnection serviceConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName name, IBinder service) {
myService = ((MyService.MyBinder) service).getService();
}
#Override
public void onServiceDisconnected(ComponentName name) {
myService = null;
}
};
#Override
protected void onResume() {
super.onResume();
// start the service
startService(serviceIntent);
// bind to the service
bindService(serviceIntent, serviceConnection, Context.BIND_AUTO_CREATE);
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
// call method within the service
myService.doServiceStuff();
break;
}
}
#Override
protected void onPause() {
super.onPause();
stopService(serviceIntent);
unbindService(serviceConnection);
}
}
//Service
public class MyService extends Service {
private final IBinder binder = new MyBinder();
#Override
public IBinder onBind(Intent arg0) {
return binder;
}
public void doServiceStuff() {
task.execute();
}
// create an inner Binder class
public class MyBinder extends Binder {
public MyService getService() {
return MyService.this;
}
}
AsyncTask<Void, Void, Void> task = new AsyncTask<Void, Void, Void>() {
#Override
protected Void doInBackground(Void... params) {
Log.d("yourTag", "long running service task");
return null;
}
};
}
Thanks javaJoe, although your answer didn't solved my problem it gave me some a good ideas.
What I did:
in the Activity onCreate, check if my service is running, if so bind it else, create new one and bind it.
Transferring arguments between the Service and the Activity using setters and getters.
in the Activity onDestroy (the problem was that the service calls self Destory) the Activity sends the final arguments through Intent to a Broadcastreciver. The Broadcastreciver than starts the Service again, initiating it with the correct arguments.
I don't know if this architecture is ideal, i'd like to get some feedback.
Here is the code:
Activity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Set Service Intent
serviceIntent = new Intent(this, UpdateService.class);
if (isMyServiceRunning()) {
//Bind to the service
bindService(serviceIntent, serviceConnection, Context.BIND_AUTO_CREATE);
}else{
updateService=new UpdateService();
//Start the service
startService(serviceIntent);
//Bind to the service
bindService(serviceIntent, serviceConnection, Context.BIND_AUTO_CREATE);
}
}
private boolean isMyServiceRunning() {
ActivityManager manager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
for (RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) {
if (UpdateService.class.getName().equals(service.service.getClassName())) {
return true;
}
}
return false;
}
private ServiceConnection serviceConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName name, IBinder service) {
updateService = ((UpdateService.MyBinder) service).getService();
//Set Initial Args
updateService.setParams(int arg0);
}
#Override
public void onServiceDisconnected(ComponentName name) {
updateService = null;
}
};
#Override
protected void onDestroy() {
//UnBind from service
unbindService(serviceConnection);
//Stop Service
stopService(serviceIntent);
//Prepare intent to broadcast reciver
Intent intent = new Intent(MainActivity.this,ServiceRunnerBCR.class);
intent.setAction(ServiceRunnerBCR.ACTION_SET_UpdateService);
intent.putExtra(ServiceRunnerBCR.keyVal_arg0, arg0);
intent.putExtra(ServiceRunnerBCR.keyVal_arg1, arg1);
//Send broadcast to start UpdateService after the activity ended
sendBroadcast(intent);
super.onStop();
}
Broadcastreciver:
public class ServiceRunnerBCR extends BroadcastReceiver {
public static final String ACTION_SET_UpdateService = "ACTION_ALARM";
public static final String keyVal_arg0="ARG0";
public static final String keyVal_arg1="ARG1";
#Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals(ACTION_SET_UpdateService)){
updateIntent(context, intent.getDoubleExtra(keyVal_arg0, 0.02), intent.getStringExtra(keyVal_arg1));
}
}
private void updateIntent(Context context, double arg0, String arg1){
Intent intent = new Intent(context,UpdateService.class);
intent.setAction(ACTION_SET_UpdateService);
intent.putExtra(keyVal_arg0, arg0);
intent.putExtra(keyVal_arg1, arg1);
synchronized (this){
try {
this.wait(6000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
context.startService(intent);
Log.d("OREN","ServiceRunner");
}
}
Service:
public class UpdateService extends Service {
private final IBinder binder = new MyBinder();
public static final String keyVal_arg0="ARG0";
public static final String keyVal_arg1="ARG1";
private Timer timer;
private HTTPHandler http = new HTTPHandler();
private int test=0;
double arg0=0;
String arg1= "";
private TimerTask updateTask = new TimerTask() {
#Override
public void run() {
test++;
Log.d("OREN", "Timer task doing work " + test + " arg0: " + arg0);
//Do some work here
}
};
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
if (intent!=null){
arg0=intent.getDoubleExtra(keyVal_arg0, 0.002);
arg1=intent.getStringExtra(keyVal_arg1);
timer = new Timer("UpdateTimer");
timer.schedule(updateTask, 1000L, 10 * 1000L);
Log.d("OREN", "ServiceStarted" + test);
}
return super.onStartCommand(intent, flags, startId);
}
#Override
public IBinder onBind(Intent intent) {
Log.d("OREN", "OnBind" + test);
return binder;
}
public void setArg0(double d){
arg0=d;
}
// create an inner Binder class
public class MyBinder extends Binder {
public UpdateService getService() {
return UpdateService.this;
}
}
#Override
public void onDestroy() {
Log.d("OREN", "OnDestroy" + test);
super.onDestroy();
}
#Override
public boolean onUnbind(Intent intent) {
Log.d("OREN", "OnUnBind" + test);
return super.onUnbind(intent);
}
}
In a game application I have the following scenario:
From the main game Activity, the player starts several game tasks that run in the background with varying duration.
The player should be able to view the progress of the running game tasks in a separate View.
To do this, I created two Activitys and a Service, defined as follows:
Service ProgressService handles several ProgressBars running simultaneously on parallel threads.
Activity WorkScreen2 creates a game task, starts the Service with startService() with task parameters passed in a Bundle.
Activity ProgressScreen binds to the Service to get and display the ProgressBars of the running tasks.
Both activities run under separate TabHosts of one TabActivity.
The problem I'm having is that the ServiceConnection.onServiceConnected() method is never called. I get a Java.lang.NullPointerException because I try to call a method of the Service object that should be assigned in this method. See code below.
I use getApplicationContext().bindService() to bind the Activity to the Service because TabSpec cannot bind to Services. This method returns true. Therefore, binding is successful.
Here is the Service:
public class ProgressService extends Service implements GameConstants {
public static final String BROADCAST_PROGRESS = "com.mycompany.android.mygame.progressbroadcast";
private static final long UPDATE_INTERVAL = 500;
private IBinder mBinder;
private List<ProgressBar> mProgressBarList;
private List<String> mStaffNameList;
private final class ServiceHandler extends Handler {
public ServiceHandler(Looper looper) {
super(looper);
}
#Override
public void handleMessage(Message msg) {
ProgressBar progressBar = new ProgressBar(ProgressService.this);
mProgressBarList.add(progressBar);
Bundle bundle = msg.getData();
String staffName = bundle.getString(WorkScreen2.STAFF_NAME);
mStaffNameList.add(staffName);
int taskDurationMillis = bundle.getInt(WorkScreen2.TASK_DURATION) * 1000;
progressBar.setMax(taskDurationMillis / 1000);
long startTimeMillis = SystemClock.uptimeMillis();
long elapsedTimeMillis = SystemClock.uptimeMillis()
- startTimeMillis;
Intent intent = new Intent();
intent.setAction(BROADCAST_PROGRESS);
while (elapsedTimeMillis < taskDurationMillis) {
try {
Thread.sleep(UPDATE_INTERVAL);
} catch (InterruptedException e) {
e.printStackTrace();
}
elapsedTimeMillis = SystemClock.uptimeMillis()
- startTimeMillis;
int elapsedTimeSeconds = (int) elapsedTimeMillis / 1000;
progressBar.setProgress(elapsedTimeSeconds);
sendBroadcast(intent);
}
progressBar.setVisibility(View.GONE);
mProgressBarList.remove(progressBar);
mStaffNameList.remove(staffName);
sendBroadcast(intent);
if (mProgressBarList.isEmpty()) {
stopSelf(msg.arg1);
}
}
}
#Override
public void onCreate() {
super.onCreate();
mBinder = new ProgressServiceBinder();
mProgressBarList = Collections
.synchronizedList(new ArrayList<ProgressBar>());
mStaffNameList = Collections.synchronizedList(new ArrayList<String>());
}
/*
* Creates a thread for each game task with parameters passed in
* <code>intent</code>
*/
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "starting service", Toast.LENGTH_LONG).show();
HandlerThread thread = new HandlerThread("ServiceStartArguments",
Process.THREAD_PRIORITY_BACKGROUND);
thread.start();
Handler serviceHandler = new ServiceHandler(thread.getLooper());
Message msg = serviceHandler.obtainMessage();
msg.arg1 = startId;
msg.setData(intent.getExtras());
serviceHandler.sendMessage(msg);
return START_STICKY;
}
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}
public class ProgressServiceBinder extends Binder {
ProgressService getService() {
return ProgressService.this;
}
}
public List<ProgressBar> getProgressBarList() {
return mProgressBarList;
}
public List<String> getStaffNameList() {
return mStaffNameList;
}
#Override
public void onDestroy() {
Toast.makeText(this, "Service done", Toast.LENGTH_SHORT).show();
}
}
And this is the Activity that binds to it:
public class ProgressScreen extends ListActivity {
private final String TAG = "ProgressScreen";
private ProgressScreenAdapter mAdapter;
private ProgressService mProgressService;
private List<ProgressBar> mProgressBarList;
private List<String> mStaffNameList;
#Override
public void onCreate(Bundle bundle) {
Log.i(TAG, "ProgressScreen oncreate");
super.onCreate(bundle);
setContentView(R.layout.progress_screen_layout);
IntentFilter filter = new IntentFilter();
filter.addAction(ProgressService.BROADCAST_PROGRESS);
registerReceiver(receiver, filter);
doBindService();
mAdapter = new ProgressScreenAdapter(this, mStaffNameList, mProgressBarList);
setListAdapter(mAdapter); // Returns true
/*
* This is where I get the NullPointerException
* mProgressService is null here
*/
mProgressBarList = mProgressService.getProgressBarList();
mStaffNameList = mProgressService.getStaffNameList();
}
#Override
protected void onResume() {
super.onResume();
IntentFilter filter = new IntentFilter();
filter.addAction(ProgressService.BROADCAST_PROGRESS);
registerReceiver(receiver, filter);
}
#Override
protected void onPause() {
super.onPause();
unregisterReceiver(receiver);
}
boolean doBindService() {
return getApplicationContext().bindService(new Intent(this, ProgressService.class), mConnection, Context.BIND_AUTO_CREATE);
}
void doUnbindService() {
getApplicationContext().unbindService(mConnection);
}
ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder binder) {
mProgressService = ((ProgressService.ProgressServiceBinder) binder).getService();
Toast.makeText(ProgressScreen.this, "Connected to ProgressService", Toast.LENGTH_SHORT).show();
}
public void onServiceDisconnected(ComponentName name) {
mProgressService = null;
}
};
private BroadcastReceiver receiver = new BroadcastReceiver () {
#Override
public void onReceive(Context context, Intent intent) {
mAdapter.notifyDataSetChanged();
}
};
}
And the Service is started from the main Activity as follows:
Intent intent = new Intent(WorkScreen2.this, ProgressService.class);
intent.putExtra(TASK_DURATION, task.getDuration());
intent.putExtra(STAFF_NAME, staff.getName());
startService(intent);
The AndroidManifest.xml contains
<service
android:name=".ProgressService"
android:label="#string/progress_service">
</service>
ServiceConnection's onServiceConnected() is called, but nobody guarantees that it will be called before onCreate continues execution. So, what happens here - you successfuly bind to the service (that's why onBind returns true), but you're not fully connected - onServiceConnected() has not yet been called, so your local mProgressService object is not yet initalized, and therefore you get the NullPointerException.
Solution:
Move these two lines:
mProgressBarList = mProgressService.getProgressBarList();
mStaffNameList = mProgressService.getStaffNameList();
from onCreate() to onServiceConnected() function (use the service object after it is initialized in onServiceConnected()).
Check AndroidManifest.xml of yours and add service that you tried to bind.
You have to return your Binder inner class from
private final IBinder mBinder = new ServiceBinder();
public class ServiceBinder extends Binder {
public PlayerActivity getService() {
return PlayerActivity.this;
}
}
#Nullable
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}