Develop Reference

How can I create a new user in Parse, without changing the current user?

I am currently making a friend request module. The user clicks "Approve" the program adds the friend to the _User class on Parse Server. I believed the code below would do it, and it does, but the problem is that is changes the current user to the new friend that has been added. So if the current user is "Bob", and Bob adds "Mike" the new current user is Mike.
I've been experimenting with signUp(), signUpInBackground(), but neither seem to work.
ParseUser newFriend = new ParseUser();
newFriend.setUsername(friendRequestFrom); //friendRequestFrom is a String that carries a name
newFriend.setPassword("12345");
newFriend.signUpInBackground(new SignUpCallback() {
#Override
public void done(ParseException e) {
if(e == null){
Log.i("Parse Result","Succesful!");
Log.i("Current User",ParseUser.getCurrentUser().getUsername());
}
else{
Log.i("Parse Result","Failed " + e.toString());
}
}
});

In order to create a new Parse user in Parse using client side code, you have to use a cloud code function hosted in your app backend.
In fact, for security reasons, client librararies are not permitted to directly add users.
In your server side, create a file (main.js) containing the following code:
Parse.Cloud.define("createNewUser", function(request, response) {
var User = Parse.Object.extend("User");
var us = new User();
us.set("username", request.params.username);
us.set("name", request.params.name);
us.set("email", request.params.email);
us.set("password", request.params.password);
us.save(null, {
useMasterKey: true,
success: function(obj) {
response.success("user added");
},
error:function(err){
response.error(err);
}
});
});
Then, you can test this function in your javascript client code as following:
var params = { username: "userEmailAddress#yahoo.fr",
email: "userEmailAddress#yahoo.fr",
name:"Here write the user name",
password:"TheUserPasswordHere"};
Parse.Cloud.run("createNewUser", params).then(function(response){console.log("response: "+response);}).catch(function (err) {
console.log("error: "+err);
});

Understand SharedPreferences Android

In android I want to make a basic login and registration application. I am following this tutorial. The application works properly and runs. I am just trying to understand the code now and after many google searches I can not understand some of the code and was wondering if somebody could help me understand it.
Below I have posted the method I do not understand and in comments highlighted what I do not understand - any clarification is much appreciated, I have also commented the code to what I believe the code does, if any of it is incorrect please tell me, you can also view all of the code on the tutorial website.
I am mainly confused about how the sharedpreferences works I have followed his tutorial on sharedpreferences too I understand that but do not understand this. Thank you and sorry if the problem is very basic
private void checkLogin(final String email, final String password) {
// Tag used to cancel the request
String tag_string_req = "req_login";
// Dialog stating trying to login
pDialog.setMessage("Logging in ...");
showDialog();
// Send the request over to the database to check details
StringRequest strReq = new StringRequest(Method.POST,
AppConfig.URL_LOGIN, new Response.Listener<String>() {
// Do this once you get a response
#Override
public void onResponse(String response) {
Log.d(loginName, "Login Response: " + response.toString());
hideDialog();
// Break the response up into individual things and store in variables
try {
JSONObject jObj = new JSONObject(response);
boolean error = jObj.getBoolean("error");
// Check for error node in json
if (!error) {
// I DO NOT UNDERSTAND THIS!!! how does this bit work?
// it sets the shared preferences login to true correct?
// but how does it set it true to only this particular user?
// Because it doesnt store the email and password along with it
// and sets its tag "isLoggedIn" and then saves it to the shared
// preferences
session.setLogin(true);
// Now store the user in SQLite
String uid = jObj.getString("uid");
JSONObject user = jObj.getJSONObject("user");
String name = user.getString("name");
String email = user.getString("email");
String created_at = user
.getString("created_at");
//I DO NOT UNDERSTAND THIS!!! Why do you need to do this & does this
//affect the MySQL DB at all?
db.addUser(name, email, uid, created_at);
// I DO NOT UNDERSTAND THIS!!! Why do you need to write LoginActivity.this
// do you not just write MainActivity?
Intent intent = new Intent(LoginActivity.this,
MainActivity.class);
startActivity(intent);
finish();
} else {
// Error in login. Get the error message
String errorMsg = jObj.getString("error_msg");
Toast.makeText(getApplicationContext(),
errorMsg, Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
// JSON error
e.printStackTrace();
Toast.makeText(getApplicationContext(), "Json error: " + e.getMessage(), Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Log.e(loginName, "Login Error: " + error.getMessage());
Toast.makeText(getApplicationContext(),
error.getMessage(), Toast.LENGTH_LONG).show();
hideDialog();
}
}) {
/***************************************************************/
//I DO NOT UNDERSTAND THIS WHOLE METHOD WHY DO YOU DO THIS?!!!
/***************************************************************/
#Override
protected Map<String, String> getParams() {
// Posting parameters to login url
Map<String, String> params = new HashMap<String, String>();
params.put("email", email);
params.put("password", password);
return params;
}
};
// FINALLY I ALSO DO NOT UNDERSTAND WHY YOU DO THIS! AND WHAT DOES IT DO
AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}

This adds a user to an SQL database:
db.addUser(name, email, uid, created_at);
There should be a class somewhere that defines the actual function, which then creates the query that actually interacts with the database.
The intent changes the activity (what is rendered on the screen and what logic is handled):
LoginActivity.this: the context in the current class - this can be simplified to just this, but it's a bit of syntactic sugar in Java that attempts to clarify which this is being referred to.
MainActivity.class: the target activity
Intent intent = new Intent(LoginActivity.this,
MainActivity.class);
The difference between two activities can be explained with the content of a game. The menu is "LoginActivity.this" and "MainActivity.class" is the actual game content
As for shared preferences, the usage is pretty straight-forward:
To obtain shared preferences, use the following method In your
activity:
SharedPreferences prefs = this.getSharedPreferences(
"com.example.app", Context.MODE_PRIVATE);
To read preferences:
String dateTimeKey = "com.example.app.datetime";
// use a default value using new Date()
long l = prefs.getLong(dateTimeKey, new Date().getTime());
To edit and save preferences
Date dt = getSomeDate();
prefs.edit().putLong(dateTimeKey, dt.getTime()).apply();
(Source, posted by naikus)
The internal mechanics aren't something you need to worry about - the thing you really need to know is that it's able to save your data in a way you can use that doesn't involve directly accessing files (which has become a maze since Android 10).
EDIT:
Based on what I saw at the tutorial, the entire thing is to check if the login information entered exists in the database. The getParams() method defines what goes into the form data

Java function returns empty string [duplicate]

This question already has answers here:
How to use Jsoup with Volley?
(3 answers)
Closed 6 years ago.
I'm trying to parse data from my server in Java with jsoup. I wrote a new function and it should return data in string format, but it returns blank string. Here is my code:
public String doc;
public String pare(final String url){
Thread downloadThread = new Thread() {
public void run() {
try {
doc = Jsoup.connect(url).get().toString();
}
catch (IOException e) {
e.printStackTrace();
}
}
};
downloadThread.start();
return doc;
}

You're returning the doc object immediately, before the thread has had a chance to add any data to it, so it should be no surprise that this returns empty. You can't return threaded information in this way, and instead will need to use some type of call-back mechanism, one that notifies you when the thread is done and when data is ready to be consumed.

On android platform, you shouldn't ask Jsoup to download anything for you. Under the hood, Jsoup make use of HttpUrlConnection. This class is notoriously slow and has some known issues.
Use a faster alternative instead: Volley.
Here is the function in your post taking advantage of Volley. In the following sample code, I'm using a CountDownLatch to wait for the data.
private static RequestQueue myRequestQueue = null;
public String pare(final String url) throws Exception {
final String[] doc = new String[1];
final CountDownLatch cdl = new CountDownLatch(1);
StringRequest documentRequest = new StringRequest( //
Request.Method.GET, //
url, //
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
doc[0] = Jsoup.parse(response).html();
cdl.coutDown();
}
}, //
new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Log.e("MyActivity", "Error while fetching " + url, error);
}
} //
);
if (myRequestQueue == null) {
myRequestQueue = Volley.newRequestQueue(this);
}
// Add the request to the queue...
myRequestQueue.add(documentRequest);
// ... and wait for the document.
// NOTA: User experience can be a concern here. We shouldn't freeze the app...
cdl.await();
return doc[0];
}

I totally agree with the above answer. You can follow any of the below tutorials for fetching data from server
http://www.androidhive.info/2014/05/android-working-with-volley-library-1/
http://www.vogella.com/tutorials/Retrofit/article.html
These two are the best libraries for Network calls in android

Before the return statement add a downloadThread.join(). This will wait until the thread has finished and put the response into doc. But: Doing so you will loose all benefit from the asynchronous execution, it's behaving the same as you just would code:
public String pare(final String url){
return Jsoup.connect(url).get().toString();
}

Volley request too slow

My app crashes because the images ArrayList is empty when I set the adapter, I figured that out by putting a toast message right after I parse my JSON request, and a Toast message after I initialize my adapter, "second" gets printed first on screen and the app crashes right after, does it have to do with my internet? Or am I missing something, here's my code, thanks!
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_page);
mViewPager = (ViewPager) findViewById(R.id.view_pager);
mVolleySingleton = VolleySingleton.getInstance();
mRequestQueue = mVolleySingleton.getRequestQueue();
//First Toast message inside this method
sendAPIRequest();
//after you get the images
mCustomSwipeAdapter = new CustomSwipeAdapter(this, images);
//SECOND TOAST
Toast.makeText(getApplicationContext(), "Second", Toast.LENGTH_LONG).show();
mViewPager.setAdapter(mCustomSwipeAdapter);
mCustomSwipeAdapter.notifyDataSetChanged();
}
public void sendAPIRequest(){
String requestURL = "";
JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, requestURL, (String) null, new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject response) {
parseJSONResponse(response);
//FIRST TOAST : SHOULD BE CALLED FIRST
Toast.makeText(getApplicationContext(), "First", Toast.LENGTH_LONG).show();
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
}
});
mRequestQueue.add(jsonObjectRequest);
}
public void parseJSONResponse(JSONObject response) {
if (response != null || response.length() != 0) {
try {
JSONObject GObject = response.getJSONObject("game");
String name = "N/A";
if (GObject.has("name") && !GObject.isNull("name")) { name = GObject.getString("name"); }
if (GObject.has("screenshots") && !GObject.isNull("screenshots")) {
JSONArray screenShotsArray = GObject.getJSONArray("screenshots");
for (int i = 0; i < screenShotsArray.length(); i++){
JSONObject screenshot = screenShotsArray.getJSONObject(i);
String screenshotURL = screenshot.getString("url");
images.add(screenshotURL);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}

Does it have to do with my internet? Or am I missing something ...
Both. It happens because you have a race condition.
From what I can make out, your images list is being populated asynchronously by the onResponse callback. Basically, that happens when your app gets the responses to the API requests that it is making. That is going to take at least milliseconds, and possibly seconds (or longer).
But your app is (so you say) crashing soon after the swipe adapter is registered, and the evidence is that the images list has not been populated.
There are three possibilities:
There is something wrong with the requests you are sending which is causing the API requests to not give you any response. (Hypothetically, you could have authentication wrong or something.)
The API requests are taking a long time because of internet connection speed, congestion, or the remote server being slow.
The API requests are taking a short time ... but the adapter registration is even quicker.
If (hypothetically) there is a problem with your requests you will need to fix that. But both of the other scenarios have to be fixed by:
modifying the code that uses the images to work properly if there are no images (yet), or
modifying the code to wait until the image loading has completed before registering the adapter.

Please use this code in your onResponse callback :
//after you get the images
mCustomSwipeAdapter = new CustomSwipeAdapter(this, images);
//SECOND TOAST
Toast.makeText(getApplicationContext(), "Second", Toast.LENGTH_LONG).show();
mViewPager.setAdapter(mCustomSwipeAdapter);
mCustomSwipeAdapter.notifyDataSetChanged();
Volley adds your requests in queue , so better do all the dependent tasks in Response or Error callback only.

Comparing values from textviews and JSONArray

Sorry for the (seemingly) lazy question, but i've been looking for a solution with no luck (in other words, I haven't found a solution that i understand).
I want to have users log in to an app by way of entering a username and password, this username and password has to match a username and password from the jsonarray which i've retrieved from a phpmyadmin database. The username and password have to be in the same row.
Here's the function I use to retrieve my jsonarray:
private void getData(){
JSONArray json;
try{
user = editText1.getText().toString();
password = editText2.getText().toString();
json = readJsonFromUrl("http://localhost/indextest.php?function=getdata");
Thread.sleep(1000);
} catch (Exception e) {
Log.e("BACKGROUND_PROC", e.getMessage());
}
}
I just need to know how to search the jsonarray for the values that i retrieve from my textviews.
If possible I would like to retrieve a value that I can easily assign to an if statement like such:
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
if ( editText1 != null && editText1.length() != 0 && editText2 != null && editText2.length() != 0){
getData();
m_ProgressDialog = ProgressDialog.show(HomeScreen.this,
"Please wait...", "Checking Details...", true);
m_ProgressDialog.setCancelable(true);
if ( /*username and password match*/){
Intent i = new Intent(this, Afterlog.class);
startActivity(i);
}
else{
Toast.makeText(HomeScreen.this, "The username and password did not match any in our database...", Toast.LENGTH_SHORT).show();
}
}
else {
Toast.makeText(HomeScreen.this, "Please enter a user name AND a password...", Toast.LENGTH_SHORT).show();
}
break;
}
}

Two things:
Take a look at GSON. It is a Google Library for encoding objects into json and then decoding json into objects. In essence, you can define a class that has the same structure as the data you are receiving in JSON and then use GSON to read the JSON and create an object of your class with the appropriate fields filled in. Your code would look something like this:
First, define your class structure for the data you are sending as JSON:
public class LoginData {
public String Username; //These identifiers must match the JSON structure
public String HashedPassword;
public LoginData(String username, String hashedPass) {
Username = username;
HashedPassword = hashedPass;
}
}
Then, once you receive the JSON, you can parse the information like this:
LoginData login = mGson.fromJson(json, LoginData.class);
It sounds like you are storing usernames and passwords in raw text and retrieving them from your database in raw text. This is a VERY BAD IDEA! Passwords should always be stored in an encrypted form (i.e. hashed). When the user provides their password to log in, you encrypt the provided password and compare the encrypted versions (i.e. compare the hash of the provided password to the stored hash from your database). This prevents people who might be listening to your network traffic from being able to capture your passwords. Instead, if they were watching your network traffic they would see the hashed password, and without knowing exactly the algorithm used to hash the passwords, they would not be able to calculate the original password.

Your code needs to run in an asyncTask because it is performing a network request:
Here is an example:
class LoginTask extends AsyncTask<String, String, JSONObject>
{
protected JSONObject doInBackground(String... urls)
{
return readJsonFromUrl(urls[0]);
}
protected void onPostExecute(JSONObject result)
{
try {
//this assumes that the response looks like this:
//{"username" : "john" , "password" : "Bsd6578" }
String responseUsername = result.getString("username");
String responsePassword = result.getString("password");
if (user.equals(responseUsername) && password.equals(responsePassword)){
Intent i = new Intent(this, Afterlog.class);
startActivity(i);
}else{
Log.d("mylog", "username and password dont match");
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Your button is should be responsible for running that task:
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
user = editText1.getText().toString();
password = editText2.getText().toString();
new LoginTask().execute()
break;
}
}

Found a very simple and to the point tutorial here:
http://www.coderzheaven.com/2012/04/22/create-simple-login-form-php-android-connect-php-android/
Thanks for all the help #meda :)