Develop Reference

Button's onClick method modifying a global variable in Fragment

The code in my fragment is structured as follows:
public class FragmentScanQR extends Fragment {
...
private Button qrFromCameraBtn;
private View rootView;
...
public View onCreateView(final LayoutInflater inflater, final ViewGroup container, Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.qrsource, container, false);
qrFromCameraBtn = (Button)rootView.findViewById(R.id.qrViaCameraBtn);
qrFromCameraBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
rootView = inflater.inflate(R.layout.fragmenttab1, container, false);
}
});
return rootView;
}
The onCreateView method of fragment returns a value of type android.view.View. The qrFromCameraBtn button's onClick method modifies the same View variable. In the output, when I click on the botton, the layout doesn't change to R.layout.fragmenttab1 (which I wish to achieve) but remains the same. How can I do this?

If I understand what you need, you want to replace your first fragment with a new one. You can do that like so:
//Where Article fragment is your new fragment.
ArticleFragment newFragment = new ArticleFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack so the user can navigate back
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();
Source: https://developer.android.com/training/basics/fragments/fragment-ui.html

If you want to just replace the layout,this link might help you.
Android - How to dynamically change fragment layout.
Just add the following code on button click method
qrFromCameraBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
RelativeLayout rl = (RelativeLayout) findViewById(R.id.about);
rl.removeAllViews();
rl.addView(View.inflate(myView.getContext(), R.layout.about, null));
}
});

Android relationships between fragments

I'm using some fragments programmatically in activity. There is one button in my first fragment and when i click to this button, it replaces to second fragment.My second fragment's background is 90% transparent, and when it starts, i can see button which is situated in first fragment, and it also works. I want to stop or do something, because i dont want to see first fragment features and use it.
First Fragment
public class RegistrationFirstFragment extends Fragment {
RegistrationSecondFragment rf;
ImageButton btnNewUser,btnNewAgent;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
//return super.onCreateView(inflater, container, savedInstanceState);
View v =inflater.inflate(R.layout.fragment_registration_first,container,false);
rf = new RegistrationSecondFragment();
btnNewUser = (ImageButton)v.findViewById(R.id.btnNewUserRegistrationFirstFragment);
btnNewAgent = (ImageButton)v.findViewById(R.id.btnNewAgentRegistrationFirstFragment);
btnNewUser.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(getActivity(), "Transaction completed succesfully", Toast.LENGTH_LONG).show();
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.flRegistrationFirst, rf);
ft.commit();
}
});
return v;
}
}
Second Fragment
public class RegistrationSecondFragment extends Fragment {
RegistrationFirstFragment rtl;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rtl = new RegistrationFirstFragment();
//return super.onCreateView(inflater, container, savedInstanceState);
View v =inflater.inflate(R.layout.fragment_registration_second,container,false);
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
// ft.replace(R.id.flRegistrationFirst, rf);
ft.remove(rtl);
ft.commit();
return v;
}
}
Main Activity
public class RegistrationActivity extends AppCompatActivity{
RegistrationFirstFragment fr;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_registration);
fr = new RegistrationFirstFragment();
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.add(R.id.flRegistrationFragment,fr);
ft.commit();
}
}

You can put
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();
(the parameter fragment would be an instance of your second fragment)
into your onClick(View view){...} method to change the fragment instead of adding it.
Next time code for understanding your problem btw ;)

Add to fragment layout android:clickable="true". Int his way fragment will catch event so the click will not be caught by "main fragment".
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true" />

Give android:clickable="true" for Second Fragment root layout parent, when ever fragment opens It catches the click event of root and ignored previous click events.
Second One: If u use replace Fragment it's better than add fragment.
getActivity().getSupportFragmentManager().beginTransaction().replace
(R.id.YOUR_CONTAINER, 'FragmentObject').addToBackStack("TAG").commitAllowingStateLoss();

nullpointer running method of fragment from activity when using views

My Fragment
public class CustomFrag extends Fragment {
private Button btn;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.button_fragment, container, false);
btn = (Button)view.findViewById(R.id.button1);
return view;
}
public void sendItem(String item) {
btn.setText(item);
}
}
And in my activity
public void loadFragment(String data) {
// Load up new fragment
Fragment fragment = new CustomFrag();
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction transaction = fm.beginTransaction();
transaction.add(R.id.contentFragment, fragment, "custFrag");
transaction.addToBackStack("custFrag");
transaction.commit();
// Required before calling fragment methods
getSupportFragmentManager().executePendingTransactions();
// Load fragment with data
CustomFrag frag = (CustomFrag) getSupportFragmentManager().findFragmentByTag("custFrag");
frag.sendItem(data);
}
I'm getting a nullpointer exception any time I attempt to use the views of my fragment. If I try to load the view inside the method as well, it will not work
i.e. inside sendItem()
btn = (Button)getView().findViewById(R.id.button1);
My layout (button_fragment) contains the button:
<Button
android:id="#+id/button1"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

Because you have executed the transaction does not mean that the fragment has actually created its view. Which is why btn is still null.
To pass data from the activity to the fragment, use the argument bundle:
Fragment fragment = new CustomFrag();
Bundle args = new Bundle();
args.putString("item", data);
fragment.setArguments(args);
Then, in onCreateView:
btn = (Button)view.findViewById(R.id.button1);
btn.setText(getArguments().getString("item"));
See this Best practice for instantiating a new Android Fragment question and the first answer.

The problem here is that the fragment's layout is not drawn yet when sendItem(...) is called. Which means btn is null at that point. Instead, this is how you're supposed to do it (see http://developer.android.com/guide/components/fragments.html):
public class CustomFrag extends Fragment {
private Button btn;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.button_fragment, container, false);
btn = (Button)view.findViewById(R.id.button1);
btn.setText(getArguments.getString("item"));
return view;
}
}
And
public void loadFragment(String data) {
// Load up new fragment
Fragment fragment = new CustomFrag();
Bundle args = new Bundle();
args.putString("item", data);
fragment.setArguments(args);
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction transaction = fm.beginTransaction();
transaction.add(R.id.contentFragment, fragment, "custFrag");
transaction.addToBackStack("custFrag");
transaction.commit();
// Required before calling fragment methods
getSupportFragmentManager().executePendingTransactions();
}
Edit:
njzk2 was faster, but I hope the details I gave will help you further. In any case, the link he gave explains nicely why you should do it like that.

Fragments the right way

I'm trying out some fragments right now. I've got a fragment with a button and when I click that button I switch to another fragment. Now when I push on the back button I return to the first fragment that's good. Now when I click again on that button a new fragment is started. So I always start a new fragment. I think thats not the way it needs to be done. Is there a better way to for example resume the already created fragment?
My code:
public static class PlaceholderFragment extends Fragment{
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
Button test = (Button)rootView.findViewById(R.id.button);
test.setOnClickListener(new OnClickListener()
{
#Override
public void onClick(View view)
{
Log.d("Test", "Button clicked.");
TestFrag newFragment = new TestFrag();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.container, newFragment);
transaction.addToBackStack(null);
transaction.commit();
}
});
return rootView;
}
}
public static class TestFrag extends Fragment {
public TestFrag() {
Log.d("Test","New fragment");
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main2, container, false);
return rootView;
}
}

When you use the fragment transaction you can specify a tag for the fragment
fragmentTransaction.add(R.id.main_fragment, newFragment, fragTag);
fragmentTransaction.commit();
Then later you can find a fragment by tag from the fragmentManager
newFragment = fragMan.findFragmentByTag(fragTag);
if newFragment then is null you should create the Fragment since it wasnt found by the tag

Thanks to Joakim:
fragmentTransaction.add(R.id.main_fragment, newFragment, fragTag); fragmentTransaction.commit();
Then later you can find a fragment by tag from the fragmentManager
newFragment = fragMan.findFragmentByTag(fragTag); if newFragment then is null you should create the Fragment since it wasnt found by the tag. If the tag isn't null you can just add and commit the new one.

Calling a fragment from another fragment on click

What I want to do is to call one fragment from another on click on item of listview. Program builds without errors however it crash on click on item. Btw I’m making here local Fragment_3 object, I have got already done it in my mainactivity, how to pass it to this function?
Fragment_1.java content:
public class Fragment_1 extends SherlockFragment implements OnItemClickListener{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// requestWindowFeature(Window.FEATURE_NO_TITLE);
View view = inflater.inflate(R.layout.fragment_1, container, false);
ListView listView = (ListView) view.findViewById(R.id.listView1);
listView.setOnItemClickListener(this);
return view;
}
#Override
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
// TODO Auto-generated method stub
Fragment Fragment3 = new Fragment_3();
Integer fragmentId = (Integer) v.getTag();
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(fragmentId, Fragment3);
fragmentTransaction.commit();
}
}

My suspicion is that v.getTag() is null; So Integer fragmentId = (Integer) v.getTag(); will end up in fragmentId being null. When unboxing that to an int you'll get a NullPointerException. Why don't you replace fragmentId in fragmentTransaction.replace(fragmentId, Fragment3); with the id of the container that holds current instance of Fragment_1?