Good morning,
I have a Fragment which its layout has a ViewPager, I provide a custom PageAdapter to show two child layouts. One layout is to fill with personal data and another layout is to fill with Address data by the user. On my fragment I want to retrieve both layouts data and fill a object Pessoa(Person) with an attribute Endereco (Address). So far my ViewPager is working and both layout are displayed, however when I try to get the fields on both layouts, either on onCreateView or onResume fragment's method, using :
viewpager.getChildAt(0).findViewById(R.id.txt1)
I got an NullPointerException, but if I add an OnPageChangeListener this works, I not sure if it's the best approach. Is There a best place to retrieve a reference to the viewpager child's layout?
Ps. I don't want to use two other Fragments in order to display each of the layouts.
PageAdapter
public class ViewPagerCadastroPessoaAdapter extends PagerAdapter {
private Context context;
private int[] views = {R.layout.layout_cadastro_dados_pessoais,R.layout.layout_cadastro_endereco };
public ViewPagerCadastroPessoaAdapter(Context context) {
this.context = context;
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
LayoutInflater inflater = LayoutInflater.from(this.context);
View layout = inflater.inflate(views[position], container, false);
container.addView(layout, position);
return layout;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((View) object);
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position){
case 0:
return "Dados Pessoais";
case 1:
return "Endereço";
}
return super.getPageTitle(position);
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}}
ViewPager's holder Fragment
public class CadastroPessoaFragment extends Fragment {
private ViewPager viewPagerCadastroPessoa;
private TabLayout tabLayoutCadastroPessoa;
public CadastroPessoaFragment() {
}
public static CadastroPessoaFragment newInstance() {
return new CadastroPessoaFragment();
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_cadastro_pessoa, container, false);
tabLayoutCadastroPessoa = root.findViewById(R.id.tabLayoutCadastroPessoa);
viewPagerCadastroPessoa = root.findViewById(R.id.viewPagerCadastroPessoa);
viewPagerCadastroPessoa.setOffscreenPageLimit(2);
viewPagerCadastroPessoa.setAdapter(new ViewPagerCadastroPessoaAdapter(getContext()));
tabLayoutCadastroPessoa.setupWithViewPager(viewPagerCadastroPessoa);
int cor = ContextCompat.getColor(getContext(), android.R.color.white);
tabLayoutCadastroPessoa.setTabTextColors(cor, cor);
//get a null pointer
viewPagerCadastroPessoa.getChildAt(0).findViewById(R.id.txt1);
viewPagerCadastroPessoa.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
//works fine
viewPagerCadastroPessoa.getChildAt(0).findViewById(R.id.txt1);
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
return root;
}
#Override
public void onResume() {
super.onResume();
//get a null pointer
viewPagerCadastroPessoa.getChildAt(0).findViewById(R.id.txt1);
}
}
Thank you all in advance
UPDATE
According with
Anton Malyshev answer
The way Viewpager creates its pages is kind of "unsynchronized", so I used the following approach to solve my problem:
On my custom adapter I definied an interface with a single method onViewPagerReady(), as my Viewpager will always have only two pages, inside instantiateItem I check when position is 1 (once position starts with 0), if position == 1 I call the method onViewPagerReady that my fragment viewpager's holder implements, so inside this method I retrieve the layout of viewpager's children
public class ViewPagerCadastroPessoaAdapter extends PagerAdapter {
public interface ViewPagerObserver{
void onViewPagerReady();
}
private Context context;
private int[] views = {R.layout.layout_cadastro_dados_pessoais,R.layout.layout_cadastro_endereco };
private ViewPagerObserver observer;
public ViewPagerCadastroPessoaAdapter(Context context, ViewPagerObserver observer) {
this.context = context;
this.observer = observer;
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
LayoutInflater inflater = LayoutInflater.from(this.context);
View layout = inflater.inflate(views[position], container, false);
container.addView(layout, position);
if(position == 1){
observer.onViewPagerReady();
}
return layout;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((View) object);
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position){
case 0:
return "Dados Pessoais";
case 1:
return "Endereço";
}
return super.getPageTitle(position);
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
}
Fragment Viewpager's Holder
#Override
public void onViewPagerReady() {
View rootCadastroDadosPessoais = viewPagerCadastroPessoa.getChildAt(0);
View rootCadastroEnderecos =viewPagerCadastroPessoa.getChildAt(1);
}
Thank you all.
Just wait until viewPagerCadastroPessoa.getChildCount() will be greater than 0. The pages in ViewPager are not created yet in onResume (they are created asynchronously).
Related
My code for this class is unable to show view at the 0th position and is also showing irrelevant data sometime. This view pager is attached with a tablayout.
I want to know why this is happening and if there is some other way to handle viewpager extending PagerAdapter.I will be happy if I will come to know about some another class relevant to PagerAdapter but without using Fragment.
public class JobcardListViewPagerAdapter extends PagerAdapter implements IWebServiceAdapter {
Context mContext;
LayoutInflater mLayoutInflater;
List<TabLayoutDetails> tabLayoutDetailsList;
ActiveJobCardListResponse activeJobCardListResponse;
Activity activity;
View itemView;
WebService webService;
public JobcardListViewPagerAdapter(Context context, List<TabLayoutDetails> tabLayoutDetailsList) {
mContext = context;
mLayoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
this.tabLayoutDetailsList = tabLayoutDetailsList;
webService = new WebService();
}
public JobcardListViewPagerAdapter() {
}
#Override
public int getCount() {
return tabLayoutDetailsList.size(); // value of tabLayoutDetailsList.size() returning 10;
}
#Override
public CharSequence getPageTitle(int position) {
return tabLayoutDetailsList.get(position).getDescription();
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == ((LinearLayout) object);
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
itemView = mLayoutInflater.inflate(R.layout.active_job_card_list_view_pager_adapter, container, false);
GetActiveJobCardList(position);
container.addView(itemView);
return itemView;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((LinearLayout) object);
}
}
I came across a strange issue in my project.
I have implemented infinite viewpager adapter using FragmentStatePagerAdapter
Code for same is:
public class DashBoardAdapter extends FragmentStatePagerAdapter {
ArrayList<AbstractFragment> fragments;
private int MAXFRAGMENTS=0;
public DashBoardAdapter(FragmentManager fm, ArrayList<AbstractFragment> fragments) {
super(fm);
this.fragments = fragments;
MAXFRAGMENTS=fragments.size();
}
#Override
public AbstractFragment getItem(int position) {
return fragments.get(position%MAXFRAGMENTS);
}
#Override
public int getCount() {
return Integer.MAX_VALUE;
}
#Override
public CharSequence getPageTitle(int position) {
return fragments.get(position%MAXFRAGMENTS).getTitle();
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
int virtualPosition = position % MAXFRAGMENTS;
return super.instantiateItem(container, virtualPosition);
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
int virtualPosition = position % MAXFRAGMENTS;
super.destroyItem(container, virtualPosition, object);
}
#Override
public void notifyDataSetChanged() {
super.notifyDataSetChanged();
MAXFRAGMENTS = fragments.size();
}
}
And the Main Activitycode(Function only) is something like this:
public void initializeViewPager()
{
verticalViewPager = (VerticalViewPager) findViewById(R.id.verticalviewpager);
enabledPages=new ArrayList<>();
enabledPages.addAll(getEnabledPages(false));
adapter=new DashBoardAdapter(getSupportFragmentManager(),enabledPages);
verticalViewPager.setAdapter(adapter);
verticalViewPager.setPageTransformer(true, new PageTransformer());
verticalViewPager.setCurrentItem(999+position);
verticalViewPager.setOffscreenPageLimit(1);
verticalViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
if(adapter!=null)
title.setText(adapter.getPageTitle(position));
}
#Override
public void onPageSelected(int position) {
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
}
private ArrayList<AbstractFragment> getEnabledPages(boolean a)
{
ArrayList<AbstractFragment> fragments=new ArrayList<>();
fragments.add(FragmentAttendance.newInstance(fragments.size()));
fragments.add(FragmentCompensation.newInstance(fragments.size()));
if(a)
fragments.add(FragmentTimeOff.newInstance(fragments.size()));
if(a)
fragments.add(FragmentCalendar.newInstance(fragments.size()));
if(a)
fragments.add(FragmentPeople.newInstance(fragments.size()));
if(a)
fragments.add(FragmentProvisions.newInstance(fragments.size()));
position = fragments.size()-(999+position)%fragments.size();
return fragments;
}
Layout of activity contains just a Viewpager.
And the Fragments, I have used is just copy of below fragment with different names
public class FragmentAttendance extends AbstractFragment {
public static final String ARG_SECTION_NUMBER = "section_number";
String title ="Testing";
public static FragmentAttendance newInstance(int sectionNumber) {
FragmentAttendance fragment = new FragmentAttendance();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
public FragmentAttendance() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.card_attendance, container, false);
return rootView;
}
#Override
public String getTitle() {
return title;
}
}
Layout of fragment has just LinearLayout with a TextView.
The code is running superb if I am adding fragments more than three fragments. Howsoever as soon as the number of added fragments gets below four. My code Works in strange behavior.
Some of errors are Fragment already initialised
Other are Forward scrolling shows fragement View Howsoever when I scroll backward No view appears.
The working code can be tested by passing true to getEnabledPages(true);
And the non working code can be tested by passing false to getEnabledPages(false);
Please someone help me in this strange behaviour.
I'm working with viewpager inside fragments. I'm using pagerAdapter to switch between two pages via XML. Here is the code:
public class DemoPagerAdapter extends FragmentPagerAdapter {
public DemoPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
Fragment f;
switch (index) {
case 0:
f = new FirstFragment();
break;
case 1:
f = new SecondFragment();
break;
}
return f;
}
#Override
public int getCount() {
return 2;
}
}
And I'm calling it like this:
public class DemoFragment1 extends Fragment {
private ViewPager viewPager;
private DemoPagerAdapter mAdapter;
public DemoFragment1() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View rootView = inflater.inflate(R.layout.security, container, false);
mAdapter = new DemoPagerAdapter(getActivity().getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
showPages(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
return rootView;
}
Everything works fine. But if I move to DemoFragment2 and then come back to DemoFragment1, PagerAdapter is not called.
Your ViewPager is nested in a Fragment, you should use the ChildFragmentManager, modify:
mAdapter = new DemoPagerAdapter(getChildFragmentManager());
I also assume the ViewPager will keep the off screen fragment in memory, thus it might not call getItem(int index) again. Add
viewPager.setOffscreenPageLimit(0);
return rootView;
Well, I encontered this issue last week.
When I put the ViewPager in the fragment with a FragmentPagerAdapter, after I move forward to anoter Fragment and back, the pager' s view not exists.
I supposed is the FragmentPagerAdapter won' t retain its view in the ViewPager ' s host Fragment, Their life cycle is not the same. Though you put the VewPager' s host Fragment in the back stack, but the FragmentPagerAdapter' s fragment not. And Then, I gave up FragmentPagerAdapter and tried android.support.v4.view.PagerAdapter, (note, it wont' t use fragment to inject view!), everything is fine!
below is the sample:
private final PagerAdapter coverPager = new PagerAdapter() {
private LayoutInflater mLayoutInflater;
#Override
public int getCount() {
return 2;
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((View) object);
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
if (mLayoutInflater == null) {
mLayoutInflater = LayoutInflater.from(getActivity());
}
switch (position) {
case 0:
View frontPage = mLayoutInflater.inflate(R.layout.profile_cover, container, false);
ImageView avatar = (ImageView) frontPage.findViewById(R.id.avatar);
Picasso.with(getActivity())
.load(mAvatarUrl)
.placeholder(R.drawable.error)
.error(R.drawable.error)
.into(avatar);
TextView screenName = (TextView) frontPage.findViewById(R.id.screen_name);
screenName.setText("#" + mScreenName);
TextView remark = (TextView) frontPage.findViewById(R.id.remark);
remark.setText(TextUtils.isEmpty(mRemark) ? mScreenName : mRemark);
if (mVerified) {
frontPage.findViewById(R.id.verified).setVisibility(View.VISIBLE);
}
container.addView(frontPage);
return frontPage;
case 1:
View introPage = mLayoutInflater.inflate(R.layout.profile_intro, container, false);
CatnutUtils.setText(introPage, R.id.description, TextUtils.isEmpty(mDescription)
? getString(R.string.no_description) : mDescription);
CatnutUtils.setText(introPage, R.id.location, mLocation);
CatnutUtils.setText(introPage, R.id.profile_url, Constants.WEIBO_DOMAIN + mProfileUrl);
container.addView(introPage);
return introPage;
default:
return null;
}
}
};
and then in your onViewCreate or OnCreateView, put mViewPager.setAdapter(coverPager);
the instantiateItem is the place to put the page' s view, similar like the FragmentPagerAdapter!
It' s just like put the FragmentAdapter' s view int the ViewPager' s host Fragment, not the other fragment!
Hope it' s helpful!
Similar question Access ViewPager views from onCreate?
I created a ViewPager where different layout can moves around. One layout has a button. My question is if a user click on this button, he will move another page. How to achieve it. Here is the viewpager adapter class:
public class SwipeAdapter extends PagerAdapter {
private LayoutInflater mInflater;
private static int[] mLayouts = { R.layout.view_layout1,
R.layout.view_layout2, R.layout.view_layout3, R.layout.view_layout4 };
SwipeAdapter(Context context) {
mInflater = LayoutInflater.from(context);
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((View) object);
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
ViewGroup pageView= (ViewGroup) mInflater.inflate(mLayouts[position],
container, false);
container.addView(pageView);
getItemPosition(pageView);
return pageView;
}
/**
* #return the mCurrentposition
*/
#Override
public int getCount() {
return mLayouts.length;
}
#Override
public boolean isViewFromObject(View view, Object obj) {
return view == obj;
}
}
I'm trying to implement ViewPager with PagerAdapter in my app. I'm mainly working off this example.
My PagerAdapter is called DataPagerAdapter and uses the following constructor and instantiateItem, where I inflate a view from data_list_view.xml:
public class DataPagerAdapter extends PagerAdapter
implements TitleProvider {
private LayoutInflater mInflater;
private static String[] titles = new String[]
{
"Page 1",
"Page 2",
"Page 3"
};
private final Context context;
public DataPagerAdapter( Context context )
{
this.context = context;
}
#Override
public String getTitle( int position )
{
return titles[ position ];
}
#Override
public int getCount()
{
return titles.length;
}
#Override
public Object instantiateItem( View pager, int position )
{
ListView v = (ListView) mInflater.inflate(R.layout.data_list_view, null);
((ViewPager)pager).addView( v, 0 );
return v;
}
#Override
public void destroyItem( View pager, int position, Object view )
{
((ViewPager)pager).removeView( (ListView)view );
}
#Override
public boolean isViewFromObject( View view, Object object )
{
return view.equals( object );
}
#Override
public void finishUpdate( View view ) {}
#Override
public void restoreState( Parcelable p, ClassLoader c ) {}
#Override
public Parcelable saveState() {
return null;
}
#Override
public void startUpdate( View view ) {}
}
And in my activity I get my adapter:
DataPagerAdapter adapter = new DataPagerAdapter( this );
And then later I want to refer to my dataListView in code:
dataListView = (ListView) findViewById(R.id.listViewData);
Problem is, the dataListView is returned as null by the findViewById call since the instantiateItem is never processed.
When is instantiateItem called and is this done automatically (as the example seems to suggest) or do I have to force it somehow?
Note, that your adapter uses deprecated methods:
public Object instantiateItem(View container, int position)
public void destroyItem(View container, int position, Object object)
The API says to use these instead:
public Object instantiateItem(ViewGroup container, int position)
public void destroyItem(ViewGroup container, int position, Object object)
In my case the problem was I set ViewPager visibility to GONE by mistake and it was not getting called . Just make viewPager visibility to visible in layout.