Android application is hanged and showing black screen for 5-6 seconds when checking if a server port is open or not using ThreadPoolExecutor

问题

I need to run a service if a server port is open. I am doing this by using below method.

public Future<Boolean> ifPortIsOpenThenStartIridiumService(final Context context, final String device_mac, final String device_imei, final String input_mobile) {
    return Executors.newFixedThreadPool(20).submit(new Callable<Boolean>() {
        @Override
        public Boolean call() {
            try {
                String SERVER_IP = "IP Address"; 
                int SERVER_PORT = Server_port; 
                int DURATION = 1000;

                Socket socket = new Socket();
                socket.connect(new InetSocketAddress(SERVER_IP, SERVER_PORT), DURATION);
                socket.close();

                Log.d(TAG, "Port is Open");

                runIridiumService(context, device_mac, device_imei, input_mobile);

                return true;
            } catch (Exception ex) {
                Log.d(TAG, "Port is not Open");
                CustomToast.showToast(context, "No Internet Access.", "If in flight, please switch to \"Aeroplane Mode\" and connect to the airline's Wi-Fi network.", 1);

                return false;
            }
        }
    });
}

Above code is working but when I run this method the application is getting hanged and black screen is shown for 5-6 seconds. I found below message on Logcat.

W/ActivityManager: Launch timeout has expired, giving up wake lock!

After that service is started and application is working well. How can I get rid of this problem? Thanks in advance.

回答1:

After some study, as far as I understood,

Android application is hanged and showing black screen for 5-6 seconds Because,

Future -

A Future represents the result of an asynchronous computation. Methods are provided to check if the computation is complete, to wait for its completion, and to retrieve the result of the computation.

So, it waits until operation is finished. You can get more info from here.

newFixedThreadPool -

At any point, at most nThreads threads will be active processing tasks. If additional tasks are submitted when all threads are active, they will wait in the queue until a thread is available.

Get more info from here.

The possible solution of your problem is to use ScheduledExecutorService.

Before that you can check Future is completed or not using

if (YOUR_FUTURE.isDone()){ result = (String) YOUR_FUTURE.get(); }

to avoid unwanted or extra loop.

来源：https://stackoverflow.com/questions/44352674/android-application-is-hanged-and-showing-black-screen-for-5-6-seconds-when-chec

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