There are mainly two types of Broadcast Receivers: Static Broadcast Receivers: These types of Receivers are declared in the manifest file and works even if the app is closed. Dynamic Broadcast Receivers: These types of receivers work only if the app is active or minimized. Since from API Level 26, most of the broadcast can only be caught by the dynamic receiver, so we have implemented dynamic receivers in our sample project given below.
There are some static fields defined in the Intent class which can be used to broadcast different events. We have taken a change of airplane mode as a broadcast event, but there are many events for which broadcast register can be used.
Do not unregister in onSaveInstanceState Bundle , because this isn't called if the user moves back in the history stack. The state of your BroadcastReceiver whether it is running or not affects the state of its containing process, which can in turn affect its likelihood of being killed by the system. For example, when a process executes a receiver that is, currently running the code in its onReceive method , it is considered to be a foreground process.
The system keeps the process running except under cases of extreme memory pressure. However, once your code returns from onReceive , the BroadcastReceiver is no longer active. The receiver's host process becomes only as important as the other app components that are running in it.
If that process hosts only a manifest-declared receiver a common case for apps that the user has never or not recently interacted with , then upon returning from onReceive , the system considers its process to be a low-priority process and may kill it to make resources available for other more important processes.
For this reason, you should not start long running background threads from a broadcast receiver. After onReceive , the system can kill the process at any time to reclaim memory, and in doing so, it terminates the spawned thread running in the process. To avoid this, you should either call goAsync if you want a little more time to process the broadcast in a background thread or schedule a JobService from the receiver using the JobScheduler , so the system knows that the process continues to perform active work.
For more information, see Processes and Application Life Cycle. The following snippet shows a BroadcastReceiver that uses goAsync to flag that it needs more time to finish after onReceive is complete. The following code snippet demonstrates how to send a broadcast by creating an Intent and calling sendBroadcast Intent. The broadcast message is wrapped in an Intent object. The intent's action string must provide the app's Java package name syntax and uniquely identify the broadcast event.
You can attach additional information to the intent with putExtra String, Bundle. You can also limit a broadcast to a set of apps in the same organization by calling setPackage String on the intent. Permissions allow you to restrict broadcasts to the set of apps that hold certain permissions. You can enforce restrictions on either the sender or receiver of a broadcast. Only receivers who have requested that permission with the tag in their manifest and subsequently been granted the permission if it is dangerous can receive the broadcast.
For example, the following code sends a broadcast:. For information on permissions and security in general, see the System Permissions. Then, to be able to send broadcasts to those receivers, the sending app must request the permission as shown below:. If you don't need to send broadcasts to components outside of your app, then send and receive local broadcasts with the LocalBroadcastManager which is available in the Support Library.
The LocalBroadcastManager is much more efficient no interprocess communication needed and allows you to avoid thinking about any security issues related to other apps being able to receive or send your broadcasts.
If many apps have registered to receive the same broadcast in their manifest, it can cause the system to launch a lot of apps, causing a substantial impact on both device performance and user experience.
To avoid this, prefer using context registration over manifest declaration. Sometimes, the Android system itself enforces the use of context-registered receivers. Do not broadcast sensitive information using an implicit intent. The information can be read by any app that registers to receive the broadcast.
There are three ways to control who can receive your broadcasts:. When you register a receiver, any app can send potentially malicious broadcasts to your app's receiver. There are three ways to limit the broadcasts that your app receives:. The namespace for broadcast actions is global. Make sure that action names and other strings are written in a namespace you own, or else you may inadvertently conflict with other apps. Because a receiver's onReceive Context, Intent method runs on the main thread, it should execute and return quickly.
If you need to perform long running work, be careful about spawning threads or starting background services because the system can kill the entire process after onReceive returns. For more information, see Effect on process state To perform long running work, we recommend:.
Do not start activities from broadcast receivers because the user experience is jarring; especially if there is more than one receiver. Instead, consider displaying a notification. Content and code samples on this page are subject to the licenses described in the Content License. App Basics. Build your first app. App resources. Resource types. App manifest file. Device compatibility. Multiple APK support.
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Now to broadcast our custom intent, let's click on Broadcast Intent button, this will broadcast our custom intent "com. You can try implementing other BroadcastReceiver to intercept system generated intents like system boot up, date changed, low battery etc. Android - Broadcast Receivers Advertisements. Previous Page. Next Page. Previous Page Print Page.
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