Android 中三种使用线程的方法

16lz 2021-01-23

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

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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：

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new MyThread().start();

2.创建一个Runnable对象

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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：

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// 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

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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();
}
}

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