How can an Android Activity interact with a Service to exchange data?

In Android, Activity and Service can interact with each other in several ways to exchange data.

1. Passing data using Intents: An Activity can start a Service using the startService() method, and pass data to the Service through an Intent. The Service can retrieve the passed data using the getExtras() method of the Intent.
2. Using a binding service: An Activity can bind to a Service using the bindService() method, and then obtain an instance of the Service through a ServiceConnection object. The Activity can interact with the Service by directly calling its public methods for data exchange.
3. Utilizing broadcasts: Activity can send data to Service through broadcasting, and Service can receive the broadcasts sent by Activity by registering a broadcast receiver, and then take appropriate actions.
4. Activity and Service can interact with each other through shared data, such as using global variables or SharedPreferences.

It is important to note that Services run on the main thread by default. If you need to carry out lengthy operations in a Service, it is recommended to use IntentService or create a new thread to avoid blocking the main thread.