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How to pass a value in snakebar of an activity class from non activity (non view )java class?

I wish to pass a argument to snakebar function ,which is in main activity function from a non activity simple java class. Simply instantiating a activity class and passing value as argument does not work as I tried below. How can I achieve it in below scenario.
public class MainActivity extends AppCompatActivity {
private ConstraintLayout coordinatorLayout;
private Button button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
coordinatorLayout=findViewById(R.id.coordinator);
button= findViewById(R.id.james);
button.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View view){
showSnackbar("its not working ");
}
});
}
public void showSnackbar(String james){
Snackbar snackbar=Snackbar.make(coordinatorLayout,james,Snackbar.LENGTH_INDEFINITE);
snackbar.show();
}
}
2nd class without activity ,simple non view class
class MyAccount extends Account
{
#Override
public void onRegState(OnRegStateParam prm)
{
MyApp.observer.notifyRegState(prm.getCode(), prm.getReason(),
prm.getExpiration());
if(prm.getReason().equals("OK")) {
/ /when ever above value equals ok , I wish to send a below message as snakebar // message on the main activity class. but below code does not works
MainActivity2 main2= new MainActivity2(); // trying to call snakebar function from main activity.
if(prm.getReason().equals("Service Unavailable")){
Log.e("javan007", prm.getReason());
main2.showSnackbar("service Unavailable");
}
}
}

how to send data from one activity to another activity in android

I have created an volley list in this i have problem to get data from adapter to activity and this activity to another activity. I have received error cannot cast activity.java to anotherActivity.java below is my code. Please help me anyone thanks.
My Interface itemclick in Adapter class
private OnItemClickGetPlaylist mListener;
public interface OnItemClickGetPlaylist{
public void OnPlaylistItemClick(String playlistName,int numOfItems,String imageViewForPlaylist);
}
public void setOnClickListenerOnPlaylist(OnItemClickGetPlaylist listener)
{
mListener = listener;
}
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String id = playlist.getId_playlist_identify();
String PlaylistName = playlist.getTitile_of_playlist();
String imageOfPlaylist = playlist.getImage_of_playlist();
int numOfPlaylistSongs = getItemCount();
SendIdToDatabase(id);
if (mListener != null)
{
mListener.OnPlaylistItemClick(PlaylistName,numOfPlaylistSongs,imageOfPlaylist);
}
else {
Toast.makeText(context, "mListeren is null" + mListener, Toast.LENGTH_SHORT).show();
}
}
});
After get data handle OnPlaylistItemClick click in Activity below Codes
public void OnItemClickHandleInPlaylistActivity(String playlistName,int numOfItems,String imageViewForPlaylist)
{
//here is the adapter item click in activity now i want to send that data to another activity without any intent please help me.
// i have implement below code but it give me cannot cast activity to another activity error.
((anotherActivity) getApplicationContext()).OnItemClickInMusicActivity(playlistName,numOfItems,imageViewForPlaylist);
}

See the solution at https://stackoverflow.com/a/47637313/2413303
public class MyApplication extends Application {
private static MyApplication INSTANCE;
DataRepository dataRepository; // this is YOUR class
#Override
public void onCreate() {
super.onCreate();
INSTANCE = this;
dataRepository = new DataRepository();
}
public static MyApplication get() {
return INSTANCE;
}
}
The DataRepository should expose LiveData:
public class DataRepository {
private final MutableLiveData<MyData> data = new MutableLiveData<>();
public LiveData<MyData> getMyData() {
return data;
}
public void updateText(String text) {
MyData newData = data.getValue()
.toBuilder() // immutable new copy
.setText(text)
.build();
data.setValue(newData);
}
}
Where the Activity subscribes to this:
public class MyActivity extends AppCompatActivity {
DataRepository dataRepository;
TextView textView;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
MyApplication app = (MyApplication)getApplicationContext();
dataRepository = app.getDataRepository();
setContentView(R.layout.main_activity);
textView = findViewById(R.id.textview);
dataRepository.getMyData().observe(this, new Observer() {
#Override
public void onChange(MyObject myObject) {
textView.setText(myObject.getText());
}
}
}
So to update this text, you need to get the DataRepository class, and call updateText on it:
DataRepository dataRepository = MyApplication.get().dataRepository();
dataRepository.updateText("my new text");
Make sure that the data in DataRepository is properly persisted somewhere, or at least can be obtained again after process death. You might want to use a database for example (but not shared preferences).

If you don't want to use Intents, maybe you can use a publish/subscribe architecture. There is a library called eventbus (org.greenrobot:eventbus) very easy to use which could achieve what you want.

Use an Application Class instead.
public class MyApplicationClass extends Application{
#Override
public void onCreate() {
super.onCreate();
///do something on create
}
getterMethods(){...}
setterMethods(){...}
}
then add android:name=".MyApplicationClass" to manifest file
Now you can access the methods in class by
MyApplicationClass applicationClass = (MyApplicationClass)getApplicationContext();
int id = applicationClass .getterMethod().getID;
String playListName = applicationClass .getterMethod().getPlayListName();
and vice versa for Setter();
after that you can use it for data getting and setting Data throughout the application.
Hope it helps :)
References:
https://guides.codepath.com/android/Understanding-the-Android-Application-Class

I find the best to use callbacks.
in ClassA:
Create interface
MyCallback callback;
viod setCallback(MyCallback callback){
this.callback = callback;
}
viod onStop(){
callback = null;
}
interface MyCallback{
void doSomething(Params params);
}
in ClassB:
implement MyCallback
public class ClassB **implements ClassA.MyCallback**
set reference in onCreate
ClassA classA = new ClassA();
classA.setCallback(this);
// override method doSomething
#override
void doSomething(Params params){
//do your thing with the params…
}
when the job is done inside class A call:
callback.doSomething(params);
destroy reference inside class B in onStop()
classA.onStop();

Which is a better way to code getActivity() , getApplicationContext()?

i'm not asking diffrence, but how to use these referenes?, Class level object to store their reference or use getter everytime which is provided by super class, Which is a better code practice: 1. call getActivity(), getApplicationContext() ..etc everytime in a local method or pass method as parameter when required in an activity or fragment.
Store their reference in a class level object and use it whereever it's required with null check in an activity or fragment.
I would like to know what is more efficient and why?
type1:
Class A extends Activity
{
#Override
public void onCreate()
{
methodA(getApplicationContext());
//or if fragment
methodA(getActivity());
Toast.makeText(getApplicationContext(),...).show();
}
private void methodA(Context mContext)
{
......
......
}
private void methodA()
{
Activity activity = getActivity();
......
......
}
}
type2:
class A extends Activity{
private Activity mContext;
private Activity mActRef; //if fragment
#Override
public void onCreate()
{
mContext = getApplicationContext();
mActRef = getActivity();//if fragment;
methodA(mContext);
//or if fragment
methodA(mActRef);
..........
.........
.........
Toast.makeText(mContext,...).show();
}
private void methodA(Context mContext)
{
......
......
}
private void methodA()
{
Toast.makeText(mContext,....).show();
}
}
}

getActivity() and getApplicationContext() both return the context and available throughout the class extend with Activity.
According to my opinion No need to create a global variable for them because they are available at class level. Both are correct but storing the context is not efficient.

How to get activity context into a non-activity class android?

I have a Activity class from where I am passing some information to a helper class(Non-activity) class. In the helper class I want to use the getSharedPreferences(). But I am unable to use it as it requires the activity context.
here is my code:
class myActivity extends Activity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.home);
Info = new Authenticate().execute(ContentString).get();
ItemsStore.SetItems(Info);
}
}
class ItemsStore
{
public void SetItems(Information info)
{
SharedPreferences localSettings = mContext.getSharedPreferences("FileName", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = localSettings.edit();
editor.putString("Url", info.Url);
editor.putString("Email", info.Email);
}
}
ANy idea how this can be achieved?

Instead of creating memory leaks (by holding activity context in a class field) you can try this solution because shared preferences do not need activity context but ... any context :) For long living objects you should use ApplicationContext.
Create the application class:
public class MySuperAppApplication extends Application {
private static Application instance;
#Override
public void onCreate() {
super.onCreate();
instance = this;
}
public static Context getContext() {
return instance.getApplicationContext();
}
}
Register it at manifest
<application
...
android:name=".MySuperAppApplication" >
...
</application>
Then you can do something like this
public void persistItems(Information info) {
Context context = MySuperAppApplication.getContext();
SharedPreferences sharedPreferences = context.getSharedPreferences("urlPersistencePreferences", Context.MODE_PRIVATE);
sharedPreferences.edit()
.putString("Url", info.Url)
.putString("Email", info.Email);
}
Method signature looks better this way because it does not need external context. This can be hide under some interface. You can also use it easily for dependency injection.
HTH

Try this:
class myActivity extends Activity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.home);
Info = new Authenticate().execute(ContentString).get();
ItemsStore.SetItems(Info, getApplicationContext());
}
}
class ItemsStore
{
public void SetItems(Information info, Context mContext)
{
SharedPreferences localSettings = mContext.getSharedPreferences("FileName",
Context.MODE_PRIVATE);
SharedPreferences.Editor editor = localSettings.edit();
editor.putString("Url", info.Url);
editor.putString("Email", info.Email);
}
}

You need to pass the context to the constructor of non activity class
ItemsStore itemstore = new ItemStore(myActivity.this);
itemstore.SetItems(Info);
Then
Context mContext;
public ItemsStore (Context context)
{
mContext =context;
}
Now mContext can be used as Activity Context.
Note: Do not keep long-lived references to a context-activity (a reference to an activity should have the same life cycle as the activity itself)

Write a public function in your activity. While creating an instance of your helper class in Activity class, pass the context of activity in constructor.
Then from your helper class, using the activity context, call the public function in activity class.

AsyncTask is restarting when i press back button

I have an activity with multiple AsyncTask's, but when i press back button, the Activity is reloaded and the AsyncTask's are executed again. what should i do to Back to the previous activity and not reload the activity and asynctask ? please help.
public class LugarActivity extends SherlockActivity {
CargarDatos cargarDatos;
CargarComentarios cargarComentarios;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_lugar);
cargarDatos = new CargarDatos();
cargarCometarios = new CargarComentarios();
loadData();
}
public void loadData(){
cargarDatos.execute();
}
public void loadOtherData(){
cargarComentarios.execute();
}
public class CargarDatos extends AsyncTask<Integer, Integer, String>{
#Override
protected String doInBackground(Integer... params) {
// here download data
}
#Override
protected void onPostExecute(String html) {
loadOtherData();
}
}
public class CargarComentarios extends AsyncTask<Integer, Integer, String>{
#Override
protected String doInBackground(Integer... params) {
// here download data
}
}
}
FIXED!
i fixed the problem with Singleton class:
public class DataManager {
private static DataManager instance = null;
protected static boolean isShowingTheView = false;
protected DataManager() { }
public static synchronized DataManager getInstance() {
if (instance == null) {
instance = new DataManager();
}
return instance;
}
}
in the activity i add this code:
DataManager dataManager = new DataManager();
if(!dataManager.isShowingTheView){
loadData();
dataManager.isShowingTheView = true;
}else{
finish();
}
and finally i override the onDestroy() method
#Override
public void onDestroy(){
dataManager.isShowingTheView = false;
super.onDestroy();
}

Remove loadData() from onCreate and call somewhere else.

Use Fragments
http://www.androiddesignpatterns.com/2013/04/retaining-objects-across-config-changes.html
A fragment can stay in memory during a configuration change and therefore you can run your asynctask inside itself. You can then query the fragment for any state information you require from your tasks and update your Activity accordingly.

If your Activity is destroyed before the other activity starts, using the back button will call onCreate again, instead of onRestart or onResume.
See here for details.
As Kuffs already mentions, using Fragments is the way to go.
Uglier solution, you could also set a shared preference holding a boolean once your AsyncTask is launched (or on its onPostExecute) so that it won't launch again after checking for that preference on your Activity's onCreate.