Develop Reference

Fragment View is Null When Called From Parent Activity

I have an activity and its child Fragment with a LinearLayout that I generate buttons inside of. When the fragment is created, everything runs fine. However, when the parent activity downloads a new item, I call the method in the fragment that is used to generate the buttons and add them to the view, but the LinearLayout returns null and I can't figure out why. I either need to fix it or find a way to "re-display" my fragment. Here is the related code:
SongFragment:
LinearLayout linearLayout;
DatabaseHelper databaseHelper;
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_song, container, false);
linearLayout = rootView.findViewById(R.id.songFragmentMainLayout);
databaseHelper = new DatabaseHelper(getActivity());
return rootView;
}
#Override
public void onResume() {
super.onResume();
RefreshButtons();
}
public void RefreshButtons(){
linearLayout.removeAllViews(); //this line is where the NullPointerException is called
...
}
MainActivity:
//refresh fragment view
SongFragment fragment = (SongFragment) sectionsPagerAdapter.getItem(0);
if(downloadQueue.size() == 0){
fragment.RefreshButtons();
Toast.makeText(context, "New songs downloaded", Toast.LENGTH_SHORT).show();
}
...
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
Fragment fragment = null;
switch (position) {
case 0:
fragment = new SongFragment();
break;
case 1:
fragment = new PlaceholderFragment();
break;
}
return fragment;
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Songs";
case 1:
return "Playlists";
}
return null;
}
}
Thanks for your help.

The method fragment.RefreshButtons(); returns an NPE because if you implemented SectionsPagerAdapter like you should, getItem() returns a new Instance of that fragment which is not yet attached to the fragment manager, therefore causing a Nullpointer exception.
So what you should do is get a currently active fragment instance like this:
Fragment frag = (Fragment) mViewPager.getAdapter().instantiateItem(mViewPager, 0);
0 is the position of your fragment, so for example if you have 3 fragments, 0 will return the first fragment instance etc...

App freezes forever when Fragment get's displayed

Since I implemented a BottomAppBar my App isn't responding when a certain Fragment should get displayed even though I haven't changed anything. There isn't an error message either and all other Fragments which are getting displayed when another item in the BottomNavigationBar is clicked work fine.
Fragment:
public class StatisticsFragment extends Fragment {
private TabLayout mTabLayout;
private ViewPager mViewPager;
private BankAccountsStatisticsFragment bankAccountsStatisticsFragment = new BankAccountsStatisticsFragment();
private BillsStatisticsFragment billsStatisticsFragment = new BillsStatisticsFragment();
private CategoriesStatisticsFragment categoriesStatisticsFragment = new CategoriesStatisticsFragment();
private GoalsStatisticsFragment goalsStatisticsFragment = new GoalsStatisticsFragment();
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View inflatedView = inflater.inflate(R.layout.fragment_statistics, container, false);
mTabLayout = (TabLayout) inflatedView.findViewById(R.id.tl_statistics);
mViewPager = (ViewPager) inflatedView.findViewById(R.id.vp_statistics);
mViewPager.setAdapter(new Adapter(getChildFragmentManager()));
mTabLayout.setupWithViewPager(mViewPager);
return inflatedView;
}
private class Adapter extends FragmentPagerAdapter {
private static final int TABS = 4;
public Adapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position){
case 0: return bankAccountsStatisticsFragment;
case 1: return billsStatisticsFragment;
case 2: return categoriesStatisticsFragment;
case 3: return goalsStatisticsFragment;
default: throw new IllegalStateException("Couldn't find a fragment for position " + position);
}
}
#Override
public CharSequence getPageTitle(int position) {
switch (position){
case 0: return getString(R.string.tab_bank_accounts);
case 1: return getString(R.string.tab_bills);
case 2: return getString(R.string.tab_categories);
default: return getString(R.string.tab_goals);
}
}
#Override
public int getCount() {
return TABS;
}
}
}
LOGCAT
LOGCAT

Inflating a Layout and creating a Fragment transition (like the "FragmentManager....replace().commit()") are done in the MainThread where the UserInterface is rendered, so the UserInterface will freeze in these moments.
I think you have to pre-load the "bad" Fragment and just HIDE it instead of Destroy it...in this way the next time you want to create it is already ready.

Access fragment variable outside of Fragment in view pager

enter image description here
Before reading the question, please refer to image.
I am using viewpager to show the fragment.
Problem
In the fragment, I have used two edittext lets say editText1, editText2 now the problem is how I will get the editText data. I can only get the editText values when user click on next button but the next button is outside of fragment. How do I access the editText outside the fragment.
Before downvoting the question, let me know the reason so that I can improve my question.
Fragment java class
// newInstance constructor for creating fragment with arguments
public static BpDetails newInstance(int page) {
BpDetails fragmentFirst = new BpDetails();
Bundle args = new Bundle();
args.putInt("someInt", page);
fragmentFirst.setArguments(args);
return fragmentFirst;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
page = getArguments().getInt("someInt", 0);
}
// Inflate the view for the fragment based on layout XML
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.bp_details, container, false);
Log.i("View ",view.toString());
Log.i("DOB is ",Long.toString(Constants.dob));
systolic =(EditText) view.findViewById(R.id.systolic);
diastolic =(EditText) view.findViewById(R.id.diastolic);
return view;
}
ViewPager Activity
vpPager = (ViewPager) findViewById(R.id.view_pager);
adapterViewPager = new MyPagerAdapter(getSupportFragmentManager());
vpPager.setAdapter(adapterViewPager);
Fragment fragment=adapterViewPager.getItem(prevPage);
if (fragment.getClass().equals(BpDetails.class)){
Log.i("Call ","Yes");
}
findViewById(R.id.btn_prev).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// checking for last page
// if last page home screen will be launched
int current = getItem(-1);
if (current!=0)
prevPage=current-1;
if (current < 4) {
// move to next screen
vpPager.setCurrentItem(current);
} else {
//final reached.
}
}
});
findViewById(R.id.btn_next).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// checking for last page
// if last page home screen will be launched
int current = getItem(+1);
if (current!=0)
prevPage=current-1;
System.out.println("Prev page "+prevPage);
if (current < 4) {
// move to next screen
Fragment prevFragment=adapterViewPager.getItem(prevPage);
} else {
//final reached.
}
}
});
}
private int getItem(int i) {
return vpPager.getCurrentItem() + i;
}
public static class MyPagerAdapter extends FragmentPagerAdapter {
private static int NUM_ITEMS = 4;
private static int mSelectedPosition;
public MyPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
//mSelectedPosition=selectedPosition;
}
// Returns total number of pages
#Override
public int getCount() {
return NUM_ITEMS;
}
// Returns the fragment to display for that page
#Override
public Fragment getItem(int position) {
switch (position) {
case 0: // Fragment # 0 - This will show FirstFragment
return BasicDetails.newInstance(0);
case 1:
return BpDetails.newInstance(1);
case 2:
return BslDetails.newInstance(2);
case 3:
return Summary.newInstance(3);
default:
return null;
}
}
}

Create two getters inside your fragment like this.
public String getSystolic(){
return this.systolic.getText().toString();
}
public String getDiastolic(){
return this.diastolic.getText().toString();
}
BpDetails fr = (BpDetails)myAdapter.getItem(myViewPager.getCurrentItem());
String systolicString = fr.getSystolic();

I had a similar issue. .getItem() instantiates a new Fragment, so upon calling myAdapter.getItem(...) you would be getting null for all elements in the Fragment, but not null for the Fragment.
When I fixed this, what I had to do was create another method inside of MyPagerAdapter called getInstantiatedFragment:
public Fragment getInstantiatedFragment(int position)
{
return fragments.get(position);
}
fragments is a new field for the class:
private ArrayList<Fragment> fragments = new ArrayList<>();
I would override getItem() (as you have done already) and change it to:
#Override
public Fragment getItem(int position)
{
switch (position) {
case 0:
BasicDetails basicDetails = BasicDetails.newInstance(0);
fragments.add(basicDetails);
return basicDetails;
...
}
where you're adding the fragment to fragments before returning, then you would call:
BpDetails fr = (BpDetails)myAdapter.getInstantiatedItem(myViewPager.getCurrentItem());
to get the instance of the created fragment and then call
String systolicString = fr.getSystolic();
if you're using the previous answer's method.
This is so that you can keep track of the instantiated fragments in fragments. I'm sure there are better ways.

How to show different layouts in each Tab in a TabLayout using Fragments

I have been trying to show different layouts in different tabs in the swipeable TabLayout using PagerTabStrip. Can anybody help?
I want to show one layout in first tab, second different layout in 2nd tab etc.
public class MainActivity extends FragmentActivity {
// create object of FragmentPagerAdapter
SectionsPagerAdapter mSectionsPagerAdapter;
// viewpager to display pages
ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create the adapter that will return a fragment for each of the five
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
}
/**
* A FragmentPagerAdapter that returns a fragment corresponding to one of
* the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#SuppressLint("NewApi")
#Override
public Fragment getItem(int position) {
switch (position) {
case 0: {
//Show 1st Layout(Here I need HELP)
//HELP HELP HELP
}case 1:
{
//Show 2nd Layout(Here I need HELP)
//HELP HELP HELP
}
default:
}
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1);
fragment.setArguments(args);
return fragment;
}
#Override
public int getCount() {
// Show 5 total pages.
return 6;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Section 1";
case 1:
return "Section 2";
case 2:
return "Section 3";
case 3:
return "Section 4";
case 4:
return "Section 5";
case 5:
return "Section 6";
}
return null;
}
}
/**
* A dummy fragment representing a section of the app, but that simply
* displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
public static final String ARG_SECTION_NUMBER = "section_number";
public DummySectionFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Create a new TextView and set its text to the fragment's section
// number argument value.
TextView textView = new TextView(getActivity());
textView.setGravity(Gravity.CENTER);
textView.setTextSize(25);
textView.setText(Integer.toString(getArguments().getInt(
ARG_SECTION_NUMBER)));
return textView;
}
}
}

View rootView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
switch (getArguments().getInt(ARG_SECTION_NUMBER))
{
case 1: {
rootView = inflater.inflate(R.layout.fragment_bba, container, false);
break;
}
case 2: {
rootView = inflater.inflate(R.layout.fragment_bcom, container, false);
break;
}
case 3: {
rootView = inflater.inflate(R.layout.fragment_bca, container, false);
break;
}
}
return rootView;

Ok for the people who want to solve this problem using design patterns.
Find full working solution Here.
If u write the fragment based on if-else condition it may solve the problem
switch(fragmentId)
{
case 1:
{
fragment 1 related stuff
}
case 2:
{
fragment 2 related stuff
}
.......
.......
and so on
But the problem with this approach is if in future,
1) you decide to add more fragments
or
2) you decide to change some functionality of existing fragment
Then you will have to modify the existing code (inside if-else condition)
Not a preferred programming practice
Instead you can follow this approach
public abstract class BasicFragment extends Fragment {
public BasicFragment newInstance()
{
Log.d("Rohit", "new Instance");
Bundle args = new Bundle();
// args.putInt(ARG_PAGE, page);
BasicFragment fragment = provideYourFragment();
fragment.setArguments(args);
return fragment;
}
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
}
public View onCreateView(LayoutInflater inflater,ViewGroup parent, Bundle savedInstanseState)
{
View view = provideYourFragmentView(inflater,parent,savedInstanseState);
return view;
}
public abstract BasicFragment provideYourFragment();
public abstract View provideYourFragmentView(LayoutInflater inflater,ViewGroup parent, Bundle savedInstanceState);
}
Your Fragment implementation
public class ImageFragment extends BasicFragment{
#Override
public BasicFragment provideYourFragment() {
return new ImageFragment();
}
#Override
public View provideYourFragmentView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.image_fragment,parent,false);
//Get your parent layout of fragment
RelativeLayout layout = (RelativeLayout)view;
//Now specific components here
ImageView imageView = (ImageView)layout.findViewById(R.id.myImage);
imageView.setImageResource(android.R.drawable.ic_media_play);
return view;
}
}
Happy coding

ViewPager fragmentstatepageadapter getItem isn't passing correct position

I have created a viewpager layout, a class that extends FragmentActivity and a fragment. What I want is that each fragment get's passed in what position it is within the viewpager. So first viewpager is created getting the argument 0, second getting 1 etc. Then if I scroll one way or another these numbers remain a true count.
The problem is the first time a fragment is created, it seems to be created twice so the position passed is 0 then 1. However I can't scroll back but I know for sure the class is being called twice. Now as I scroll forward the position increases incrementally by one. However if I scroll back it drops immediately to three on just one page back, then continues to drop past the 1 to 0 so now I can finally see my layout for 0.
I have this:
private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
public ScreenSlidePagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
PracticeFragment fragment = new PracticeFragment();
getAll.putInt("position", position);
fragment.setArguments(getAll);
return fragment;
}
#Override
public int getCount() {
return numberofQ;
}
}
It first of all runs getItem twice before even going to my fragment class so that the position is 0 then 1. Then when it gets to my fragment class it makes a layout fine, I scroll through a few (3 or 4) new pages and it adds one to the position each time then when I scroll back it says it is zero or two then the numbers continue to be just as sporadic. Finally suddenly when I scroll back to the beginning the position is again 0 so my fragment for position 0 is suddenly displayed.
I don't understand what's happening, so I'm wondering what the mistake is?
public class PracticeFragment extends Fragment {
TextView question, explain;
private ScrollView sv;
private boolean starActionBar;
private final static int version = Consts.SDKversion;
ArrayList<RadioButton> rbArray;
ArrayList<LinearLayout> lArray;
ArrayList<ImageView> ivArray;
int iRow;
SQLite info;
private String correctAnswer;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
info = new SQLite(getActivity());
starActionBar = PreferenceManager.getDefaultSharedPreferences(
getActivity()).getBoolean("star", true);
setHasOptionsMenu(true);
}
#Override
public void onViewStateRestored(Bundle savedInstanceState) {
super.onViewStateRestored(savedInstanceState);
for (RadioButton r : rbArray) {
if (r.isChecked()) {
r.performClick();
}
}
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.activity_pm_fragment, menu);
super.onCreateOptionsMenu(menu, inflater);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ViewGroup rootView = (ViewGroup) inflater.inflate(
R.layout.activity_main, container, false);
lArray = new ArrayList<LinearLayout>();
rbArray = new ArrayList<RadioButton>();
ivArray = new ArrayList<ImageView>();
lArray.add((LinearLayout) rootView.findViewById(R.id.PM_LinLay0));
lArray.add((LinearLayout) rootView.findViewById(R.id.PM_LinLay1));
lArray.add((LinearLayout) rootView.findViewById(R.id.PM_LinLay2));
lArray.add((LinearLayout) rootView.findViewById(R.id.PM_LinLay3));
lArray.add((LinearLayout) rootView.findViewById(R.id.PM_LinLay4));
for (LinearLayout l : lArray) {
l.setOnTouchListener(PracticeFragment.this);
l.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
if (((ViewGroup) v).getChildAt(0).isEnabled()) {
((ViewGroup) v).getChildAt(0).performClick();
}
}
});
}
rbArray.add((RadioButton) rootView.findViewById(R.id.radio0));
rbArray.add((RadioButton) rootView.findViewById(R.id.radio1));
rbArray.add((RadioButton) rootView.findViewById(R.id.radio2));
rbArray.add((RadioButton) rootView.findViewById(R.id.radio3));
rbArray.add((RadioButton) rootView.findViewById(R.id.radio4));
ivArray.add((ImageView) rootView.findViewById(R.id.ivradio0));
ivArray.add((ImageView) rootView.findViewById(R.id.ivradio1));
ivArray.add((ImageView) rootView.findViewById(R.id.ivradio2));
ivArray.add((ImageView) rootView.findViewById(R.id.ivradio3));
ivArray.add((ImageView) rootView.findViewById(R.id.ivradio4));
rootView.findViewById(R.id.bNext).setVisibility(View.GONE);
rootView.findViewById(R.id.bPrevious).setVisibility(View.GONE);
sv = (ScrollView) rootView.findViewById(R.id.svMain);
info.open();
iRow = Integer.valueOf(info.getEverything(getArguments(), getArguments().getInt("position"), "next"));
Cursor c = info.getCursor(iRow);
((TextView) rootView.findViewById(R.id.tvQuestion))
.setText((getArguments().getInt("position") + 1) + ") " + c.getString(2));
explain = (TextView) rootView.findViewById(R.id.tvExplain);
explain.setText(c.getString(9));
explain.setVisibility(View.GONE);
correctAnswer = c.getString(8);
String[] aArray = { c.getString(3), c.getString(4), c.getString(5),
c.getString(6), c.getString(7) };
c.close();
info.close();
int o = 0;
int pos = 0;
for (String s : aArray) {
LinearLayout l = lArray.get(pos);
if (s.contentEquals("BLANK")) {
l.setVisibility(View.GONE);
} else {
l.setVisibility(View.VISIBLE);
rbArray.get(pos).setText(s);
rbArray.get(pos).setOnClickListener(null);
if (o % 2 == 0) {
l.setBackgroundColor(Consts.colorAlt);
}
o++;
}
pos++;
}
return rootView;
}
}
However if I comment out everything but the viewgroup and return rootview - still the same problem.

initialize the getAll every time as a new object in getItem()
make your fragment class static
and create one method in PracticeFragment
static PracticeFragment newInstance(int num) {
PracticeFragment f = new PracticeFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
and change in adapter
#Override
public Fragment getItem(int position) {
return PracticeFragment.newInstance(position);
}

Subclassing it fixed the problem!