user3384985 user3384985 - 6 months ago 37
Android Question

Android check null or empty string in Android

In my trying

AsyncTask
I get email address from my server. In
onPostExecute()
I have to check is email address
empty
or
null
. I used following code to check it:

if (userEmail != null && !userEmail.isEmpty()) {
Toast.makeText(getActivity(), userEmail, Toast.LENGTH_LONG).show();
UserEmailLabel.setText(userEmail);
}


But in my
Toast
I see
null
is printed. My full code:

private class LoadPersonalData extends AsyncTask<String, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}

protected Void doInBackground(String... res) {
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("user_id", PrefUserName));
params.add(new BasicNameValuePair("type", type_data));
JSONObject json = jsonParser.makeHttpRequest(Url, "POST", params);
String result = "";
try {
result = json.getString("message");
} catch (JSONException e) {
e.printStackTrace();
}
if (result.equals("success")) {
try {
userEmail = json.getString("email");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}

@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
if (userEmail != null && !userEmail.isEmpty()) {
Toast.makeText(getActivity(), userEmail, Toast.LENGTH_LONG).show();
UserEmailLabel.setText(userEmail);
}
}


How can I check for
null
and
empty
string? Thanks in advance.

Answer

From @Jon Skeet comment, really the String value is "null". Following code solved it

if (userEmail != null && !userEmail.isEmpty() && !userEmail.equals("null")) 
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