Develop Reference

Unknown field "a" appears in firestore when saving fcm token to database

I am grabbing the android device token and saving it to firestore. This works in most of the cases totally fine. Now I encountered a device where it does not work. Oddly enough I end up with attributes in firestore that my model does not reflect and I do not understand where those attributes and their values come from.
This is my method to retrieve the token:
public static void updateToken(String userId, FcmToken.Action action) {
if (StringUtils.checkNull(userId)) return;
//FCM
FirebaseMessaging.getInstance().getToken().addOnCompleteListener(task -> {
if (!task.isSuccessful()) {
Log.w(TAG, "Could not get firebase token. ", task.getException());
return;
}
String token = task.getResult();
Log.i(TAG, "[FCM TOKEN]: " + token);
//Do not ask firebase to write an existing token again,
//this only creates traffic and costs but does not change the database
String storedToken = FcmProvider.loadToken(false);
if (StringUtils.checkNull(storedToken) || !token.equals(storedToken) || action == FcmToken.Action.DELETE) {
FcmToken fcmToken = new FcmToken(token, userId, action);
FcmRepo.getInstance().setToken(fcmToken, documentId -> {
Log.d(TAG, "Token " + action + " successfully");
FcmProvider.saveToken(token);
}, e -> {
Log.d(TAG, "Failed to " + action + " token. " + e);
});
} else {
Log.d(TAG, "Stored token is identical. No update needed");
}
});
}
This is the FcmToken class (And I assume the way I use the field values here are the issue, yet I do not understand the outcome)
#Getter
#Setter
#IgnoreExtraProperties
public class FcmToken {
private String userId;
private FieldValue fcmToken;
#ServerTimestamp
private Date ut;
public enum Action {SET, DELETE}
public FcmToken(String fcmToken, String userId, Action action) {
this.userId = userId;
if (action == Action.SET) this.fcmToken = FieldValue.arrayUnion(fcmToken);
else if (action == Action.DELETE) this.fcmToken = FieldValue.arrayRemove(fcmToken);
}
}
For completness this is the method I use to set the token:
public void setToken(#NonNull FcmToken fcmToken, #Nullable OnSetSuccessListener callbackSuccess, #Nullable OnFailureListener callbackFailure) {
getFcmRef().document(fcmToken.getUserId()).set(fcmToken, SetOptions.merge()).addOnCompleteListener(task ->...);
}
Now this is what ends up in my firestore for that user only:
This HAS to to come from the app itself. There is no other way this document could have been created:
If I use another device or the emulator the result looks like expected. Where does the "a" field come from? Why is it assigned to userId and why is there no fcmToken field?
The problem is, that I do not have physical access to the phone that produces this behaviour (Samsung S21 Ultra, Android 12). I need to debug this without having access to the log outputs.
But I know that the task comes back successfully (I used another version to save the error in the token field and there was none).
Any ideas?

This typically means that you didn't configure ProGuard correctly, and it's minifying the classes that you're writing to the database.
You'll need to prevent ProGuard from modifying the classes that you use to interact with the database. See the Firebase documentation on configuring ProGuard (the link is for the Realtime Database, but the same applies to Firestore), or one of these previous questions about configuring ProGuard for Firebase.

How to decode SafetyNet JWS response?

I am investigating SafetyNet provided by Google within my Android Application.
To start with I simply called the SafetyNet attest API and Base64 decoded the parts as shown in the Google supplied examples.
SafetyNet.getClient(this).attest(NONCE, <API KEY>)
.addOnSuccessListener(this, new OnSuccessListener<SafetyNetApi.AttestationResponse>() {
#Override
public void onSuccess(final SafetyNetApi.AttestationResponse attestationResponse) {
initialDataExtraction(attestationResponse.getJwsResult());
}
})
.addOnFailureListener(this, new OnFailureListener() {
#Override
public void onFailure(#NonNull final Exception exception) {
if (exception instanceof ApiException) {
final ApiException apiException = (ApiException) exception;
Log.e(TAG, "onFailure: " + apiException.getMessage() + " " + apiException.getStatusCode());
} else {
Log.e(TAG, "Error: ", exception);
}
}
});
I extract the JWS parts as follows:-
private byte[] initialDataExtraction(final String jwsResult) {
final String[] jwsResultParts = jwsResult.split("[.]");
if (jwsResultParts.length == 3) {
final byte[] header = Base64.decode(jwsResultParts[0], Base64.NO_WRAP);
final byte[] data = Base64.decode(jwsResultParts[1], Base64.NO_WRAP);
final byte[] signature = Base64.decode(jwsResultParts[2], Base64.NO_WRAP);
Log.d(TAG, "initialDataExtraction: header = " + new String(header, UTF_8));
Log.d(TAG, "initialDataExtraction: data = " + new String(data, UTF_8));
Log.d(TAG, "initialDataExtraction: signature = " + new String(signature, UTF_8));
return data;
} else {
Log.e(TAG, "initialDataExtraction: Failure: Illegal JWS signature format. The JWS consists of " + jwsResultParts.length + " parts instead of 3.");
return null;
}
}
I am using android.util.Base64 to decode the parts and the majority of the time the decoding completes OK.
Occasionally I receive this exception though:-
java.lang.IllegalArgumentException: bad base-64
at android.util.Base64.decode(Base64.java:161)
at android.util.Base64.decode(Base64.java:136)
at android.util.Base64.decode(Base64.java:118)
when decoding the Signature part.
What am I doing wrong when decoding to see this intermittent error?
I then moved onto to using a JWT library to decode the tokens.
first I tried group: 'com.auth0.android', name: 'jwtdecode', version: '1.1.1'
the code I tried is
final JWT jwt = new JWT(jwsResult);
which consistently fails with the following error
com.auth0.android.jwt.DecodeException: The token's payload had an invalid JSON format.
at com.auth0.android.jwt.JWT.parseJson(JWT.java:235)
at com.auth0.android.jwt.JWT.decode(JWT.java:203)
at com.auth0.android.jwt.JWT.<init>(JWT.java:40)
Caused by: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected a string but was BEGIN_ARRAY at line 1 column 23 path $.
at com.google.gson.Gson.fromJson(Gson.java:899)
at com.google.gson.Gson.fromJson(Gson.java:852)
at com.google.gson.Gson.fromJson(Gson.java:801)
This exception seems to be caused by the Auth0 library being unable to parse headers 4.1.6. "x5c" (X.509 Certificate Chain) Header format which is odd as the JWS Spec clearly states the value is represented by a JSON aray:-
The "x5c" (X.509 Certificate Chain) Header Parameter contains the
X.509 public key certificate or certificate chain [RFC5280]
corresponding to the key used to digitally sign the JWS. The
certificate or certificate chain is represented as a JSON array of
certificate value strings.
However If I copy and paste the same jws result string into a pure java project and use compile 'com.auth0:java-jwt:3.3.0' and use this code:-
String token = "<JWS TOKEN>";
try {
final DecodedJWT jwt = JWT.decode(token);
System.out.println("Header = " + jwt.getHeader());
System.out.println("Payload = " + jwt.getPayload());
System.out.println("Signature = " + jwt.getSignature());
} catch (JWTDecodeException exception){
throw new RuntimeException(exception);
}
The Jws Token is decoded successfully.
What am I doing wrong within my Android application that stops the auth0 android jwt library working as desired?
I then tried 'io.jsonwebtoken:jjwt:0.9.0' library within my Android application.
When I execute this code:-
Jwts.parser().parse(jwsResult).getBody();
it fails with:-
java.lang.IllegalArgumentException: A signing key must be specified if the specified JWT is digitally signed.
at io.jsonwebtoken.lang.Assert.notNull(Assert.java:85)
at io.jsonwebtoken.impl.DefaultJwtParser.parse(DefaultJwtParser.java:331)
What signing key do I need to pass to Jwts? The only key I have is my API key held in the Google API Console, is this the key I should employ?
when I pass it as follows:
Jwts.parser().setSigningKey<API KEY>.parse(jwsResult).getBody();
this fails with:-
java.lang.IllegalArgumentException: Key bytes can only be specified for HMAC signatures. Please specify a PublicKey or PrivateKey instance.
at io.jsonwebtoken.lang.Assert.isTrue(Assert.java:38)
at io.jsonwebtoken.impl.DefaultJwtParser.parse(DefaultJwtParser.java:324)
What is the correct approach to decode and consume the Jws result received from SafetyNet attest API call?
I discovered a fix for the java.lang.IllegalArgumentException: bad base-64 issue from this question Base64: java.lang.IllegalArgumentException: Illegal character
simply replace characters in jws token before decoding
token.replace('-', '+').replace('_', '/')

I identified this library not only does it do the job it works fine on Android.
// https://mvnrepository.com/artifact/com.nimbusds/nimbus-jose-jwt
implementation group: 'com.nimbusds', name: 'nimbus-jose-jwt', version: '5.1'
try {
final JWSObject jwsObject = JWSObject.parse(jwsResult);
System.out.println("header = " + jwsObject.getHeader());
System.out.println("header = " + jwsObject.getHeader().getX509CertChain());
System.out.println("payload = " + jwsObject.getPayload().toJSONObject());
System.out.println("signature = " + jwsObject.getSignature());
System.out.println("signature = " + jwsObject.getSignature().decodeToString());
} catch (ParseException e) {
e.printStackTrace();
}
Some nice examples are provided:-
https://connect2id.com/products/nimbus-jose-jwt/examples

uber requestRide() method Response Error 401: Unauthorized

I am getting Error when I try to call requestRide() method on Uber api. The response body is null and the response message is "Unauthorized" with error code 401; whereas the onResponse() callback method is executing but onFailure() callback method is not executing.
Here is my code for calling requestRide() and implementing the callback interface...
private void requestForNewRide(RidesService service, int position){
RideRequestParameters rideRequestParameters = new RideRequestParameters.Builder().setPickupCoordinates(PICKUP_LATITUDE, PICKUP_LONGITUDE)
.setProductId(productIds.get(position))
.setFareId(fareIds.get(position))
.setDropoffCoordinates(DROPOFF_LATITUDE, DROPOFF_LONGITUDE)
.build();
service.requestRide(rideRequestParameters).enqueue(new Callback<Ride>() {
#Override
public void onResponse(Call<Ride> call, Response<Ride> response) {
if (response.isSuccessful()) {
Toast.makeText(CustomActivity.this, "Request ride success", Toast.LENGTH_SHORT).show();
try {
//ride details
String rideId = response.body().getRideId();
String rideStatus = response.body().getStatus();
Integer rideEta = response.body().getEta(); //estimated time of arrival in min
Float rideSurgeMultiplier = response.body().getSurgeMultiplier(); //rise in price
Driver rideDriver = response.body().getDriver();
Location rideLocation = response.body().getLocation();
Vehicle rideVehicle = response.body().getVehicle();
//ride driver details
String driverName = rideDriver.getName();
String driverPhoneNumber = rideDriver.getPhoneNumber();
String driverPictureUri = rideDriver.getPictureUrl();
Float driverRating = rideDriver.getRating();
//ride Location details
Float rideLocationLatitude = rideLocation.getLatitude();
Float rideLocationLongitude = rideLocation.getLongitude();
Integer rideLocationBearing = rideLocation.getBearing();
//ride Vehicle details
String rideVehicleLicencePlate = rideVehicle.getLicensePlate();
String rideVehicleMake = rideVehicle.getMake();
String rideVehicleModel = rideVehicle.getModel();
String rideVehiclePictureUrl = rideVehicle.getPictureUrl();
//Log
Log.d("uberridedetails", "rideId: " + rideId);
Log.d("uberridedetails", "rideStatus: " + rideStatus);
Log.d("uberridedetails", "rideEta: " + rideEta);
Log.d("uberridedetails", "rideSurgeMultiplier: " + rideSurgeMultiplier);
Log.d("uberridedetails", "driverName: " + driverName);
Log.d("uberridedetails", "driverPhoneNumber: " + driverPhoneNumber);
Log.d("uberridedetails", "driverPictureUri: " + driverPictureUri);
Log.d("uberridedetails", "driverRating: " + driverRating);
Log.d("uberridedetails", "rideLocationLatitude: " + rideLocationLatitude);
Log.d("uberridedetails", "rideLocationLongitude: " + rideLocationLongitude);
Log.d("uberridedetails", "rideLocationBearing: " + rideLocationBearing);
Log.d("uberridedetails", "rideVehicleLicencePlate: " + rideVehicleLicencePlate);
Log.d("uberridedetails", "rideVehicleMake: " + rideVehicleMake);
Log.d("uberridedetails", "rideVehicleModel: " + rideVehicleModel);
Log.d("uberridedetails", "rideVehiclePictureUrl: " + rideVehiclePictureUrl);
} catch (Exception e) {
e.printStackTrace();
}
}else {
Toast.makeText(CustomActivity.this, "Error: "+response.message(), Toast.LENGTH_SHORT).show();
}
}
#Override
public void onFailure(Call<Ride> call, Throwable t) {
Toast.makeText(CustomActivity.this, "Failed to request ride", Toast.LENGTH_SHORT).show();
}
});
}
I have already checked the param productId and FareId is valid, which I am getting from the api itself (by calling estimateRide() I get Price object from that I have got the fareId. And by calling getProducts() on RideService object I have got the productId.
This is the code for set up...
SessionConfiguration config = new SessionConfiguration.Builder()
.setClientId(getResources().getString(R.string.client_id))
.setRedirectUri(getResources().getString(R.string.redirect_url))
.setEnvironment(SessionConfiguration.Environment.SANDBOX)
.setScopes(Arrays.asList(Scope.PROFILE, Scope.RIDE_WIDGETS, Scope.REQUEST, Scope.REQUEST_RECEIPT))
.build();
UberSdk.initialize(config);
And ...
LoginCallback loginCallback = new LoginCallback() {
#Override
public void onLoginCancel() {
// User canceled login
Toast.makeText(CustomActivity.this, "User canceled login", Toast.LENGTH_SHORT).show();
}
#Override
public void onLoginError(#NonNull AuthenticationError error) {
// Error occurred during login
Toast.makeText(CustomActivity.this, "Error occurred during login", Toast.LENGTH_SHORT).show();
}
#Override
public void onLoginSuccess(#NonNull AccessToken accessToken) {
// Successful login! The AccessToken will have already been saved.
Toast.makeText(CustomActivity.this, "Successful login! The AccessToken will have already been saved.", Toast.LENGTH_SHORT).show();
createSession();
}
#Override
public void onAuthorizationCodeReceived(#NonNull String authorizationCode) {
Toast.makeText(CustomActivity.this, "Authorization code received", Toast.LENGTH_SHORT).show();
createSession();
}
};
AccessTokenManager accessTokenManager = new AccessTokenManager(getApplicationContext());
LoginManager loginManager = new LoginManager(accessTokenManager, loginCallback);
loginManager.setRedirectForAuthorizationCode(true);
loginManager.login(this);
mAccessTokenManager = accessTokenManager;
mLoginManager = loginManager;
Note1: These are the scopes I am using...
Scope.PROFILE, Scope.RIDE_WIDGETS, Scope.REQUEST, Scope.REQUEST_RECEIPT
Note2: I am logging in with my developer account.
Let me know if I should mention any other details.

Absolutely I have found out the solution on my own.
I noticed that the onLoginSuccess() callback method is being called only when I am using GENERAL SCOPEs.
Whenever I am using a RESTRICTED SCOPE, the method is not being called, instead another callback method named onAuthorizationCodeReceived() is being called.
Then I have found out, whenever the onAuthorizationCodeReceived() method is called, there is no access token saved in the AccessTokenManager object. Thus without the access token, when I try to request a ride Error returns "Unauthorized".
So, I tried to figure out how to generate Access token using the authorization code. I found no doc regarding this process in the Android section. Then I have found out the solution in the REST web service api.
Here is the LINK of my answer...
NOTE: There is no mention of the callback method onAuthorizationCodeReceived() in the Uber Doc.

Android : How to get larger profile pic from Facebook using FirebaseAuth?

I am using FirebaseAuth to login user through FB. Here is the code:
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
private CallbackManager mCallbackManager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FacebookSdk.sdkInitialize(getApplicationContext());
// Initialize Firebase Auth
mAuth = FirebaseAuth.getInstance();
mAuthListener = firebaseAuth -> {
FirebaseUser user = firebaseAuth.getCurrentUser();
if (user != null) {
// User is signed in
Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
} else {
// User is signed out
Log.d(TAG, "onAuthStateChanged:signed_out");
}
if (user != null) {
Log.d(TAG, "User details : " + user.getDisplayName() + user.getEmail() + "\n" + user.getPhotoUrl() + "\n"
+ user.getUid() + "\n" + user.getToken(true) + "\n" + user.getProviderId());
}
};
}
The issue is that the photo in I get from using user.getPhotoUrl() is very small. I need a larger image and can't find a way to do that. Any help would be highly appreciated.
I have already tried this
Get larger facebook image through firebase login
but it's not working although they are for swift I don't think the API should differ.

It is not possible to obtain a profile picture from Firebase that is larger than the one provided by getPhotoUrl(). However, the Facebook graph makes it pretty simple to get a user's profile picture in any size you want, as long as you have the user's Facebook ID.
String facebookUserId = "";
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
ImageView profilePicture = (ImageView) findViewById(R.id.image_profile_picture);
// find the Facebook profile and get the user's id
for(UserInfo profile : user.getProviderData()) {
// check if the provider id matches "facebook.com"
if(FacebookAuthProvider.PROVIDER_ID.equals(profile.getProviderId())) {
facebookUserId = profile.getUid();
}
}
// construct the URL to the profile picture, with a custom height
// alternatively, use '?type=small|medium|large' instead of ?height=
String photoUrl = "https://graph.facebook.com/" + facebookUserId + "/picture?height=500";
// (optional) use Picasso to download and show to image
Picasso.with(this).load(photoUrl).into(profilePicture);

Two lines of code. FirebaseUser user = firebaseAuth.getCurrentUser();
String photoUrl = user.getPhotoUrl().toString();
photoUrl = photoUrl + "?height=500";
simply append "?height=500" at the end

If someone is looking for this but for Google account using FirebaseAuth. I have found a workaround for this. If you detail the picture URL:
https://lh4.googleusercontent.com/../.../.../.../s96-c/photo.jpg
The /s96-c/ specifies the image size (96x96 in this case)so you just need to replace that value with the desired size.
String url= FirebaseAuth.getInstance().getCurrentUser().getPhotoUrl();
url = url.replace("/s96-c/","/s300-c/");
You can analyze your photo URL to see if there is any other way to change its size.
As I said in the begining, this only works for Google accounts. Check #Mathias Brandt 's answer to get a custom facebook profile picture size.
EDIT 2020:
Thanks to Andres SK and #alextouzel for pointing this out. Photo URLs format have changed and now you can pass URL params to get different sizes of the picture. Check https://developers.google.com/people/image-sizing.

photoUrl = "https://graph.facebook.com/" + facebookId+ "/picture?height=500"
You can store this link to firebase database with user facebookId and use this in app.
Also you can change height as a parameter

Not for Android, but for iOS, but I thought it could be helpful for other people (I didn't find a iOS version of this question).
Based the provided answers I created a Swift 4.0 extension that adds a function urlForProfileImageFor(imageResolution:) to the Firebase User object. You can either ask for the standard thumbnail, a high resolution (I put this to 1024px but easily changed) or a custom resolution image. Enjoy:
extension User {
enum LoginType {
case anonymous
case email
case facebook
case google
case unknown
}
var loginType: LoginType {
if isAnonymous { return .anonymous }
for userInfo in providerData {
switch userInfo.providerID {
case FacebookAuthProviderID: return .facebook
case GoogleAuthProviderID : return .google
case EmailAuthProviderID : return .email
default : break
}
}
return .unknown
}
enum ImageResolution {
case thumbnail
case highres
case custom(size: UInt)
}
var facebookUserId : String? {
for userInfo in providerData {
switch userInfo.providerID {
case FacebookAuthProviderID: return userInfo.uid
default : break
}
}
return nil
}
func urlForProfileImageFor(imageResolution: ImageResolution) -> URL? {
switch imageResolution {
//for thumnail we just return the std photoUrl
case .thumbnail : return photoURL
//for high res we use a hardcoded value of 1024 pixels
case .highres : return urlForProfileImageFor(imageResolution:.custom(size: 1024))
//custom size is where the user specified its own value
case .custom(let size) :
switch loginType {
//for facebook we assemble the photoUrl based on the facebookUserId via the graph API
case .facebook :
guard let facebookUserId = facebookUserId else { return photoURL }
return URL(string: "https://graph.facebook.com/\(facebookUserId)/picture?height=\(size)")
//for google the trick is to replace the s96-c with our own requested size...
case .google :
guard var url = photoURL?.absoluteString else { return photoURL }
url = url.replacingOccurrences(of: "/s96-c/", with: "/s\(size)-c/")
return URL(string:url)
//all other providers we do not support anything special (yet) so return the standard photoURL
default : return photoURL
}
}
}
}

Note: From Graph API v8.0 you must provide the access token for every UserID request you do.
Hitting the graph API:
https://graph.facebook.com/<user_id>/picture?height=1000&access_token=<any_of_above_token>
With firebase:
FirebaseUser user = mAuth.getCurrentUser();
String photoUrl = user.getPhotoUrl() + "/picture?height=1000&access_token=" +
loginResult.getAccessToken().getToken();
You get the token from registerCallback just like this
LoginManager.getInstance().registerCallback(mCallbackManager, new FacebookCallback<LoginResult>() {
#Override
public void onSuccess(LoginResult loginResult) {
FirebaseUser user = mAuth.getCurrentUser();
String photoUrl = user.getPhotoUrl() + "/picture?height=1000&access_token=" + loginResult.getAccessToken().getToken();
}
#Override
public void onCancel() {
Log.d("Fb on Login", "facebook:onCancel");
}
#Override
public void onError(FacebookException error) {
Log.e("Fb on Login", "facebook:onError", error);
}
});
This is what documentation says:
Beginning October 24, 2020, an access token will be required for all
UID-based queries. If you query a UID and thus must include a token:
use a User access token for Facebook Login authenticated requests
use a Page access token for page-scoped requests
use an App access token for server-side requests
use a Client access token for mobile or web client-side requests
We recommend that you only use a Client token if you are unable to use
one of the other token types.

I use this code in a Second Activity, after having already logged in, for me the Token that is obtained in loginResult.getAccessToken().getToken(); It expires after a while, so researching I found this and it has served me
final String img = mAuthProvider.imgUsuario().toString(); // is = mAuth.getCurrentUser().getPhotoUrl().toString;
final String newToken = "?height=1000&access_token=" + AccessToken.getCurrentAccessToken().getToken();
Picasso.get().load(img + newToken).into("Image reference");

Check below response
final graphResponse = await http.get(
'https://graph.facebook.com/v2.12/me?fields=name,picture.width(800).height(800),first_name,last_name,email&access_token=${fbToken}');

monitor web browser programmatically in Android?

I've got a tricky question here. I need users to make a payment to a bank (namely Barclaycard) in UK. To do so, I have a https URL , I add the parameters (such as amount to pay, order reference, etc) to the URL, start this http connection as an Intent.ActionView, which will redirect the user to the browser where he can enter his credit card details on the bank's webpage and make the payment to our account successfully. So far so good ?
The code I use is below (I changed values for privacy reasons) The problem is, I need to get back to the app when the user has completed/failed/cancelled the payment. Barclaycardautomatically redirects to a particular URL when the payment has succeeded, another one if it failed. Is there no way of knowing when Barclaycard payment has succeeded so that then I would go back to the android app somehow ?
Button cardbutton = (Button) findViewById(R.id.card_button);
cardbutton.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View arg0)
{
String preHashString = new String();
String proHashString = new String();
String SHAPassPhrase = new String();
SHAPassPhrase = "GSvTh£h70ZkHdAq9b"; // FOR TEST ENVIRONMENT
preHashString = preHashString + "AMOUNT=" + String.valueOf((int) (order.getPaymentAmount() * 100.00)) + SHAPassPhrase;
preHashString = preHashString + "BGCOLOR=cccccc" + SHAPassPhrase;
preHashString = preHashString + "CN=" + user.getString("name") + SHAPassPhrase;
preHashString = preHashString + "CURRENCY=GBP" + SHAPassPhrase;
preHashString = preHashString + "LANGUAGE=en_US" + SHAPassPhrase;
preHashString = preHashString + "ORDERID=" + order.getOrderId() + SHAPassPhrase;
try
{
proHashString = SHA1(preHashString);
}
catch (NoSuchAlgorithmException e)
{
e.printStackTrace();
}
catch (UnsupportedEncodingException e)
{
e.printStackTrace();
}
String redirecturl = "https://mdepayments.epdq.co.uk/ncol/test/orderstandard.asp";
redirecturl += "?AMOUNT=" + String.valueOf((int) (order.getPaymentAmount() * 100));
redirecturl += "&CN=" + user.getString("name");
redirecturl += "&CURRENCY=GBP";
redirecturl += "&LANGUAGE=en_US";
redirecturl += "&ORDERID=" + order.getOrderId();
redirecturl += "&SHASIGN=" + proHashString;
Intent i = new Intent(Intent.ACTION_VIEW, Uri.parse(redirecturl));
startActivity(i);
}
});

You can have your own Webview in place inside your app, with some done / close button somewhere.. Then you can track all urls getting open in your WebView and do your stuff accordingly..User will stay in your app always..that solves your purpose..
For tracking all urls inside your WebView you need to register one WebViewClient and ovveride below function
public boolean shouldOverrideUrlLoading (WebView view, String url)
Have a look at WebView here and WebViewClient here

You should never be doing such things on user device. Someone can decompile your code and change it, so your app will "think" they made the payment.
This may lead to small problems like they using app for free to severe problems like you being forced to make all the payments.
Either use server-side solution or in-app-purchase from Google.

If your user gets redirected to a new URL you could use a ContentObserver that observes the bookmark history for any changes:
public class UrlObserver extends ContentObserver {
#Override
public void onChange(boolean selfChange) {
super.onChange(selfChange);
// check last URL in history
}
}
Reading the history can be done by:
private static final Uri CONTENT_URI = Browser.BOOKMARKS_URI;
Cursor cursor = context.getContentResolver().query(
CONTENT_URI, Browser.HISTORY_PROJECTION, null, null, null);
Registration of the content observer works with:
UrlObserver observer = new UrlObserver();
context.getContentResolver().registerContentObserver(CONTENT_URI, true, observer);
Once a particular URL has been detected, you can invoke an intent to bring your activity back to front.
This is a sample app which might help you in this case.
I'm not 100% sure what happens if the same site is used for the form transmission. It might be that the content observer won't trigger. In that case you might find some useful log entries.
Note: Chrome and the Android standard browser use different URLs for the query. Search the internet to find the right one.
Hope this helps .... Cheers!