android thread实例
本文转载自http://blog.csdn.net/z496844387/article/details/6412507
创建线程的方法：
官网的说法：
There are basically two main ways of having a Thread execute application code. One is providing a new class that extends Thread and overriding its run() method. The other is providing a new Thread instance with a Runnable object during its creation. In both cases, the start() method must be called to actually execute the new Thread.
扩展Thread的示例代码：
public class CommonTestActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); new Thread(){ public void run(){ System.out.println("Thread is running."); } }.start(); }} 使用Runnable的示例代码：
public class CommonTestActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); new Thread(r).start(); } Runnable r = new Runnable() { @Override public void run() { System.out.println("Runnable running "); } }; } 经典实例：
多个窗口一起卖火车票问题。假设有3个窗口同时售票，共有10张火车票代售。启动三个线程卖共同的10张票。1. 使用下面的代码试图实现功能
public class CommonTestActivity extends Activity{private Button mybutton;private TextView mytext;protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);mybutton = (Button) findViewById(R.id.button);mytext = (TextView) findViewById(R.id.text); mybutton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stub MyThread myThread1 = new MyThread(); MyThread myThread2= new MyThread(); MyThread myThread3 = new MyThread(); myThread1.start(); myThread2.start(); myThread3.start(); } }); }class MyThread extends Thread {private int tickets = 10;public void run() {for (int i = 0; i < 200; i++) {if (tickets > 0) {System.out.println(Thread.currentThread().getName() + "==>"+ tickets--);}}}}}输出如下
11-17 22:45:01.234: I/System.out(672): Thread-10==>1011-17 22:45:01.234: I/System.out(672): Thread-10==>911-17 22:45:01.234: I/System.out(672): Thread-10==>811-17 22:45:01.234: I/System.out(672): Thread-10==>711-17 22:45:01.234: I/System.out(672): Thread-10==>611-17 22:45:01.234: I/System.out(672): Thread-10==>511-17 22:45:01.234: I/System.out(672): Thread-10==>411-17 22:45:01.234: I/System.out(672): Thread-10==>311-17 22:45:01.244: I/System.out(672): Thread-10==>211-17 22:45:01.244: I/System.out(672): Thread-10==>111-17 22:45:01.244: I/System.out(672): Thread-11==>1011-17 22:45:01.244: I/System.out(672): Thread-11==>911-17 22:45:01.244: I/System.out(672): Thread-11==>811-17 22:45:01.244: I/System.out(672): Thread-11==>711-17 22:45:01.244: I/System.out(672): Thread-11==>611-17 22:45:01.254: I/System.out(672): Thread-11==>511-17 22:45:01.254: I/System.out(672): Thread-11==>411-17 22:45:01.254: I/System.out(672): Thread-11==>311-17 22:45:01.254: I/System.out(672): Thread-11==>211-17 22:45:01.254: I/System.out(672): Thread-11==>111-17 22:45:01.264: I/System.out(672): Thread-12==>1011-17 22:45:01.264: I/System.out(672): Thread-12==>911-17 22:45:01.264: I/System.out(672): Thread-12==>811-17 22:45:01.264: I/System.out(672): Thread-12==>711-17 22:45:01.264: I/System.out(672): Thread-12==>611-17 22:45:01.274: I/System.out(672): Thread-12==>511-17 22:45:01.274: I/System.out(672): Thread-12==>411-17 22:45:01.274: I/System.out(672): Thread-12==>311-17 22:45:01.274: I/System.out(672): Thread-12==>211-17 22:45:01.274: I/System.out(672): Thread-12==>1
分析：
运行结果与预期不一致，分析可以看出3个线程各种卖各自的10张票，而不是共同的10张票。
在上面的代码中，只能保证：每个线程都将启动，每个线程都将运行直到完成。一系列线程以某种顺序启动并不意味着将按该顺序执行。对于任何一组启动的线程来说，调度程序不能保证其执行次序，持续时间也无法保证。
2. 只修改onClick里面的代码，并分析运行结果
public void onClick(View v) { //实例化线程对象 MyThread myThread = new MyThread(); new Thread(myThread, "窗口1").start(); new Thread(myThread, "窗口2").start(); new Thread(myThread, "窗口3").start(); } 输出如下
11-17 22:49:17.314: I/System.out(708): 窗口1==>1011-17 22:49:17.314: I/System.out(708): 窗口1==>911-17 22:49:17.314: I/System.out(708): 窗口1==>811-17 22:49:17.314: I/System.out(708): 窗口1==>711-17 22:49:17.314: I/System.out(708): 窗口1==>611-17 22:49:17.324: I/System.out(708): 窗口1==>511-17 22:49:17.324: I/System.out(708): 窗口1==>411-17 22:49:17.324: I/System.out(708): 窗口1==>311-17 22:49:17.324: I/System.out(708): 窗口1==>211-17 22:49:17.324: I/System.out(708): 窗口1==>1
分析：
我认为此处3个窗口已经是在卖共同的10张票了，只不过由于没有进行线程同步才造成数据混乱。
线程的同步是为了防止多个线程访问一个数据对象时，对数据造成的破坏。
3. 下面继续修改代码，验证我刚得猜测。
public void onClick(View v) {
//实例化线程对象
MyThread myThread = new MyThread();
new Thread(myThread, "窗口1").start();
new Thread(myThread, "窗口2").start();
new Thread(myThread, "窗口3").start();
}
class MyThread extends Thread{
private int tickets = 10;
public void run() {
for(int i = 0; i< 200; i++){
sell();
}
}
public synchronized void sell(){
if(tickets > 0)
{
System.out.println(Thread.currentThread().getName() + "==>" + tickets--);
}
}
}
运行结果：
05-11 08:53:31.986: INFO/System.out(7116): 窗口1==>10
05-11 08:53:32.006: INFO/System.out(7116): 窗口1==>9
05-11 08:53:32.016: INFO/System.out(7116): 窗口1==>8
05-11 08:53:32.066: INFO/System.out(7116): 窗口1==>7
05-11 08:53:32.086: INFO/System.out(7116): 窗口1==>6
05-11 08:53:32.106: INFO/System.out(7116): 窗口1==>5
05-11 08:53:32.106: INFO/System.out(7116): 窗口1==>4
05-11 08:53:32.126: INFO/System.out(7116): 窗口1==>3
05-11 08:53:32.146: INFO/System.out(7116): 窗口1==>2
05-11 08:53:32.146: INFO/System.out(7116): 窗口1==>1
分析：
一个对象只有一个锁。所以，如果一个线程获得该锁，就没有其他线程可以获得锁，直到第一个线程释放（或返回）锁。这也意味着任何其他线程都不能进入该对象上的synchronized方法或代码块，直到该锁被释放。
释放锁是指持锁线程退出了synchronized同步方法或代码块。
上述代码没有Thread.sleep(10)，换句话说线程一一直处于运行状态，没有释放锁，没有给其他线程运行的机会。
4. 根据上述分析，修改代码如下：
public void onClick(View v) {
//实例化线程对象
MyThread myThread = new MyThread();
new Thread(myThread, "窗口1").start();
new Thread(myThread, "窗口2").start();
new Thread(myThread, "窗口3").start();
}
class MyThread extends Thread{
private int tickets = 10;
public void run() {
for(int i = 0; i< 200; i++){
try{
sell();
Thread.sleep(10);
}catch (InterruptedException e) {
System.out.println("我被打断了" + Thread.currentThread().getName());
e.printStackTrace();
}
}
}
public synchronized void sell(){
if(tickets > 0)
{
System.out.println(Thread.currentThread().getName() + "==>" + tickets--);
}
}
}
运行结果：
05-11 09:17:07.496: INFO/System.out(7898): 窗口1==>10
05-11 09:17:07.528: INFO/System.out(7898): 窗口1==>9
05-11 09:17:07.546: INFO/System.out(7898): 窗口1==>8
05-11 09:17:07.577: INFO/System.out(7898): 窗口1==>7
05-11 09:17:07.626: INFO/System.out(7898): 窗口3==>6
05-11 09:17:07.626: INFO/System.out(7898): 窗口2==>5
05-11 09:17:07.636: INFO/System.out(7898): 窗口1==>4
05-11 09:17:07.646: INFO/System.out(7898): 窗口2==>3
05-11 09:17:07.646: INFO/System.out(7898): 窗口1==>2
05-11 09:17:07.656: INFO/System.out(7898): 窗口3==>1
分析：
此次得出的正是我们想要的结果！O(∩_∩)O~
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