Java GUI, need to pause a method without freezing GUI aswell

Question

I know that this problem is caused by the sleep or wait calling on the main thread and that the answer on how to solve this will be to put the method into a seperate thread and then make that thread sleep. But the code is a mess and don't really have the time to sort it out and split it up into separate threads and was wondering if there is any other way of doing this? Even if it is not the cleanest or most common practice for working with GUIs. I only need about a seconds pause from the method.

Answer 1

You can't do it without creating a separate thread. Creating a thread in Java is easy. The only thing to pay attention to is that you can only touch the UI through the main thread. For this reason you need to use something like SwingUtilities.invokeLater().

Answer 2

It is not possible to sleep on an event thread and not cause a GUI freeze. However in Swing, the event thread is created and managed behind the scenes - you main thread (the one originating from main() method) is not the event thread.

So, you can safely sleep on your main thread.

Answer 3

Using a separate thread for the code is your only solution. Every action started by the Swing thread must be delegated to a separate thread if it would otherwise block the GUI.

Answer 4

I wrote a super simple delay function for java that doesn't let your GUI freeze . It has worked everytime i have used it and i guess it will work for you too.

     void Delay(Long ms){

       Long dietime = System.currentTimeMillis()+ms;
       while(System.currentTimeMillis()<dietime){
           //do nothing
       }
   }

For eg : To delay a thread by 5 millisecods use Delay(5L)

Answer 5

And where would one declare this thread. Please bear in mind any, any reference to a function that contains thread sleep will cause the main thread to pause. Because the main thread will have to wait the the sub thread to pause.

The reality is that threads don't realy work as seperate independant thread because a thread must be started from another thread. In other words if you are creating desktop application, and even if you don't work with other threads, your application is a one threaded application. Now if you start working with threads & putting them to sleep, you will soon find out that that you won't be able to do anything else in the application. No & no the other threads won't even run because they are waiting the first thread to finish sleeping. Why is this? Cause the thread are sub threads of the main thread and it is the main thread that is waiting for that sleep sub thread to wake up. You can't design a threadless application either as java is single main threaded application. Any, yes any, thread further defined in your application always runs inside in the main thread.

Unless somebody can prove me wrong, you obviously whould never pause your main thread as this would lock up your app. However as soon you define another thread and suspend it with sleep() this also locks up your app as the thread was defined in subclass of the main application and therefore the main thread.

So to put a very very long story to bed, pausing a user defined thread, is almost exactly the same as if your called the Thread.sleep() for anywhere in your app, it pauses the entire application.