我在清单文件中获得了互联网权限。我的移动网络连接也正常。
/**
* Created by Yogesh on 5/07/2016.
*/
public class All_Item_Fragment extends android.support.v4.app.ListFragment {
// Declare Variables
JSONArray jsonarray = null;
ListView list;
ListViewAdapter adapter;
ArrayList<HashMap<String, String>> itemlist;
static String NAME = "name";
static String DESCRIPTION = "Description";
static String PRICE = "price";
static String IMAGE = "image_path";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.all_item_layout, container, false);
itemlist = new ArrayList<HashMap<String, String>>();
new ReadJSON().execute();
list = (ListView) view.findViewById(android.R.id.list);
return view;
}
private class ReadJSON extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected Void doInBackground(Void... params) {
// Create an array
itemlist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
JSONObject jsonobject = JSONfunctions.getJSONfromURL("http://mahatiffin.com/web/selectallmenu.php");
try {
// Locate the array name in JSON
jsonarray = jsonobject.getJSONArray("AllMenu");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
// Retrive JSON Objects
map.put("name", jsonobject.getString("name"));
map.put("Description", jsonobject.getString("Description"));
map.put("price", jsonobject.getString("price"));
map.put("image_path", jsonobject.getString("image_path"));
// Set the JSON Objects into the array
itemlist.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void args) {
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(getActivity(), itemlist);
// Set the adapter to the ListView
list.setAdapter((ListAdapter) adapter);
}
}
}
public class JSONfunctions {
public static JSONObject getJSONfromURL(String url) {
InputStream is = null;
String result = "";
JSONObject jArray = null;
// Download JSON data from URL
try {
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;
}
}
在may片段页面中没有任何内容显示只显示空白页面..
05-18 17：43：11.730 27019-27019 / com.androidbelieve.MahaTiffin D / dalvikvm：VFY：将代码0x6f替换为0x0000 05-18 17：43：11.740 27019-27082 / com.androidbelieve.MahaTiffin E / log_tag：转换结果java.lang.NullPointerException时出错 05-18 17：43：11.740 27019-27082 / com.androidbelieve.MahaTiffin E / log_tag：解析数据时出错org.json.JSONException：字符0处的输入结束 05-18 17：43：11.770 27019-27082 / com.androidbelieve.MahaTiffin W / dalvikvm：threadid = 12：线程退出，未捕获异常（group = 0x40e11378） 05-18 17：43：11.770 27019-27082 / com.androidbelieve.MahaTiffin E / AndroidRuntime：FATAL EXCEPTION：AsyncTask＃1 java.lang.RuntimeException：执行doInBackground（）时发生错误 在android.os.AsyncTask $ 3.done（AsyncTask.java:299） at java.util.concurrent.FutureTask $ Sync.innerSetException（FutureTask.java:273） at java.util.concurrent.FutureTask.setException（FutureTask.java:124） at java.util.concurrent.FutureTask $ Sync.innerRun（FutureTask.java:307） at java.util.concurrent.FutureTas ...（FutureTask.java:137） 在android.os.AsyncTask $ SerialExecutor $ 1.run（AsyncTask.java:230） 在java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1076） at java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:569） 在java.lang.Thread.run（Thread.java:856） 引起：java.lang.NullPointerException 在com.androidbelieve.MahaTiffin.All_Item_Fragment $ ReadJSON.doInBackground（All_Item_Fragment.java:58） 在com.androidbelieve.MahaTiffin.All_Item_Fragment $ ReadJSON.doInBackground（All_Item_Fragment.java:43） 在android.os.AsyncTask $ 2.call（AsyncTask.java:287） at java.util.concurrent.FutureTask $ Sync.innerRun（FutureTask.java:305） at java.util.concurrent.FutureTas ...（FutureTask.java:137） 在android.os.AsyncTask $ SerialExecutor $ 1.run（AsyncTask.java:230） 在java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1076） at java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:569） 在java.lang.Thread.run（Thread.java:856） 05-18 17：43：12.420 27019-27019 / com.androidbelieve.MahaTiffin W / FragmentManager：moveToState：Veg_Item_Fragment的片段状态{415d7030＃1 id = 0x7f0c00a0 android：switcher：2131493024：1}未内联更新;预期状态3发现2 05-18 17：43：12.530 27019-27104 / com.androidbelieve.MahaTiffin E / log_tag：http连接错误java.net.UnknownHostException：无法解析主机＆＃34; mahatiffin.com＆＃34;：没有与之关联的地址主机名 05-18 17：43：12.540 27019-27104 / com.androidbelieve.MahaTiffin E / log_tag：转换结果java.lang.NullPointerException时出错 05-18 17：43：12.540 27019-27104 / com.androidbelieve.MahaTiffin E / log_tag：解析数据时出错org.json.JSONException：字符0处的输入结束 05-18 17：43：12.570 27019-27104 / com.androidbelieve.MahaTiffin W / dalvikvm：threadid = 14：线程退出时未捕获异常（group = 0x40e11378） 05-18 17：43：12.570 27019-27104 / com.androidbelieve.MahaTiffin I / Process：发送信号。 PID：27019 SIG：9
我该如何解决这个问题..
答案 0 :(得分：5)
原因：当您无法解析您提供的网址的DNS记录时，通常会触发UnknownHostException。该操作有一个合理的超时，但如果您的Wi-Fi连接较弱或设备上没有足够的信号，则在发送请求和接收响应之间可能会中断通信，因此您的设备没有收到回复，因此它认为这是DNS超时。
长话短说，有两个主要的例外原因：
解决方案：请求之前检查互联网的可用性
public static boolean isInternetOn(Context context) {
if (isMobileOrWifiConnectivityAvailable(context)) {
try {
HttpURLConnection urlc = (HttpURLConnection) (new URL("http://www.google.com").openConnection());
urlc.setRequestProperty("User-Agent", "Test");
urlc.setRequestProperty("Connection", "close");
urlc.setConnectTimeout(1500);
urlc.connect();
return (urlc.getResponseCode() == 200);
} catch (Exception e) {
DebugLog.console("Couldn't check internet connection Exception is : " + e);
}
} else {
DebugLog.console("Internet not available!");
}
return false;
}
public static boolean isMobileOrWifiConnectivityAvailable(Context ctx) {
boolean haveConnectedWifi = false;
boolean haveConnectedMobile = false;
try {
ConnectivityManager cm = (ConnectivityManager) ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo[] netInfo = cm.getAllNetworkInfo();
for (NetworkInfo ni : netInfo) {
if (ni.getTypeName().equalsIgnoreCase("WIFI"))
if (ni.isConnected()) {
haveConnectedWifi = true;
}
if (ni.getTypeName().equalsIgnoreCase("MOBILE"))
if (ni.isConnected()) {
haveConnectedMobile = true;
}
}
} catch (Exception e) {
DebugLog.console("[ConnectionVerifier] inside isInternetOn() Exception is : " + e.toString());
}
return haveConnectedWifi || haveConnectedMobile;
}
答案 1 :(得分：0)
connection successful
{
"AllMenu": [{
"0": "3",
"menu_id": "3",
"1": "Aloo Parathas",
"name": "Aloo Parathas",
"2": "170",
"price": "170",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/1.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/1.jpg",
"5": "Regular-menu",
"menu_cat": "Regular-menu",
"6": "1",
"type_id": "1"
}, {
"0": "7",
"menu_id": "7",
"1": "ZzaxZxszsc",
"name": "ZzaxZxszsc",
"2": "343",
"price": "343",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/2.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/2.jpg",
"5": "Regular-menu",
"menu_cat": "Regular-menu",
"6": "1",
"type_id": "1"
}, {
"0": "8",
"menu_id": "8",
"1": "sdcsdvsd",
"name": "sdcsdvsd",
"2": "435",
"price": "435",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/3.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/3.jpg",
"5": "Special-menu",
"menu_cat": "Special-menu",
"6": "2",
"type_id": "2"
}, {
"0": "9",
"menu_id": "9",
"1": "sadcasc",
"name": "sadcasc",
"2": "435",
"price": "435",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/4.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/4.jpg",
"5": "Regular-menu",
"menu_cat": "Regular-menu",
"6": "2",
"type_id": "2"
}, {
"0": "10",
"menu_id": "10",
"1": "sadcasc",
"name": "sadcasc",
"2": "456",
"price": "456",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/5.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/5.jpg",
"5": "Regular-menu",
"menu_cat": "Regular-menu",
"6": "1",
"type_id": "1"
}, {
"0": "11",
"menu_id": "11",
"1": "sda",
"name": "sda",
"2": "234",
"price": "234",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/6.JPG",
"image_path": "http:\/\/mahatiffin.com\/uploads\/6.JPG",
"5": "Special-menu",
"menu_cat": "Special-menu",
"6": "2",
"type_id": "2"
}, {
"0": "12",
"menu_id": "12",
"1": "sadcasc",
"name": "sadcasc",
"2": "324",
"price": "324",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/7.JPEG",
"image_path": "http:\/\/mahatiffin.com\/uploads\/7.JPEG",
"5": "Regular-menu",
"menu_cat": "Regular-menu",
"6": "1",
"type_id": "1"
}, {
"0": "14",
"menu_id": "14",
"1": "sadcasc",
"name": "sadcasc",
"2": "232",
"price": "232",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/1.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/1.jpg",
"5": "Special-menu",
"menu_cat": "Special-menu",
"6": "1",
"type_id": "1"
}, {
"0": "15",
"menu_id": "15",
"1": "sadcasc",
"name": "sadcasc",
"2": "325",
"price": "325",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/2.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/2.jpg",
"5": "Special-menu",
"menu_cat": "Special-menu",
"6": "2",
"type_id": "2"
}, {
"0": "16",
"menu_id": "16",
"1": "sadcasc",
"name": "sadcasc",
"2": "344",
"price": "344",
"3": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"Description": "fjhsjfh jfhrwkjfh wejfhwkh ewjfhwjeh ewjfhkwe ewbfjeh wejhfkjwhhef ehfkwh wewjrh",
"4": "http:\/\/mahatiffin.com\/uploads\/4.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/4.jpg",
"5": "Regular-menu",
"menu_cat": "Regular-menu",
"6": "1",
"type_id": "1"
}, {
"0": "18",
"menu_id": "18",
"1": "edfwdfewr",
"name": "edfwdfewr",
"2": "23",
"price": "23",
"3": "xasx scasc dqedqd edbhwd dwh3ej1 1wh1e2ue 3eh3ue e2euh23ueej ewnwencj",
"Description": "xasx scasc dqedqd edbhwd dwh3ej1 1wh1e2ue 3eh3ue e2euh23ueej ewnwencj",
"4": "http:\/\/mahatiffin.com\/uploads\/4.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/4.jpg",
"5": "Regular-menu",
"menu_cat": "Regular-menu",
"6": "2",
"type_id": "2"
}, {
"0": "19",
"menu_id": "19",
"1": "Aloo Gobi",
"name": "Aloo Gobi",
"2": "250",
"price": "250",
"3": "Aloo Sabzi, 2 Puris, Rice, Dal, Shrikhand",
"Description": "Aloo Sabzi, 2 Puris, Rice, Dal, Shrikhand",
"4": "http:\/\/mahatiffin.com\/uploads\/1.jpg",
"image_path": "http:\/\/mahatiffin.com\/uploads\/1.jpg",
"5": "Special-menu",
"menu_cat": "Special-menu",
"6": "1",
"type_id": "1"
}]
}
删除String＆＃34;连接成功＆＃34;来自Php Json的页面开头。
2）问题类强制转换异常：如下所示：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.all_item_layout, container, false);
itemlist = new ArrayList<HashMap<String, String>>();
new ReadJSON().execute();
list = (ListView) view.findViewById(android.R.id.list);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(getActivity(), itemlist);
// Set the adapter to the ListView
list.setAdapter((ListAdapter) adapter);
return view;
}
和
@Override
protected void onPostExecute(Void args) {
adapter.notifydatasetchanged();
}
和
删除＆＃34; itemlist = new ArrayList＆gt;（）; ＆＃34;来自doInBackground()方法。