使用线程创建的三种方式实现j2me联网功能

By | 2009年8月14日

在j2me联网时,在eclipse控制台下有一个警告:“若要避免潜在的死锁,应该在commandAction()处理程序之外的其他线程中执行可能会阻塞的,操作(如网络连接)。
为了避免潜在的死锁,我们经常把把联网的代码部分写到一个线程中去执行。
而实际应用中,网络连接的事务也都是使用一个单独的线程进行的。

线程的创建可以使用Runnable接口来实现,也可以使用Thread类实现,还可以以匿名内部类的方式创建。在本文中,分别用这三种方式给出了j2me联网的例子。
代码均测试通过。可以直接使用。
1.通过继承Thread类创建
  import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class OpenConn implements Runnable {
 private HttpURLConnection conn;
 private URL url;
 // Thread thread1;
 public OpenConn(String url) throws MalformedURLException {
  this.url = new URL(url);
 }
 public void run() {
  try {
   conn = (HttpURLConnection) url.openConnection();
  } catch (IOException e) {
   e.printStackTrace();
   url = null;
  }
 }
 public HttpURLConnection getConn() {
  return conn;
 }
 public static void main(String[] args) throws Exception {
  // 创建Runnable类
  OpenConn openConn = new OpenConn(“http://www.google.com“);
  // 创建线程
  Thread thread = new Thread(openConn);
  // openConn.thread1=thread;
  thread.start();
  thread.join(10000);// wait 10 seconds
  HttpURLConnection c = openConn.getConn();
  if (c != null) {
   System.out.println(“连接网络成功…”);
   BufferedReader r = new BufferedReader(new InputStreamReader(c
     .getInputStream()));
   String s = r.readLine();
   while (s != null) {
    System.out.println(s);
    s = r.readLine();
   }
  } else {
   System.out.println(“超时错误,连接网络失败…”);
  }
 }

2.通过引用Runnable接口创建
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class OpenConn2 extends Thread {
 private HttpURLConnection conn;
 private URL url;
 public OpenConn2(String url) throws MalformedURLException {
  this.url = new URL(url);
 }
 public void run() {
  try {
   conn = (HttpURLConnection) url.openConnection();
  } catch (IOException e) {
   e.printStackTrace();
   url = null;
  }
 }
 public HttpURLConnection getConn() {
  return conn;
 }
 public static void main(String[] args) throws Exception {
  OpenConn2 openConn = new OpenConn2(“http://www.google.com“);
  openConn.start();
  openConn.join(10000);// wait 10 seconds
  HttpURLConnection c = openConn.getConn();
  if (c != null) {
   System.out.println(“连接网络成功…”);
   BufferedReader r = new BufferedReader(new InputStreamReader(c
     .getInputStream()));
   String s = r.readLine();
   while (s != null) {
    System.out.println(s);
    s = r.readLine();
   }
  } else {
   System.out.println(“超时错误,连接网络失败…”);
  }
 }
}
3.以匿名内部类的方式创建
即在一个方法中创建线程,当方法被调用时,线程即启动,如下:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class OpenConn3 {
 private HttpURLConnection conn;
 private URL url;
 
 public static void main(String[] args){
  try{
   OpenConn3 open3= new OpenConn3();
   open3.strartMyThread();
  }catch(Exception ex){
   System.out.println(ex.toString());
  }
 }
  public void strartMyThread() throws Exception{
   this.url =new URL(“http://www.google.com“);
         java.lang.Runnable runner=new Runnable(){
          public void run(){
           try {
            conn = (HttpURLConnection) url.openConnection();
           } catch (IOException e) {
            e.printStackTrace();
            url = null;
           }
          }
         };
         Thread openConn=new Thread(runner);
         openConn.start();
         openConn.join(10000);// wait 10 seconds
   if (conn != null) {
    System.out.println(“连接网络成功…”);
    BufferedReader r = new BufferedReader(new InputStreamReader(conn
      .getInputStream()));
    String s = r.readLine();
    while (s != null) {
     System.out.println(s);
     s = r.readLine();
    }
   } else {
    System.out.println(“超时错误,连接网络失败…”);
   }
  }
}

One thought on “使用线程创建的三种方式实现j2me联网功能

  1. Kinsta Post author

    这个方法在使用J2ME发送短信时也非常的适用,可以避免midlet加载Canvas或者Form时发生的主线程暂停或死锁现象!

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