从Thread返回值
从Thread返回值
我有一个方法HandlerThread。一个值在内部发生变化Thread，我想将它返回给test()方法。有没有办法做到这一点？
public void test(){
Thread uiThread = new HandlerThread("UIHandler"){
public synchronized void run(){
int value;
value = 2; //To be returned to test()
}
};
uiThread.start();}
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3回答
-
隔江千里
您可以使用本地最终变量数组。变量必须是非基本类型，因此您可以使用数组。您还需要同步两个线程，例如使用CountDownLatch：public void test(){ final CountDownLatch latch = new CountDownLatch(1); final int[] value = new int[1]; Thread uiThread = new HandlerThread("UIHandler"){ @Override public void run(){ value[0] = 2; latch.countDown(); // Release await() in the test thread. } }; uiThread.start(); latch.await(); // Wait for countDown() in the UI thread. Or could uiThread.join(); // value[0] holds 2 at this point.}你也可以使用Executor和之Callable类的：public void test() throws InterruptedException, ExecutionException{ ExecutorService executor = Executors.newSingleThreadExecutor(); Callable<Integer> callable = new Callable<Integer>() { @Override public Integer call() { return 2; } }; Future<Integer> future = executor.submit(callable); // future.get() returns 2 or raises an exception if the thread dies, so safer executor.shutdown();} -
子衿沉夜
通常你会这样做 public class Foo implements Runnable { private volatile int value; @Override public void run() { value = 2; } public int getValue() { return value; } }然后你可以创建线程并检索值（假设已经设置了值）Foo foo = new Foo();Thread thread = new Thread(foo);thread.start();thread.join();int value = foo.getValue();tl;dr线程无法返回值（至少没有回调机制）。您应该像普通类一样引用一个线程并询问该值。 -
白猪掌柜的
您正在寻找的可能是Callable<V>接口代替Runnable，并使用Future<V>对象检索值，这也让您等到计算出值。你可以通过一个ExecutorService你可以得到的来实现这一目标Executors.newSingleThreadExecutor()。public void test() { int x; ExecutorService es = Executors.newSingleThreadExecutor(); Future<Integer> result = es.submit(new Callable<Integer>() { public Integer call() throws Exception { // the other thread return 2; } }); try { x = result.get(); } catch (Exception e) { // failed } es.shutdown();}
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