Is this a prefect way to stop handlerthread?

Question

I always create two handler: one is wraping on main thread, another is wraping on a single thread.

Is this a best method to start and stop these in an Activity lifecycle?

HandlerThread safeThread = null;
Handler safeHandler = null;
Handler handler = null;


@Override
    public void onStart() {

if (safeThread == null) {
            safeThread = new HandlerThread("safeThread");
            safeThread.start();
            safeHandler = new Handler(safeThread.getLooper());
        } else if (safeThread.getState() == Thread.State.NEW) {
            safeThread.start();
            safeHandler = new Handler(safeThread.getLooper());
        } else if (safeThread.getState() == Thread.State.WAITING) {
            safeHandler = new Handler(safeThread.getLooper());
        } else if (safeThread.getState() == Thread.State.TERMINATED) {
            safeThread = null;
            safeThread = new HandlerThread("safeThread");
            safeThread.start();
            safeHandler = new Handler(safeThread.getLooper());
        }
}




protected void onStop() {
        Log.d("x", "onStop is executed");
        safeHandler = null;
        safeThread.quit();
        safeThread.interrupt();
        safeThread = null;
        super.onStop();
    }

Answer 1

I know it's a somewhat old question, but I stumble across it looking for the same answer and further researching I don't believe the current answer applies very well to HandlerThread (although absolutely correct for normal threads)

HandlerThread have a builtin quit() and quitSafely(API18) methods to stop the thread. https://developer.android.com/reference/android/os/HandlerThread.html#quit()

the difference between the two is only if the messages in queue will be processed before it stops or not.

so to answer, it's as simple as:

safeThread.quit();

Answer 2

If you start the thread like this:

HandlerThread thread = new HandlerThread("MyHandlerThread");
thread.start();

The safest way to stop it would be:

thread.quitSafely();

quitSafely ensures that all pending messages are processed before the thread stops.

Note: My original answer included an additional call to thread.join, but I found the join call does not release reliably when used after quitSafely.