I have a button inside of a fragment that I need to be able to access in the activity to change it's text. I am using this code in my main activity:
CategoryFragment frag = new CategoryFragment();
getSupportFragmentManager().beginTransaction().add(R.id.activity_main, frag).commit();
frag.setButtonText(i);
The problem is the button is never initialized using the onCreateView() method (that method never even gets called) which causes a null pointer exception. I tried adding an onCreate() method in the fragment, which gets called, but I have to get the view in order to initialize my button. Since the view hasn't yet been initialized, I get another null pointer exception from the view. Here is my best attempt at the onCreate():
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
button = (Button) getView().findViewById(R.id.buttonFrag);
}
In OnCreateView() do like this :
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.yout_layout, container, false);
button = (Button) rootView.findViewById(R.id.buttonFrag);
return rootView;
}
You have completely misunderstood the way Fragment and Activity work with each other. An Activity mainly has the duty to "show" the Fragment, and you need to initialize the Button using your CategoryFragment class.
Override Category Fragment's onActivityCreated() and then add the following:
Button button = (Button) getView.findViewById(R.id.your_views_id);
button.setButton("Voila");
Study about Activity and Fragment Interaction. This might help u. http://simpledeveloper.com/how-to-communicate-between-fragments-and-activities/
You can use “static factory method” Refer following code
public class CategoryFragment extends Fragment {
/**
* Static factory method that takes an int parameter,
* initializes the fragment's arguments, and returns the
* new fragment to the client.
*/
public static CategoryFragment newInstance(String i) {
CategoryFragment f = new CategoryFragment();
Bundle args = new Bundle();
args.putInt("buttonText", i);
f.setArguments(args);
return f;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam = getArguments().getString("buttonText");
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view=inflater.inflate(R.layout.fragment_category, container, false);
Button b=(Button) view.findViewById(R.id.button);
b.setText(mParam);
return view;
}
}
and from your activity just call
getSupportFragmentManager().beginTransaction().add(R.id.activity_main, CategoryFragment.newInstance(i)).commit();
Related
I have seen Link1 for this issue but could understand it right. I have a fragment that loads a list. When i click the list item it opens another activity. But i press back button it loads the list again. I want it to be at the same scroll position where it was before. In above mentioned link it specifies to use flag but i haven't got the point.
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dashboard);
android.app.Fragment fragment = new MeFragment();
getFragmentManager().beginTransaction().replace(R.id.layout_FragmentsContainer, fragment).addToBackStack(null).commit();
}
}
public class MeFragment extends Fragment
{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
return inflater.inflate(R.layout.fragment_me, container, false);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
meLV = (ListView) getView().findViewById(R.id.lv_Inbox);
loadingListProgress = (ProgressBar) getView().findViewById(R.id.progress_LoadingList);
meList = new ArrayList<Message>();
meAdapter = new MessagesListAdapter(getActivity(), meList);
//addFooter();
meLV.setAdapter(meAdapter);
meLV.setOnItemClickListener(this);
pageCount = 0;
loadmoreProgressDialog = new ProgressDialog(getActivity());
loadmoreProgressDialog.setTitle("Please wait ...");
loadmoreProgressDialog.setMessage("Loading more ...");
loadmoreProgressDialog.setCancelable(true);
loadUserMessages();
meLV.setOnScrollListener(new EndlessScrollListener() {
#Override
public void onLoadMore(int page, int totalItemsCount) {
// TODO Auto-generated method stub
//addFooter();
loadmoreProgressDialog.show();
loadUserMessages();
}
});
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// TODO Auto-generated method stub
Utils.showToast_msg(getActivity(), "MessageItemClicked");
ReferralDetailFragment fragment = new ReferralDetailFragment();
getFragmentManager().beginTransaction().replace(R.id.layout_FragmentsContainer, fragment).addToBackStack(null).commit();
}
}
public class ReferralDetailFragment extends Fragment implements OnClickListener {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.inflate(R.layout.fragment_referraldetail,container, false);
linkToAcknowledge = (TextView) view.findViewById(R.id.lbl_Link_to_Acknowledge);
return view;
}
}
I implemented a simple solution for this in my app, basically when you press back to go to the fragment again, onCreateView() is called. Here in onCreateView() you have done all initialization, so we change
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.inflate(R.layout.fragment_me, container, false);
/*
*Whatever you want to do
*
*/
return view;
}
to:
View view;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
if(view==null){
view = inflater.inflate(R.layout.fragment_me, container, false);
/*
*Whatever you want to do
*
*/
}
else{
((ViewGroup)view.getParent()).removeView(view);
}
return view;
}
Here, we move View view outside and make it a class variable. So if it is the first time the fragment is called, it is null and the initialization occurs, otherwise it goes to else black. Else block is required because onCreateView() adds whatever it returns as a child of the view's parent, so since view is already there, we remove it and onCreateView automatically adds it again.
According to our exchange in the comments, I completely deletde my answer and re-write a new one.
I copy/paste the code from one of my apps and removing the useless things and changing the names. Hope there is not too many typing mistakes, at that it is the minimum required to have it working.
When I pop back to FirstFragment from SecondFragment, the scroll position of FirstFragment is the same as when I clicked an item to load the SecondFragment.
Note that I don't extend FragmentActivity. I have an activity which loads the fragments.
Extend/modify to match your needs.
MainActivity :
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_layout);
}
}
FirstFragment Class :
public class FirstFragment extends Fragment implements OnItemClickListener {
private ListView mListView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.first_fragment_layout, container, false);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mListView = (ListView) getView().findViewById(R.id.listview_first_fragment);
mListView.setAdapter(mAdapter); // depends on your adapter
mListView.setOnItemClickListener(this);
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
mListView.setItemChecked(position, true);
//in case you need, set the bundle here, for example pass the position
Bundle arguments = new Bundle();
arguments.putInt("position", position);
SecondFragment secondFragment = new SecondFragment();
secondFragment.setArguments(arguments);
getFragmentManager().beginTransaction().replace(R.id.fragment_container, secondFragment).addToBackStack(null).commit();
}
}
SecondFragment Class :
public class SecondFragment extends Fragment {
private Integer mPosition;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.second_fragment_layout, container, false);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Bundle arguments = getArguments();
if (arguments == null) {
mPosition= 0;
} else {
mPosition= arguments.getInt("Position");
}
}
}
What you are trying to achieve may be done with help of savedInstanceState. i also had this kind of problem which i resolved by using add() method instead of replace() in transition.
If you can change your method or already not using add() than give it a shot.
and if add() method didn't do the trick then check the implementation of savedInstanceState.
correctly save instance state.
How to save states of fragment views.
Basically the situation is like this: I have an Activity, which displays a three Fragments within a FragmentPagerAdapter, and within one of these Fragment, I nest another Fragment. I added the fragments like this:
fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.add(rootView.getId(), new MainPageFragment(), "lpt2");
fragmentTransaction.commit();
When I try to call getParentFragment() inside of MainPageFragment(), it returns null.
How can that be? I checked multiple posts here on stackoverflow as well as on other blogs, and they all came to the conclusion that if you nest one fragment within another one, calling getParentFragment should return its parent fragment. Returning null means, that the parent is an activity as stated here. Which is not the case. Please tell me I'm making some kind of silly mistakes :\
This is the Fragment that is a child to the main Activity
public class MainPage extends Fragment {
private FragmentTransaction fragmentTransaction;
private View rootView;
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
global_var = new Global();
rootView = inflater.inflate(R.layout.main_page, container, false);
return rootView;
}
#Override
public void onViewCreated (View view, Bundle savedInstanceState) {
fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.add(rootView.getId(), new MainPageFragment(), "lpt2");
fragmentTransaction.commit();
}
}
This is the Fragment which is a child to the Main Page Fragment
public class MainPageFragment extends Fragment{
private View rootView;
private Fragment parentFragment;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.main_page_list, container, false);
if (getParentFragment() == null) Log.i("damn", "it");
return rootView;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onViewCreated(view, savedInstanceState);
}
}
Please tell me if I need to provide more code, I extracted things like ListView and so on because I thought it would be irrelevant.
Edit: I'm using android.support.v4.app
Check that you have pass FragmentManager reference to all of your Fragments from your FragmentPagerAdapter and then use getParentFragment(). May be this will help you.
I'm using loader in my ListView fragment, and it's getting recreated on pressing "back" button. Can you tell me how to handle this senario?
Here is my ListView fragment code. Here I have a boolean variable that I'm setting as true on clicking on list item. but once the back button is pressed onCreateView will get called so the backbutton will be false.
public class GTFragment extends SherlockFragment implements LoaderCallbacks<Cursor>{
ListView mTListview = null;
GoogleTasksAdapter mGTasksAdapter = null;
private SQLiteCursorLoader mTLoader=null;
private LoaderManager mTLoaderManager;
private String mSelectedListID = null;
private boolean mIsBackbuttonisPressed = false;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.task_home_activity, container, false);
if(!mIsBackbuttonisPressed)
getLoaderManager().initLoader(0, null, this);
mTListview = (ListView) view.findViewById(R.id.id_task_list_home_activity);
mGTasksAdapter = new GoogleTasksAdapter(getActivity());
mTListview.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> listview,
View clickedview, int position, long arg3) {
// TODO Auto-generated method stub
GoogleTaskItem item = new GoogleTaskItem();
Cursor coursor = ((GoogleTasksAdapter)listview.getAdapter()).getCursor();
if(coursor.moveToPosition(position))
{
mIsBackbuttonisPressed = true;
GoogleTaskController.get_googletask_controllerObj()
.LaunchTaskPreviewActivity();
}
}
});
mTListview.setAdapter(mGTasksAdapter);
mIsBackbuttonisPressed = false;
return view;
}
My fragment activity class code
public class TLActivity extends SherlockFragmentActivity {
LeftSliderTaskListOptions mTaskOptionsFragment = null;
GoogleTasksFragment mTFragment = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
setContentView(R.layout.layout_gt_list);
// FragmentTransaction tfragment = this.getSupportFragmentManager().beginTransaction();
mTFragment = new GTasksFragment();
t.replace(R.id.id_tfragment, mTFragment);
t.commit();
}
instead of
t.replace(R.id.id_tfragment, mTFragment);
use
t.add(R.id.id_tfragment, mTFragment);
It worked for me
I don't think that the accepted answer is right because Fragment.onSaveInstanceState will not be called until the activity hosting it needs to save its state: The docs states:
There are many situations where a fragment may be mostly torn down
(such as when placed on the back stack with no UI showing), but its
state will not be saved until its owning activity actually needs to
save its state.
In other words: if you're using a Activity with multiple fragments for each screen (which is very common), the fragment state will not be saved when you move the next screen.
You also can't use Fragment.setRetainInstance because he's meant only to fragments that aren't on the back stack.
Most of the time, you don't have to think about this but sometimes it's important. Like when you have scrolled a list and want to "remember" the scroll location.
I took a long time to realize that the fragments put on the back stack are kind of saved and you can reuse the view that you already created instead of creating one every time the fragment calls onCreateView. My setup is something like this:
public abstract class BaseFragment extends Fragment {
private boolean mSaveView = false;
private SoftReference<View> mViewReference;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if (mSaveView) {
if (mViewReference != null) {
final View savedView = mViewReference.get();
if (savedView != null) {
if (savedView.getParent() != null) {
((ViewGroup) savedView.getParent()).removeView(savedView);
return savedView;
}
}
}
}
final View view = inflater.inflate(getFragmentResource(), container, false);
mViewReference = new SoftReference<View>(view);
return view;
}
protected void setSaveView(boolean value) {
mSaveView = value;
}
}
public class MyFragment extends BaseFragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
setSaveView(true);
final View view = super.onCreateView(inflater, container, savedInstanceState);
ListView placesList = (ListView) view.findViewById(R.id.places_list);
if (placesList.getAdapter() == null) { // this check is important so you don't restart your adapter
placesList.setAdapter(createAdapter());
}
}
}
You have multiple options to rectify this issue.
Override onSaveInstanceState like this:
#Override
public void onSaveInstanceState (Bundle outState) {
super.onSaveInstanceState(outState);
outState.putBoolean("mIsBackbuttonisPressed", mIsBackbuttonisPressed);
}
and then in your onCreateView you can get your variable back by:
if (savedInstanceState != null)
mIsBackbuttonisPressed = savedInstanceState.getBoolean("mIsBackbuttonisPressed", false);
You can set this.setRetainInstance(true); in your onCreate method of your fragment.
If you could post your Activity code with creates your fragment I can also tell you other options. (P.S I cannot write it as a comment so posting it in the answer.)
I am a beginner in coding for Android and i am trying to do an application with two fragments. Unfortunately, when i add code to set action to my layout, it makes my application crash, so i'm wondering where i should put my code on the fragment file. If i take out the function onCreate, the application doesn't crash and my layout is good.
Here is my code. Thank you so much for your answer.
public class FragmentOne extends Fragment{
public static final String TAG = "FragmentOne";
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = View.inflate(getActivity(), R.layout.fragmentone, null);
return v;
}
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final EditText etData = (EditText) getView().findViewById(R.id.etData);
}
}
First of all I can see a few mistakes in your code.First of all as #user1873880 mentioned, onCreate() is always called before onCreateView(), so you should consider dealing with your views in onCreateView(). Second mistake which I can see is that you are not creating your View as it's designed to be used on Fragment. In my opinion the way your Fragment should look is like this :
public class FragmentOne extends Fragment {
private static final String TAG = "FragmentOne";
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
// create your view using LayoutInflater
return inflater.inflate(R.layout.fragmentone, container, false);
}
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// do your variables initialisations here except Views!!!
}
public void onViewCreated(View view, Bundle savedInstanceState){
super.onViewCreated(view, savedInstanceState);
// initialise your views
EditText etData = (EditText) view.findViewById(R.id.etData);
}
}
Hope this helps you! : )
The reason is that onCreate is invoked before onCreateView, so you can manipulate with your views only after onCreateView callback. For more information check Fragment lifecycle here.
I am trying to implement Fragments in my Project using the https://github.com/JakeWharton/Android-ViewPagerIndicator plugin.
My Fragment
public final class NearByFragment extends Fragment {
private static String TAG = "bMobile";
public static NearByFragment newInstance(String content) {
NearByFragment fragment = new NearByFragment();
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
Log.d(TAG, "onCreate");
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(TAG, "onCreateView");
return inflater.inflate(R.layout.fragment_search_nearby, null);
}
}
Now I want to execute some code like start start a new thread and download a JSON from the server and then assign a list view from the content I download. In fragments we are assigning views in onCreateView. so where should I write the
listview = (ListView) findViewById(R.id.list_items);
((TextView) findViewById(R.id.title_text))
.setText(R.string.description_blocked);
and other code to generate the Fragment view ?
You can search within the view that you just inflated:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(TAG, "onCreateView");
View v = inflater.inflate(R.layout.fragment_search_nearby, null);
listview = (ListView)v.findViewById(R.id.list_items);
((TextView)v.findViewById(R.id.title_text))
.setText(R.string.description_blocked);
return v;
}
You can also use the Fragment.getView() function elsewhere in your code and call that view's findViewById() member.
You can use getActivity().findByView() from the Fragment if you want to have access to the layout elements. Alternatively, you can just put the findByView() call in the main Activity.