Android Thread interrupt 中断JAVA线程(转)

转载自：http://hi.baidu.com/%E3%C6%CE%C4%B7%E5/blog/item/d8959f1b6716c8168618bfbb.html

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？

 

 1 class ATask implements Runnable{    
 2    
 3     private double d = 0.0;    
 4         
 5     public void run() {    
 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!");    
 9                 
10             for (int i = 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 }

 

 

 

 1 public class InterruptTaskTest {    
 2         
 3     public static void main(String[] args) throws Exception{    
 4         //将任务交给一个线程执行    
 5          Thread t = new Thread(new ATask());    
 6          t.start();    
 7             
 8         //运行一断时间中断线程    
 9          Thread.sleep(100);    
10          System.out.println("****************************");    
11          System.out.println("Interrupted Thread!");    
12          System.out.println("****************************");    
13          t.interrupt();    
14      }    
15 }    
16 

 

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:

......
I am running!
I am running!
I am running!
I am running!
****************************
Interrupted Thread!
****************************
I am running!
I am running!
I am running!
I am running!
I am running!
....

 

 

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)

 

 

 1 class ATask implements Runnable{    
 2    
 3     private double d = 0.0;    
 4         
 5     public void run() {    
 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!");    
10                     
11                 for (int i = 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 }   
22 

程序运行结果如下:

I am running!
I am running!
****************************
Interrupted Thread!
****************************
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．

 

 1 class ATask implements Runnable{    
 2    
 3     private double d = 0.0;    
 4         
 5     public void run() {    
 6             
 7         //检查程序是否发生中断    
 8         while (!Thread.interrupted()) {    
 9              System.out.println("I am running!");    
10    
11             for (int i = 0; i < 900000; i++) {    
12                  d = d + (Math.PI + Math.E) / d;    
13              }    
14          }    
15    
16          System.out.println("ATask.run() interrupted!");    
17      }    
18 }   
19 

 

 

程序运行结果如下：

I am running!
I am running!
I am running!
I am running!
I am running!
I am running!
I am running!
****************************
Interrupted Thread!
****************************
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:

 

 1 class ATask implements Runnable{    
 2    
 3     private double d = 0.0;    
 4         
 5     public void run() {    
 6             
 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 (int i = 0; i < 900000; i++) {    
16                  d = d + (Math.PI + Math.E) / d;    
17              }    
18          }    
19             
20          } catch (InterruptedException e) {    
21              System.out.println("Exiting by Exception");    
22          }    
23             
24          System.out.println("ATask.run() interrupted!");    
25      }    
26 }   
27 

 

 

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：

I am running!
Calculating
I am running!
Calculating
I am running!
Calculating
I am running!
****************************
Interrupted Thread!
****************************
Exiting by Exception
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：

I am running!
Calculating
I am running!
Calculating
I am running!
Calculating
****************************
Interrupted Thread!
****************************
ATask.run() interrupted!