我将从相当长的任务中解决这个问题。我想要做的是我正在对JSON url进行HTTPRESPONSE调用，以解析包含文本和图像的数据。但是当互联网连接很弱时，它只是继续加载进度对话框并最终强制关闭。我该如何应对呢？下面是我的Asynctask和HTTP加载代码片段
MovieFragment.java
private class DownloadJSON extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(getActivity());
// Set progressdialog title
mProgressDialog.setTitle("Loading Movies . . ");
// Set progressdialog message
mProgressDialog.setMessage("Loading...");
mProgressDialog.setCancelable(false);
mProgressDialog.setCanceledOnTouchOutside(false);
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params) {
// Create an array
arraylist = new ArrayList<HashMap<String, String>>();
languagelist = new ArrayList<String>();
// Retrieve JSON Objects from the given URL address
try {
jsonobject = JSONfunctions.getJSONfromURL("MY_WEBSITE/movie_schedule.json");
} catch (JSONException e1) {
Toast.makeText(getActivity(),"Error!",5000).show();
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (Exception e) {
Toast.makeText(getActivity(),"Error!",5000).show();
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
jsonarray = jsonobject.getJSONArray("Movie_list");
languagelist.add("Select Language");
languagelist.add("All");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
HashMap<String, String> lang = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
// Retrive JSON Objects
map.put("releaseYear", jsonobject.getString("releaseYear"));
map.put("title", jsonobject.getString("title"));
map.put("rating", jsonobject.getString("rating"));
map.put("description", jsonobject.getString("description"));
map.put("image", jsonobject.getString("image"));
map.put("date", jsonobject.getString("date"));
map.put("venue", jsonobject.getString("venue"));
map.put("time", jsonobject.getString("time"));
map.put("trailer", jsonobject.getString("trailer"));
map.put("language", jsonobject.getString("language"));
map.put("trailer", jsonobject.getString("trailer"));
map.put("type", jsonobject.getString("type"));
// Set the JSON Objects into the array
arraylist.add(map);
if(!languagelist.contains(jsonobject.getString("language"))) {
languagelist.add(jsonobject.getString("language"));
}
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
Toast.makeText(getActivity(),"Error!",5000).show();
}
return null;
}
@Override
protected void onPostExecute(Void args) {
// Locate the listview in fragment_event.xml
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(getActivity(), R.layout.dropdown_item, languagelist);
ArrayAdapter<String> dataAdapter1 = new ArrayAdapter<String>(getActivity(), R.layout.dropdown_item, date);
dataAdapter.setDropDownViewResource(R.layout.selected_item);
dataAdapter.notifyDataSetChanged();
s2.setAdapter(dataAdapter);
s1.setAdapter(dataAdapter1);
listview = (ListView) getView().findViewById(R.id.listview);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(getActivity(), arraylist);
// Set the adapter to the ListView
listview.setAdapter(adapter);
// Close the progressdialog
mProgressDialog.dismiss();
}
@Override
public void onCancelled() {
super.onCancelled();
mProgressDialog.dismiss();
Toast toast = Toast.makeText(getActivity(), "Error connecting to Server", Toast.LENGTH_LONG);
toast.setGravity(Gravity.TOP, 25, 400);
toast.show();
}
}
JSONfunctions.java
public class JSONfunctions {
public static JSONObject getJSONfromURL(String url) throws Exception {
InputStream is = null;
String result = "";
JSONObject jArray = null;
// Download JSON data from URL
try {
//DefaultHttpClient postClient = new DefaultHttpClient(httpParams);
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
// Convert response to string
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();
result = sb.toString();
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
try {
jArray = new JSONObject(result);
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
return jArray;
}
}
答案 0 :(得分：2)
我知道这个问题已发布一年了。但我遇到了同样的问题，并认为我应该留下一些东西。
在讨论here时，我已经结束使用以下内容。
public boolean hasInternetAccess(Context context) {
if (isNetworkAvailable(context)) {
try {
HttpURLConnection urlc = (HttpURLConnection)
(new URL("http://clients3.google.com/generate_204")
.openConnection());
urlc.setRequestProperty("User-Agent", "Android");
urlc.setRequestProperty("Connection", "close");
urlc.setConnectTimeout(1500);
urlc.connect();
return (urlc.getResponseCode() == 204 &&
urlc.getContentLength() == 0);
} catch (IOException e) {
Log.e("LOGGER", "Error checking internet connection", e);
}
} else {
Log.d("LOGGER", "No network available!");
}
return false;
}
使用以下方法检查互联网连接：
private static boolean isNetworkAvailable(Context context) {
ConnectivityManager connectivityManager
= (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
return activeNetworkInfo != null;
}
应该从AsyncTask或与UI线程不同的线程调用该方法。
在AsyncTask中可能如下所示：
protected String doInBackground(String... args) {
isConnected = hasInternetAccess(mContext);
return null;
}