Android 中三种使用线程的方法

Android 中三种使用线程的方法

public class

Thread

extends Object
implements Runnable

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 aRunnable object during its creation（提供给它的实例化）. In both cases, the start() method must be called to actually execute the new Thread.

 

 

Thread()

Constructs a new   Thread  with no   Runnable  object and a newly generated name.

 

Thread(Runnable runnable)

Constructs a new   Thread  with a   Runnable  object and a newly generated name.

 在多线程编程这块，我们经常要使用Handler，Thread和Runnable这三个类，那么他们之间的关系你是否弄清楚了呢?

　　首先说明Android的CPU分配的最小单元是线程，Handler一般是在某个线程里创建的，因而Handler和Thread就是相互绑定的，一一对应。

　　而Runnable是一个接口，Thread是Runnable的子类。所以说，他俩都算一个进程。

　　HandlerThread顾名思义就是可以处理消息循环的线程，他是一个拥有Looper的线程，可以处理消息循环。

　　与其说Handler和一个线程绑定，不如说Handler是和Looper一一对应的。

Handler是沟通Activity 与Thread/runnable的桥梁。而Handler是运行在主UI线程中的，它与子线程可以通过Message对象来传递数据

1.通过继承Thread类，并改写run方法来实现一个线程

 

 public class MyThread extends Thread {

     //继承Thread类，并改写其run方法

     private final static String TAG = "My Thread ===> ";

     public void run(){
         Log.d(TAG, "run");
         for(int i = 0; i<100; i++)
         {
             Log.e(TAG, Thread.currentThread().getName() + "i =  " + i);
         }
     }
 }

 

启动线程：

 

 new MyThread().start();

 

2.创建一个Runnable对象

 

 public class MyRunnable implements Runnable{
     private final static String TAG = "My Runnable ===> ";

     @Override
     public void run() {
         // TODO Auto-generated method stub
         Log.d(TAG, "run");
         for(int i = 0; i<1000; i++)
         {
             Log.e(TAG, Thread.currentThread().getName() + "i =  " + i);
         }
     }
 }

 

启动线程：

 

 // providing a new Thread instance with a Runnable object during its creation.
         new Thread(new MyRunnable()).start();

 

3.通过Handler启动线程

 

 public class MainActivity extends Activity {

     private final static String TAG = "UOfly Android Thread ==>";
     private int count = 0;
     private Handler mHandler = new Handler();
     private Runnable mRunnable = new Runnable() {
         public void run() {
             Log.e(TAG, Thread.currentThread().getName() + " " + count);
             count++;
             setTitle("" + count);
             // 每3秒执行一次
             mHandler.postDelayed(mRunnable, 3000);  //给自己发送消息，自运行
         }
     };
     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);
         // 通过Handler启动线程
         mHandler.post(mRunnable);  //发送消息，启动线程运行
     }

       @Override
          protected void onDestroy() {
              //将线程销毁掉
              mHandler.removeCallbacks(mRunnable);
              super.onDestroy();
          }

 }