我在stackOverflow中找到了与此主题相关的几个问题，但无法找到合适的答案。在我的应用程序中，我打算通过单独的线程进行网络通信。所以我使用asynctask.But甚至在使用asynctask之后我发现了networkOnMainThreadException.Here是我的代码：
private static final String CATEGORY_ALL_FETCHING_URL = "http://qpon.es/coupon/index.php/welcome/categories/all";
private static final String CATEGORY_IMAGE_URL = "http://qpon.es/images/coupons/";
private static final String TAG_CATEGORY_ID = "id";
private static final String TAG_CATEGORY_NAME = "name";
private static final String TAG_CATEGORY_IMAGE = "img";
private static final String TAG_CATEGORY_CREATE_DATE = "created";
private static final String CATEGORY_INTENT = "category";
private ProgressDialog downloadingStatusIndicator = null;
private ArrayList<Category> categoryList = null;
private CustomCategoryAdapter customAdapter = null;
private class CateoryListDataGenerator extends
AsyncTask<String, Void, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
downloadingStatusIndicator = new ProgressDialog(getActivity());
downloadingStatusIndicator.setTitle(R.string.categoryDownloadTitle);
downloadingStatusIndicator.setMessage("Retrieving Categories...");
downloadingStatusIndicator.show();
}
@Override
protected String doInBackground(String... params) {
// TODO Auto-generated method stub
String response = "";
try {
Log.d("BACK THREAD STARTS", "YES");
categoryList = new ArrayList<Category>();
response = JSONParser
.getRemoteResponse(CATEGORY_ALL_FETCHING_URL);
// Thread.sleep(2000);
} catch (Exception e) {
Log.d("BACKGROUD", e.getMessage());
}
return response;
}
@Override
protected void onPostExecute(String response) {
JSONArray categoriesJSON = null;
try {
categoriesJSON = new JSONArray(response);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
for (int i = 0; i < categoriesJSON.length(); i++) {
Log.d("LOOP BEGINS", "YES");
Category eachCategory = new Category();
JSONObject eachCategoryJSON = null;
try {
eachCategoryJSON = categoriesJSON.getJSONObject(i);
eachCategory.setCategoryName(eachCategoryJSON
.getString(TAG_CATEGORY_NAME));
eachCategory.setCategoryCreateDate(eachCategoryJSON
.getString(TAG_CATEGORY_CREATE_DATE));
eachCategory.setCategoryImagePath(CATEGORY_IMAGE_URL
+ eachCategoryJSON.getString(TAG_CATEGORY_IMAGE));
eachCategory.setCategoryID(eachCategoryJSON
.getInt(TAG_CATEGORY_ID));
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
categoryList.add(eachCategory);
Log.d("CATEGORY INSERTED", categoryList.toString());
}
Log.d("CATEGORY LIST", categoryList.toString());
if (categoryList != null || categoryList.size() > 0) {
customAdapter.notifyDataSetChanged();
for (int i = 0; i < categoryList.size(); i++) {
customAdapter.add(categoryList.get(i));
}
downloadingStatusIndicator.dismiss();
customAdapter.notifyDataSetChanged();
}
Toast.makeText(getActivity(), response, Toast.LENGTH_SHORT).show();
}
}
在JSONParder的setRemoteRenponse（）方法中：
boolean isURLFetched = false;
while(!isURLFetched){
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse execute = client.execute(httpGet);
content = execute.getEntity().getContent();
isURLFetched = true;
} catch (UnsupportedEncodingException e) {
Log.d("HERE", "ONE");
e.printStackTrace();
} catch (ClientProtocolException e) {
Log.d("HERE", "TWO");
e.printStackTrace();
} catch (IOException e) {
Log.d("HERE", "THREE");
e.printStackTrace();
}
}
try {
BufferedReader buffer = new BufferedReader(new InputStreamReader(
content));
String s = "";
while ((s = buffer.readLine()) != null) {
response += s;
}
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
return response;
最后创建了asynctask类对象＆amp;在片段的onActivityCreated（）方法中执行：
CateoryListDataGenerator dataGenerator = new CateoryListDataGenerator();
dataGenerator.execute(new String[] { CATEGORY_ALL_FETCHING_URL });
我在这里做错了吗？我也包含了INTERNET权限。目前，我已经更改了线程策略，以便在android 3.0或更高版本上运行此应用程序，但这不是解决方案。
这是logcat消息：
05-24 17:11:36.025: E/AndroidRuntime(708): FATAL EXCEPTION: main
05-24 17:11:36.025: E/AndroidRuntime(708): android.os.NetworkOnMainThreadException
05-24 17:11:36.025: E/AndroidRuntime(708): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
05-24 17:11:36.025: E/AndroidRuntime(708): at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
05-24 17:11:36.025: E/AndroidRuntime(708): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
05-24 17:11:36.025: E/AndroidRuntime(708): at java.net.InetAddress.getAllByName(InetAddress.java:214)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:341)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:315)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpEngine.connect(HttpEngine.java:310)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:289)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:239)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:273)
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:168)
05-24 17:11:36.025: E/AndroidRuntime(708): at com.example.couponapp.adapters.CustomCategoryAdapter.getScaledBitmapFromFile(CustomCategoryAdapter.java:83)
05-24 17:11:36.025: E/AndroidRuntime(708): at com.example.couponapp.adapters.CustomCategoryAdapter.getView(CustomCategoryAdapter.java:58)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.AbsListView.obtainView(AbsListView.java:2267)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.ListView.makeAndAddView(ListView.java:1769)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.ListView.fillDown(ListView.java:672)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.ListView.fillFromTop(ListView.java:733)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.ListView.layoutChildren(ListView.java:1608)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.AbsListView.onLayout(AbsListView.java:2102)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.View.layout(View.java:13754)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewGroup.layout(ViewGroup.java:4362)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:948)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.View.layout(View.java:13754)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewGroup.layout(ViewGroup.java:4362)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.View.layout(View.java:13754)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewGroup.layout(ViewGroup.java:4362)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.View.layout(View.java:13754)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewGroup.layout(ViewGroup.java:4362)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.View.layout(View.java:13754)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewGroup.layout(ViewGroup.java:4362)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.View.layout(View.java:13754)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewGroup.layout(ViewGroup.java:4362)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1866)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1687)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.Choreographer.doCallbacks(Choreographer.java:555)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.Choreographer.doFrame(Choreographer.java:525)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.os.Handler.handleCallback(Handler.java:615)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.os.Handler.dispatchMessage(Handler.java:92)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.os.Looper.loop(Looper.java:137)
05-24 17:11:36.025: E/AndroidRuntime(708): at android.app.ActivityThread.main(ActivityThread.java:4745)
05-24 17:11:36.025: E/AndroidRuntime(708): at java.lang.reflect.Method.invokeNative(Native Method)
05-24 17:11:36.025: E/AndroidRuntime(708): at java.lang.reflect.Method.invoke(Method.java:511)
05-24 17:11:36.025: E/AndroidRuntime(708): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
05-24 17:11:36.025: E/AndroidRuntime(708): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-24 17:11:36.025: E/AndroidRuntime(708): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：3)
看起来问题不在这里。从日志中，从适配器中，
05-24 17:11:36.025: E/AndroidRuntime(708): at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:168) 05-24 17:11:36.025: E/AndroidRuntime(708): at com.example.couponapp.adapters.CustomCategoryAdapter.getScaledBitmapFromFile(CustomCategoryAdapter.java:83) 05-24 17:11:36.025: E/AndroidRuntime(708): at com.example.couponapp.adapters.CustomCategoryAdapter.getView(CustomCategoryAdapter.java:58) 05-24 17:11:36.025: E/AndroidRuntime(708): at android.widget.AbsListView.obtainView(AbsListView.java:2267)
您可以看到getView（）方法正在尝试加载图像，而图像反过来正在发出网络请求以从某处获取图像。
检查你到底在做什么。
com.example.couponapp.adapters.CustomCategoryAdapter.getScaledBitmapFromFile(CustomCategoryAdapter.java:83) 05-24 17:11:36.025: E/AndroidRuntime(708): at com.example.couponapp.adapters.CustomCategoryAdapter.getView(CustomCategoryAdapter.java:58)
在方法getScaledBitmapFromFile中，我怀疑你正在进行网络调用，这是在UIThread上。
答案 1 :(得分：2)
请将onPostExecute中的代码放回doInBackground，并在onPostExecute中返回要放入适配器的结果。
您的问题必须是JSONArray，请参阅文档......它不是线程安全的;）。
答案 2 :(得分：0)
如果答案是Luserdroid还不清楚那么：
你应该把你的处理代码放在doInBackground里面，我错误地将处理代码放在由主线程执行的onPostExecute内，因此我遇到了同样的问题。