Develop Reference

Best approach to make a login screen

I am writing here because this is my last solution of understanding this type of programming.The problem is that I got stuck on what to use to handle the connection to a server and log-in. Should I use async task, handler or thread ? I didn't find a concrete answer stating which one to use, only found that async task is used to download images or other download stuffs.
Until now I have used a thread to connect to the server. The problem I encountered was when I catch the exception ( Putting invalid username/password ) and try to log-in again. ( I needed to "close" the last thread and start one again )
After this I started to use async task but I don't really understand how it should work and I am stuck on a toast of invalid username/password.
private class connectStorage extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... params) {
try {
api = DefaultClientFactory.create(host, getUser, getPassword);
if (api.getAuthToken().trim().length() > 3) {
//TO DO LAYOUT CHANGE;
}
} catch (StorageApiException e) {
e.printStackTrace();
Log.i("TEST", "" + e.getMessage());
}
return null;
}
Also, I am 100% sure that calling inflate in the doInBackground method won't work too ( there I wanted to change the activity ).
I am starting the async task on a button press.

When you are using asynctask
You have doInBackground and onPostExecute
So basically get a json or string or boolean as a result from doinbackground
and in onpostexecute check if the login in succesful or not if its succesful save the data from server and start an intent to go to another activity or toast the user that that user login details are wrong and try again.
So your asynctask can be an inner class of your activity class which is login and onClickSubmit button call the asynctask class and on post execute parse the json and according to the result decide what to do
Example:
public class SignInAsycTask extends AsyncTask<RequestParams, Void, String> {
#Override
protected String doInBackground(RequestParams... params) {
return new HttpManager().sendUserData(params[0]);
}
#Override
protected void onPostExecute(String result) {
String[] details = parseJsonObject(result);
if (details != null) {
user.setUser_id(Integer.valueOf(details[0]));
user.setName(details[1]);
if (details.length > 2) {
user.setProfilePic(details[2]);
}
setSharedPreferences();
startActivity(new Intent(Signin.this, MainActivity.class));
finish();
} else {
Toast.makeText(Signin.this, "please try again",
Toast.LENGTH_LONG).show();
}
}
}
public String[] parseJsonObject(String result) {
JSONObject obj = null;
try {
obj = new JSONObject(result);
if (obj.has("success")) {
if (obj.getInt("success") == 1) {
if (obj.has("user_pic")) {
return new String[] {
String.valueOf(obj.getInt("user_id")),
obj.getString("user_name"),
obj.getString("user_pic") };
} else {
return new String[] {
String.valueOf(obj.getInt("user_id")),
obj.getString("user_name"), };
}
} else {
return null;
}
} else {
return null;
}
} catch (JSONException e) {
e.printStackTrace();
return null;
}
}
here my RequestParams are just a object where I stored all the details like url parameters to send etc and the output of the doinbackground is a String and I am parsing it in my postexecute method

Twitter OAuth issue: error 401

i am trying to get twitter work.
Error which i receive is:
Authorization failed (server replied with a 401). This can happen if the consumer key was not correct or the signatures did not match
I have already checked a lot of same issues here, on stackoverflow and here what i already tried:
1) checked consumer key (it is the same with that on dev.twitter.com)
2) added Callback URL for my app on dev.twitter.com
3) updated library to twitter-4j-core-3.0.5.jar
4) checked if time of my tablet is correct (set Eastern European Time)
Also i must say that some month ago Twitter in application worked properly. Then somehow it broke down.
Here is my code:
class GetOAuthVerifierTask extends AsyncTask<Void, Void, String> {
private Context context;
public GetOAuthVerifierTask(Context context) {
this.context = context;
dialog = ProgressDialog.show(TwitterActivity.this, getString(CANNOT_GET_REQUEST_TOKEN), null);
}
#Override
protected String doInBackground(Void... params) {
TwitterUtils twitterUtils = TwitterUtils.getInstance();
OAuthConsumer consumer = twitterUtils.createConsumer();
OAuthProvider provider = twitterUtils.createProvider();
try {
final String url = provider.retrieveRequestToken(consumer,
twitterUtils.getCallbackURL(context));
twitterUtils.setConsumerToken(context, consumer.getToken());
twitterUtils.setConsumerSekretToken(context, consumer.getTokenSecret());
return url;
} catch (Exception e) {
Logger.debug("Can not retrieve request token");
Logger.error(e.getMessage(), e);
return null;
}
}
#Override
protected void onPostExecute(String url) {
dialog.dismiss();
if (url != null){
// HERE IT WORKS CORRECT
web.loadUrl(url);
}
else{
Toast.makeText(TwitterActivity.this, getString(DOWNLOAD_WAIT_MESSAGE),
Toast.LENGTH_LONG).show();
}
}
}
class GetAccessTokenTask extends AsyncTask<Uri, Void, Boolean> {
#Override
protected void onPreExecute() {
dialog = ProgressDialog.show(TwitterActivity.this, getString(CANNOT_GET_REQUEST_TOKEN), null);
}
#Override
protected Boolean doInBackground(Uri... params) {
TwitterUtils twitterUtils = TwitterUtils.getInstance();
String oauthVerifier = params[0].getQueryParameter(OAuth.OAUTH_VERIFIER);
OAuthConsumer consumer = twitterUtils.createConsumer();
consumer.setTokenWithSecret(twitterUtils.getConsumerToken(TwitterActivity.this),
twitterUtils.getConsumerSekretToken(TwitterActivity.this));
OAuthProvider provider = twitterUtils.createProvider();
try {
provider.retrieveAccessToken(consumer, oauthVerifier);
twitterUtils.setAccessToken(TwitterActivity.this, consumer.getToken());
twitterUtils.setAccessTokenSecret(TwitterActivity.this, consumer.getTokenSecret());
} catch (Exception e) {
Logger.debug("Can not retrieve access token");
Logger.error(e.getMessage(), e);
return false;
}
return true;
}
#Override
protected void onPostExecute(Boolean result) {
dialog.dismiss();
if (result) {
TwitterActivity.this.sendMessage();
TwitterActivity.this.finish();
} else {
// HERE I GET 401
Toast.makeText(TwitterActivity.this, getString(DOWNLOAD_WAIT_MESSAGE),
Toast.LENGTH_LONG).show();
}
}
}

Just found the solution:
i added line
provider.setOAuth10a(true); (for my OAuthProvider)
The explanation was found in source code:
// 1.0a expects the callback to be sent while getting the request token.
// 1.0 service providers would simply ignore this parameter.

In the last month, has been a change to the Twitter API. You can now only call it using HTTPS.
You should ensure that the URL you / your library is using starts with
https://api.twitter.com/1.1/
(Notice the extra s after the http.)
You may need to check with the maintainer of twitter4j.

How can i Handle special kind of exception in doinBackground() method

I am making an android app which requires it to fetch some information from a remote server and therefore i have to make a http request in a async task.Now the problem is that that the response sometimes take more than 2 secs and when it does it give http timeout exception but most of the time it works just fine .So i want to implement the functionality that when i recieve a http timeout exception i want to retry the request again(try the doinBackground again,because network call can only be made in thread other than the main thread) because chances are that it will be successful and all the things that need to be fetched from the remote server will occur in CallRemoteServer() method
Now in my program i have implemented something like this
new AsyncTask<Void, Void, Void>() {
private boolean httpResponseOK = true;
#Override
protected Void doInBackground(Void... params) {
try {
CallRemoteServer();
}
} catch (Exception e) {
httpResponseOK = false;
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Void result) {
if (httpResponseOK == false) {
//Show an alert dialog stating that unable to coonect
}
else
{
//update UI with the information fetched
}
});
Can someone advice me how can i implement something which i have mentioned above ,i mean that if i get some other exception other than timeout than show an alert dialog otherwise retry atleast five time more CallRemoteServer method before showing the dialog that unable to connect.
I am not able to think of any good way to implement this logic.
Thanks in advance

You're probably getting a ConnectTimeoutException (or check in the logs what is the IOException you're getting). I would first try to extend the timeout. Some similar answers for this can be found here or here.
However, an auto-reconnect mechanism is a must to have. I would implement it using recursive code:
final int maxAttempts = 5;
protected MyServerData callRemoteServer(int attempt) throws IOException {
try {
// do the IO stuff and in case of success return some data
} catch (ConnectTimeoutException ex) {
if(attempt == maxAttempts) {
return callRemoteServer(attempt + 1);
} else {
throw ex;
}
}
}
Your doInBackground method should look like:
#Override
protected Void doInBackground(Void... params) {
try {
callRemoteServer(0);
}
catch (Exception e) {
e.printStackTrace();
}
return null;
}
In this way if the connection timeouts it will attempt to retry for 5 max times (you can set the max attempts to anything you like). Just make sure to return some data from this IO operation as that is the most valuable asset from that method anyway ...
For this reason I would change it to following:
private class MyAsynckTask extends AsyncTask<Void, Void, MyServerData> {
#Override
protected MyServerData doInBackground(Void... params) {
try {
return callRemoteServer(0);
}
catch (Exception e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(MyServerData result) {
if(result != null) {
// display data on UI
}
}
}

Importing gmail contacts using GoogleAuthUtil

I'm trying to add import contacts from gmail account function in my android app. So the first problem is to get access token from gmail. I've found that there is GoogleAuthUtil class which can help me with it.
Here is my code:
private void importContactsFromGmail() {
showProgressDialog();
GetTokenTask getTokenTask = new GetTokenTask();
getTokenTask.execute();
String token = "";
try {
token = getTokenTask.get();
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(token);
hideProgressDialog();
}
private class GetTokenTask extends AsyncTask<Void, Void, String> {
#Override
protected String doInBackground(Void... params) {
String token = "";
try {
token = GoogleAuthUtil.getToken(activity, <My_gmail_account>, "https://www.google.com/m8/feeds/");
} catch (Exception e) {
e.printStackTrace();
}
return token;
}
}
Now after calling GoogleAuthUtil.getToken my app completely freezes(no errors in Logcat). I completely stuck and I need your help.
What is wrong with my code? Maybe I should import contacts in some other way?

Not sure if this is related but calling the .get() method on the main thread is not correct because is blocking method.
What if you use the AsyncTask in this way?
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new GetTokenTask().execute();
}
static class GetTokenTask extends AsyncTask<Void, Void, String> {
#Override
protected String doInBackground(Void... unused) {
String token = "";
try {
token = GoogleAuthUtil.getToken(activity, <My_gmail_account>, "https://www.google.com/m8/feeds/");
} catch (Exception e) {
e.printStackTrace();
}
return token;
}
#Override
protected void onPostExecute(String token) {
Toast.makeText(MainActivity.this, token, Toast.LENGTH_SHORT).show();
}
}
}
(I wrote without compiling it, maybe it needs to be adjusted)

On Android devices, Gmail contacts are synced locally onto the device and are available via a public Contacts Provider, therefore there's no reason you'd need to use the Google API to pull what is already available. There is a whole training series dedicated specifically to retrieving a list of contacts.
Note that the Contacts training series does assume you have knowledge of Content Providers already, so it may be helpful to read up on the basics of Content Providers as well.

Error creating an AsyncTask

I'm creating a login form. When the user logs in, it will lead to the home page.
I create an activity that has an AsyncTask. Here's the relevant part of my code:
public class iniTask extends AsyncTask<String, Void, String> {
private ProgressDialog Dialog = new ProgressDialog(GPSTracerActivity.this);
protected void onPreExecute() {
Dialog.setMessage("Connect to server...");
Dialog.show();
}
protected String doInBackground(String... url_req) {
String url = url_req[0];
try {
Log.v("doing background", executeHttpGet(url));
return executeHttpGet(url);
} catch(Exception e) {
Log.v("Exception doing background","Exception:"+e.getMessage());
return "";
}
}
protected void onPostExecute(String result) {
try {
Dialog.dismiss();
// here when thing go wrong
startNewAction(result);
} catch(Exception e) {
Log.v("Exception process response","Exception:"+e.getMessage());
}
}
}
Here's startNewAction(result):
public void startNewAction(String result){
if (result.substring(0, 6) == "300 OK"){
Intent i = new Intent(GPSTracerActivity.this, Home.class);
startActivity(i);
}
}
The task starts correctly, but when I call startNewAction(result),
it does not call a new activity. Why?
NOTE : when i enable if structure to test string == 300 OK it is not work ! why
I see this in logcat:
07-16 14:57:23.345: WARN/InputManagerService(37): Window already focused, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy#40777ee0

In your onPostExecute dismiss the dialog first.
Dialog.dismiss();

I just found the solution,there is an error because of the way i compare the string,
It should be,
if (result.substring(0, 6).equals("300 OK") ){
Intent i = new Intent(GPSTracerActivity.this, Home.class);
startActivity(i);
}
Anyway, Thanks for ideas !!!