android.os.NetworkOnMainThreadException与android 4.2
这个问题在这里已经有了答案：
在setContentView（R.layout.activity_main）之后将代码写入您的MainActivity文件中;
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
并将import语句导入到您的java文件中。
import android.os.StrictMode;
这是正确的方法：
public class JSONParser extends AsyncTask <String, Void, String>{
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
@Override
protected String doInBackground(String... params) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpGet httpPost = new HttpGet(url);
HttpResponse getResponse = httpClient.execute(httpPost);
final int statusCode = getResponse.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK) {
Log.w(getClass().getSimpleName(),
"Error " + statusCode + " for URL " + url);
return null;
}
HttpEntity getResponseEntity = getResponse.getEntity();
//HttpResponse httpResponse = httpClient.execute(httpPost);
//HttpEntity httpEntity = httpResponse.getEntity();
is = getResponseEntity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
Log.d("IO", e.getMessage().toString());
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
protected void onPostExecute(String page)
{
//onPostExecute
}
}
调用它（从主）：
mJSONParser = new JSONParser();
mJSONParser.execute();
请确保您不会在UI线程上执行任何网络访问，而是在异步任务中执行此操作
之所以你的应用程序崩溃在Android 3.0及以上版本，但在Android 2.x上正常工作，是因为HoneyComb对UI线程的滥用要严格得多。 例如，当运行HoneyComb或更高版本的Android设备检测到UI线程上的网络访问时，将引发NetworkOnMainThreadException。
看到这个
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