Question

我想从远程数据库中获取一些数据，并且在我的活动的AsyncTask子类中有一些网络，但是当我尝试加载我的程序时，它显示了NetworkOnMainThreadException。

这是我的代码：

public class MyMapLocationActivity extends MapActivity {

private MapView mapView;
private static String url_product_details = "http://myurl.com/readfromdb";
private static final String TAG_SUCCESS = "success";
private static final String TAG_LATITUDE = "latitude";
private static final String TAG_LONGITUDE = "longitude";
private static final String TAG_POINT = "point";

    JSONParser jsonParser = new JSONParser();

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main); 

    mapView = (MapView) findViewById(R.id.mapview);
    mapView.setBuiltInZoomControls(true);

    ReadLocations Read = new ReadLocations();
    Read.execute();
}

//And my networking AsyncTask:

class ReadLocations extends AsyncTask<String, String, String> {


    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }


   @Override
    protected String doInBackground(String... args) {
       Log.d("debug", "START DOINBACKGROUND");


       runOnUiThread(new Runnable() {
           public void run() {
               // Check for success tag
               int success;
               try {

                   // Building Parameters
                   List<NameValuePair> params = new ArrayList<NameValuePair>();
                   params.add(new BasicNameValuePair("id", "16"));

                   // getting product details by making HTTP request
                   // Note that product details url will use GET request
                   Log.d("debug", "before http request");

                   JSONObject json = jsonParser.makeHttpRequest(
                           url_product_details, "POST", params);
                   Log.d("debug", "after http request");

                   // json success tag
                   success = json.getInt(TAG_SUCCESS);

                   if (success == 1) {
                       // successfully received product details
                       JSONArray productObj = json
                               .getJSONArray(TAG_POINT); // JSON Array

                       // get first product object from JSON Array
                       JSONObject product = productObj.getJSONObject(0);

                   }else{
                       // product with pid not found
                   }
               } catch (JSONException e) {
                   e.printStackTrace();
               }
           }
       });

        return null; 
    }



  @Override
    protected void onPostExecute(String text) {
        // dismiss the dialog once done
   Log.d("debug", "ONPOSTEXECUTE");

    }

LogCat显示“在http请求之前”，但没有显示我的“在http请求之后”检查。

有什么问题？

Answer 1

您的网络代码位于应用程序的 MainUiThread 不在工作线程中...

删除

runOnUiThread(new Runnable() {
           public void run() {

来自doInBackground()

并将 WebRequest 代码仅放在AsyncTask的doInBackground()中。

<强>更新

实际上doInBackground()的 AsyncTask 实现是错误的。由于doInBackground()在工作线程中运行以进行冗长且与网络相关的操作。并且您正尝试使用runOnUiThread()来运行 MainUiThread ，而不是规则。如果您想要进行任何与UI相关的工作，请在onPostExecute() onPreExecute()中进行和其他ASyncTask方法。

Answer 2

快来看看这段代码：

@Override
protected String doInBackground(String... args) {
   Log.d("debug", "START DOINBACKGROUND");

           // Check for success tag
           int success;
           try {

               // Building Parameters
               List<NameValuePair> params = new ArrayList<NameValuePair>();
               params.add(new BasicNameValuePair("id", "16"));

               // getting product details by making HTTP request
               // Note that product details url will use GET request
               Log.d("debug", "before http request");

               JSONObject json = jsonParser.makeHttpRequest(
                       url_product_details, "POST", params);
               Log.d("debug", "after http request");

               // json success tag
               success = json.getInt(TAG_SUCCESS);

               if (success == 1) {
                   // successfully received product details
                   JSONArray productObj = json
                           .getJSONArray(TAG_POINT); // JSON Array

                   // get first product object from JSON Array
                   JSONObject product = productObj.getJSONObject(0);

               }else{
                   // product with pid not found
               }
           } catch (JSONException e) {
               e.printStackTrace();
           }

           return null; 
}

您的代码的问题在于您只在主UI线程上运行网络功能，使用：runOnUiThread(new Runnable() {...}。

doInBackground（）自动在单独的后台非ui线程上运行，您无需显式创建线程。

Answer 3

那是因为您在UI线程上运行网络代码...您的doInBackground在UI线程上显式运行网络代码。

网络是在AsyncTask和NetworkOnMainThreadException错误中

3 个答案: