安卓3.0之后的网络访问问题

在Activity中使用如下web请求

String url = "http://maps.google.com/maps/api/directions/xml?origin=22.592700,113.969100" +
    "&destination=23.046604,113.397510&sensor=false&mode=walking";

  HttpGet get = new HttpGet(url);
  String strResult = "";
  try {
   HttpParams httpParameters = new BasicHttpParams();
   HttpConnectionParams.setConnectionTimeout(httpParameters, 6000);
   HttpClient httpClient = new DefaultHttpClient(httpParameters);

   HttpResponse httpResponse = null;
   httpResponse = httpClient.execute(get);

   if (httpResponse.getStatusLine().getStatusCode() == 200){
    strResult = EntityUtils.toString(httpResponse.getEntity());
   }
  } catch (Exception e) {
   e.printStackTrace();
  }

发现请求总是无法得到，在浏览器中尝试发现请求语句没有问题

DDMS报错为：android.os.NetworkOnMainThreadException

经查询发现原来Android3.0以上对网络请求做了更严格的限制，若要继续按照以前的方式继续使用网络请求，须做一些特别的声明。

 

解决办法：

在Activiey的OnCreate方法中添加以下代码

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());