在android 2.3上设计的下载程序，在android 4.0上运行时报android.os.NetworkOnMainThreadException异常，原来在4.0中，访问网络不能在主程序中进行，有两个方法可以解决，一个是在主程序中增加：

 

// 详见StrictMode文档
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
        .detectDiskReads()
        .detectDiskWrites()
        .detectNetwork()   // or .detectAll() for all detectable problems
        .penaltyLog()
        .build());
StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
        .detectLeakedSqlLiteObjects()
        .detectLeakedClosableObjects()
        .penaltyLog()
        .penaltyDeath()
        .build());

// 详见StrictMode文档        StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()                .detectDiskReads()                .detectDiskWrites()                .detectNetwork()   // or .detectAll() for all detectable problems                .penaltyLog()                .build());        StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()                .detectLeakedSqlLiteObjects()                .detectLeakedClosableObjects()                .penaltyLog()                .penaltyDeath()                .build());

另一种是启动线程执行下载任务：

       public void onCreate(Bundle savedInstanceState) {

      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
      // 启动线程执行下载任务
      new Thread(downloadRun).start();
  }

  /**
   * 下载线程
   */
  Runnable downloadRun = new Runnable(){

@Override
publicvoid run() {
    // TODO Auto-generated method stub
    updateListView();
}
  };

super.onCreate(savedInstanceState);        setContentView(R.layout.main);        // 启动线程执行下载任务        new Thread(downloadRun).start();    }        /**     * 下载线程     */    Runnable downloadRun = new Runnable(){		@Override		public void run() {			// TODO Auto-generated method stub			updateListView();		}    };