Childfragment background color (magically) changed - android

TL;DR Within a ViewPager, I have a Fragment with two child fragments, when I change the background color of list in one child fragment, it sometimes also change the background color of the other child fragment.
So, I have ViewPager with 2 fragments, fragment 1 (FragmentOne) has 2 child fragment, FragmentOneA and FragmentOneB, fragment 2 is FragmentTwo.
FragmentOneA is just a Fragment and FragmentOneB is a ListFragment.
In FragmentOneB, I set color between odd row and even row. Odd row is yellow, even row just white.
So within the ViewPager, the fragment I show first in FragmentOne is FragmentOneA, then I pressed button in FragmentOneA to replace that fragment with FragmentOneB.
This happened:
1) I pressed button in FragmentOneA to replace it with FragmentOneB. Then I pressed Back button to pop the stack. I did that few times.
2) At sometime, the background color in FragmentOneA was changed to yellow. And then I did number 1) again and at some time, the background was changed back to white.
I just don't understand why this happened.
Image of FragmentOneA before event 1) with white background:
Image of FragmentOneB that's shown after I click that blue button "Cari penerbangan":
Image of FragmentOneA after I did event number 1) a few times:
The code of Activity that holds the ViewPager:
public class MyActivity extends ActionBarActivity {
private static final int NUM_PAGES = 2;
private ViewPager viewPager;
private PagerAdapter adapter;
private FragmentManager fragmentManager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragmentManager = getSupportFragmentManager();
adapter = new PagerAdapter(fragmentManager);
viewPager = (ViewPager) findViewById(R.id.pager);
viewPager.setAdapter(adapter);
}
#Override
public void onBackPressed() {
Fragment fragment = (Fragment) getSupportFragmentManager().findFragmentByTag("android:switcher:" + R.id.pager + ":"viewPager.getCurrentItem());
if (fragment != null) { // could be null if not instantiated yet
if (fragment.getView() != null) {
// Pop the backstack on the ChildManager if there is any. If
// not, close this activity as normal.
if (!fragment.getChildFragmentManager().popBackStackImmediate()) {
finish();
}
}
}
}
private class PagerAdapter extends FragmentPagerAdapter {
public PagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
FragmentOne d = new FragmentOne();
return d;
case 1:
return new FragmentTwo();
}
return null;
}
#Override
public int getCount() {
return NUM_PAGES;
}
}
}
The code of FragmentOne:
public class FragmentOne extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
FrameLayout root = new FrameLayout(getActivity());
root.setId(R.id.layout_root);
FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
transaction.add(R.id.layout_root, new FragmentOneA());
transaction.commit();
return root;
}
}
The code of FragmentOneA when the blue button get clicked:
FragmentTransaction transaction = getParentFragment().getChildFragmentManager().beginTransaction();
transaction.addToBackStack(null);
transaction.replace(R.id.layout_root, new FragmentOneB());
transaction.commit();
Long post, but I've reviewed my code many times, so if you know anything please give me some answers. Many thanks for you..
My point is, I just want to use odd-even row color, but somehow that affects my other fragment.

Related

Replaceable Fragment in ViewPager2

I have a Fragment (lets call it RootFragment) containing aViewPager2 that switches between two fragments on tab1 and tab2. Only considering the fragment on tab2, it starts as showing Fragment 1, which contains a button. When the button is pressed, I'd like Fragment 2 to show up over Fragment 1 and added to the backstack for that page.
Here is the code for the RootFragment.
public class RootFragment extends Fragment {
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container,
#Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.root_fragment, container, false);
ViewPager2 pager = view.findViewById(R.id.myPager);
FragmentStateAdapter pagerAdapter = new ScreenSlidePagerAdapter(this);
pager.setAdapter(pagerAdapter);
TabLayout tabLayout = view.findViewById(R.id.myTabLayout);
new TabLayoutMediator(tabLayout, pager, (tab, position) -> {
if (position == 0) {
tab.setText("tab1");
} else {
tab.setText("tab2");
}
}).attach();
return view;
}
private static class ScreenSlidePagerAdapter extends FragmentStateAdapter {
public ScreenSlidePagerAdapter(Fragment fragment) {
super(fragment);
}
#NonNull
#Override
public Fragment createFragment(int position) {
if (position == 0) {
return new FragmentTab1(); // don't care about this right now
} else {
return new Fragment1();
}
}
#Override
public int getItemCount() {
return 2;
}
}
}
My initial thought would be to use a FragmentManager transaction in Fragment1 when the button is pressed to add Fragment 2 and update the backstack. However, I'm unsure what the correct container argument would be to use in that transaction.
Is the best way to achieve this to create a dummy Fragment just containing a FragmentContainerView as the Fragment instantiated by the ViewPager2's getFragment, have that fragment initially replace itself with Fragment1, then use that parent container for the transaction? Or is there a better way that avoids adding a dummy Fragment?

Change Title TextView when call one fragment to another fragment

I am working on the application in which I added a Navigation Drawer with Tabs. So, for the Navigation Drawer menu option I create a fragment for each option and it works well...
In my main Activity I inflate my TabFragment (contains fragment_1, or fragment_2) as UI, and on the Fragment_1 there is one Button and when I click the button I want to open the Navigation Drawer fragment....
My Navigation Drawer fragment opens fine, but the problem is when my Navigation drawer fragment is open my titleBar doesn't change as per the fragment title...
Note: I know when we open a fragment we have to replace the fragment View to the new fragment View but I want to open a Fragment as an Activity
Picture1: When I click on Button the Second Picture appears, but I want to change the TitleView and remove the Navigation drawer icon.
Edit
In my MainActivity, I inflate Tabfragment as
mFragmentTransaction=mFragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.containerView, new TabFragment()).commit();
MyTabFragment :
public class TabFragment extends Fragment {
public TabFragment() {
// Required empty public constructor
}
public static TabLayout tabLayout;
public static ViewPager viewPager;
public static int int_items = 2 ;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View x=inflater.inflate(R.layout.content_main_menu,null);
tabLayout=(TabLayout) x.findViewById(R.id.tabs);
viewPager =(ViewPager) x.findViewById(R.id.viewpager);
viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));
tabLayout.post(new Runnable() {
#Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
}
});
return x;
}
class MyAdapter extends FragmentPagerAdapter{
public MyAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position){
case 0:
return new HomeFragment();
case 1:
return new Offers();
}
return null;
}
#Override
public int getCount() {
return int_items;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position){
case 0 :
return "Home";
case 1:
return "Offers";
}
return null;
}
}
}
On Button click in HomeFragment(or fragment_1)
Fragment fragment = new NavigationDrawerFragment();
FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.containerView, fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
I just find my Question's Answer..
Before i tried to call fragment to fragment class that's why my ContainerView Remains same in the NavigationDrawer Fragment. So Now this time, I am Creating a new Activity and in this Activity I inflate the navigation Drawer fragment, due to this my previous ContainerView is Replaced by the New Activity layout

How to access particular page of ViewPager by Button click, not by sliding

I have three Fragments attached to ViewPager. If i am Fragment1, and i have a button on Fragment1, i want on button click of that 'Fragment', access the Fragment3 but on the same time if i slide the page,i don't want to access the Fragment3. while sliding i want to access only up to Fragment2. How can i do this.
TabPagerAdapter.java:-
public class TabPagerAdapter extends FragmentStatePagerAdapter
{
public TabPagerAdapter(FragmentManager fragmentManager)
{
super(fragmentManager);
}
#Override
public Fragment getItem(int position)
{
switch (position)
{
case 0:
return new Fragment1();
case 1:
return new Fragment2();
case 2:
return new Fragment3();
}
return null;
}
#Override
public int getCount()
{
return 3;
}
I have implemented something very similar: Previously I had four fragments in my ViewPager, but then decided that I want to integrate two of those fragments more intimately by reducing the number of fragment that I can reach by sliding and switching back and forth between two fragments by using a button. The implementation took me a while, though. I did not manage to mess with the index of my fragmentList properly. In the end, the trick was to take out those two fragments from the ViewPager altogether and add a HolderFragment instead. Within this fragment I implemented the fragment transaction for hiding one and showing the other fragment.
Here is the code from my HolderFragment:
public class HolderFragment extends Fragment {
private Context context;
private Fragment currentFragment;
#Override
public void onAttach(Context context) {
super.onAttach(context);
this.context = context;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
View view = inflater.inflate(R.layout.fragment_holder, container, false);
OneFragment oneFragment =
(OneFragment) Fragment.instantiate(context, OneFragment.class.getName());
OtherFragment otherFragment =
(OtherFragment) Fragment.instantiate(context, OtherFragment.class.getName());
// oneFragment selected on view creation
FragmentManager fm = this.getChildFragmentManager();
fm.beginTransaction().add(R.id.holder_fragment_holder, oneFragment).commit();
fm.beginTransaction().add(R.id.holder_fragment_holder, otherFragment).hide(mediaFragment)
.commit();
currentFragment = oneFragment;
return view;
}
public void switchFragments(Fragment fragment) {
if (!fragment.equals(currentFragment)) {
this.getChildFragmentManager().beginTransaction().hide(currentFragment).commit();
currentFragment = fragment;
this.getChildFragmentManager().beginTransaction().show(currentFragment).commit();
}
}
}
Then, whenever the switch button is pressed just call holderFragment.switchFragments(oneFragment) or holderFragment.switchFragments(otherFragment) from the activity that holds the ViewPager (and a reference to the HolderFragment).
Try this
mViewPager.setCurrentItem(your_position, true);

Fragment in ViewPager not restored after popBackStack

Problem
A Fragment is not reattached to its hosting ViewPager after returning from another fragment.
Situation
One Activity hosting a Fragment whose layout holds a ViewPager (PageListFragment in the example below). The ViewPager is populated by a FragmentStateViewPagerAdapter. The single Fragments hosted inside the pager (PageFragment in the example below) can open sub page lists, containing a new set of pages.
Behaviour
All works fine as long as the back button is not pressed. As soon as the user closes one of the sub PageLists the previous List is recreated, but without the Page that was displayed previously. Swiping through the other pages on the parent PageList still works.
Code
A sample application can be found on github:
Activity
public class MainActivity extends FragmentActivity {
private static final String CURRENT_FRAGMENT = MainActivity.class.getCanonicalName() + ".CURRENT_FRAGMENT";
public static final String ARG_PARENTS = "Parents";
public void goInto(String mHostingLevel, String mPosition) {
Fragment hostingFragment = newHostingFragment(mHostingLevel, mPosition);
addFragment(hostingFragment);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addBaseFragment();
}
private void addBaseFragment() {
Fragment hostingFragment = newHostingFragment("", "");
addFragment(hostingFragment);
}
private Fragment newHostingFragment(String mHostingLevel, String oldPosition) {
Fragment hostingFragment = new PageListFragment();
Bundle args = new Bundle();
args.putString(ARG_PARENTS, mHostingLevel + oldPosition +" > ");
hostingFragment.setArguments(args);
return hostingFragment;
}
private void addFragment(Fragment hostingFragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragmentSpace, hostingFragment, CURRENT_FRAGMENT);
transaction.addToBackStack(null);
transaction.commit();
}
}
PageListFragment
public class PageListFragment extends Fragment {
private String mParentString;
public PageListFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_hosting, container, false);
}
#Override
public void onResume() {
mParentString = getArguments().getString(MainActivity.ARG_PARENTS);
ViewPager viewPager = (ViewPager) getView().findViewById(R.id.viewPager);
viewPager.setAdapter(new SimpleFragmentStatePagerAdapter(getFragmentManager(),mParentString));
super.onResume();
}
private static class SimpleFragmentStatePagerAdapter extends FragmentStatePagerAdapter {
private String mHostingLevel;
public SimpleFragmentStatePagerAdapter(FragmentManager fm, String hostingLevel) {
super(fm);
this.mHostingLevel = hostingLevel;
}
#Override
public android.support.v4.app.Fragment getItem(int position) {
PageFragment pageFragment = new PageFragment();
Bundle args = new Bundle();
args.putString(MainActivity.ARG_PARENTS, mHostingLevel);
args.putInt(PageFragment.ARG_POSITION, position);
pageFragment.setArguments(args);
return pageFragment;
}
#Override
public int getCount() {
return 5;
}
}
}
PageFragment
public class PageFragment extends Fragment {
public static final String ARG_POSITION = "Position";
private String mHostingLevel;
private int mPosition;
public PageFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View contentView = inflater.inflate(R.layout.fragment_page, container, false);
setupTextView(contentView);
setupButton(contentView);
return contentView;
}
private void setupTextView(View contentView) {
mPosition = getArguments().getInt(ARG_POSITION);
mHostingLevel = getArguments().getString(MainActivity.ARG_PARENTS);
TextView text = (TextView) contentView.findViewById(R.id.textView);
text.setText("Parent Fragments " + mHostingLevel + " \n\nCurrent Fragment "+ mPosition);
}
private void setupButton(View contentView) {
Button button = (Button) contentView.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openNewLevel();
}
});
}
protected void openNewLevel() {
MainActivity activity = (MainActivity) getActivity();
activity.goInto(mHostingLevel, Integer.toString(mPosition));
}
}
After a lengthy investigation it turns out to be a problem with the fragment manager.
When using a construct like the one above the fragment transaction to reattach the fragment to the page list is silently discarded. It is basically the same problem that causes a
java.lang.IllegalStateException: Recursive entry to executePendingTransactions
when trying to alter the fragments inside the FragmentPager.
The same solution, as for problems with this error, is also applicable here. When constructing the FragmentStatePagerAdapter supply the correct child fragment manager.
Instead of
viewPager.setAdapter(new SimpleFragmentStatePagerAdapter(getFragmentManager(),mParentString));
do
viewPager.setAdapter(new SimpleFragmentStatePagerAdapter(getChildFragmentManager(),mParentString));
See also: github
What Paul has failed to mention is, if you use getChildFragmentManager, then you will suffer the "blank screen on back pressed" issue.
The hierarchy in my case was:
MainActivity->MainFragment->TabLayout+ViewPager->AccountsFragment+SavingsFragment+InvestmentsFragment etc.
The problem I had was that I couldn't use childFragmentManagerfor the reason that a click on the item Account view (who resides inside one of the Fragments of the ViewPager) needed to replace MainFragment i.e. the entire screen.
Using MainFragments host Fragment i.e. passing getFragmentManager() enabled the replacing, BUT when popping the back-stack, I ended up with this screen:
This was apparent also by looking at the layout inspector where the ViewPager is empty.
Apparently looking at the restored Fragments you would notice that their View is restored but will not match the hierarchy of the popped state. In order to make the minimum impact and not force a re-creation of the Fragments I re-wrote FragmentStatePagerAdapter with the following changes:
I copied the entire code of FragmentStatePagerAdapter and changed
#NonNull
#Override
public Object instantiateItem(#NonNull ViewGroup container, int position) {
// If we already have this item instantiated, there is nothing
// to do. This can happen when we are restoring the entire pager
// from its saved state, where the fragment manager has already
// taken care of restoring the fragments we previously had instantiated.
if (mFragments.size() > position) {
Fragment f = mFragments.get(position);
if (f != null) {
return f;
}
}
...
}
with
#NonNull
#Override
public Object instantiateItem(#NonNull ViewGroup container, int position) {
// If we already have this item instantiated, there is nothing
// to do. This can happen when we are restoring the entire pager
// from its saved state, where the fragment manager has already
// taken care of restoring the fragments we previously had instantiated.
if (mFragments.size() > position) {
Fragment f = mFragments.get(position);
if (f != null) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
mCurTransaction.detach(f);
mCurTransaction.attach(f);
return f;
}
}
...
}
This way I am effectively making sure that that the restored Fragments are re-attached to the ViewPager.
Delete all page fragments, enabling them to be re-added later
The page fragments are not attached when you return to the viewpager screen as the FragmentStatePagerAdapter is not re-connecting them. As a work-around, delete all the fragments in the viewpager after popbackstack() is called, which will allow them to be re-added by your initial code.
[This example is written in Kotlin]
//Clear all fragments from the adapter before they are re-added.
for (i: Int in 0 until adapter.count) {
val item = childFragmentManager.findFragmentByTag("f$i")
if (item != null) {
adapter.destroyItem(container!!, i, item)
}
}

Android: FragmentPagerAdapter: getItem method called twice on First time

In My application, I have used the ViewPager.
Like,
(say main.xml)
<android.support.v4.view.ViewPager
android:id="#+id/viewPager"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_above="#+id/register_header" />
And Create ViewPager object and ViewPagerAdapter(which extends FragmentPagerAdapter) object in FragmentActivity.
_mViewPager = (ViewPager) findViewById(R.id.viewPager);
_adapter = new ViewPagerAdapter(getApplicationContext(),
getSupportFragmentManager());
_mViewPager.setAdapter(_adapter);
And the Adapter class is like,
public class ViewPagerAdapter extends FragmentPagerAdapter {
private Context _context;
private FragmentManager manager;
private Fragment f;
private String classname="ViewPagerAdapter";
public ViewPagerAdapter(Context context, FragmentManager fm) {
super(fm);
_context=context;
manager=fm;
}
#Override
public Fragment getItem(int position) {
Log.i(classname,"getItem called"+position);
f = new Fragment();
f=MyFragment.newInstance();
Bundle args = new Bundle();
args.putInt("position", position);
f.setArguments(args);
return f;
}
#Override
public int getCount() {
return User.getPageCount();
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
}
And in MyFragment Class,
In onResume , I have to store the wigets object to the common static variable.
public void onResume() {
super.onResume();
pageIndex = getArguments().getInt("position");
User.useTextview1=textview1;
User.useTextview2= textview2;
User.current_pageIndex=pageIndex;
}
I have to update the textviews got from the User class in the FragmentActivity.
My Problem is getItem() method is called twice on First time
In Fact , the view displayed in the emulator is 0th index, but got 1st Index value in the FragmentActivity.
If I stopped the calling of getItem() method on second time, I can able to get the 0th index TextView reference in the FragmentActivity.
Please provide me the best way to do this.
Thanks
The FragmentPagerAdapter instantiates 2 Fragments on start, for index 0 and for index 1. If you want to get data from the Fragment which is on the screen, you can use setOnPageChangeListener for the Pager to get current position. Then have SparseArray with WeakReference to your fragments. Update that array in the getItem call. When onPageSelected gets called use that position to get reference to right Fragment and update User data.
Initialization of array:
private SparseArray<WeakReference<MyFragment>> mFragments = new SparseArray<WeakReference<MyFragment>>(3);
in getItem method i wrote this..
#Override
public Fragment getItem(int index) {
EditFragment frag = new EditFragment();
Bundle args = new Bundle();
args.putSerializable("currentItem", itemsList.get(index));
frag.setArguments(args);
return (frag);
}
here itemsList.get(index) is the model class object which i will use in EditFragment class.
here is that.
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View result = inflater.inflate(R.layout.pager_fragment_layout, container, false);
image = (ImageView)result.findViewById(R.id.pager_image);
text = (TextView)result.findViewById(R.id.pager_item_desc);
ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(getActivity()).build();
ImageLoader.getInstance().init(config);
imLoader = ImageLoader.getInstance();
****NOTE
final SwapItems itemList = (SwapItems) getArguments().getSerializable("currentItem");
imagePath = itemList.getPaths().get(0);
imLoader.displayImage(imagePath,image);
text.setText(itemList.getItemDescription());
image.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Fragment fragment = new ItemImagesFragment();
FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Bundle bundle = new Bundle();
bundle.putSerializable("val", itemList);
fragment.setArguments(bundle);
fragmentTransaction.replace(R.id.content_frame, fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
});
return result;
}
NOTE: here i am getting swapitems model object from previous getItem method is 'final'. this solves my issue. Earlier i was initialized the same object with static as modifier.
hope yours will also clear
My Problem is getItem() method is called twice on First time
This is not the problem, this is default feature of FragmentPagerAdapter. Its good for you to swipe from this page to the next one and previous one.
the view displayed in the emulator is 0th index, but got 1st Index value in the FragmentActivity
I got the same issue, and I know why. This because you used same Fragment in View Pager.
How to fix this is separate Fragments by using different Fragment.
I faced the same issue - getItem() method was called twice. I don't know about your purposes of using that method by mine was to trigger changes in a hosting activity when new slide appears.
Well, first of all getItem() is not a right method to get event of appearing new slide.
I used ViewPager.OnPageChangeListener listener on ViewPager itself for this purpose.
Here is what I did:
In Activity that holds slide fragments:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.signature_wizard_activity);
// Instantiate a ViewPager and a PagerAdapter.
mPager = (ViewPager) findViewById(R.id.pager);
mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mPagerAdapter);
mPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
onSlideChanged(position); // change color of the dots
}
#Override
public void onPageSelected(int position) {}
#Override
public void onPageScrollStateChanged(int state) {}
});
}
onPageScrolled() is called every time your slide appears, as a parameter it gets current position of the slide that is shown. Nice thing is that it is called including the first time it appears, not just when slide was changed.
When it can be used?
For example if you have some wizard activity with ViewPager where you slide fragments with some hints, you probable would like to have a bar with grey dots below the slider that would represent the number of slides in total, and one of the dots will be different color representing the current slide.
In this case ViewPager.OnPageChangeListener and method onPageScrolled() will be the best option.
Or if you have buttons PREV. and NEXT which change slides and you want to disable PREV. button on the first slide and disable NEXT button on the last slide. Here is how you do it inside onPageScrolled() method:
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
if(position == 0){
prevBtn.setTextColor(ContextCompat.getColor(SignatureWizardActivity.this, R.color.main_grey_500));
prevBtn.setEnabled(false);
}else{
prevBtn.setTextColor(ContextCompat.getColor(SignatureWizardActivity.this, R.color.main_blue));
prevBtn.setEnabled(true);
}
if(position == NUM_PAGES -1){
nextBtn.setTextColor(ContextCompat.getColor(SignatureWizardActivity.this, R.color.main_grey_500));
nextBtn.setEnabled(false);
}else{
nextBtn.setTextColor(ContextCompat.getColor(SignatureWizardActivity.this, R.color.main_blue));
nextBtn.setEnabled(true);
}
}
where NUM_PAGES is a constant with total number of slides
you can use this method to update your views
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser) {
// Fetch data or something...
}
}

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