Callable如何防止call（）返回值

Question

有没有办法防止call（）返回值，直到例如设置了布尔值？这样我可以控制futureCall.get（）何时完成？

主类：

ExecutorService executor = Executors.newCachedThreadPool();
Future<List<Float>> futureCall = executor.submit((Callable<List<Float>>) new AxisMeasuring(2,100,this));
List<Float> jumpValues;
try {
    jumpValues = futureCall.get();
} catch (InterruptedException | ExecutionException e) {
    e.printStackTrace();
}

可调用类：

public class AxisMeasuring implements SensorEventListener, Callable<List<Float>>{

    AxisMeasuring(int _axis, final int _timeDelay, Context _context) {
        axis = _axis;
        final Context context = _context;
        timeDelay = _timeDelay;

        handler = new Handler();
        runnable = new Runnable() {
            @Override
            public void run() {
                values.add(value);

                if (!hadZeroValue && value <= 1) {
                    hadZeroValue = true;
                }
                if (hadZeroValue && value >= 12) {
                    Log.d("Debug","Point reached");
                } else {
                    handler.postDelayed(runnable, timeDelay);
                }
            }
        };
        handler.post(runnable);
    }

    @Override
    public List<Float> call() throws Exception {

        return values;
    }
}

futureCall.get（）立即返回null。

Answer 1

是的，使用CountDownLatch计数1。

CountDownLatch latch = new CountDownLatch(1);

并将此锁存传递给AxisMeasuring：

public class AxisMeasuring implements SensorEventListener, Callable<List<Float>>{

    private CountDownLatch latch;

    AxisMeasuring(int _axis, final int _timeDelay, Context _context, CountDownLatch latch) {
        latch = latch;
        ...
    }

    @Override
    public List<Float> call() throws Exception {
        latch.await();  // this will get blocked until you call latch.countDown after,  for example, a Boolean is set
        return values;
    }
}

在其他线程中，您可以将latch.countDown()称为信号。