Develop Reference

App title doesn't change after returning to previous fragment

I've been developing an android app which I included the default Navigation-Drawer from Android Studio and so on. In my home fragment, I've implemented CarViews, and then set those cardview(s) OnClickListener to replace the fragment with traditional procedure.
After the fragment replacement and new page comes, I wanted to change the Actionbar title.
So in the onCreateView(...) method, I tried,
((AppCompatActivity)getActivity()).getSupportActionBar().setTitle("B");
It worked. But after pressing the hardware back button to go back to the stacked fragment, the title remains changed & it doesn't change to "Home" again. I've tried other ways. Here's my following codes. Thanks in advance.
public class HomeFragment extends Fragment implements View.OnClickListener {
public View onCreateView(#NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_home, container, false);
Objects.requireNonNull(((AppCompatActivity) Objects.requireNonNull(getActivity())).getSupportActionBar()).setTitle("Home");
CardView cardView1 = root.findViewById(R.id.doctor_on);
CardView cardView2 = root.findViewById(R.id.ambulance_e);
CardView cardView3 = root.findViewById(R.id.maintainance_s);
cardView1.setOnClickListener(this);
cardView2.setOnClickListener(this);
cardView3.setOnClickListener(this);
return root;
}
#Override
public void onClick(View v) {
int id = v.getId();
switch (id) {
case R.id.doctor_on:
FragmentTransaction fragmentTransaction = Objects.requireNonNull(getActivity()).getSupportFragmentManager().beginTransaction();
Fragment fragment1 = new doctors();
fragmentTransaction.replace(R.id.container1, fragment1).addToBackStack(getString(R.string.menu_home)).commit();
return;
case R.id.ambulance_e:
//Put Actions
FragmentTransaction fragmentTransaction2 = Objects.requireNonNull(getActivity()).getSupportFragmentManager().beginTransaction();
Fragment fragment2 = new ambulance();
fragmentTransaction2.replace(R.id.container1, fragment2).addToBackStack(getString(R.string.menu_home)).commit();
return;
case R.id.maintainance_s:
//Put Actions
FragmentTransaction fragmentTransaction3 = Objects.requireNonNull(getActivity()).getSupportFragmentManager().beginTransaction();
Fragment fragment3 = new maintanance();
fragmentTransaction3.replace(R.id.container1, fragment3).addToBackStack(getString(R.string.menu_home)).commit();
return;
}
}
#Override
public void onResume() {
super.onResume();
((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("Home");
}
}
To the next fragment(where I change the titlebar and pressed back button):
public class doctors extend Fragment{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
((AppCompatActivity)getActivity()).getSupportActionBar().setTitle("B");
View root = inflater.inflate(R.layout.fragment_doctors, container, false);
return root;
}
}

And in the doctors Fragment... Should fix the title error.
#Override
public void onDestroyView() {
super.onDestroyView();
Objects.requireNonNull(((AppCompatActivity) Objects.requireNonNull(getActivity()))
.getSupportActionBar())
.setTitle(getString(R.string.your_title_here));
}

You have to override the method onBackPressed() and write the code:
#Override
public View onBackPressed(){
//Here goes the code that head back to your main fragment
FragmentTransaction fragmentTransaction3 = Objects.requireNonNull(getActivity()).getSupportFragmentManager().beginTransaction();
Fragment fragment3 = new maintanance();
fragmentTransaction3.replace(R.id.container1, fragment3).addToBackStack(getString(R.string.menu_home)).commit();
}
}`

Add below code in Home Fragment...
#Override
public void onHiddenChanged(Boolean hidden) {
super.onHiddenChanged(hidden);
((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("Home");
}

Android Fragment in Activity and isFinishing

In my application i am using some fragments, in a viewpager.
I want to show a dialog in a fragment like this:
final Dialog dialog = new Dialog(activity, R.style.DialogTheme);
dialog.show();
The activity is set in the onCreateView like this:
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
activity = getActivity();
}
This is working perfectly, but in some cases like if the app goes in background, and the user comes back to the app, i got an error "Fragment not attached to activity" in the line "dialog.show()".
So to prevent this error i use this:
if(!activity.isFinishing())
dialog.show();
else
Toast.makeText(activity, "Error", Toast.LENGTH_SHORT).show();
I think this is definitly not the best way...
Is there maybe a solution like reloading the app if the activity isFinishing or even a better solution?

override onAttach method
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
if (activity instanceof YourActiivty) {
//here is your code
} else {
}
}

public class MyFragment extends Fragment
#Override
public void setMenuVisibility(final boolean visible) {
super.setMenuVisibility(visible);
if (visible) {
...
}
}

Try to use DialogFragment rather than showing dialog by Dialog class, it will give you more stable view ,just extend your class by "DialogFragment"
public class DemoDialogFragment extends DialogFragment{
public DemoDialogFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fragment_demo_dialog, container, false);
-----------
return rootView;
}
and make function in you activity for calling it
public void showDialogFrag(DialogFragment dialogFragment, String tag) {
dialogFragment.show(getSupportFragmentManager(), tag);
}
Then call this function by this from any fragment
((MainActivity) getActivity()).showDialogFrag(new DemoDialogFragment(), Constant.FragmentTags.DemoDialogFragment);

How can I replace a Fragment from within onTouch() of another Fragment?

I need to display a Fragment when the user touches the TextView of another Fragment. Here's what I have:
public class FindPeopleHelpFragment extends Fragment {
public FindPeopleHelpFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_find_people_help, container, false);
((AppCompatActivity)getActivity()).getSupportActionBar().setTitle(R.string.find_people_help);
TextView welcome_home = (TextView) view.findViewById(R.id.find_people_help);
welcome_home.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent evt) {
if (evt.getAction() == MotionEvent.ACTION_DOWN) {
EditProfileFragment editProfileFragment = new EditProfileFragment();
FragmentManager manager = getActivity().getSupportFragmentManager();
manager.beginTransaction().replace(R.id.fragment_container, editProfileFragment, editProfileFragment.getTag()).commit();
}
return true;
}
});
// Inflate the layout for this fragment
return view;
}
}
The issue is that onTouch() returns a boolean, but when replacing the Fragment, I need to return a View. Otherwise I get the following.
10-05 15:00:51.057 25152-25152/wegrok.chiaramail.com E/AndroidRuntime: FATAL EXCEPTION: main
Process: wegrok.chiaramail.com, PID: 25152
java.lang.IllegalArgumentException: No view found for id 0x7f0f00b1 (wegrok.chiaramail.com:id/fragment_container) for fragment FindPeopleHelpFragment{c052157 #1 id=0x7f0f00b1}
Anyone know how to deal with this?

You need to make these Fragment transactions from your Activity. The Activity that hosted the Fragment should have a public function for handling the fragment switching so that when the TextView of your Fragment1 is clicked, the public method of the Activity will be called to make the Fragment switch.
So you might consider having an Activity like this.
public class YourActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_layout);
// The Fragment 1 will be loaded by default
switchToFragment1();
}
public void switchToFragment1() {
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragment_container, new Fragment1()).commit();
}
public void switchToFragment2() {
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragment_container, new Fragment2()).commit();
}
}
Now from your Fragment1, you need to implement an onClick listener in to the TextView, so that when the TextView is clicked, Fragment1 switches to Fragment2.
textView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
((YourActivity) getActivity()).switchToFragment2();
}
});)
Hope that helps.

Is it possible to convert Blank Activities to Fragment Activities

I currently have an Unit Converter app that I'm working in.
Here I've used multiple Blank Activities. Where each Unit's Activity can be opened using MainActivity. But now I want to make it tablet friendly.
Hence I want to use FragmentActivity now. Is it possible to convert the Blank Activities to Fragment Activities.?

All you need to do is take all View-specific logic from the Activity to a Fragment, then load the Fragment in your Activity.
For example,
public class MainActivity extends Activity {
#InjectView(R.id.button)
public Button button;
#OnClick(R.id.button)
public void onButtonClick(View view) {
Toast.makeText(this, "Hello!", Toast.LENGTH_SHORT).show();
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.inject(this);
}
}
This type of logic goes in
public class MainFragment extends Fragment {
#InjectView(R.id.button)
public Button button;
#OnClick(R.id.button)
public void onButtonClick(View view) {
Toast.makeText(this, "Hello!", Toast.LENGTH_SHORT).show();
}
#Override
public void onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_main, container, false);
ButterKnife.inject(this, view);
return view;
}
}
And your Activity needs to display this fragment either statically, or dynamically. If you go dynamical, you'll need the following lines in your Activity:
public class MainActivity extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FragmentManager fm = getSupportFragmentManager();
if(savedInstanceState == null) {
fm.beginTransaction()
.add(R.id.container, new MainFragment())
.commit();
}
fm.addOnBackStackChangedListener(new OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
if(getSupportFragmentManager().getBackStackEntryCount() == 0) finish();
}
});
}
}
If you go static, then you need to specify the fragments in your layout XML for the activity.
http://developer.android.com/guide/components/fragments.html#Adding

I would visit the Android website as they give a fairly good explanation on how fragments work.
You can learn how to add them to your existing application by another Android link here.

"Can not perform this action after onSaveInstanceState" when fragment is replaced

In my project context, I have a Button b in a Fragment f(1) in an Activity a.
Fragment f(x) is an instance of F where content depends of argument x
I need to replace the current instance f(1) by an instance f(2) on b click event:
From Activity a:
private void setFragment(int x) {
Bundle args = new Bundle();
args.putInt("x", x);
F f = new F();
f.setArguments(args);
f.setListener(new F.Listener() {
public void onButtonClick(int x) {
setFragment(x);
}
});
getSupportFragmentManager()
.beginTransaction()
.replace(ID, f)
.commit();
}
From Fragment f:
b.setOnClickListener(new View.onClickListener() {
public void onClick(View view) {
listener.onButtonClick(x + 1);
}
});
My problem is:
An Exception is throw on b click event only if a configuration state change occurs:
java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
Please, what is my error? I read many posts on this Exception but I don't found any solution
Edit: I just make a test without AsyncTask, see the code:
Try to rotate the screen and push the button
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle state) {
super.onCreate(state);
setContentView(R.layout.activity_main);
if (state == null) {
setFragment(1);
}
}
private void setFragment(int id) {
Bundle args = new Bundle();
args.putInt("id", id);
MyFragment myFragment = new MyFragment();
myFragment.setArguments(args);
myFragment.setListener(new MyFragment.Listener() {
#Override
public void onClick(int id) {
setFragment(id);
}
});
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.fragment, myFragment)
.commit();
}
public static class MyFragment extends Fragment{
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup view, Bundle state) {
return new Button(getActivity()) {
{
setText(String.valueOf(getArguments().getInt("id")));
setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
listener.onClick(getArguments().getInt("id") + 1);
}
});
}
};
}
private static interface Listener {
public void onClick(int id);
}
private Listener listener;
public void setListener(Listener listener) {
this.listener = listener;
}
}
}

The problem is the way you are setting the listener.
You are setting the listener, then you rotate your device from landscape to portrait. What happens after the rotation is:
Android create a brand new instance of MainActivity.
FragmentManager create a new instance of MyFragment internally and re-adds it automatically to the activity as it was before orientation change.
If you click on the button, the listener will be called. However, the listener is the listener of the previous activity (before rotation) which has been destroyed.
So not only you have a Memory Leak (the old activity can not be garbage collected, because it's referenced from here) but you also get this error.
How to do it correctly:
Well, the problem is NOT only setRetainInstanceState() you have not understood the Android Fragments lifecycle correctly. As mentioned above, Fragments are controlled by the FragmentManager (FragmentTransaction). So, yes everytime you rotate your screen a new Fragment instance will be created, but FragmentManager will attach them automatically for you (it's a little bit strange, but thats how Fragment works)
I would recommend to use an EventBus. The fragment will fire an Event onClick() and the activity will receive this event since it's subscribed. I recomment GreenDao EventBus.
Otherwise you can have a look at the official docs, but from my point of view they are teaching not a good solution, because your fragment and activity are hardly connected (not modular). They say you should use onAttach() like you can see in the sample from the documentation: http://developer.android.com/guide/components/fragments.html#EventCallbacks
Btw. a similar problem can occur if you are not using Fragment arguments for "passing" data. For more details read this blog: http://hannesdorfmann.com/android/fragmentargs/