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how to change fragment views programmatically from the parent activity

I am having a fragment that contains for example one button, I want to allow the Activity containing the fragment to change this button view like for example color and title or src Image.
What's the best way to do that ?
Update : sorry If I wasn't clear enough but I want the activity to change the whole view as it's likes , like setting the padding, the color or anything.
It will create the view programmatically and the fragment should replace the old view by the new one and change the view's ID so that the fragment code isn't affected. And If i created methods in the fragment that takes these views when should the Main activity call them ? since the activity has to wait for the layout of the fragment to be created.

1. You must get you fragment from your activity
val fragment = supportFragmentManager.findFragmentByTag("tag")
or
val fragment = supportFragmentManager.findFragmentById(R.id.fragment)
2. Create a method that will do what you wants in you fragment and call this method from the activity
fragment.hideButton()
or you can use interface

Try this way according to your requirement
public abstract class BaseFragment extends Fragment {
BaseActivity yourActivity;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
yourActivity = (BaseActivity) context;
}
#Override
public void onDetach() {
yourActivity = null;
super.onDetach();
}
public void refreshview(){}
public void setDada(Data data){}
#override
publicn void onStart(){
yourActivity.setCurrentOpenedFragment(this);
}
}
Create the BaseActivity class
public abstract class BaseActivity extends AppCompatActivity{
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
public void setCurrentOpenedFragment(BaseFragment currentFragment){}
}
Extends the BaseFragment in your fragment i.e.
public class YourFragment extends BaseFragment{
View view;
Button button;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment, container, false);
button = (Button)view.findViewById(R.id.button);
return view;
}
#override
publicn void onStart(){
super.onStart();
//yourActivity.setCurrentOpenedFragment(this);
}
Data data;
#override
public void setDada(Data data){
this.data = data;
}
#Override
public void refreshview() {
button.setcolor(data.getcolor());
}
}
Write the below line of code in your Activity class
public class YourActivity extends BaseActivity{
public static final byte NONE = -1;
public static final byte HOME = 1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_activity);
changeFragment(new YourFragment(), HOME);
initview();
}
public void initview(){
Button b = (Button)findViewById(R.id.button);
b.setOnClickListener(new OnClickListener(){
if(currentFragmentOnDrawer != null){
Data data = new Data();
data.setColor(getResource().getcolor(R.color.red));
currentFragmentOnDrawer.setDada(data);
currentFragmentOnDrawer.refreshview()
}
});
}
BaseFragment currentFragmentOnDrawer;
#Override
public void setCurrentOpenedFragment(BaseFragment currentFragment) {
super.setCurrentOpenedFragment(currentFragment);
this.currentFragmentOnDrawer = currentFragment;
}
public void changeFragment(Fragment targetFragment, byte state) {
FragmentTransaction ft = getSupportFragmentManager()
.beginTransaction();
ft.replace(R.id.main_fragment, targetFragment, "" + state);
ft.addToBackStack("" + state);
ft.commit();
}
}
Hope it will help for you

android- How to make an existing fragment implement an activity's listener?

I'm going from a Fragment -> Activity. In the activity I make an interface and when the user clicks a button I pass in a string to an interface object I create and call finish(). In the fragment I implement that interface and want to get that string. But in the activity I get a crash saying the listener is null.
public class SampleActivity extends AppCompatActivity
{
private Button button;
private MatchActivity.OnMatchCompleteListener onMatchCompleteListener;
public interface OnMatchCompleteListener
{
public void matchComplete(String matchID);
}
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = (Button) findViewById(R.id.someButton);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
onMatchCompleteListener.matchComplete("finished");
finish();
}
});
}
}
Fragment
public class SampleFragment extends Fragment implements SampleActivity.OnMatchCompleteListener{
private View rootView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.fragment_login , container, false);
return rootView;
}
#Override
public void matchComplete(String matchID) {
Log.d("TEST",matchID);
}
}

if you have your fragment in the R.layout.activity_main and your fragment id is R.id.fragment use this:
onMatchCompleteListener =
((SampleFragment)getFragmentManager().findFragmentById(R.id.fragment))
otherwise use this solution:
SampleFragment fragment = new SampleFragment();
onMatchCompleteListener = fragment;
getFragmentManager().beginTransaction().add(R.layout.activity_main, fragment, "TAG_SIMPLE").commit();

send data from activity to its fragment?

i'm trying to send data from activity to fragment
here is the activity code :
Bundle args=new Bundle();
args.putString("username", username);
ViewEmpAttend fragobj=new ViewEmpAttend();
fragobj.setArguments(args);
here is the fragment code :
username=this.getArguments().getString("username");
but this code gives me an error said "null object reference" in the onCreateView method in (Fragment Class) .
please help :)

Try to retrieve arguments from onCreate of Fragment
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
String username = this.getArguments().getString("username");
}

In activity define one method.
public class MainActivity extends AppCompatActivity {
String name;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//your code
}
//define this method
public String getName(){
this.name = username;
}}
In fragment use following code.
String userName = ((activityName) getActivity()).getName();//you will get name here.

For something simple like that, i will just create a constructor method in the fragment to pass in a string.
for example
public class MyFragment extends Fragment{
private String myString;
public MyFragment (){
// Recommended Empty Constructor
}
public MyFragment (String yourString){
this.myString = yourString;
}
}
On your Activity class you can pass in the string direct to your fragment constructor
public MyClass extends Activity{
#override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
openFragment();
}
public void openFragment(){
MyFragment fragment = new Fragment("yourString");
// Here begin the fragment transaction
}
}

onAttach() activity parameter null?

I have a main activity class, and a private inner class within the main activity. The private inner class has methods that when called will display fragments. This inner class implements an interface defined in the Fragment's class, to be used as a sort of callback. It is probably easiest to show through code.
public class MainActivity extends FragmentActivity {
//on a button clicked
EditItemManger em = new EditItemManager();
em.begin();
private class EditItemManager implements on EditItemFragment.EditedItemClickedListener{
//consructor, other stuff. no onCreate method because this inner class does not (explicity??) extend activty
public void begin(){
EditItemFragment editItemFrag = new EditItemFragment();
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(editItemFrag, EDIT_FRAG_TAG)
fragmentTransaction.commit();
}
#Override
public void onEditItemClicked() {
editFinish();
}
public void editFinish()
{
// other stuff
}
}
}
My EditItemFragment class, where the onAttach method always has a null activity parameter
public class EditItemFragment extends DialogFragment {
protected EditedItemClickedListener editedItemClickedListener;
protected ImageButton button;
public EditItemFragment(){}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
final Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.edit_name_fragment, container, false);
button = (ImageButton) view.findViewById(R.id.submit_new_item_button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
editedItemClickedListener.onEditedItemButtonClicked();
}
});
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
editedItemClickedListener= (EditedItemClickedListener) activity;
} catch (ClassCastException e) {
e.printStackTrace();
}
}
public interface OnEditNameButtonClickedListener {
public void onEditNameButtonClicked();
}
So because the parameter in onAttach() in my Fragment class is always null, it eventually causes a null pointer exception. I am wondering if it is because the fragment is called from a class that is not extending activity. The problem is that if this class extends activity, there will be an issue with trying to commit the Fragment Transaction

I guest your onAttach returns nullpointer exception. Its because your parent Activity the main activity doesnt implement your custom interface so it return null. See the code below let me know if it help you:
public class MainActivity extends FragmentActivity implements EditItemFragment.EditedItemClickedListener{
private DialogFragment editItemDialog;
//Do your code here
#Override
public void onEditItemClicked() {
editFinish();
}
public void showDialog(){
//this is for showing your custom dialog fragment
editItemDialog = EditItemFragment.newInstance();
editItemDialog.show(getSupportFragmentManager(),"editItemDialog");
}
}
this is for your EditItemFragment:
public class EditItemFragment extends DialogFragment{
//Do your code here
public static EditItemFragment newInstance(){
EditItemFragment editItemDialog = new EditItemFragment();
return editItemDialog;
}
}

Return data from DialogFragment to MainActivity

I'm trying return a String from the DialogFragment, following this instructions https://stackoverflow.com/a/14808425/2933117 , but I only get logcat error
java.lang.ClassCastException: com.example.testinterface.MainActivity cannot be cast to com.example.testinterface.InterDialog$EditNameDialogListener
I appreciate any help or explanation of why I get an error, thanks in advance.
Here is my code:
MainActivity
public class MainActivity extends FragmentActivity {
private Button Btn;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Btn=(Button)findViewById(R.id.button1);
Btn.setOnClickListener(new View.OnClickListener(){
public void onClick (View view) {
FragmentManager fm = getSupportFragmentManager();
InterDialog pruebafragment = new InterDialog();
pruebafragment.show(fm,"MyFragment");
}
});
}
public void onFinishEditDialog (String inputText) {
Toast.makeText(this, "Hi, " + inputText, Toast.LENGTH_SHORT).show();
}
}
and DialogFragment
public class InterDialog extends DialogFragment {
public interface EditNameDialogListener {
void onFinishEditDialog(String inputText);
}
public InterDialog() {
// Empty constructor required for DialogFragment
}
EditNameDialogListener activity;
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.new_layout, container);
activity = (EditNameDialogListener) getActivity();
Button button = (Button)view.findViewById(R.id.Btnreturn);
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
activity.onFinishEditDialog("errorrrr");
getDialog().dismiss();
}
});
return view;
}
}

The line:
activity = (EditNameDialogListener) getActivity();
is what is breaking it. Make sure your activity implements the EditNameDialogListener interface by doing
public class MainActivity extends FragmentActivity implements EditNameDialogListener {
Hope that helps