Android Thread interrupt 中断JAVA线程

假如我们有一个任务如下，交给一个Java线程来执行，如何才能保证调用interrupt()来中断它呢？

Java代码

1. classATaskimplementsRunnable{
3. privatedoubled =0.0;
5. publicvoidrun() {
6. //死循环执行打印"I am running!" 和做消耗时间的浮点计算
7. while(true) {
8. System.out.println("I am running!");
10. for(inti =0; i <900000; i++) {
11. d = d + (Math.PI + Math.E) / d;
12. }
13. //给线程调度器可以切换到其它进程的信号
14. Thread.yield();
15. }
16. }
17. }
19. publicclassInterruptTaskTest {
21. publicstaticvoidmain(String[] args)throwsException{
22. //将任务交给一个线程执行
23. Thread t =newThread(newATask());
24. t.start();
26. //运行一断时间中断线程
27. Thread.sleep(100);
28. System.out.println("****************************");
29. System.out.println("Interrupted Thread!");
30. System.out.println("****************************");
31. t.interrupt();
32. }
33. }

运行这个程序，我们发现调用interrupt()后，程序仍在运行，如果不强制结束，程序将一直运行下去，如下所示:

Java代码

1. ......
2. I am running!
3. I am running!
4. I am running!
5. I am running!
6. ****************************
7. Interrupted Thread!
8. ****************************
9. I am running!
10. I am running!
11. I am running!
12. I am running!
13. I am running!
14. ....

虽然中断发生了，但线程仍然在进行，离开线程有两种常用的方法：
抛出InterruptedException和用Thread.interrupted()检查是否发生中断,下面分别看一下这两种方法：
1.在阻塞操作时如Thread.sleep()时被中断会抛出InterruptedException(注意，进行不能中断的IO操作而阻塞和要获得对象的锁调用对象的synchronized方法而阻塞时不会抛出InterruptedException)

Java代码

1. classATaskimplementsRunnable{
3. privatedoubled =0.0;
5. publicvoidrun() {
6. //死循环执行打印"I am running!" 和做消耗时间的浮点计算
7. try{
8. while(true) {
9. System.out.println("I am running!");
11. for(inti =0; i <900000; i++) {
12. d = d + (Math.PI + Math.E) / d;
13. }
14. //休眠一断时间,中断时会抛出InterruptedException
15. Thread.sleep(50);
16. }
17. }catch(InterruptedException e) {
18. System.out.println("ATask.run() interrupted!");
19. }
20. }
21. }

程序运行结果如下:

Java代码

1. I am running!
2. I am running!
3. ****************************
4. Interrupted Thread!
5. ****************************
6. ATask.run() interrupted!

可以看到中断任务时让任务抛出InterruptedException来离开任务．

2.Thread.interrupted()检查是否发生中断.Thread.interrupted()能告诉你线程是否发生中断,并将清除中断状态标记，所以程序不会两次通知你线程发生了中断．

Java代码

1. classATaskimplementsRunnable{
3. privatedoubled =0.0;
5. publicvoidrun() {
7. //检查程序是否发生中断
8. while(!Thread.interrupted()) {
9. System.out.println("I am running!");
11. for(inti =0; i <900000; i++) {
12. d = d + (Math.PI + Math.E) / d;
13. }
14. }
16. System.out.println("ATask.run() interrupted!");
17. }
18. }

程序运行结果如下：

Java代码

1. I am running!
2. I am running!
3. I am running!
4. I am running!
5. I am running!
6. I am running!
7. I am running!
8. ****************************
9. Interrupted Thread!
10. ****************************
11. ATask.run() interrupted!

我们可结合使用两种方法来达到可以通过interrupt()中断线程.请看下面例子:

Java代码

1. classATaskimplementsRunnable{
3. privatedoubled =0.0;
5. publicvoidrun() {
7. try{
8. //检查程序是否发生中断
9. while(!Thread.interrupted()) {
10. System.out.println("I am running!");
11. //point1 before sleep
12. Thread.sleep(20);
13. //point2 after sleep
14. System.out.println("Calculating");
15. for(inti =0; i <900000; i++) {
16. d = d + (Math.PI + Math.E) / d;
17. }
18. }
20. }catch(InterruptedException e) {
21. System.out.println("Exiting by Exception");
22. }
24. System.out.println("ATask.run() interrupted!");
25. }
26. }

在point1之前处point2之后发生中断会产生两种不同的结果，可以通过修改InterruptTaskTest main()里的Thread.sleep()的时间来达到在point1之前产生中断或在point2之后产生中断.
如果在point1之前发生中断，程序会在调用Thread.sleep()时抛出InterruptedException从而结束线程．这和在Thread.sleep()时被中断是一样的效果.程序运行结果可能如下：

Java代码

1. I am running!
2. Calculating
3. I am running!
4. Calculating
5. I am running!
6. Calculating
7. I am running!
8. ****************************
9. Interrupted Thread!
10. ****************************
11. Exiting by Exception
12. ATask.run() interrupted!

如果在point2之后发生中断，线程会继续执行到下一次while判断中断状态时．程序运行结果可能如下：

Java代码

1. I am running!
2. Calculating
3. I am running!
4. Calculating
5. I am running!
6. Calculating
7. ****************************
8. Interrupted Thread!
9. ****************************
10. ATask.run() interrupted!