Android，Java：ExecutorService在关机后执行

Question

I have a ExecutorService :

private final ExecutorService listenDataExecutorService = 
                              Executors.newSingleThreadExecutor();

In same case I need executor to stop doing his job. For this I call listenDataExecutorService.shutdown();

Then after some time, I need this executor to do this job again. But when I call listenDataExecutorService.execute() exception is thrown.

How can I execute new task for executor after shutdown ?

Answer 1

Once an executor service has been shut down it can't be reactivated. Create a new executor service to restart execution:

listenDataExecutorService = Executors.newSingleThreadExecutor();

(You'd have to drop the final modifier though.)

Another option is to cancel all pending tasks instead, and then reschedule them when you want to resume execution.

Answer 2

First you have to remove final access level modifier to re-create ExecutorService at latter stage. final modifier does not allow you to change the reference of ExecutorService later during re-initialization.

In same case I need executor to stop doing his job. For this I call listenDataExecutorService.shutdown();

You have to call three methods in a right sequence to shutdown the ExecutorService : shutdown, awaitTermination, shutdownNow

Have a look at below post:

How to properly shutdown java ExecutorService

Then after some time, I need this executor to do this job again. But when I call listenDataExecutorService.execute() exception is thrown.

How can I execute new task for executor after shutdown ?

Before you call execute on that ExecutorService , that service should not be in shutdown state. Make sure that ExecutorService is in proper state to accept tasks => Your application code should properly handle " shutdown " and " re-creation " of ExecutorService .