Question

How can I detect when a json value is null?
for example: [{“username”:null},{“username”:”null”}]

The first case represents an unexisting username and the second a user named “null”. But if you try to retrieve them both values result in the string “null”

JSONObject json = new JSONObject("{\"hello\":null}");
json.put("bye", JSONObject.NULL);
Log.e("LOG", json.toString());
Log.e("LOG", "hello="+json.getString("hello") + " is null? "
                + (json.getString("hello") == null));
Log.e("LOG", "bye="+json.getString("bye") + " is null? "
                + (json.getString("bye") == null));

The log output is

{"hello":"null","bye":null}
hello=null is null? false
bye=null is null? false

Answer 1

Try with json.isNull( "field-name" ).

Reference: http://developer.android.com/reference/org/json/JSONObject.html#isNull%28java.lang.String%29