Develop Reference

ChildEventListener not populating listview properly

I am trying to work with ChildEventListener in Firebase to populate the listView with the "title" field of every child nodes. But it's not working properly. My first activity is AuthActivity, which contains googleSignIn Button, by which the user can log in or authenticate. After that, in MainActivity a listView supposes to populate with the data using ChildEventListener datasnapshot. But it remains blank.
The interesting part is, If I go back to the AuthActivity with the back button pressed and again click the login button, it agains taking me to the MainActivity and somehow this time it's shows the listView with the correct data. And after closing the app, the same error happens. I am not getting any errors in the Logcat.
Here is my AuthActivity File
public class AuthActivity extends AppCompatActivity {
public static final int RC_SIGN_IN = 100;
SignInButton signInButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_auth);
signInButton = findViewById(R.id.signInButton);
signInButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// Choose authentication providers
List<AuthUI.IdpConfig> providers = Arrays.asList(
new AuthUI.IdpConfig.GoogleBuilder().build());
// Create and launch sign-in intent
startActivityForResult(
AuthUI.getInstance()
.createSignInIntentBuilder()
.setAvailableProviders(providers)
.build(),
RC_SIGN_IN);
}
});
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == RC_SIGN_IN) {
IdpResponse response = IdpResponse.fromResultIntent(data);
if (resultCode == RESULT_OK) {
Intent intent = new Intent(AuthActivity.this, MainActivity.class);
startActivity(intent);
} else {
Toast.makeText(this, "Login Failed! Please try again.", Toast.LENGTH_LONG).show();
}
}
}
}
And The MainActivity File
public class MainActivity extends AppCompatActivity {
public static final int RC_SIGN_IN = 100;
ListView listView;
ArrayList<String> titlesArray;
FirebaseDatabase database;
DatabaseReference databaseReference;
FirebaseUser user;
ChildEventListener childEventListener;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = findViewById(R.id.listView);
titlesArray = new ArrayList();
//Get the associated login user info
user = FirebaseAuth.getInstance().getCurrentUser();
//Write a message to the database
database = FirebaseDatabase.getInstance();
databaseReference = database.getReference().child("notes").child(user.getUid());
//Adding adapter to the list of titles
ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, titlesArray);
listView.setAdapter(adapter);
childEventListener = new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
Note notes = dataSnapshot.getValue(Note.class);
titlesArray.add(notes.getTitle());
}
#Override
public void onChildChanged(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
}
#Override
public void onChildRemoved(#NonNull DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(MainActivity.this, "Loading failed!", Toast.LENGTH_SHORT).show();
}
};
databaseReference.addChildEventListener(childEventListener);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.sign_out_menu:
AuthUI.getInstance()
.signOut(this);
return true;
case R.id.add_new:
Intent intent = new Intent(MainActivity.this, AddActivity.class);
startActivity(intent);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}

It is because you are not notifying adapter after getting data from firebase callback.
Just replace your listener like below.
childEventListener = new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
Note notes = dataSnapshot.getValue(Note.class);
titlesArray.add(notes.getTitle());
adapter.notifyDataSetChanged();
}
#Override
public void onChildChanged(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
}
#Override
public void onChildRemoved(#NonNull DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(MainActivity.this, "Loading failed!", Toast.LENGTH_SHORT).show();
}
};

Is there a way to reference a variable outside onCreate method?

I can't seem to reference a variable outside the onCreate method. Is there a way to overcome this? I'm a student and still learning. If anyone can help, that would be great. Thank you. I would like to reference the "url" variable to the "onItemClick" method, it says "Cannot resolve symbol".
Here is my code :
public class CominSoonActivity extends AppCompatActivity implements RecyclerViewClickItemInterface {
DatabaseReference reference;
RecyclerView recyclerView;
ArrayList<Event> list;
MyAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_comin_soon);
recyclerView = findViewById(R.id.myRecycler);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
list = new ArrayList<Event>();
adapter = new MyAdapter(CominSoonActivity.this, list, this);
recyclerView.setAdapter(adapter);
reference = FirebaseDatabase.getInstance().getReference().child("EventDisplay");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot dataSnapshot1: dataSnapshot.getChildren())
{
Event e = dataSnapshot1.getValue(Event.class);
String url = (String) dataSnapshot1.child("website").getValue();
list.add(e);
adapter.notifyDataSetChanged();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(CominSoonActivity.this, "Opps.... Something went wrong", Toast.LENGTH_SHORT).show();
}
});
//add back button
if (getSupportActionBar() != null) {
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
}
#Override
public void onItemClick(int position) {
//Uri uri = Uri.parse("http://fareezdanial19.wixsite.com/merlimaulibrary");
Uri uri = Uri.parse(url);
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}
//taking the user back to the previous activity
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if(item.getItemId() == android.R.id.home) {
Intent homeActivity = new Intent(getApplicationContext(), HomeActivity.class);
startActivity(homeActivity);
finish();
}
return super.onOptionsItemSelected(item);
}
}

You can do it like this,
public class CominSoonActivity extends AppCompatActivity implements RecyclerViewClickItemInterface {
DatabaseReference reference;
RecyclerView recyclerView;
ArrayList<Event> list;
MyAdapter adapter;
String url;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_comin_soon);
recyclerView = findViewById(R.id.myRecycler);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
list = new ArrayList<Event>();
adapter = new MyAdapter(CominSoonActivity.this, list, this);
recyclerView.setAdapter(adapter);
reference = FirebaseDatabase.getInstance().getReference().child("EventDisplay");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot dataSnapshot1: dataSnapshot.getChildren())
{
Event e = dataSnapshot1.getValue(Event.class);
url = (String) dataSnapshot1.child("website").getValue();
list.add(e);
adapter.notifyDataSetChanged();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(CominSoonActivity.this, "Opps.... Something went wrong", Toast.LENGTH_SHORT).show();
}
});
//add back button
if (getSupportActionBar() != null) {
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
}
#Override
public void onItemClick(int position) {
//Uri uri = Uri.parse("http://fareezdanial19.wixsite.com/merlimaulibrary");
if(!url.isEmpty()){
Uri uri = Uri.parse(url);
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}
}
//taking the user back to the previous activity
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if(item.getItemId() == android.R.id.home) {
Intent homeActivity = new Intent(getApplicationContext(), HomeActivity.class);
startActivity(homeActivity);
finish();
}
return super.onOptionsItemSelected(item);
}
}

In Firebase calss Adapter is fill with nothing

In FirebaseHelper Class I declare retrieve ArrayList method witch return spacecrafts ArrayList and it call fetchData method to add new Item in spacecrafts , In MainActivity I fill my adapter with helper.retrieve on the onCreate method , and make Dialog to add user Items when click saveBtn witch fill my adapter with helper.retrieve also , but adapter is fill with nothing , I make Toast to detect the problem and found that spacecrafts.size is fill every time with new Item but helper.retrieve().size every time =0 , Can anyone Shows me my mistake ?
here is FirebaseHelper Class :
class FirebaseHelper {
private DatabaseReference db;
private ArrayList<Spacecraft> spacecrafts=new ArrayList<>();
int x;
public FirebaseHelper(DatabaseReference db) {
this.db = db;
}
public Boolean save(Spacecraft spacecraft)
{
Boolean saved ;
if(spacecraft==null)
{
saved =false;
}else
{
try
{
db.child("Spacecraft").push().setValue(spacecraft);
saved =true;
}catch (DatabaseException e)
{
e.printStackTrace();
saved =false;
}
}
return saved;
}
private void fetchData(DataSnapshot dataSnapshot)
{
spacecrafts.clear();
for (DataSnapshot ds : dataSnapshot.getChildren())
{
Spacecraft spacecraft=ds.getValue(Spacecraft.class);
spacecrafts.add(spacecraft);
x=spacecrafts.size();
}
}
ArrayList<Spacecraft> retrieve()
{
db.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
fetchData(dataSnapshot);
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
fetchData(dataSnapshot);
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return spacecrafts;
}
}
and here is Main Activity class :
public class MainActivity extends AppCompatActivity {
DatabaseReference db;
FirebaseHelper helper;
MyAdapter adapter;
private RecyclerView rv;
EditText nameEditTxt,propTxt,descTxt;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.content_main);
rv= (RecyclerView) findViewById(R.id.rv);
rv.setLayoutManager(new LinearLayoutManager(this));
db= FirebaseDatabase.getInstance().getReference();
helper=new FirebaseHelper(db);
adapter=new MyAdapter(this,helper.retrieve());
rv.setAdapter(adapter);
Toast.makeText(MainActivity.this, "helper.retrieve().size() = " + helper.retrieve().size(), Toast.LENGTH_SHORT).show();
Toast.makeText(MainActivity.this, "spacecrafts.size() = " + helper.x, Toast.LENGTH_SHORT).show();
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
displayInputDialog();
Toast.makeText(MainActivity.this, "spacecrafts.size() = " + helper.x, Toast.LENGTH_SHORT).show();
Toast.makeText(MainActivity.this, "helper.retrieve().size() = " + helper.retrieve().size(), Toast.LENGTH_SHORT).show();
}
});
}
private void displayInputDialog()
{
final Dialog d=new Dialog(this);
d.setTitle("Save To Firebase");
d.setContentView(R.layout.input_dialog);
nameEditTxt= (EditText) d.findViewById(R.id.nameEditText);
propTxt= (EditText) d.findViewById(R.id.propellantEditText);
descTxt= (EditText) d.findViewById(R.id.descEditText);
Button saveBtn= (Button) d.findViewById(R.id.saveBtn);
saveBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//GET DATA
String name=nameEditTxt.getText().toString();
String propellant=propTxt.getText().toString();
String desc=descTxt.getText().toString();
//SET DATA
Spacecraft s=new Spacecraft();
s.setName(name);
s.setPropellant(propellant);
s.setDescription(desc);
if(name.length() > 0)
{
if(helper.save(s))
{
nameEditTxt.setText("");
propTxt.setText("");
descTxt.setText("");
adapter=new MyAdapter(MainActivity.this,helper.retrieve());
Toast.makeText(MainActivity.this, "spacecrafts.size() = " + helper.x, Toast.LENGTH_SHORT).show();
Toast.makeText(MainActivity.this, "helper.retrieve().size() = " + helper.retrieve().size(), Toast.LENGTH_SHORT).show();
rv.setAdapter(adapter);
adapter.notifyDataSetChanged();
d.hide();
}
}else
{
Toast.makeText(MainActivity.this, "Name Must Not Be Empty", Toast.LENGTH_SHORT).show();
}
}
});
d.show();
}
}

Firebase operations are run asynchronously that means they are run on a separate thread, So your method ArrayList<Spacecraft> retrieve() returns the list before it is populated.

I try this and its work
private void fetchData(DataSnapshot dataSnapshot)
{
// spacecrafts.clear();
for (DataSnapshot ds : dataSnapshot.getChildren())
{
Spacecraft spacecraft=ds.getValue(Spacecraft.class);
spacecrafts.add(spacecraft);
x=spacecrafts.size();
}
}
ArrayList<Spacecraft> retrieve()
{
db.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
// try to clear spacecrafts here
spacecrafts.clear();
fetchData(dataSnapshot);
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
// and here
spacecrafts.clear();
fetchData(dataSnapshot);
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return spacecrafts;
}
}

Firebase database listview open another activity

I am using firebase database where I am saving data manually and retrieving data in the app and that is working well but I want that when user clicks the listview item that must open another activity and within that must retrieve another table.
Here is below my code
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
private ProgressDialog progressDialog;
DatabaseReference mref =
FirebaseDatabase.getInstance().getReference("users");
ListView mlistview;
ArrayList<String> arrayList=new ArrayList<>();
ArrayAdapter<String> arrayAdapter;
private BottomNavigationView.OnNavigationItemSelectedListener
mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.navigation_home:
progressDialog.show();
startActivity(new
Intent(profilemain.this,profilemain.class));
return true;
case R.id.navigation_dashboard:
Toast.makeText(profilemain.this,"hi
hello",Toast.LENGTH_SHORT).show();
return true;
case R.id.navigation_notifications:
Toast.makeText(profilemain.this,"hi
hello",Toast.LENGTH_SHORT).show();
return true;
case R.id.navigation_signout:
Toast.makeText(profilemain.this,"You have successfully
Signed out",Toast.LENGTH_SHORT).show();
mAuth.signOut();
return true;
}
return false;
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_profilemain);
progressDialog.setMessage("loading");
progressDialog.setTitle("database is");
mlistview=(ListView) findViewById(R.id.listview);
Firebase.setAndroidContext(this);
DatabaseReference ref = FirebaseDatabase.getInstance()
.getReference("users");
//mref=new Firebase("https://stark-1dffd.firebaseio.com/users");
arrayAdapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,arrayList);
mlistview.setAdapter(arrayAdapter);
mref.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String value= dataSnapshot.getValue(String.class);
arrayList.add(value);
arrayAdapter.notifyDataSetChanged();
//
//
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
mAuth = FirebaseAuth.getInstance();
mAuthListener = new FirebaseAuth.AuthStateListener() {
#Override
public void onAuthStateChanged(#NonNull FirebaseAuth firebaseAuth) {
if (firebaseAuth.getCurrentUser()==null){
startActivity(new
Intent(profilemain.this,MainActivity.class));
}
}
};
}
#Override
protected void onStart() {
super.onStart();
mAuth.addAuthStateListener(mAuthListener);
}

add an ItemClickListener on your ListView
mlistview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent in = new Intent(MyActivity.this, DetailActivity.class);
in.putExtra("data", arrayList.get(position);// add the selected String from the ListView
startActivity(in);
}
});
and read the data from the other activity:
String data = getIntent().getStringExtra("data");

the result of pressing button is displayed after two presses

I have an activity for searching in firebase, it contains edittext for typing the text and button when I press the button The results supposed to appear in the recyclerview but when I press the button the first time nothing appears unless I press the button for the second time
the code of findDataActivity
public class FindDataActivity extends AppCompatActivity {
DatabaseReference db;
FirebaseHelper helper;
MyAdapter adapter;
RecyclerView rv;
EditText findETxt;
Button findBtn;
ArrayList<Paints> p;
String s;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_find_data);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
ActionBar actionBar = getSupportActionBar();
if(actionBar != null)
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
//SETUP RECYCLER
rv = (RecyclerView) findViewById(R.id.rvsearch);
rv.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
//INITIALIZE FIREBASE DB
db = FirebaseDatabase.getInstance().getReference("Database");
adapter = new MyAdapter(FindDataActivity.this, p);
rv.setAdapter(adapter);
findBtn = (Button) findViewById(R.id.find_btn);
helper = new FirebaseHelper(db);
}
public void search(View view) {
db.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
findETxt = (EditText) findViewById(R.id.findETxt);
s = findETxt.getText().toString();
p=helper.retrieveSearch(s);
adapter = new MyAdapter(FindDataActivity.this, p);
rv.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id=item.getItemId();
if(id == android.R.id.home){
onBackPressed();
return true;
}
return super.onOptionsItemSelected(item);
}
}
the code of firebase
public class FirebaseHelper {
DatabaseReference db;
Boolean saved=null;
Boolean saved1=null;
ArrayList<Paints> paints=new ArrayList<>();
ArrayList<String> keys=new ArrayList<>();
public FirebaseHelper(DatabaseReference db) {
this.db = db;
}
//READ THEN RETURN ARRAYLIST FOR SEARCH ITEMS IN CASE OF SEARCHING ABOUT ITEM
public ArrayList<Paints> retrieveSearch(final String item) {
db.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
fetchDataSearch(dataSnapshot,item);
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
fetchDataSearch(dataSnapshot,item);
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return paints;
}
//IMPLEMENT FETCH DATA AND FILL ARRAYLIST FOR SEARCH
private void fetchDataSearch( DataSnapshot dataSnapshot,String item)
{
paints.clear();
//sorting and searching
final DatabaseReference myRef = db.child("items");
Query query = myRef.orderByChild("type").startAt(item)
.endAt(item + "\uf8ff");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot messageSnapshot : dataSnapshot.getChildren()) {
Paints paint=messageSnapshot.getValue(Paints.class);
paints.add(paint);
//Toast.makeText(FindDataActivity.this, "found " + type + " unit: " + unit + " price " + price, Toast.LENGTH_LONG).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

In your MyAdapter class you must create a method like this:
public void updateAdapter(ArrayList<Paints> paint){
this.paint= paint;
notifyDataSetChanged();
}
In your search method replace adapter.notifyDataSetChanged(); for adapter.updateAdapter(p);