Java中实现异步转同步的几种方式
Android常见的异步转同步的方式是通过Callback + Handler的方式来完成，常见的例子是在子线程请求网络，成功后调用Callback，然后通过Handler发送消息给主线程，让子线程更新UI。当然了，实际开发还有好多方式可以实现这种操作。
这里展示Java中的几种异步转同步的方式。
注意：这里只讲实现，不讲原理，具体原理请自行Google。
1、CountDownLatch
CountDownLatch是一个同步工具类，它允许一个或多个线程一直等待，直到其他线程的操作执行完后再执行。
这里有三个子任务Task1、Task2和Task3，我们想在Task2和Task3都执行完了以后，才执行Task1。实现如下：
1、先自定义一个Runnable，run方法中会打印当前线程，在线程执行完毕后会调用CountDownLatch#countDown()方法。
/**
* 自定义Runnable
*/
private static class CustomRunnable implements Runnable {
private CountDownLatch countDownLatch;
private String name;
private int delayTime;
public CustomRunnable(CountDownLatch countDownLatch, String name, int delayTime) {
this.countDownLatch = countDownLatch;
this.name = name;
this.delayTime = delayTime;
}
@Override
public void run() {
LogUtils.e(TAG, "开始执行" + name);
ThreadUtils.logCurrThreadName(TAG + " " + name);
try {
TimeUnit.SECONDS.sleep(delayTime);
} catch (InterruptedException e) {
e.printStackTrace();
}
LogUtils.e(TAG, name + "执行完毕");
if (countDownLatch != null) {
countDownLatch.countDown();
}
}
}
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2、 ①初始化CountDownLatch，这里传入了2，这是因为Task1等待的任务有2个，Task2和Task3. ②创建自定义Runnable Task1，线程内部调用CountDownLatch#await()方法开始等待。 ③创建线程池，依次提交任务Task1、Task2、Task3。
public void onBtnJavaCountDownLatchClicked() {
/**
* Task2和Task3都执行完了以后，才执行Task1
*/
countDownLatch = new CountDownLatch(2);
Runnable Task1 = () -> {
LogUtils.e(TAG, "开始执行Task1");
ThreadUtils.logCurrThreadName(TAG + " Task1");
try {
// 注意这里是await方法，不是wait方法，不要问我为什么，难受。
countDownLatch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
LogUtils.e(TAG, "Task1执行完毕");
};
// 创建线程池
ExecutorService executors = Executors.newFixedThreadPool(3);
// 执行任务。
executors.submit(Task1);
executors.submit(new CustomRunnable(countDownLatch, "Task2", 3));
executors.submit(new CustomRunnable(countDownLatch, "Task3", 5));
// 任务完成后关闭线程池
executors.shutdown();
}
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输出结果：
05-24 11:14:32.632 2018-2052/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 开始执行Task1 05-24 11:14:32.633 2018-2052/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity Task1: sub Thread,name --> pool-2-thread-1 05-24 11:14:32.634 2018-2053/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 开始执行Task2 05-24 11:14:32.634 2018-2053/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity Task2: sub Thread,name --> pool-2-thread-2 05-24 11:14:32.635 2018-2054/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 开始执行Task3 05-24 11:14:32.635 2018-2054/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity Task3: sub Thread,name --> pool-2-thread-3 05-24 11:14:35.635 2018-2053/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: Task2执行完毕 05-24 11:14:37.636 2018-2054/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: Task3执行完毕 05-24 11:14:37.636 2018-2052/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: Task1执行完毕 复制代码
我们先提交了Task1任务，它先执行，当执行到CountDownLatch#await()方法时开始等待，等待Task2和Task3都执行完毕后，Task1才继续执行，上述log印证了这点。
大家可以想象，如果这里没有CountDownLatch，那么Task1、Task2和Task3这三个任务会各自独立执行，互不影响。
添加了CountDownLatch后，我们做到了让任务Task2和Task3都执行完以后，再继续执行Task1的任务，代码是不是很简单。
2、CyclicBarrier
CyclicBarrier是一个同步辅助类，它允许一组线程互相等待，直到到达某个公共屏障点 (common barrier point)。
①新建CyclicBarrier，它有两个参数，第一个参数表示如果有10个线程到达屏障位置时，就会执行第二个Runnable参数的run方法。
CyclicBarrier cyclicBarrier = new CyclicBarrier(10, () -> {
LogUtils.e(TAG, "所有任务都执行完毕了");
ThreadUtils.logCurrThreadName(TAG + " barrierAction");
});
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②创建10个任务，每个任务执行完毕后都会调用CyclicBarrier#await()方法。 ③将这10个任务都放入线程池中去执行。
List<Runnable> runnables = new ArrayList<>();
for (int i = 0; i < 10; i++) {
int finalI = i;
Runnable runnable = () -> {
LogUtils.e(TAG, "当前是第" + finalI + "个任务，开始执行");
ThreadUtils.logCurrThreadName(TAG + " 子任务");
try {
TimeUnit.SECONDS.sleep(finalI);
} catch (InterruptedException e) {
e.printStackTrace();
}
LogUtils.e(TAG, "当前是第" + finalI + "个任务，执行完毕");
try {
cyclicBarrier.await();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (BrokenBarrierException e) {
e.printStackTrace();
}
};
runnables.add(runnable);
}
ExecutorService executorService = Executors.newCachedThreadPool();
for (Runnable r : runnables) {
executorService.submit(r);
}
executorService.shutdown();
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输出结果：
05-24 11:55:04.272 2018-2190/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第2个任务，开始执行 05-24 11:55:04.272 2018-2190/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-3 05-24 11:55:04.272 2018-2191/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第3个任务，开始执行 05-24 11:55:04.272 2018-2191/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-4 05-24 11:55:04.273 2018-2188/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第0个任务，开始执行 05-24 11:55:04.273 2018-2188/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-1 05-24 11:55:04.273 2018-2188/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第0个任务，执行完毕 05-24 11:55:04.273 2018-2189/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第1个任务，开始执行 05-24 11:55:04.273 2018-2189/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-2 05-24 11:55:04.274 2018-2192/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第4个任务，开始执行 05-24 11:55:04.274 2018-2192/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-5 05-24 11:55:04.275 2018-2193/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第5个任务，开始执行 05-24 11:55:04.275 2018-2193/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-6 05-24 11:55:04.275 2018-2194/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第6个任务，开始执行 05-24 11:55:04.275 2018-2194/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-7 05-24 11:55:04.277 2018-2197/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第9个任务，开始执行 05-24 11:55:04.278 2018-2197/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-10 05-24 11:55:04.278 2018-2195/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第7个任务，开始执行 05-24 11:55:04.278 2018-2195/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-8 05-24 11:55:04.279 2018-2196/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第8个任务，开始执行 05-24 11:55:04.279 2018-2196/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 子任务: sub Thread,name --> pool-3-thread-9 05-24 11:55:05.274 2018-2189/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第1个任务，执行完毕 05-24 11:55:06.272 2018-2190/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第2个任务，执行完毕 05-24 11:55:07.273 2018-2191/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第3个任务，执行完毕 05-24 11:55:08.276 2018-2192/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第4个任务，执行完毕 05-24 11:55:09.277 2018-2193/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第5个任务，执行完毕 05-24 11:55:10.280 2018-2194/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第6个任务，执行完毕 05-24 11:55:11.282 2018-2195/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第7个任务，执行完毕 05-24 11:55:12.282 2018-2196/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第8个任务，执行完毕 05-24 11:55:13.278 2018-2197/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 当前是第9个任务，执行完毕 05-24 11:55:13.278 2018-2197/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 所有任务都执行完毕了 05-24 11:55:13.278 2018-2197/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity barrierAction: sub Thread,name --> pool-3-thread-10 复制代码
从输出结果可以看出，当在10个线程中调用了CyclicBarrier#await()方法后，我们的CyclicBarrier对象初始化时传入的Runnable对象的run方法会被调用。
3、FutureTask
这里提供三种实现方式：
①Callable + Future + ExecutorService
第一步，先自定义一个Callable对象，在call方法中进行计算并将结果返回。
class CustomCallable implements Callable<Integer> {
@Override
public Integer call() throws Exception {
LogUtils.e(TAG, "在子线程进行计算");
ThreadUtils.logCurrThreadName(TAG + " Task start");
int sum = 0;
for (int i = 0; i < 20; i++) {
Thread.sleep(100);
sum += i;
ThreadUtils.logCurrThreadName(TAG + " Task sum:" + sum);
}
ThreadUtils.logCurrThreadName(TAG + " Task end");
return sum;
}
}
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第二步，创建线程池，通过submit方法提交刚才的自定义Callable，并通过Future接受返回结果。
第三步，通过Future#get()方法完成异步转同步操作。
public void onBtnJavaCallableFutureClicked() {
// Callable + Future + ExecutorService
ThreadUtils.logCurrThreadName(TAG + " main start");
ExecutorService executorService = Executors.newCachedThreadPool();
CustomCallable task = new CustomCallable();
Future<Integer> result = executorService.submit(task);
executorService.shutdown();
ThreadUtils.logCurrThreadName(TAG + " main 111");
try {
LogUtils.e(TAG, "task执行结果:" + result.get());
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
ThreadUtils.logCurrThreadName(TAG + " main 222:" + i);
}
ThreadUtils.logCurrThreadName(TAG + " main 主线程任务执行完毕");
}
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输出结果：
05-24 12:06:36.609 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main start: main Thread,name --> main 05-24 12:06:36.613 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 111: main Thread,name --> main 05-24 12:06:36.614 2314-2344/com.tiny.demo.firstlinecode E/FutureTaskActivity: 在子线程进行计算 05-24 12:06:36.614 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task start: sub Thread,name --> pool-2-thread-1 05-24 12:06:36.714 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:0: sub Thread,name --> pool-2-thread-1 05-24 12:06:36.814 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:1: sub Thread,name --> pool-2-thread-1 05-24 12:06:36.915 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:3: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.016 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:6: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.116 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:10: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.217 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:15: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.318 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:21: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.418 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:28: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.519 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:36: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.620 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:45: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.620 2314-2344/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task end: sub Thread,name --> pool-2-thread-1 05-24 12:06:37.622 2314-2314/com.tiny.demo.firstlinecode E/FutureTaskActivity: task执行结果:45 05-24 12:06:37.622 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:0: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:1: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:2: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:3: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:4: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:5: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:6: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:7: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:8: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:9: main Thread,name --> main 05-24 12:06:37.623 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 主线程任务执行完毕: main Thread,name --> main 复制代码
可以看到，在调用了Future#get方法后，主线程一直在等待子线程的执行结果，当子线程的计算执行完毕后，就继续执行主线程的代码。
②Callable + FutureTask + ExecutorService
与上面的demo类似，只不过我们把Future换成FutureTask。
public void onBtnJavaCallableFutureTaskClicked() {
// Callable + FutureTask + ExecutorService
ThreadUtils.logCurrThreadName(TAG + " main start");
ExecutorService executorService = Executors.newCachedThreadPool();
CustomCallable task = new CustomCallable();
FutureTask<Integer> futureTask = new FutureTask<>(task);
executorService.submit(futureTask);
executorService.shutdown();
ThreadUtils.logCurrThreadName(TAG + " main 111");
try {
LogUtils.e(TAG, "task执行结果:" + futureTask.get());
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
ThreadUtils.logCurrThreadName(TAG + " main 222:" + i);
}
ThreadUtils.logCurrThreadName(TAG + " main 主线程任务执行完毕");
}
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输出结果：
05-24 12:10:08.028 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main start: main Thread,name --> main 05-24 12:10:08.029 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 111: main Thread,name --> main 05-24 12:10:08.030 2314-2362/com.tiny.demo.firstlinecode E/FutureTaskActivity: 在子线程进行计算 05-24 12:10:08.030 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task start: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.131 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:0: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.232 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:1: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.333 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:3: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.434 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:6: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.534 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:10: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.635 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:15: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.735 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:21: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.836 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:28: sub Thread,name --> pool-3-thread-1 05-24 12:10:08.937 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:36: sub Thread,name --> pool-3-thread-1 05-24 12:10:09.038 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:45: sub Thread,name --> pool-3-thread-1 05-24 12:10:09.038 2314-2362/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task end: sub Thread,name --> pool-3-thread-1 05-24 12:10:09.038 2314-2314/com.tiny.demo.firstlinecode E/FutureTaskActivity: task执行结果:45 05-24 12:10:09.038 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:0: main Thread,name --> main 05-24 12:10:09.038 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:1: main Thread,name --> main 05-24 12:10:09.038 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:2: main Thread,name --> main 05-24 12:10:09.039 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:3: main Thread,name --> main 05-24 12:10:09.039 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:4: main Thread,name --> main 05-24 12:10:09.039 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:5: main Thread,name --> main 05-24 12:10:09.039 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:6: main Thread,name --> main 05-24 12:10:09.039 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:7: main Thread,name --> main 05-24 12:10:09.039 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:8: main Thread,name --> main 05-24 12:10:09.039 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:9: main Thread,name --> main 05-24 12:10:09.039 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 主线程任务执行完毕: main Thread,name --> main 复制代码
可以看到，输出结果跟上个例子一致。
③Callable + FutureTask + Thread
这里我们将上面例子中的线程池换成Thread，其他不变。
public void onViewClicked() {
// Callable + FutureTask + Thread
ThreadUtils.logCurrThreadName(TAG + " main start");
CustomCallable task = new CustomCallable();
FutureTask<Integer> futureTask = new FutureTask<>(task);
Thread thread = new Thread(futureTask);
thread.start();
ThreadUtils.logCurrThreadName(TAG + " main 111");
try {
LogUtils.e(TAG, "task执行结果:" + futureTask.get());
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
ThreadUtils.logCurrThreadName(TAG + " main 222:" + i);
}
ThreadUtils.logCurrThreadName(TAG + " main 主线程任务执行完毕");
}
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输出结果：
05-24 12:12:08.493 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main start: main Thread,name --> main 05-24 12:12:08.495 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 111: main Thread,name --> main 05-24 12:12:08.496 2314-2377/com.tiny.demo.firstlinecode E/FutureTaskActivity: 在子线程进行计算 05-24 12:12:08.496 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task start: sub Thread,name --> Thread-215 05-24 12:12:08.596 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:0: sub Thread,name --> Thread-215 05-24 12:12:08.698 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:1: sub Thread,name --> Thread-215 05-24 12:12:08.798 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:3: sub Thread,name --> Thread-215 05-24 12:12:08.899 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:6: sub Thread,name --> Thread-215 05-24 12:12:09.000 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:10: sub Thread,name --> Thread-215 05-24 12:12:09.100 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:15: sub Thread,name --> Thread-215 05-24 12:12:09.202 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:21: sub Thread,name --> Thread-215 05-24 12:12:09.303 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:28: sub Thread,name --> Thread-215 05-24 12:12:09.404 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:36: sub Thread,name --> Thread-215 05-24 12:12:09.506 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task sum:45: sub Thread,name --> Thread-215 05-24 12:12:09.507 2314-2377/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity Task end: sub Thread,name --> Thread-215 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/FutureTaskActivity: task执行结果:45 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:0: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:1: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:2: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:3: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:4: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:5: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:6: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:7: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:8: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 222:9: main Thread,name --> main 05-24 12:12:09.507 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: FutureTaskActivity main 主线程任务执行完毕: main Thread,name --> main 复制代码
输出效果与上面一致。
4、rxjava
RxJava在处理异步任务方面特别强悍，这里通过两个例子说明。
map——让异步任务顺序执行
首先，我们通过一个例子让几个异步任务依次顺序执行，下一个任务的启动依赖于上一个任务的结果。
这里我们举一个注册完成后直接登录的例子。
大体流程如下：
注册请求 --> 注册响应 --> 登录请求 --> 登录响应 复制代码
①先创建四个Bean，用于模拟数据转换。分别是注册请求Bean，注册请求响应Bean，登录请求Bean，登录请求相应Bean。
下面这个是注册请求Bean的部分代码，相应的getter/setter方法和toString方法已省略。
public class RegisterReqBean {
private String name;
private String phone;
private String pwd;
public RegisterReqBean(String name, String phone, String pwd) {
this.name = name;
this.phone = phone;
this.pwd = pwd;
}
...
}
复制代码
注册请求相应Bean：
public class RegisterRespBean {
private String name;
private String pwd;
private String msg;
...
}
复制代码
登录请求Bean：
public class LoginReqBean {
private String name;
private String pwd;
private String msg;
...
}
复制代码
登录请求响应Bean：
public class LoginRespBean {
private String name;
private String pwd;
private String msg;
...
}
复制代码
②创建对应的Observable对象，准备好数据转换的素材。
RegisterReqBean registerReqBean = new RegisterReqBean("猫了个咪", "13333333333", "123456");
Observable registerRequest = Observable.create(new ObservableOnSubscribe<RegisterReqBean>() {
@Override
public void subscribe(ObservableEmitter<RegisterReqBean> emitter) throws Exception {
LogUtils.e(TAG, "注册请求 registerReqBean:" + registerReqBean);
ThreadUtils.logCurrThreadName(TAG + " 注册请求成功");
emitter.onNext(registerReqBean);
LogUtils.e(TAG, "发送注册请求");
emitter.onComplete();
LogUtils.e(TAG, "发送注册请求完成");
}
});
// 模拟注册响应。将RegisterReqBean转化为RegisterRespBean。
Function mockRegisterResp = new Function<RegisterReqBean, RegisterRespBean>() {
@Override
public RegisterRespBean apply(RegisterReqBean registerReqBean) throws Exception {
RegisterRespBean registerRespBean = new RegisterRespBean(registerReqBean.getName(),
registerReqBean.getPwd(), "恭喜您注册成功");
LogUtils.e(TAG, "注册响应 registerRespBean:" + registerRespBean);
TimeUnit.SECONDS.sleep(5);// 模拟网络延迟
ThreadUtils.logCurrThreadName(TAG + " 注册响应成功");
return registerRespBean;
}
};
// 模拟登录请求。将RegisterRespBean转化为LoginReqBean。
Function mockLoginReq = new Function<RegisterRespBean, LoginReqBean>() {
@Override
public LoginReqBean apply(RegisterRespBean registerRespBean) throws Exception {
LoginReqBean loginReqBean = new LoginReqBean(registerRespBean.getName() + " 我要登陆", registerRespBean.getPwd());
LogUtils.e(TAG, "登录请求 loginReqBean:" + loginReqBean);
ThreadUtils.logCurrThreadName(TAG + " 登录请求成功");
return loginReqBean;
}
};
// 模拟登录响应。将LoginReqBean转化为LoginRespBean。
Function mockLoginResp = new Function<LoginReqBean, LoginRespBean>() {
@Override
public LoginRespBean apply(LoginReqBean loginReqBean) throws Exception {
LoginRespBean loginRespBean = new LoginRespBean(loginReqBean.getName(),
loginReqBean.getPwd(), "恭喜您登录成功");
LogUtils.e(TAG, "登录响应 loginRespBean:" + loginRespBean);
TimeUnit.SECONDS.sleep(5);// 模拟网络延迟
ThreadUtils.logCurrThreadName(TAG + " 登录响应成功");
return loginRespBean;
}
};
// 模拟接受登录响应结果。
Observer<LoginRespBean> resultObserver = new Observer<LoginRespBean>() {
@Override
public void onSubscribe(Disposable d) {
LogUtils.e(TAG, "onSubscribe");
}
@Override
public void onNext(LoginRespBean loginRespBean) {
LogUtils.e(TAG, "onNext 登录成功，可以更新UI了。 loginRespBean:" + loginRespBean);
ThreadUtils.logCurrThreadName(TAG + " ");
}
@Override
public void onError(Throwable e) {
LogUtils.e(TAG, "onError e:" + e.getMessage());
}
@Override
public void onComplete() {
LogUtils.e(TAG, "onComplete");
}
};
复制代码
③使用map操作符进行转化
registerRequest.subscribeOn(Schedulers.io())
.observeOn(Schedulers.newThread())
.map(mockRegisterResp)
.observeOn(Schedulers.io())
.map(mockLoginReq)
.observeOn(Schedulers.newThread())
.map(mockLoginResp)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(resultObserver);
复制代码
最后的输出结果：
05-24 13:22:17.823 2314-2314/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: onSubscribe
05-24 13:22:17.826 2314-2619/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 注册请求 registerReqBean:RegisterReqBean{name='猫了个咪', phone='13333333333', pwd='123456'}
05-24 13:22:17.826 2314-2619/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 注册请求成功: sub Thread,name --> RxCachedThreadScheduler-1
05-24 13:22:17.827 2314-2619/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 发送注册请求
05-24 13:22:17.827 2314-2619/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 发送注册请求完成
05-24 13:22:17.830 2314-2620/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 注册响应 registerRespBean:RegisterRespBean{name='猫了个咪', pwd='123456', msg='恭喜您注册成功'}
05-24 13:22:22.833 2314-2620/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 注册响应成功: sub Thread,name --> RxNewThreadScheduler-1
05-24 13:22:22.835 2314-2622/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 登录请求 loginReqBean:LoginReqBean{name='猫了个咪 我要登陆', pwd='123456'}
05-24 13:22:22.835 2314-2622/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 登录请求成功: sub Thread,name --> RxCachedThreadScheduler-2
05-24 13:22:22.836 2314-2623/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: 登录响应 loginRespBean:LoginRespBean{name='猫了个咪 我要登陆', pwd='123456', msg='恭喜您登录成功'}
05-24 13:22:27.838 2314-2623/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity 登录响应成功: sub Thread,name --> RxNewThreadScheduler-2
05-24 13:22:27.838 2314-2314/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: onNext 登录成功，可以更新UI了。 loginRespBean:LoginRespBean{name='猫了个咪 我要登陆', pwd='123456', msg='恭喜您登录成功'}
05-24 13:22:27.838 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity : main Thread,name --> main
05-24 13:22:27.838 2314-2314/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: onComplete
复制代码
merge——多个异步任务执行完毕后在执行目标任务
等待多个任务完成后再执行目标任务，不保证顺序。
public void onBtnJavaRxjavaMergeClicked() {
/**
* 等待多个任务完成后再执行，不保证顺序
*/
Observable o1 = Observable.create((ObservableOnSubscribe<String>) e -> {
ThreadUtils.logCurrThreadName(TAG + " Observable1");
TimeUnit.SECONDS.sleep(5);
e.onNext("第一个Observable");
e.onComplete();
}).subscribeOn(Schedulers.newThread());
Observable o2 = Observable.create((ObservableOnSubscribe<String>) e -> {
ThreadUtils.logCurrThreadName(TAG + " Observable2");
TimeUnit.SECONDS.sleep(3);
e.onNext("第二个Observable");
e.onComplete();
}).subscribeOn(Schedulers.newThread());
Observable o3 = Observable.create((ObservableOnSubscribe<String>) e -> {
ThreadUtils.logCurrThreadName(TAG + " Observable3");
TimeUnit.SECONDS.sleep(1);
e.onNext("第三个Observable");
e.onComplete();
}).subscribeOn(Schedulers.newThread());
/**
* 三个任务都发送了onComplete事件后，订阅者的onComplete方法才会调用。
*/
Observable.merge(o1, o2, o3)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer() {
@Override
public void onSubscribe(Disposable d) {
LogUtils.e(TAG, "onSubscribe");
}
@Override
public void onNext(Object o) {
LogUtils.e(TAG, "onNext: " + o);
ThreadUtils.logCurrThreadName(TAG + " onNext");
}
@Override
public void onError(Throwable e) {
LogUtils.e(TAG, "onError");
}
@Override
public void onComplete() {
LogUtils.e(TAG, "onComplete");
}
});
}
复制代码
输出结果：
05-24 13:26:59.176 2314-2314/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: onSubscribe 05-24 13:26:59.179 2314-2644/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity Observable1: sub Thread,name --> RxNewThreadScheduler-3 05-24 13:26:59.181 2314-2645/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity Observable2: sub Thread,name --> RxNewThreadScheduler-4 05-24 13:26:59.181 2314-2646/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity Observable3: sub Thread,name --> RxNewThreadScheduler-5 05-24 13:27:00.183 2314-2314/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: onNext: 第三个Observable 05-24 13:27:00.183 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity onNext: main Thread,name --> main 05-24 13:27:02.183 2314-2314/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: onNext: 第二个Observable 05-24 13:27:02.184 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity onNext: main Thread,name --> main 05-24 13:27:04.180 2314-2314/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: onNext: 第一个Observable 05-24 13:27:04.181 2314-2314/com.tiny.demo.firstlinecode E/tiny_module: AsyncToSyncActivity onNext: main Thread,name --> main 05-24 13:27:04.181 2314-2314/com.tiny.demo.firstlinecode E/AsyncToSyncActivity: onComplete 复制代码
当三个Observable都发送了onComplete事件后，Observer的onComplete方法才会调用。
正文到此结束
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文章和留言都翻到11页了 没有OOM
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朋友，翻页到11页，及以后，会出现OOM，无法访问
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搞个gitee的项目
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版本号是多少，你可以下载哪个代码仓库，jdk选1.8 直接跑就行
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