看到别人并发任务提交的场景

一个个的job被封装为一个命令

private static AtomicInteger sequencing = new AtomicInteger(0);

    private static class Command implements Comparable<Command> {
        public Runnable runnable;
        public MessagingListener listener;
        public String description;
        boolean isForegroundPriority;

        int sequence = sequencing.getAndIncrement();

        @Override
        public int compareTo(@NonNull Command other) {
            if (other.isForegroundPriority && !isForegroundPriority) {
                return 1;
            } else if (!other.isForegroundPriority && isForegroundPriority) {
                return -1;
            } else {
                return (sequence - other.sequence);
            }
        }
    }

这些个命令被放到blockquene中

private final BlockingQueue<Command> queuedCommands = new PriorityBlockingQueue<>();
private void put(String description, MessagingListener listener, Runnable runnable) {
        putCommand(queuedCommands, description, listener, runnable, true);
    }

    private void putBackground(String description, MessagingListener listener, Runnable runnable) {
        putCommand(queuedCommands, description, listener, runnable, false);
    }

    private static void putCommand(BlockingQueue<Command> queue, String description, MessagingListener listener,
            Runnable runnable, boolean isForeground) {
        int retries = 10;
        Exception e = null;
        while (retries-- > 0) {
            try {
                Command command = new Command();
                command.listener = listener;
                command.runnable = runnable;
                command.description = description;
                command.isForegroundPriority = isForeground;
                queue.put(command);
                return;
            } catch (InterruptedException ie) {
                SystemClock.sleep(200);
                e = ie;
            }
        }
        throw new Error(e);
    }

一个while(true)去不停的取任务执行，执行失败继续放到blockquene中等待重试。

private final BlockingQueue<Command> queuedCommands = new PriorityBlockingQueue<>();
private void runInBackground() {
        Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
        while (!stopped) {
            String commandDescription = null;
            try {
                final Command command = queuedCommands.take();

                if (command != null) {
                    commandDescription = command.description;

                    Timber.i("Running command '%s', seq = %s (%s priority)",
                            command.description,
                            command.sequence,
                            command.isForegroundPriority ? "foreground" : "background");

                    try {
                        command.runnable.run();
                    } catch (UnavailableAccountException e) {
                        // retry later
                        new Thread() {
                            @Override
                            public void run() {
                                try {
                                    sleep(30 * 1000);
                                    queuedCommands.put(command);
                                } catch (InterruptedException e) {
                                    Timber.e("Interrupted while putting a pending command for an unavailable account " +
                                            "back into the queue. THIS SHOULD NEVER HAPPEN.");
                                }
                            }
                        }.start();
                    }

                    Timber.i(" Command '%s' completed", command.description);
                }
            } catch (Exception e) {
                Timber.e(e, "Error running command '%s'", commandDescription);
            }
        }
    }