CODEWITHSUNDEEP
javaandroidmultithreading
Vektor88
Vektor88

Reputation: 4930

Interrupt ThreadPoolExecutor current threads and empty its queue

I am currently working on an application that has in its main layout a ListView, its items are wrappers for real files contained in a directory. When the list is populated I execute an AsyncTask that should retrieve some data from a Properties file and, if such data is not retrieved, I add a Runnable to a ThreadPoolExecutor to get that data from a website, save it into the Properties and then load the Properties.

If I decide to change the directory, a List.clear() is performed before the app populates it with the new items.

As a consequence, if there are currently working/pending Threads inside the ThreadPoolExecutor, they continue being executed and make my application crash, because the item inside the List doesn't exist anymore.

I've read some questions but none of them satisfied me. How can I prevent currently active Threads from accessing the List and empty the queue of the ThreadPoolExecutor? Alternatively, how can I design a runnable in such way that if it's not needed anymore it doesn't interfere with the List?

Update: In my method to repopulate the List I did the following before doing clear():

if(mBlockingQueue.size()>0){
    mBlockingQueue.drainTo(new ArrayList<Runnable>()); //I don't want to keep the workers
    mThreadPoolExecutor.shutDownNow(); //This will execute .interrupt(); on the working Threads
}

Update2: This is not enough: After creating your executor use the following

myThreadPoolExecutor.setRejectedExecutionHandler(new RejectedExecutionHandler() {
    @Override
    public void rejectedExecution(Runnable r,ThreadPoolExecutor executor) {
        //Do nothing
    }
});

Upvotes: 2

Views: 456

Answers (1)

phemt.latd
phemt.latd

Reputation: 1803

You can use this code to have a paused tasks list:

BlockingQueue<Runnable> queue = threadPool.getQueue();
List<Runnable> list = new ArrayList<Runnable>();
int tasks = queue.drainTo(list);

Then you can follow this documentation and find a way to use remove on the BlockingQueue

BlockingQueue

Upvotes: 1

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