Java异步方法调用

Question

我已经有一个线程要做以下工作：

public class DetectionHandler extends TimerTask {

@Override
public void run() {
bluetoothAddresses = BluetoothModule.scanAddresses();
wiFiAddresses = WiFiModule.scanAddresses();
...//when scanning is finished, continue work
}

我希望扫描是并行的。所以我假设我必须异步调用这两个方法。当扫描完成后，我可以继续在 DetectionHandler 类中工作。

我尝试过 BluetoothModule 和 WiFiModule 实现 Runnable 的方式，但没有运气。天呐

Answer 1

使用ExecutorService 你可以这样写：

ArrayList<Callable<Collection<Address>>> tasks = new ArrayList<Callable<Collection<Address>>>();
tasks.add(new Callable<Collection<Address>>() {
  public Collection<Address> call() throws Exception {
    return BluetoothModule.scanAddresses();
  }
});
tasks.add(new Callable<Collection<Address>>() {
  public Collection<Address> call() throws Exception {
    return WiFiModule.scanAddresses();
  }
});

ExecutorService executorService = Executors.newFixedThreadPool(2);
List<Future<Collection<Address>>> futures = executorService.invokeAll(tasks);

Answer 2

从Executors 获取一个 ExecutorService 并给它一个FutureTask。

然后您可以通过在返回的 Future 上调用阻塞 get() 来等待结果。扫描将并行运行，但您的运行方法（此处显示）仍将等待扫描完成。

有点像：

     FutureTask<List<Address>> btFuture =
       new FutureTask<List<Address>>(new Callable<List<Address>>() {
         public List<Address> call() {
           return BluetoothModule.scanAddresses();
       }});
     executor.execute(btFuture);

     FutureTask<List<Address>> wfFuture =
       new FutureTask<List<Address>>(new Callable<List<Address>>() {
         public List<Address> call() {
           return WifiModule.scanAddresses();
       }});
     executor.execute(wfFuture);

    btAddresses = btFuture.get(); // blocks until process finished
    wifiAddresses = wfFuture.get(); // blocks

不过要小心，无论调用返回什么，get 都会返回。异常被包装在 ExecutionException 中。