Develop Reference

How do you programmatically set ViewPager tabs from inside a fragment?

I have a database that provides an array of Strings, accessed from within a Fragment. I want these Strings to go back to the activity attached to the Fragment and set the titles of the tabs in a ViewPager. How can I do this?
This is how I want to do it:
Database String[] → Fragment → Attached activity's ViewPager → New
tabs
Edit: Here is my entire Activity and PagerAdapter code.
Here is my Fragment code

Suppose you have array of Strings and you want to send them to your activity from Fragment, make an interface like
public class MyFragment extends Fragment {
CustomStrings mCallback;
// Container Activity must implement this interface
public interface CustomStrings {
public void onStringRecieved(String[] stringss);
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception
try {
mCallback = (CustomStrings) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnHeadlineSelectedListener");
}
}
And then simple use this when you need to send data
mCallback.onStringRecieved(yourStrings); //your data here
And then in your activity implement it
public class MainActivity extends Activity
implements MyFragment.CustomStrings{
...
public void onStringRecieved(String[] stringss) {
// Do something here to use these strings
Toast.makeText(getContext(), ""+strings, Toast.LENGTH_SHORT).show();
}
Hope this solves your problem, for more information refer this

Create generic/base form class regardless if activity or fragment

I'm trying to create a generic/base form regardless if it is an activity or fragment. To make it simple, a Form can submit so:
class BaseFormActivity extends AppCompatActivity {
public abstract void submitForm();
#Override
public void setContentView(int layoutResID) {
ConstraintLayout activityBaseForm = (ConstraintLayout) getLayoutInflater().inflate(R.layout.activity_base_form, null);
FrameLayout frameBaseForm = activityBaseForm.findViewById(R.id.frame_base_form);
getLayoutInflater().inflate(layoutResID, frameBaseForm, true);
findViewById(R.id.btn_submit).setOnClickListener(v -> submitForm()) // for the sake of simplicity, there's a button that will trigger submitForm() method
super.setContentView(activityBaseForm);
}
}
Here, I just include some default layout for a form, and a button for submit that triggers the abstract method submitForm(). But, this is only for android activities. How can I make this also available for fragments without writing a BaseFormFragment? I don't want to repeat default behaviors from activity to the fragment and vice versa.

Consider it as a sample Presenter class which handle your button click and get all form fields and send to server
public class MyPresenter {
private MyPresenterIView iViewInstance;
public MyPresenter(MyPresenterIView iView){
this.iViewInstance=iView;
}
public void onSubmitClick(){
//write your logic here
String fieldOneText=iViewInstance.getFieldOneText();
sendToServer(fieldOneText);
}
private void sendToServer(String stringInfo){
//send info to server
}
}
MyPresenterIView Interface
public interface MyPresenterIView{
String getFieldOneText();
}
And use Presenter in your Activity or Fragment
//implement MyPresenterIView to your Activity or Fragment
public class MyActivity extent SomeActivity implements MyPresenterIView{
private MyPresenter myPresenter;
//in onCreate or onCreateView(if its a fragment) initialize myPresenter
protected void onCreate(..){
myPresenter=new MyPresenter(this);//this will enforce Activity/Fragment to implement IView
}
#Override //comes from MyPresenterIView
public String getFieldOneText(){
return ((EditText)findViewById(R.id.edttext_field_one)).getText().toString().trim();
}
}

Communication between Fragments without Using Interface

I was trying to communicate between two fragments, but I'm just a beginner so I want to know if there is any solution not using interface....
If there are Fragment A, B, and their Activity:
Sending values from Fragment A to Activity
(In here, Fragment A is a current state)
Sending values from Activity to Fragment B
I know direct communication between two fragments is almost impossible,
but I don't think that makes me to use an interface.
Also, is there any method to use like putExtra() for fragment? I only know using Serializable.

Have a look at the Android deverlopers page: http://developer.android.com/training/basics/fragments/communicating.html#DefineInterface
Basically, you define an interface in your Fragment A, and let your Activity implement that Interface. Now you can call the interface method in your Fragment, and your Activity will receive the event. Now in your activity, you can call your second Fragment to update the textview with the received value
// You Activity implements your interface
public class YourActivity implements FragmentA.TextClicked{
#Override
public void sendText(String text){
// Get Fragment B
FraB frag = (FragB)
getSupportFragmentManager().findFragmentById(R.id.fragment_b);
frag.updateText(text);
}
}
// Fragment A defines an Interface, and calls the method when needed
public class FragA extends Fragment{
TextClicked mCallback;
public interface TextClicked{
public void sendText(String text);
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception
try {
mCallback = (TextClicked) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement TextClicked");
}
}
public void someMethod(){
mCallback.sendText("YOUR TEXT");
}
#Override
public void onDetach() {
mCallback = null; // => avoid leaking, thanks #Deepscorn
super.onDetach();
}
}
// Fragment B has a public method to do something with the text
public class FragB extends Fragment{
public void updateText(String text){
// Here you have it
}
}

You can communicate between fragments directly by using EventBus - send ordinary or sticky events by one fragment and subscribe to that event in another one.
If don't want message to be lost, use sticky events - it work as sticky Intent in Android. It will be around until it is removed by targer fragment or because another event is pending.

Yes you can transfer data between fragments using bundle like you do in Activity using putExtra
Bundle = bundle = new Bundle();
bundle.putString("key","value");
bundle.putSerializable("serialzedKey",SerializedValue);
FragmentTransaction fts = ((BaseActivity) mContext).getSupportFragmentManager().beginTransaction();
fragment.setArguments(bundle);
fts.add(R.id.fragmentHolder, fragment);
fts.addToBackStack(fragment.getClass().getSimpleName());
fts.commit();
In other fragment you can retrieve data using getArguments()
String key = getArguments().getString("key");
SerializedModel = getArguments().getSerializable("serialzedKey");

you can call a method from the parent activity class that calls a method from fragment B like ((YourActivity)getActivity()).callMethod(T yourData)

Take a look at my Github repo on using interfaces to communicate between fragments.
This is just a really simple example but displays the key concepts.
https://github.com/stoddayy/FragmentInteractionExample

Fragment interface call-back not storing passed values

The interface
public interface GameSelectedListener {
public void onGameSelectedListener(int gameID, Boolean isCustom);
}
Inside FragmentA in the on attach I set the gameSelectedListener in on attach.
public void onAttach(Activity activity)
{
super.onAttach(activity);
gameSelectedListener = (GameSelectedListener)activity;
}
In one part of the code some data is sent
gameSelectedListener.onGameSelectedListener(groupItems.get(groupPosition).iD, isCustom);
Main activity which implements the interface and calls a method in FragmentB
#Override
public void onGameSelectedListener(int gameID, Boolean isCustom) {
// TODO Auto-generated method stub`enter code here`
FB.setGameID(gameID, isCustom);
}
Inside Fragment B is the setGameID method which just sets some data inside that fragment.
public void setGameID(int gameID, Boolean isCustom)
{
this.gameID = gameID;
this.isCustom = isCustom;
}
With log statements (not shown here). The data generated by fragment A is successfully sent to main activity. I log the values of the variables in setGameID method of fragment B also appear correctly to that generated by fragment A.
However here is the problem
I get null pointer exceptions when using gameID and isCustom from the FragmentB. So I set some default values to check it and I noticed that the value change made in setGameID does not effect the global variables even though when logging the values in setGameID show the correct values. Note that these two variables are not changed anywhere else in the code. Just in setGameID method.
I don't know if this helps but my fragments are java fragments (not XML based)
In main activity I create an instance of Fragment B in order to call setGameID. Note I declare this in the global area only.
FragmentB FB = new FragmentB();
Heres how it looks so far
Activity A -> Fragment Transaction add Fragment A -> From Fragment A Button click-> fragment replace A with B
EDIT Added some more code: Issue could be here.
gameSelectedListener.onGameSelectedListener(groupItems.get(groupPosition).iD, isCustom);
fragment = FragmentB.newInstance();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(Container.getId(), fragment, tag);
fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
I think the problem could well be here because I invoke the listener and then make a the Fragment B instance. Could this be it?

Use an EventBus instead of a listener! This design pattern mentioned in the official android docs is bullshit!
https://github.com/greenrobot/EventBus
class FragmentB extends Fragment {
private int id;
public static FragmentB newInstance(int id){
Bundle args = new Bundle();
args.putInt("id", id);
FragmentB frag = new FragmentB();
frag.setArguments(args);
}
public void onCreate(Bundle b){
super.onCreate(b);
this.id = getArguments().getInt("id);
}
}

When you replace Fragment A by Fragment B.
#Override
public void onGameSelectedListener(int gameID, Boolean isCustom) {
...// rest of the code
Bundle args = new Bundle();
args.putInt("id", gameID);
args.putBoolean("bool", isCustom);
FB.setArguments(args);
}
In Fragment B
int value = getArguments().getInt("id");

Access other fragment data

I'm having some trouble, and I have done research on the problem but it did not help me.
I have a Main.java class, which is template made pager view of fragments.
I did not modify it in any way, except for getItem() method which now returns my own fragments.
My fragment A is collecting accelerometer data, saving last 120 records in an ArrayList.
It also has graph plots, with Series objects, which I would like to access from fragment B.
This is what I want to do:
In fragment B user presses a button "record data"
This results in fragment A boolean field "recordingOn" changing to true
Now in fragmentA onSensorChange method, after checking for "recordingOn", if it's true it will pass data to an ArrayList that is a field in fragment B
How do I access these fields?

from fragment call
Fragment frag = getActivity().getFragmentManager()..findFragmentByTag("fragment to find tag");

Greensy answer is a valid option (I upvoted him) but you can also refrain from doing so much DataPassing between fragments and let the Activity be a manager for all that.
For that you can create public methods and interfaces in the fragments and let/force the activity implement the interfaces.
Simple example:
public class Act extends Activity implements OnClickListener{
#Override
OnClick(View v){
if(v.getId()==R.id.btn_recordData){
fragA.startRecording();
}
}
}
then FragA you must create that method:
public class FragA extends Fragment{
private boolean isRecording
public void startRecording(){ isRecording = true; // also init the sensor stuff }
public void stopRecording() { isRecording = false; // also stop the sensor stuff }
}
then on FragB you can:
public class FragB extends Fragment{
onCreateView(...){
// initialise all the views and find the button, let's call it Button btn;
btn.setOnClickListener((OnClickListener)getActivity());
}
}
does that make sense?

A way to do that is to use your own Application class and store your ArrayList in there
You can then access it in any point of your application, if you got a Context :
ArrayList<AccelerometerData> myAccelerometerData = ((MyApplication) mContext.getApplicationContext()).getAccelerometerData();
Be carefull about this solution since your ArrayList will be alive during all the application run