Develop Reference

Why the body of onStartCommand() is getting executed only once?

To know the difference between IntentService and Service in Android, I created the below posted small test of a Service class. The MainActivity has a Button, when pressed, the
service will be started using startService() as shown below in the code, which will result in a call to onStartCommand(). In onStartCommand(), i run a loop for 10 seconds, and I
expected that, that loop will block the UI "the butoon". Actually that what happened exactly when I first time start the Service, but when I press the button after the 10 seconds
elapsed, it will result in a call to onStartCommand() but the log message inside the onStartCommand() never get displayed plus the UI is never blocked.
can anyone please explain what the body of the onStartCommand() is executed and blocks the UI only when the Service first started and never afterwards?
MainActivity
public class MainActivity extends AppCompatActivity {
private Button mbtnSend = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.mbtnSend = (Button) findViewById(R.id.btn_send);
this.mbtnSend.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(getApplicationContext(), MyService.class);
startService(intent);
}
});
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
registerReceiver(this.mBCR_VALUE_SENT, new IntentFilter(MyIntentService.INTENT_ACTION));
this.mbtnSend = (Button) findViewById(R.id.btn_send);
this.mbtnSend.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(getApplicationContext(), MyIntentService.class);
intent.putExtra("intent_key", ++i);
startService(intent);
}
});
}
}
MyIntentService:
public class MyService extends Service{
private final String TAG = this.getClass().getSimpleName();
private long mStartTime;
#Override
public void onCreate() {
super.onCreate();
Log.w(TAG, SubTag.msg("onCreate"));
this.mStartTime = TimeUtils.getTSSec();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.w(TAG, SubTag.msg("onStartCommand"));
while ( (TimeUtils.getTSSec() - this.mStartTime) <=10) {
Log.w(TAG, SubTag.msg("time: " + (TimeUtils.getTSSec() - this.mStartTime)));
SystemClock.sleep(1000);
}
return Service.START_STICKY;
}
#Nullable
#Override
public IBinder onBind(Intent intent) {
Log.w(TAG, SubTag.msg("onBind"));
return null;
}
#Override
public void onDestroy() {
super.onDestroy();
Log.w(TAG, SubTag.msg("onDestroy"));
}
}

You are setting mStartTime to TimeUtils.getTSSec() in onCreate(), which means that it will get intialized only once.
Afterwards, onStartCommand() is called, but the mStartTime timestamp is not being updated, so the while loop never runs.
I believe that moving the line where you initialize mStartTime to onStartCommand() before the while loop will make your thread hang again.

How to update the UI of Activity from BroadCastReceiver

I am learning Android concepts Activity and BroadCastReceiver. I want to update the content of Activity from the BroadtCastReceiver both are in different java class.
It is something like
MyActivity.java and MyBroadtCastReceiver.java
Is this possible to do this in Android ?

A BroadcastReceiver can be used in many ways but when it comes to something as specific as updating the UI components of an Activity, there is little advantage to declaring / defining a BroadcastReceiver in it's own Java class file.
Reasoning - the BroadcastReceiver has to have some prior "knowledge" of the Activity and what it is required to do in order to update the UI. In effect the BroadcastReceiver is tied to the Activity itself and it makes sense to declare / define it as an inner class.
Another important aspect is the Activity needs to be in a "running" (i.e., visible) state in order to guarantee manipulation of UI components. In this case, registering the receiver in onResume() and unregistering in onPause() will help prevent problems.
Using a generic template I'd do something like the following...
class MyActivity extends Activity {
boolean mIsReceiverRegistered = false;
MyBroadcastReceiver mReceiver = null;
// onCreate(...) here
#Override
protected void onResume() {
// Other onResume() code here
if (!mIsReceiverRegistered) {
if (mReceiver == null)
mReceiver = new MyBroadcastReceiver();
registerReceiver(mReceiver, new IntentFilter("YourIntentAction"));
mIsReceiverRegistered = true;
}
}
#Override
protected void onPause() {
if (mIsReceiverRegistered) {
unregisterReceiver(mReceiver);
mReceiver = null;
mIsReceiverRegistered = false;
}
// Other onPause() code here
}
private void updateUI(Intent intent) {
// Do what you need to do
}
private class MyBroadcastReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
updateUI(intent);
}
}
}
EDIT: A couple of extra notes...
The life-cycle of a BroadcastReceiver is between entering and leaving onReceive(...). Once it has returned from onReceive(...) the instance remains in a dormant state waiting for the next broadcast.
Directly related to point 1 - a BroadcastReceiver isn't designed for "heavy lifting". Basically the onReceive(...) method should be kept as simple as possible. Any methods it calls should also be as light-weight as possible...get in, do your stuff, get out then wait for the next broadcast. If updating the UI is going to take some time (perhaps updating a ListView by re-querying a database for a large amount of data for example), consider calling code which performs asynchronously (an AsyncTask for example).

Yes its possible. This is what i do.
Class i send the broadcast from (BackgroundActivity.java):
public static final String BROADCAST_BUFFER_SEND_CODE = "com.example.SEND_CODE";
onCreate(){
bufferIntentSendCode = new Intent(BROADCAST_BUFFER_SEND_CODE);
}
private void sendBufferingBroadcastSendCode() {
bufferIntentSendCode.putExtra("buffering", "1");
sendBroadcast(bufferIntentSendCode);
}
The class it will receive the broadcast(SendCode.java):
onResume(){
registerReceiver(broadcastBufferReceiver, new IntentFilter(BackgroundActivity.BROADCAST_BUFFER_SEND_CODE));
}
// set up broadcast receiver
private BroadcastReceiver broadcastBufferReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent bufferIntent) {
SendCode.this.LoadMessages(alarmNumber);
}
};
I unregister it in onPause
this.unregisterReceiver(broadcastBufferReceiver);

Register a new BroadcastReceiver object in your activity with same intent-filters as your MyBroadtCastReceiver. Since BroadcastReceiver and MyBroadtCastReceiver has same intent-filters both of their onReceive() will be invoked. Whatever update that you want to do in Activity can be done in onReceive of your BroadcastReceiver.

You can do like this:
public class MyActivity extends Activity{
// used to listen for intents which are sent after a task was
// successfully processed
private BroadcastReceiver mUpdateReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
new UpdateUiTask().execute();
}
};
#Override
public void onResume() {
registerReceiver(mUpdateReceiver, new IntentFilter(
YOUR_INTENT_ACTION));
super.onResume();
}
#Override
public void onPause() {
unregisterReceiver(mUpdateReceiver);
super.onPause();
}
// used to update the UI
private class UpdateUiTask extends AsyncTask<Void, Void, String> {
#Override
protected void onPreExecute() {
}
#Override
protected String doInBackground(Void... voids) {
Context context = getApplicationContext();
String result = "test";
// Put the data obtained after background task.
return result;
}
#Override
protected void onPostExecute(String result) {
// TODO: UI update
}
}
}

Squonk-s answer only works, if the Activity is active currently.
If you dont want to declare / define your BroadcastReceiver (BR) in an other Activity, or if you want to make some changes even if the app is not foreground, than your solution would look something like this.
First, you declare the BR, and save, or override the data needed to show in Acitvity.
public class MyBR extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
// override the data. Eg: save to SharedPref
}
}
Then in Activity, you show the data
TextView tv = findViewById(R.id.tv);
tv.setText(/*get the data Eg: from SharedPref*/);
And you should use a Timer to refresh the tv as well:
Timer timer = new Timer();
timer.schedule(new TimerTask() {
#Override
public void run() {
runOnUiThread(new Runnable() {
#Override
public void run() {
TextView tv = findViewById(R.id.tv);
tv.setText(/*get the data Eg: from SharedPref*/);
}
});
}
}, REFRESH_RATE, REFRESH_RATE);
REFRESH_RATE could be something like 1 second, but you decide.

try like this it may help you.
Define this method in activity's oncreate method in which you want to update ui,
BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
//your code to update ui
}
};
LocalBroadcastManager.getInstance(this).registerReceiver(mMessageReceiver, new IntentFilter("giveyourappname"));
Define this action at place from where you want to update ui,
try{
ActivityManager am = (ActivityManager) this .getSystemService(ACTIVITY_SERVICE);
List<RunningTaskInfo> taskInfo = am.getRunningTasks(1);
ComponentName componentInfo = taskInfo.get(0).topActivity;
Log.d("Activity", "Current Activity ::" + taskInfo.get(0).topActivity.getClassName());
Log.d("Package", "Package Name : "+ componentInfo.getPackageName());
if(componentInfo.getPackageName().equals("your application package name")){
Intent intent = new Intent("giveyourappname");
//add data you wnat to pass in intent
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}
}catch(Throwable e){
e.printStackTrace();
}

Communication between Activity and Service

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 .

Misleading documentation on BroadcastReceiver?

Does anyone know what this line supposed to mean in the Android documentation (enter link description here): "
Note: If registering a receiver in your Activity.onResume() implementation, you should unregister it in Activity.onPause(). (You won't receive intents when paused, and this will cut down on unnecessary system overhead).
The first sentence is clear, one should release resources if they aren't needed. But what about the bracketed text? Apparently an app in the background receives the broadcast intents if it is stopped (At least on Android 4.2). It won't get the broadcast when it is destroyed. Code to try:
public class MyActivity extends Activity {
private BroadcastReceiver mBroadcastReceiver;
String a = "1234";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mBroadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
Log.d("|BR", "onReceive() - 1" + " intent: " + intent);
a = intent.getStringExtra("ASDF");
}
};
this.registerReceiver(mBroadcastReceiver, new IntentFilter(MyService.RECEIVE));
}
#Override
protected void onResume() {
super.onResume();
Log.d("|BR", "onResume()" + " a: " + a);
}
#Override
protected void onPause() {
super.onPause();
Log.d("|BR", "onPause()");
}
/** Event handler for a button in the main.xml */
public void createService(View view) {
Log.d("|BR", "createService()");
Intent intent = new Intent(MyService.DO);
this.startService(intent);
}
}
public class MyService extends Service {
public static final String DO = MyService.class.getName() + ".DO";
public static final String RECEIVE = MyService.class.getName() + ".RECEIVE";
public Executor executor;
#Override
public void onCreate() {
super.onCreate();
executor = Executors.newSingleThreadExecutor();
}
#Override
public int onStartCommand(final Intent intent, final int flags, final int startId) {
String action = intent.getAction();
Log.d("|BR", "onStartCommand() - 1");
if(DO.equals(action)) {
executor.execute(new MyRunnable());
Log.d("|BR", "onStartCommand() - 2");
}
return START_NOT_STICKY;
}
#Override
public android.os.IBinder onBind(final Intent intent) {
return null;
}
private class MyRunnable implements Runnable {
#Override
public void run() {
Log.d("|BR", "run() - 1");
try {
Thread.sleep(1000 * 8);
} catch (InterruptedException e) {
e.printStackTrace();
}
Log.d("|BR", "run() - 2");
Intent intent = new Intent(RECEIVE);
intent.putExtra("ASDF", "QWER");
MyService.this.sendBroadcast(intent);
Log.d("|BR", "run() - 3");
}
}
}
Press the button, press home button, wait 8 seconds. Result:
09:05:48.622 D/|BR: onResume() a: 1234
09:05:53.297 D/|BR: createService()
09:05:53.297 D/|BR: onStartCommand() - 1
09:05:53.307 D/|BR: onStartCommand() - 2
09:05:53.307 D/|BR: run() - 1
09:05:54.558 D/|BR: onPause()
09:06:01.306 D/|BR: run() - 2
09:06:01.316 D/|BR: onReceive() - 1 intent: Intent { act=com.example.broadcastReceive.MyService.RECEIVE flg=0x10 (has extras) }
09:06:01.316 D/|BR: run() - 3
09:06:14.139 D/|BR: onResume() a: QWER

It simply means that you won't receive broadcasts if you've unregistered the BroadcastReceiver in your onPause().

Dependening on what you do in the receiver, it might be very CPU/Battery consuming. If it is, you want it to be executed as rarely as possible and thats what this sentence wants to say.
Have you ever ran code, that receives GPS information? It lets your battery live for at max 2 hours. So, every second counts, when this is switched on. onResume and onPause are best places to turn on/off this feature. Using onStart, onStop or even onCreate, onDestroy would mean, that the feature is turned on (and consumes battery) longer then necessary.

Set a Listener in a Service-based Class

Hy i have a problem to set the ServiceUpdateUIListener in the service to update the UI. It's wrong to make a new Service object and set there the listener and put it in an intent.
Code source is at http://developerlife.com/tutorials/?p=356 there i can't find how the set the listener and start the service right.
Calling:
TimerService service = new TimerService();
TimerService.setUpdateListener(new ServiceUpdateUIListener() {
#Override
public void updateUI(String time) {
clock.setText(time);
}
});
Intent i = new Intent(Timer.this,service.class); //service cannot be resolved to a type
i.putExtra("ms", ms);
startService(i);
Service:
public class TimerService extends Service{
CountDownTimer timer;
Chronometer clock;
public static ServiceUpdateUIListener UI_UPDATE_LISTENER;
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onStart(Intent intent, int startId) {
// TODO Auto-generated method stub
int ms = intent.getIntExtra("ms", 0);
timer = new CountDownTimer(ms,1000){
#Override
public void onTick(long millisUntilFinished) {
int seconds = (int) (millisUntilFinished / 1000) % 60 ;
int minutes = (int) ((millisUntilFinished / (1000*60)) % 60);
int hours = (int) ((millisUntilFinished / (1000*60*60)) % 24);
clock.setText( String.format("%02d:%02d:%02d", hours,minutes,seconds));
Log.e("Timer", String.valueOf(millisUntilFinished));
}
#Override
public void onFinish() {
// TODO Auto-generated method stub
}
}.start();
super.onStart(intent, startId);
}
public static void setUpdateListener(ServiceUpdateUIListener l) {
UI_UPDATE_LISTENER = l;
}

The Service documentation has fairly complete sample code for implementing a service in your app that another part of your app can bind to and make calls on:
http://developer.android.com/reference/android/app/Service.html#LocalServiceSample
Just put your setUpdateListener() method on the Service, and call it once you get onServiceConnected() with the service.
So your code would be something like this:
public interface UpdateListener {
public void onUpdate(long value);
}
class LocalService {
// Like in the Service sample code, plus:
public static String ACTION_START = "com.mypackage.START";
private final ArrayList<UpdateListener> mListeners
= new ArrayList<UpdateListener>();
private final Handler mHandler = new Handler();
private long mTick = 0;
private final Runnable mTickRunnable = new Runnable() {
public void run() {
mTick++;
sendUpdate(mTick);
mHandler.postDelayed(mTickRunnable, 1000);
}
}
public void registerListener(UpdateListener listener) {
mListeners.add(listener);
}
public void unregisterListener(UpdateListener listener) {
mListeners.remove(listener);
}
private void sendUpdate(long value) {
for (int i=mListeners.size()-1; i>=0; i--) {
mListeners.get(i).onUpdate(value);
}
}
public int onStartCommand(Intent intent, int flags, int startId) {
if (ACTION_START.equals(intent.getAction()) {
mTick = 0;
mHandler.removeCallbacks(mTickRunnable);
mHandler.post(mTickRunnable);
}
return START_STICKY;
}
public void onDestroy() {
mHandler.removeCallbacks(mTickRunnable);
}
Now you can start the service to get it to start counting, and anyone can bind to it to register a listener to receive callbacks as it counts.
It is really hard though to answer your question very well because you aren't really saying what you actually want to accomplish. There are a lot of ways to use services, either starting or binding or mixing the two together, depending on exactly what you want to accomplish.
Now you can implement your client code again based on the sample:
public class SomeActivity extends Activity implements UpdateListener {
private LocalService mBoundService;
private ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
mBoundService = ((LocalService.LocalBinder)service).getService();
mBoundService.registerListener(this);
}
public void onServiceDisconnected(ComponentName className) {
mBoundService = null;
}
};
void doBindService() {
bindService(new Intent(Binding.this,
LocalService.class), mConnection, Context.BIND_AUTO_CREATE);
mIsBound = true;
}
void doUnbindService() {
if (mIsBound) {
if (mBoundService != null) {
mBoundService.unregisterListener(this);
}
unbindService(mConnection);
mIsBound = false;
}
}
protected void onDestroy() {
super.onDestroy();
doUnbindService();
}

I don't know exactly what you want, but this is not the way to do it. It seems you're mixing up a lot of things.
The tutorial itself is a bad example to my opinion, keeping a static reference to an activity in a service seems to me bad practice; you would use binding to bind your service to an activity, or if you don't want to you can pass Intents around.
As far as I know instantiating a service like you do and setting a listener on it like that doesn't work. You get an error in the startService() call because the service instance isn't a class obviously; you should use TimerService.class instead. In your service you have an onStart(); onStart() is a deprecated function, you should use onStartCommand() instead.
Now, if you have an activity in which you want to show a clock you don't need nor want the service to update its UI directly of course, but if you'd want the service to calculate a new clock tick for you, just call startService(); As long as your service is alive, sending a new start service intent will just call the onStartCommand() with the intent you're sending along.
If your clock is in an activity, setup a broadcast receiver inside your activity that and let your service broadcast an intent that can be received by the broadcast receiver you setup, with your new clock value passed along.

MrJre is correct that onStart is depreciated and that you should be using onStartCommand().
If you want to get this to work, there is a better way.
I am doing something similar, as in wanting to update a UI from results happening in a service. This was not particularly easy. (In my opinion)
Here's how to do it: (First off scrap your existing code)
In UI class add:
public Intent service;
service = new Intent(thisContext, TimerService.class);
service.putExtra("ms", ms);
startService(service);
//bind service to the UI **Important**
bindService();
IntentFilter timerFilter = new IntentFilter("TimerIntent"); // Filter that gets stuff from the service
registerReceiver(myReceiver, timerFilter);
void bindService() {
Intent newIntent = new Intent(this, TimerService.class);
bindService(newIntent, mConnection, Context.BIND_AUTO_CREATE);
mIsBound = true;
}
private ServiceConnection mConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className, IBinder binder) {
s = ((TimerService.MyBinder) binder).getService();
}
#Override
public void onServiceDisconnected(ComponentName className) {
s = null;
}
};
public void releaseBind() {
if (mIsBound) {
unbindService(mConnection);
mIsBound = false;
}
}
// Now in this class we need to add in the listener that will update the UI (the receiver registered above)
private BroadcastReceiver myReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
//Get Bundles
Bundle extras = intent.getExtras();
/* DO ANY UI UPDATING YOU WANT HERE (set text boxes, etc.) TAKING INFO FROM THE "extras" Bundle ie: setting the clock*/
//ie: int timerTest = extras.getInt("0");
// Now update screen with value from timerTest
}
};
Service File:
public class TimerService extends Service {
public TimerService () {
super();
}
private final IBinder mBinder = new MyBinder();
public Timer clockTimer = new Timer();
public int timer = 0;
// We return the binder class upon a call of bindService
#Override
public IBinder onBind(Intent arg0) {
return mBinder;
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
// After service starts this executes
Bundle extras;
extras = intent.getExtras();
/* Call a function to do stuff here. Like if you are a clock call a timer function updates every second */
// Here's an example, modify to fit your needs.
clock();
return START_STICKY;
}
public class MyBinder extends Binder {
TimerService getService() {
return TimerService.this;
}
}
public void clock() {
clockTimer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
try {
// Some function ie: Time = Time + 1 //
/* MAKE SURE YOU BROADCAST THE RECEIVER HERE. This is what you send back to the UI. IE:*/
timer = timer+ 1; // increment counter
Intent intent = new
//Bundle the timervalue with Intent
intent.putExtra("0", timer);
intent.setAction("TimerIntent");
sendBroadcast(intent); // finally broadcast to the UI
} catch(Exception ie) {
}
}
},
0, // Delay to start timer
1000); // how often this loop iterates in ms (so look runs every second)
}
There might be some syntax errors in this code as I've just modified my existing and working code to try and fit your needs. There will obviously need to also be some modifications depending on what you want to do. But follow this framework and you will be able to do what you are trying to do.
This works for me, so hopefully you can modify this to work for you. (Only thing I've left out are the imports, but you should be able to easily figure that out)
Key points:
Bind service to UI
Register listener in UI file to respond to the broadcast from inside the service.
Cheers.