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Learn more. How can download file in service in android Ask Question. Asked 5 years ago. Active 5 years ago. Viewed 7k times. This is useful if you need to update a TextView.
How can i write this codes in service? Improve this question. Add a comment. Active Oldest Votes. The service can run in the background indefinitely, even if the component that started it is destroyed. As such, the service should stop itself when its job is complete by calling stopSelf , or another component can stop it by calling stopService. An application component such as an activity can start the service by calling startService and passing an Intent that specifies the service and includes any data for the service to use.
The service receives this Intent in the onStartCommand method. For instance, suppose an activity needs to save some data to an online database. The activity can start a companion service and deliver it the data to save by passing an intent to startService. The service receives the intent in onStartCommand , connects to the Internet, and performs the database transaction. When the transaction is complete, the service stops itself and is destroyed. Caution: A service runs in the same process as the application in which it is declared and in the main thread of that application by default.
If your service performs intensive or blocking operations while the user interacts with an activity from the same application, the service slows down activity performance. To avoid impacting application performance, start a new thread inside the service. The Service class is the base class for all services. When you extend this class, it's important to create a new thread in which the service can complete all of its work; the service uses your application's main thread by default, which can slow the performance of any activity that your application is running.
The Android framework also provides the IntentService subclass of Service that uses a worker thread to handle all of the start requests, one at a time. Using this class is not recommended for new apps as it will not work well starting with Android 8 Oreo, due to the introduction of Background execution limits.
Moreover, it's deprecated starting with Android The following sections describe how you can implement your own custom service, however you should strongly consider using WorkManager instead for most use cases. Consult the guide to background processing on Android to see if there is a solution that fits your needs. You can extend the Service class to handle each incoming intent.
Here's how a basic implementation might look:. The example code handles all incoming calls in onStartCommand and posts the work to a Handler running on a background thread. It works just like an IntentService and processes all requests serially, one after another.
You could change the code to run the work on a thread pool, for example, if you'd like to run multiple requests simultaneously. Notice that the onStartCommand method must return an integer. The integer is a value that describes how the system should continue the service in the event that the system kills it.
The return value from onStartCommand must be one of the following constants:. For more details about these return values, see the linked reference documentation for each constant. You can start a service from an activity or other application component by passing an Intent to startService or startForegroundService. The Android system calls the service's onStartCommand method and passes it the Intent , which specifies which service to start. Note : If your app targets API level 26 or higher, the system imposes restrictions on using or creating background services unless the app itself is in the foreground.
If an app needs to create a foreground service, the app should call startForegroundService. That method creates a background service, but the method signals to the system that the service will promote itself to the foreground.
Once the service has been created, the service must call its startForeground method within five seconds. For example, an activity can start the example service in the previous section HelloService using an explicit intent with startService , as shown here:. The startService method returns immediately, and the Android system calls the service's onStartCommand method.
If the service isn't already running, the system first calls onCreate , and then it calls onStartCommand. If the service doesn't also provide binding, the intent that is delivered with startService is the only mode of communication between the application component and the service.
However, if you want the service to send a result back, the client that starts the service can create a PendingIntent for a broadcast with getBroadcast and deliver it to the service in the Intent that starts the service.
The service can then use the broadcast to deliver a result. Multiple requests to start the service result in multiple corresponding calls to the service's onStartCommand. However, only one request to stop the service with stopSelf or stopService is required to stop it. A started service must manage its own lifecycle. That is, the system doesn't stop or destroy the service unless it must recover system memory and the service continues to run after onStartCommand returns.
The service must stop itself by calling stopSelf , or another component can stop it by calling stopService. Once requested to stop with stopSelf or stopService , the system destroys the service as soon as possible. If your service handles multiple requests to onStartCommand concurrently, you shouldn't stop the service when you're done processing a start request, as you might have received a new start request stopping at the end of the first request would terminate the second one.
To avoid this problem, you can use stopSelf int to ensure that your request to stop the service is always based on the most recent start request. That is, when you call stopSelf int , you pass the ID of the start request the startId delivered to onStartCommand to which your stop request corresponds. Then, if the service receives a new start request before you are able to call stopSelf int , the ID doesn't match and the service doesn't stop.
Caution: To avoid wasting system resources and consuming battery power, ensure that your application stops its services when it's done working. If necessary, other components can stop the service by calling stopService. Even if you enable binding for the service, you must always stop the service yourself if it ever receives a call to onStartCommand. For more information about the lifecycle of a service, see the section below about Managing the Lifecycle of a Service.
A bound service is one that allows application components to bind to it by calling bindService to create a long-standing connection. It generally doesn't allow components to start it by calling startService. 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.
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.
Multiple clients can bind to the service simultaneously. When a client is done interacting with the service, it calls unbindService to unbind. When there are no clients bound to the service, the system destroys the service. There are multiple ways to implement a bound service, and the implementation is more complicated than a started service.
For these reasons, the bound service discussion appears in a separate document about Bound Services. When a service is running, it can notify the user of events using Toast Notifications or Status Bar Notifications.
A toast notification is a message that appears on the surface of the current window for only a moment before disappearing. A status bar notification provides an icon in the status bar with a message, which the user can select in order to take an action such as start an activity.
Usually, a status bar notification is the best technique to use when background work such as a file download has completed, and the user can now act on it. When the user selects the notification from the expanded view, the notification can start an activity such as to display the downloaded file.
The lifecycle of a service is much simpler than that of an activity. However, it's even more important that you pay close attention to how your service is created and destroyed because a service can run in the background without the user being aware. The service lifecycle—from when it's created to when it's destroyed—can follow either of these two paths:. The service is created when another component calls startService. The service then runs indefinitely and must stop itself by calling stopSelf.
Another component can also stop the service by calling stopService. When the service is stopped, the system destroys it. The service is created when another component a client calls bindService. The client then communicates with the service through an IBinder interface. The client can close the connection by calling unbindService. Multiple clients can bind to the same service and when all of them unbind, the system destroys the service.
The service does not need to stop itself. These two paths aren't entirely separate. You can bind to a service that is already started with startService.
For example, you can start a background music service by calling startService with an Intent that identifies the music to play. Later, possibly when the user wants to exercise some control over the player or get information about the current song, an activity can bind to the service by calling bindService. In cases such as this, stopService or stopSelf doesn't actually stop the service until all of the clients unbind. Like an activity, a service has lifecycle callback methods that you can implement to monitor changes in the service's state and perform work at the appropriate times.
The following skeleton service demonstrates each of the lifecycle methods:. Note: Unlike the activity lifecycle callback methods, you are not required to call the superclass implementation of these callback methods. Figure 2. The service lifecycle. The diagram on the left shows the lifecycle when the service is created with startService and the diagram on the right shows the lifecycle when the service is created with bindService.
Figure 2 illustrates the typical callback methods for a service. Although the figure separates services that are created by startService from those created by bindService , keep in mind that any service, no matter how it's started, can potentially allow clients to bind to it.
A service that was initially started with onStartCommand by a client calling startService can still receive a call to onBind when a client calls bindService. By implementing these methods, you can monitor these two nested loops of the service's lifecycle:. Note : The onCreate and onDestroy methods are called for all services, whether they're created by startService or bindService. If the service is started, the active lifetime ends at the same time that the entire lifetime ends the service is still active even after onStartCommand returns.
If the service is bound, the active lifetime ends when onUnbind returns. Note: Although a started service is stopped by a call to either stopSelf or stopService , there isn't a respective callback for the service there's no onStop callback.
Unless the service is bound to a client, the system destroys it when the service is stopped— onDestroy is the only callback received. For more information about creating a service that provides binding, see the Bound Services document, which includes more information about the onRebind callback method in the section about Managing the lifecycle of a bound service.
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