android - What is a Sticky Broadcast?

Question

I came across this term in the android documentation with the accompanying definition

These are broadcasts whose data is held by the system after being finished, so that clients can quickly retrieve that data without having to wait for the next broadcast.

What does it mean? Can someone elaborate its use with a particular example? I believe we have to request a permission for using this intent? Why so?

<uses-permission android:name="android.permission.BROADCAST_STICKY"/> - Allows an application to broadcast sticky intents.

Answer 1

If an Activity calls onPause with a normal broadcast, receiving the Broadcast can be missed. A sticky broadcast can be checked after it was initiated in onResume.

Update 6/23/2020

Sticky broadcasts are deprecated.

See sendStickyBroadcast documentation.

This method was deprecated in API level 21.

Sticky broadcasts should not be used. They provide no security (anyone can access them), no protection (anyone can modify them), and many other problems. The recommended pattern is to use a non-sticky broadcast to report that something has changed, with another mechanism for apps to retrieve the current value whenever desired.

Implement

Intent intent = new Intent("some.custom.action");
intent.putExtra("some_boolean", true);
sendStickyBroadcast(intent);

Resources

• Related post: What is the difference between sendStickyBroadcast and sendBroadcast in Android?

• See removeStickyBroadcast(Intent), and on API Level 5 +, isInitialStickyBroadcast() for usage in the Receiver's onReceive.