Callable 如何防止 call() 返回值

Question

有没有办法防止 call() 在例如设置布尔值之前返回值？这样我就可以控制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，将 aCountDownLatch与 count 一起使用1。

CountDownLatch latch = new CountDownLatch(1);

并将此闩锁传递给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latch.countDown()作为信号调用。