Reading a json file from sdcard returns - null pointer exception

Question

I searched all through the related threads and i was not successful , any related answers are welcomed .

I have a JSON data as a .json file in SDCard inside the .NewFolder folder , i want to read the data in the file and parse , find the timestamp and want to rewrite it if the timestamp is different .

The below is the code i use , and i get the data in aBuffer and the value in jdata_fromfile but i get nullPointerException while parsing .

myFile = new File(Environment.getExternalStorageDirectory() + "/.NewFolder/" +str.get(i));
if(myFile.exists())
{
    FileInputStream fIn = new FileInputStream(myFile);
    BufferedReader myReader = new BufferedReader(new InputStreamReader(fIn));
    String aDataRow = "";
    String aBuffer = "";
    while ((aDataRow = myReader.readLine()) != null) 
    {
        aBuffer += aDataRow;
    }
    myReader.close();
    jdata_fromfile = new JSONObject(aBuffer);

    String timestamp_fromfile = jdata_fromfile.getString(str_timestamp.get(i));
    timestamp_val_fromfile.add(timestamp_fromfile);
}
else
{
    myFile.createNewFile();
    writedate_tofile(value_json.toString());
    timestamp_val_fromfile.add("xxx");
}

And also that , when i open the file in the Notepad , it is all in a single line showing only a part of the data and when i copy to http://jsonformatter.curiousconcept.com

i get the whole data and a valid json . i could see the rest of the data in the notepad when i do - ctrl+end and press enter .

why is this and where do i go wrong ?

This is my Error - log

02-13 18:44:52.109: E/aBuffer value(7134):  is {"Status":{"Itemlist":[{"x - Drinks":{"Details":[{"type":"","image":"","price":"","name":"Minerals"},{"type":"","image":"","price":"","name":"Milk Shakes"},{"type":"","image":"","price":"","name":"Milk"},{"type":"","image":"","price":"","name":"Mineral Water"},{"type":"","image":"","price":"","name":"Hot Beverages"},{"type":"","image":"","price":"","name":"Chocolate Muffin and Ice Cream"}, ........................................................................{"type":"","image":"","price":"","name":"Blu
02-13 18:44:52.189: E/jdata_fromfile value(7134):  is {"x Time_stamp":"2013-02-12 12:30:00","Status":{"Itemlist":[{"x - Sides":{"Details":[{"type":"","image":"","name":"Onion Rings (6)","price":""},{"type":"","image":"","name":"Sausage Portion (Minimum 2 per portion)","price":""},.................................................................................................................... ,"x - Burgers":{"Details":[{"type":"","image":"","name":"x 5oz Burger","price":""},{"type":"","image":"","name":"x 5oz Cheese Burger","price":""},{"type":"","image":"","name":"x 5oz with Bacon and Cheese","price":""},{"type":"","imag
02-13 18:44:52.189: E/Reading from internal file - Exception e(7134): java.lang.NullPointerException

Thanks in advance .

In which line do you get the NullPointerException? Just post the stacktrace. — svennergr
– svennergr, Commented Feb 13, 2013 at 13:00
i am using the above code in a try-catch , and i get : 02-13 18:33:15.909: E/Reading from internal file - Exception e(6632): java.lang.NullPointerException — VIGNESH
– VIGNESH, Commented Feb 13, 2013 at 13:07
the dots represents the datas , i have cut shoted some and posted — VIGNESH
– VIGNESH, Commented Feb 13, 2013 at 13:24

kushdilip · Accepted Answer · 2013-03-11 17:17:15Z

I don't know what's wrong with above code but here is the solution using different JSON library.

I was using following code in one of my android application and it works perfectly for reading any json file from android file system. Instead of using Android's JSON library, I used json-simple.jar from http://code.google.com/p/json-simple/

Put above jar in libs folder of your Android project. And also set following permission in .Manifest file.

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

Then put follwing code in separate Thread.

JSONParser parser  = new JSONParser();
try { 
    String PATH = Environment.getExternalStorageDirectory() + "/Download/list.json";
    Object object = parser.parse(new FileReader(PATH));             
    JSONObject jsonObject = (JSONObject) object;
    //Use JSONArray instead of JSONObject if json file contains array of JSONs
    //
    // Do anything with jsonObject  
    //
} catch(Exception e) {
    // TODO: handle exception
}

Here my list.json file is at location /mnt/sdcard/Download.

For reference here is an example using above library in simple java project.

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