android.os.NetworkOnMainThreadException

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();
		}
    };