java - 在Android中，什么线程可运行传递给Executors.newSingleThreadScheduledExecutor运行？

Question

在Android中，什么线程可运行传递给ScheduledExecutorService#schedule(Runnable command, long delay, TimeUnit unit)从 Executors#newSingleThreadScheduledExecutor() 返回运行在？

至于我的努力，我运行以下代码:

        final ScheduledExecutorService ses = Executors.newSingleThreadScheduledExecutor();
        ses.schedule(new Runnable() {
            @Override
            public void run() {
                inflate.setBackgroundDrawable(background);
            }
        }, 200, TimeUnit.MILLISECONDS);
        ses.shutdown();

在 Moto G 2013、Android 5.0.2 上，setBackgroundDrawable 操作工作正常，意味着它在主 (UI) 线程上运行。

具体来说，这对于所有 Android 版本和设备都是如此吗？链接的 javadoc 页面对此没有任何说明。我想避免像服务可以生成一个新的单线程来运行操作之类的陷阱。

Answer 1

调用Executors.newSingleThreadScheduledExecutor()时，将创建一个新的Thread(属于同一ThreadGroup)。隐式使用的 DefaultThreadFactory 看起来像这样

static class DefaultThreadFactory implements ThreadFactory {
   private static final AtomicInteger poolNumber = new AtomicInteger(1);
   private final ThreadGroup group;
   private final AtomicInteger threadNumber = new AtomicInteger(1);
   private final String namePrefix;

   DefaultThreadFactory() {
       SecurityManager s = System.getSecurityManager();
       group = (s != null)? s.getThreadGroup() :
                            Thread.currentThread().getThreadGroup();
       namePrefix = "pool-" +
                     poolNumber.getAndIncrement() +
                    "-thread-";
   }

   public Thread newThread(Runnable r) {
       Thread t = new Thread(group, r,
                             namePrefix + threadNumber.getAndIncrement(),
                             0);
       if (t.isDaemon())
           t.setDaemon(false);
       if (t.getPriority() != Thread.NORM_PRIORITY)
           t.setPriority(Thread.NORM_PRIORITY);
       return t;
   }
}

如果你想重用 UI-Thread，你应该编写自己的 ThreadFactory 返回 UI-Thread 并调用 Executors.newSingleThreadScheduledExecutor(yourNewlyCreatedThreadFactory)