在解析服务器上的一些json数据时,我遇到了一个严重的问题。当it服务器返回一些json数据时,我的程序处理得很好。但当服务器返回null时,我应用程序会给我例外。
我搜索了很多问题和答案。最大的答案是使用isNull()方法来处理JSON的null返回类型。但在编写isNull方法之前,我们必须编写
JSONObject json = new JSONObject("returned string");
当有数据需要解析时,这句话很好,但当字符串为null时,它会给我异常。
我想我的问题可能会让人有些困惑。所以我在这里给出了一些我的代码。
URL Url = new URL(URL + "?userId=3");
HttpURLConnection urlConnection = (HttpURLConnection) Url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
// gets the server json data
StringBuilder sb = new StringBuilder();
BufferedReader bufferedReader = new BufferedReader(
new InputStreamReader(urlConnection.getInputStream()));
String next = "";
while ((next = bufferedReader.readLine()) != null)
{
StringTokenizer tokens = new StringTokenizer(next);
while(tokens.hasMoreTokens())
{
Log.d("Tokens", tokens.nextToken());
}
Log.d("next value", next);
JSONObject json = new JSONObject(next);
if (json.isNull("Location")) {
Log.d("Json is null", "Ok");
serverLatitude = String.valueOf(lati);
serverLongitude = String.valueOf(longi);
}
else {
Log.d("Json not null", "Ok");
lat = json.getString("Latitude");
lon = json.getString("Longitude");
if (lat != null && lon != null) {
serverLatitude = lat;
serverLongitude = lon;
} else {
}
}
当服务器中有数据时,它可以正常工作。但当服务器返回null时,它会给我一个错误。有人能帮我解决这个问题吗?
编辑
这是服务器返回null时的logcat。
08-26 14:53:22.996: D/Tokens(31397): null
08-26 14:53:22.996: D/next value(31397): null
08-26 14:53:22.996: D/Here lat(31397): 12.90871405
08-26 14:53:22.996: W/System.err(31397): org.json.JSONException: Value null of type org.json.JSONObject$1 cannot be converted to JSONObject
08-26 14:53:22.996: W/System.err(31397): at org.json.JSON.typeMismatch(JSON.java:107)
08-26 14:53:22.996: W/System.err(31397): at org.json.JSONObject.<init> (JSONObject.java:158)
08-26 14:53:22.996: W/System.err(31397): at org.json.JSONObject.<init>(JSONObject.java:171)
08-26 14:53:22.996: W/System.err(31397): at com.monday.trackloc.NewService$FetchCordinates.fetchLastInsertedRow(NewService.java:264)
08-26 14:53:22.996: W/System.err(31397): at com.monday.trackloc.NewService$FetchCordinates.insertDataToServer(NewService.java:126)
08-26 14:53:22.996: W/System.err(31397): at com.monday.trackloc.NewService$FetchCordinates.onPostExecute(NewService.java:108)
08-26 14:53:22.996: W/System.err(31397): at com.monday.trackloc.NewService$FetchCordinates.onPostExecute(NewService.java:1)
08-26 14:53:22.996: W/System.err(31397): at android.os.AsyncTask.finish(AsyncTask.java:417)
08-26 14:53:22.996: W/System.err(31397): at android.os.AsyncTask.access$300(AsyncTask.java:127)
08-26 14:53:22.996: W/System.err(31397): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
08-26 14:53:23.006: W/System.err(31397): at android.os.Handler.dispatchMessage(Handler.java:99)
08-26 14:53:23.006: W/System.err(31397): at android.os.Looper.loop(Looper.java:130)
08-26 14:53:23.006: W/System.err(31397): at android.app.ActivityThread.main(ActivityThread.java:3806)
08-26 14:53:23.006: W/System.err(31397): at java.lang.reflect.Method.invokeNative(Native Method)
08-26 14:53:23.006: W/System.err(31397): at java.lang.reflect.Method.invoke(Method.java:507)
08-26 14:53:23.006: W/System.err(31397): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-26 14:53:23.006: W/System.err(31397): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-26 14:53:23.006: W/System.err(31397): at dalvik.system.NativeStart.main(Native Method)
08-26 14:53:23.006: D/AndroidRuntime(31397): Shutting down VM
08-26 14:53:23.006: W/dalvikvm(31397): threadid=1: thread exiting with uncaught exception (group=0x40018560)
08-26 14:53:23.006: E/AndroidRuntime(31397): FATAL EXCEPTION: main
08-26 14:53:23.006: E/AndroidRuntime(31397): java.lang.NumberFormatException:
08-26 14:53:23.006: E/AndroidRuntime(31397): at org.apache.harmony.luni.util.FloatingPointParser.parseDouble(FloatingPointParser.java:267)
08-26 14:53:23.006: E/AndroidRuntime(31397): at java.lang.Double.parseDouble(Double.java:318)
08-26 14:53:23.006: E/AndroidRuntime(31397): at com.monday.trackloc.NewService$FetchCordinates.insertDataToServer(NewService.java:130)
08-26 14:53:23.006: E/AndroidRuntime(31397): at com.monday.trackloc.NewService$FetchCordinates.onPostExecute(NewService.java:108)
08-26 14:53:23.006: E/AndroidRuntime(31397): at com.monday.trackloc.NewService$FetchCordinates.onPostExecute(NewService.java:1)
08-26 14:53:23.006: E/AndroidRuntime(31397): at android.os.AsyncTask.finish(AsyncTask.java:417)
08-26 14:53:23.006: E/AndroidRuntime(31397): at android.os.AsyncTask.access$300(AsyncTask.java:127)
08-26 14:53:23.006: E/AndroidRuntime(31397): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
08-26 14:53:23.006: E/AndroidRuntime(31397): at android.os.Handler.dispatchMessage(Handler.java:99)
08-26 14:53:23.006: E/AndroidRuntime(31397): at android.os.Looper.loop(Looper.java:130)
08-26 14:53:23.006: E/AndroidRuntime(31397): at android.app.ActivityThread.main(ActivityThread.java:3806)
08-26 14:53:23.006: E/AndroidRuntime(31397): at java.lang.reflect.Method.invokeNative(Native Method)
08-26 14:53:23.006: E/AndroidRuntime(31397): at java.lang.reflect.Method.invoke(Method.java:507)
08-26 14:53:23.006: E/AndroidRuntime(31397): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-26 14:53:23.006: E/AndroidRuntime(31397): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-26 14:53:23.006: E/AndroidRuntime(31397): at dalvik.system.NativeStart.main(Native Method)
谢谢
我用不同的方法解决了它。但它运行良好。
我想我必须先把注意力集中在琴弦上。
解决方案如下:
while ((next = bufferedReader.readLine()) != null) {
Log.d("next value", next);
Log.d("Here lat", String.valueOf(lati));
if (!next.contentEquals("null")) {
JSONObject json = new JSONObject(next);
Log.d("Json not null", "Ok");
serverLatitude = json.getString("Latitude");
serverLongitude = json.getString("Longitude");
} else {
emptyRow = true;
Log.d("Json is null", "Ok");
serverLatitude = String.valueOf(lati);
serverLongitude = String.valueOf(longi);
}
}
我看到返回的字符串实际上包含"null"。所以我只是把"null"放在if条件中,现在它完全有效了。
我知道这不是解决这个问题的完美方法。如果有人对这个问题有任何好的解决方案,请在这里提供。感谢