I create a service that is running in the background for the entire duration of application.
I chose an IntentService for this.
For me intent.putExtra(....) work only on start the service.
My problem is that sometimes I want to passing data from Activity to IntentService not only at start.
Thank You
Just transfer data to IntentService by start, because the IntentService will always has the only one instance in the whole application life cycle.
You can use bind interface to interact with service public methods.
From documentation:
public class LocalService extends Service {
// Binder given to clients
private final IBinder mBinder = new LocalBinder();
// Random number generator
private final Random mGenerator = new Random();
/**
* 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 {
LocalService getService() {
// Return this instance of LocalService so clients can call public methods
return LocalService.this;
}
}
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}
/** method for clients */
public int getRandomNumber() {
return mGenerator.nextInt(100);
}
}
Related
I am totally confused with bound services. My questions are:
What is the meaning of binding?
What does the Binder class do?
What is meant by "returns an IBinder for interacting with the service"?
What is the IBinder object?
How does the onBind() method work?
These are the a questions on bound services. Please explain in detail. I have already read the documentation, but it is still unclear to me.
Bound service:
A bound service is one that allows application components to bind to it by calling bindService() to create a long-standing connection.
Create a bound service when you want to interact with the service from activities and other components in your application or to expose some of your application's functionality to other applications through interprocess communication (IPC).
To create a bound service, implement the onBind() callback method to return an IBinder that defines the interface for communication with the service. Other application components can then call bindService() to retrieve the interface and begin calling methods on the service. The service lives only to serve the application component that is bound to it, so when there are no components bound to the service, the system destroys it. You do not need to stop a bound service in the same way that you must when the service is started through onStartCommand().
IBinder:
To create a bound service, you must define the interface that specifies how a client can communicate with the service. This interface between the service and a client must be an implementation of IBinder and is what your service must return from the onBind() callback method. After the client receives the IBinder, it can begin interacting with the service through that interface.
onBind():
The system invokes this method by calling bindService() when another component wants to bind with the service (such as to perform RPC). In your implementation of this method, you must provide an interface that clients use to communicate with the service by returning an IBinder. You must always implement this method; however, if you don't want to allow binding, you should return null.
this is an example works as completion to the answer above
inside your service class, initialize the IBinder interface with the object created by our inner class (check step 2)
create an inner class extends Binder that has a getter function, to gain access to the service class
in your service class ovveride onBind function, and use it to return the instance we created in step 1
**The code will clear it for you **
public class MyServiceClass extends Service {
//binder given to client
private final IBinder mBinder = new LocalBinder();
//our inner class
public LocalBinder extends Binder {
public MyServiceClass getService() {
return MyServiceClass.this;
}
}
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}
public void doSomeWork(int time){ //we will call this function from outside, which is the whole idea of this **Binding**}
}
Next step is binding itself
in your MainClass or whatever where you want to bind your service,
Defines callbacks for service binding, passed to bindService()
private ServiceConnection serviceConnection = new ServiceConnection(){
#Override
public void onServiceConnected(ComponentName className, IBinder service) {
MyServiceClass.LocalBinder binder =(MyServiceClass.LocalBinder)service;
timerService = binder.getService();
}
#Override
public void onServiceDisconnected(ComponentName arg0) {
//what to do if service diconnect
}
};
the moment of binding
Intent intent = new Intent(this, MyServiceClass.class);
bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);
to unbind the service
unbindService(serviceConnection);
then you call the public function we created before in the Service class using the help of [timerService = binder.getService();]
timerService.doSomeWork(50);
In my application I am using an IntentService to download a file from a cloud. And showing the progress in NotificationManager. I need to show the status (Downloading/Completed or Failed) in the Activity which stared the IntentService too.
My problem is once I closed the app and open it back, I want to get the status of downloading from IntentService.
Which is the best way to do this?
You can let your Activity bind to your Service, by calling bindService() in your Activity. As per the documentation:
A service is "bound" when an application component binds to it by
calling bindService(). A bound service offers a client-server
interface that allows components to interact with the service, send
requests, get results, and even do so across processes with
interprocess communication (IPC). A bound service runs only as long as
another application component is bound to it. Multiple components can
bind to the service at once, but when all of them unbind, the service
is destroyed.
Also:
You should create a bound service when you want to interact with the
service from activities and other components in your application or to
expose some of your application's functionality to other applications,
through interprocess communication (IPC).
The documentation provides a fully functional example of this. Below is taken from the provided link.
Service class:
public class LocalService extends Service {
// Binder given to clients
private final IBinder mBinder = new LocalBinder();
// Random number generator
private final Random mGenerator = new Random();
/**
* 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 {
LocalService getService() {
// Return this instance of LocalService so clients can call public methods
return LocalService.this;
}
}
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}
/** method for clients */
public int getRandomNumber() {
return mGenerator.nextInt(100);
}
}
Activity class:
public class BindingActivity extends Activity {
LocalService mService;
boolean mBound = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
#Override
protected void onStart() {
super.onStart();
// Bind to LocalService
Intent intent = new Intent(this, LocalService.class);
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
}
#Override
protected void onStop() {
super.onStop();
// Unbind from the service
if (mBound) {
unbindService(mConnection);
mBound = false;
}
}
/** Called when a button is clicked (the button in the layout file attaches to
* this method with the android:onClick attribute) */
public void onButtonClick(View v) {
if (mBound) {
// Call a method from the LocalService.
// 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.
int num = mService.getRandomNumber();
Toast.makeText(this, "number: " + num, Toast.LENGTH_SHORT).show();
}
}
/** Defines callbacks for service binding, passed to bindService() */
private ServiceConnection mConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className,
IBinder service) {
// We've bound to LocalService, cast the IBinder and get LocalService instance
LocalBinder binder = (LocalBinder) service;
mService = binder.getService();
mBound = true;
}
#Override
public void onServiceDisconnected(ComponentName arg0) {
mBound = false;
}
};
}
In your Service, you can define public methods that your Activity can call, such as polling for your download progress. Please refer to the documentation for explanation in detail.
There are couple of ways to have communication connection between Service and Activity. I would suggest these 2
First, you can use the great library Otto. With Otto, you can also have #Produce annotated method. With this method you will return the latest information about the download. When you #Subscribe in your Activity you will get the latest info immediately. https://github.com/square/otto
If you are using Android built-in DownloadManager it returns the updates and results with a Broadcast, you can register to that Broadcast both in your Service and Activity. This way you will be able to update both of them. I suggest you to use DownloadManager, it is awesome.
http://developer.android.com/reference/android/app/DownloadManager.html
I'm developing android wear project with Service extends WearableListenerService.
When I'm trying to add Service binder I see this error
private final IBinder mBinder = new LocalBinder();
public class LocalBinder extends Binder {
DataLayerListenerService getService() {
return DataLayerListenerService.this;
}
}
#Override
public IBinder onBind(Intent intent) {
return mBinder;
}
Error:(196, 20) error: onBind(Intent) in DataLayerListenerService cannot override onBind(Intent) in WearableListenerService
overridden method is final
Is it possible to bind WearableListenerService somehow? How to pass data from WearableListenerService to Activity without using broadcasts?
You not have to use Bind.
You can communicate through mGoogleApiClient.
Sending data from an Activity to WearableListenerService
This Answer help your problem solve.
I'm creating an app that reads every Service that has an IntentFilter that matches a custom action by using this:
Intent intent = new Intent(ACTION);
List<ResolveInfo> infos = getActivity().getPackageManager()
.queryIntentServices(intent, 0);
I have no problem retrieving the Services, but when I try to bind them to the current Activity, my IBinder implementation is not passed to onServiceConnected(ComponentName, IBinder). Instead, a BinderProxyis being passed.
How can I get my LocalBinder from that BinderProxy?
EDIT:
Here's my implementation:
public abstract class LocalService extends Service {
private LocalBinder mBinder = new LocalBinder();
public class LocalBinder extends Binder {
public LocalService getServiceInstance() {
return LocalService.this;
}
}
#Override
public final IBinder onBind(Intent intent) {
return mBinder;
}
public abstract List<Category> getInitialCategories();
public abstract void onObjectSelected(Item object,
LocalCallback callback);
}
What I want to do is to be able to call the last 2 methods from other people's implementations of my LocalService.
I don't think you can do that.
You're binding to a service in a different process. It would be impossible to get a reference to your actual LocalBinder instance, because processes cannot share object instances.
I haven't tested this scenario myself, but according to the documentation if you need IPC for Services you have two alternatives, either a Messenger or AIDL. The first one seems much simpler.
If you need your interface to work across different processes, you can
create an interface for the service with a Messenger. In this manner,
the service defines a Handler that responds to different types of
Message objects. This Handler is the basis for a Messenger that can
then share an IBinder with the client, allowing the client to send
commands to the service using Message objects. Additionally, the
client can define a Messenger of its own so the service can send
messages back.
This is the simplest way to perform interprocess communication (IPC),
because the Messenger queues all requests into a single thread so that
you don't have to design your service to be thread-safe.
I have an Android service, created in OnCreate of first Activity of the application using StartService(). I need this service to be running throughout the life span of the application ie, all the activities in the application. But the service should not consume the resources after user pressed Home key or Back button. Is there any elegant way to do that other than stopping the service in onPause() method of all the activities?
Instead of using StartService, you can call bindService in onResume and unbindService in onPause. Your service will stop when there are no open bindings.
You'll need to create a ServiceConnection to get access to the service. For instance, here's a class nested inside MyService:
class MyService {
public static class MyServiceConnection implements ServiceConnection {
private MyService mMyService = null;
public MyService getMyService() {
return mMyService;
}
public void onServiceConnected(ComponentName className, IBinder binder) {
mMyService = ((MyServiceBinder)binder).getMyService();
}
public void onServiceDisconnected(ComponentName className) {
mMyService = null;
}
}
// Helper class to bridge the Service and the ServiceConnection.
private class MyServiceBinder extends Binder {
MyService getMyService() {
return MyService.this;
}
}
#Override
public IBinder onBind(Intent intent) {
return new MyServiceBinder();
}
#Override
public boolean onUnbind(Intent intent) {
return false; // do full binding to reconnect, not Rebind
}
// Normal MyService code goes here.
}
One can use this helper class to get access to the service via:
MyServiceConnection mMSC = new MyService.MyServiceConnection();
// Inside onResume:
bindService(new Intent(this, MyService.class), mMSC, Context.BIND_AUTO_CREATE);
// Inside onPause:
unbindService(mMSC);
// To get access to the service:
MyService myService = mMSC.getMyService();
You could do what Darrell suggests but put that code in a new class that extends Activity and then extend that on all your normal Activities.
I don't know any other more elegant way of achieving your goals.