Develop Reference

Fragments not being loaded using PagerAdapter [ANDROID]

In my app i am using pager adapter to load 2 fragments, the fragments are not getting loaded and view pager remains null. Where i am going wrong? Any help will be appreciated
Here is my code
I am setting this adapter to my view pager from activity
public class ViewPagerActivityAdapter extends PagerAdapter {
ArrayList<Fragment> tablist;
public ViewPagerActivityAdapter(ArrayList<Fragment> tablist) {
this.tablist = tablist;
}
#Override
public int getCount() {
return tablist.size();
}
#Override
public boolean isViewFromObject(View view, Object object) {
return false;
}
#Override
public Object instantiateItem(ViewGroup collection, int position) {
return null;
}
#Override
public void destroyItem(ViewGroup collection, int position, Object view) {
}
}
Activity Part
private ViewPagerActivityAdapter viewPagerAdapter;
private ArrayList<Fragment> fragments_faq;
fragments_faq = new ArrayList<>();
FragmentOne frag1 = new FragmentOne();
tablayout.addTab(tablayout.newTab().setText("fragone"));
fragments_faq.add(frag1);
FragmentTwo frag2 = new FragmentTwo();
tablayout.addTab(tablayout.newTab().setText("fragtwo"));
fragments_faq.add(frag2);
private void setPagerAdapter() {
viewPagerAdapter = new ViewPagerActivityAdapter(fragments_faq);
viewpager.setAdapter(viewPagerAdapter);
viewpager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tablayout));
viewpager.setOffscreenPageLimit(2);
tablayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewpager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}

#Override
public Fragment getItem(int position) {
return this.fragments.get(position);
}
for details check this gist
https://gist.github.com/vinay6kr/33359c3f3b0e9f28e33bd383b01e9d9f

if you want to show fragments in viewpager you should use FragmentStatePagerAdapter
public class MyViewPagerAdapter extends FragmentStatePagerAdapter {
CharSequence Titles[];
public MyViewPagerAdapter(FragmentManager fm, CharSequence mTitles[]) {
super(fm);
this.Titles = mTitles;
}
#Override
public Fragment getItem(int position) {
if (position == 0)
return new Fragment1().getInstance();
else if (position == 1)
return new Fragment2().getInstance();
}
#Override
public CharSequence getPageTitle(int position) {
return Titles[position];
}
#Override
public int getCount() {
return Titles.length;
}
}
and to Set them
void setUpTabs() {
String Titles[] = {"Frag1","Frag2"};
MyViewPagerAdapter adapter = new MyViewPagerAdapter(this.getSupportFragmentManager(), Titles);
viewPager.setAdapter(adapter);
}

You can try like adapter look like
class ViewPagerActivityAdapter extends FragmentPagerAdapter {
// fragments to instantiate in the viewpager
private List<Fragment> fragments;
// constructor
public ViewPagerActivityAdapter(FragmentManager fm,List<Fragment> fragments) {
super(fm);
this.fragments = fragments;
}
// return access to fragment from position, required override
#Override
public Fragment getItem(int position) {
return this.fragments.get(position);
}
// number of fragments in list, required override
#Override
public int getCount() {
return this.fragments.size();
}
}
Add Fragment
List<Fragment> fragments = new Vector<Fragment>();
fragments.add(Fragment.instantiate(this,
FragmentOne.class.getName()));
fragments.add(Fragment.instantiate(this,
FragmentTwo.class.getName()));
Add to view Pager
ViewPagerActivityAdapter mPagerAdapter;
this.mPagerAdapter = new ViewPagerActivityAdapter(
super.getSupportFragmentManager(), fragments);
mPager = (ViewPager) super.findViewById(R.id.pager);
mPager.setAdapter(this.mPagerAdapter);

You should use FragmentPagerAdapter or FragmentStatePagerAdapter for this.Here is sample code.
public class ViewPagerActivityAdapter extends FragmentPagerAdapter {
ArrayList<Fragment> tablist;
public ViewPagerActivityAdapter(ArrayList<Fragment> tablist) {
this.tablist = tablist;
}
#Override
public int getCount() {
return tablist.size();
}
#Override
public Fragment getItem(int position) {
return tablist.get(position);
}
}

Get PagerSlidingTabStrip page title onPageSelected

I'm trying to get the selected page title from a PagerSlidingTabStrip to display on a toast. The page titles are generated from a dynamic list. I am able to get the current page position to display on a toast using:
tabStrip.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
Toast.makeText(getActivity(), "Page position: " + position, Toast.LENGTH_SHORT).show();
}
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
How can I get the current/selected page title?

Create your own adapter for the PagerSlidingTabStrip(this is a viewpager right?) that will manage the titles and also positions.
ViewPager viewPager;
ViewPagerAdapter vpAdapter;
In mainActivity
viewPager = (ViewPager) findViewById(R.id.pager);
vpAdapter = new ViewPagerAdapter(getSupportFragmentManager(), 2, this, clock, history);
ViewPagerAdapter
public class ViewPagerAdapter extends FragmentPagerAdapter {
private int nTabs;
private Context context;
private Fragment fragment1, fragment2;
private CharSequence[] titles;
public ViewPagerAdapter(FragmentManager fm, int nTabs, Context context, Fragment fragment1, Fragment fragment2) {
super(fm);
this.fragment1= fragment1;
this.fragment2= fragment2;
this.context =context;
this.nTabs = nTabs;
titles = new CharSequence[]{context.getText(R.string.Title_tab1), context.getText(R.string.Title_tab2)};
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return fragment1;
case 1:
return fragment2;
default:
return fragment1;
}
}
#Override
public int getCount() {
return nTabs;
}
#Override
public CharSequence getPageTitle(int position) {
return titles[position];
}
}
and don't forget to set the adapter on the viewpager
viewPager.setAdapter(vpAdapter);

How to prevent Fragment from loading data every time from server when swiping Tabs in TabLayout in android?

I am a newbie with Fragments. I have 5 different Fragmentsin my TabLayout. In each fragment I am loading data from the server.
My problem is as follows:
When the first fragment loads it calls the function and loads data from the server and displays on the RecyclerView.
Then When I swipe to the second tab the server data loads and so on. But when I swipe again to say fragment one the data is loading again from the server and the RecyclerView needs to be set again.
Is there anyway where I can load the server data only once (without saving it to a local database) and set the recyclerview only once so that no matter how many times I swipe the tab the data does not load again? I have referred here but i really didnt understand how to solve my problem.I am posting a snippet of my code.
TabActivity
public class TabActivity extends AppCompatActivity {
ViewPager viewpager;
Toolbar toolbar;
TabLayout tablayout;
ViewPagerAdapter viewPagerAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tab_activity);
initialize();
}
private void initialize() {
viewpager = (ViewPager) findViewById(R.id.viewpager);
toolbar = (Toolbar) findViewById(R.id.toolbar);
tablayout = (TabLayout) findViewById(R.id.tablayout);
setSupportActionBar(toolbar);
viewPagerAdapter=new ViewPagerAdapter(getSupportFragmentManager());
viewpager.setAdapter(viewPagerAdapter);
tablayout.setTabsFromPagerAdapter(viewPagerAdapter);
tablayout.setupWithViewPager(viewpager);
}
}
class ViewPagerAdapter extends FragmentStatePagerAdapter implements ViewPager.OnPageChangeListener {
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:return LocatedEvents.newInstance();
case 1:return QrCodeScanner.newInstance();
case 2:return NewsFeed.newInstance();
case 3:return CreatePoll.newInstance();
case 4:return MyProfile.newInstance();
}
return NewsFeed.newInstance();
}
#Override
public int getCount() {
return 5;
}
#Override
public CharSequence getPageTitle(int position) {
return "Tab " + (position + 1);
}
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
}
#Override
public void onPageScrollStateChanged(int state) {
}
}
NewsFeed Fragment
public class NewsFeed extends Fragment {
#Nullable
public static NewsFeed newInstance() {
return new NewsFeed();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.newsfeed_fragment, container, false);
load_data();
return view;
}
}

Avoid creating new Fragments every time in
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return LocatedEvents.newInstance();
case 1:
return QrCodeScanner.newInstance();
case 2:
return NewsFeed.newInstance();
case 3:
return CreatePoll.newInstance();
case 4:
return MyProfile.newInstance();
}
return NewsFeed.newInstance();
}
Make an array of fragments and pass it to your Adapter.Something like this
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dashboard);
initFragments();
}
private void initFragments() {
ArrayList < Fragment > fragmentArrayList = new ArrayList < > ();
fragmentArrayList.add(LocatedEvents.newInstance());
fragmentArrayList.add(QrCodeScanner.newInstance());
fragmentArrayList.add(NewsFeed.newInstance());
fragmentArrayList.add(MyProfile.newInstance();
viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager(), fragmentArrayList); viewpager.setAdapter(viewPagerAdapter); tablayout.setTabsFromPagerAdapter(viewPagerAdapter); tablayout.setupWithViewPager(viewpager);
}
And in your adapter change it to
private ArrayList < Fragment > fragments;
public ViewPagerAdapter(FragmentManager fm, ArrayList < Fragment > fragments) {
super(fm);
this.fragments = fragments;
}
#Override
public Fragment getItem(int position) {
return fragments.get(position);
}
#Override
public int getCount() {
return fragments.size();
}

Tabs with fragment in activity

I have 2 tabs and 2 fragments.I did all for this guide
http://www.truiton.com/2015/06/android-tabs-example-fragments-viewpager/
but now I see tabs but dont see my fragments.What is the problem?
ViewPagerAdapter:
public class ViewPagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public ViewPagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
#Override
public android.support.v4.app.Fragment getItem(int position) {
switch (position) {
case 0:
Direct tab1 = new Direct();
return tab1;
case 1:
AdventuresFragment tab2 = new AdventuresFragment();
return tab2;
default:
return null;
}
}
#Override
public int getCount() {
return mNumOfTabs;
}
}
Activity with using this adapter:
public class TabsActivity extends Activity {
Fragment directFragmentTab = new Direct();
Fragment adventuresFragmentTab = new AdventuresFragment();
#TargetApi(Build.VERSION_CODES.LOLLIPOP)
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tabs_activity);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
}
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.addTab(tabLayout.newTab().setText("Tab 1"));
tabLayout.addTab(tabLayout.newTab().setText("Tab 2"));
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
final PagerAdapter adapter = new PagerAdapter
() {
#Override
public int getCount() {
return 0;
}
#Override
public boolean isViewFromObject(View view, Object object) {
return false;
}
};
viewPager.setAdapter(adapter);
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
}

In your activity you are using the PagerAdapter class while your fragment handling class is named ViewPagerAdapter. You want to use the ViewPagerAdapter class instead.

Accessing Fragment from viewpager returns null everytime?

My host activity has a viewpager with two fragments A and B.My activity code looks like this:
public class MainActivity extends AppCompatActivity implements
OnDataLoadedListener {
private ViewPager pager;
private MyPagerAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pager = (ViewPager) findViewById(R.id.pager);
adapter = new MyPagerAdapter(getSupportFragmentManager());
pager.setAdapter(adapter);
final int pageMargin = (int) TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_DIP, 4, getResources()
.getDisplayMetrics());
pager.setPageMargin(pageMargin);
tabLayout.setupWithViewPager(pager);
}
public class MyPagerAdapter extends FragmentPagerAdapter {
private final String[] TITLES = { "A",
"B" };
public MyPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public CharSequence getPageTitle(int position) {
return TITLES[position];
}
#Override
public int getCount() {
return TITLES.length;
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return A.getInstance();
case 1:
return B.getInstance();
}
return null;
}
}
public Fragment findFragmentByPosition(int position) {
return getSupportFragmentManager().findFragmentByTag(
"android:switcher:" + pager.getId() + ":"
+ adapter.getItemId(position));
}
Now when activity start viewpager get populated with fragment properly and I try to access fragmentby using following code:
if (AFragment == null)
AFragment = (A) findFragmentByPosition(0);
if (BFragment == null)
BFragment = (B) findFragmentByPosition(1);
But AFragment and BFragment always contains null.I have read other simmilar question but it didn't help either.I need access to fragments as I want to call some methods defined in fragment from host activity.
Code to get an instance of fragment:
public static AFragment getInstance() {
AFragment fragment = new AFragment();
return fragment;
}

I'm think that the problem is that you need to move the method to the Adapter, because you need the original instance of the FragmentManager :
public class MyPagerAdapter extends FragmentPagerAdapter {
FragmentManager fm;
private final String[] TITLES = { "A",
"B" };
public MyPagerAdapter (FragmentManager fm) {
super(fm);
this.fm = fm;
}
#Override
public CharSequence getPageTitle(int position) {
return TITLES[position];
}
#Override
public int getCount() {
return TITLES.length;
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return A.getInstance();
case 1:
return B.getInstance();
}
return null;
}
public Fragment findFragmentByPosition(int position, int pagerId) {
return fm.findFragmentByTag(
"android:switcher:" + pagerId + ":"
+ getItemId(position));
}
}
So now you can call:
adapter.findFragmentByPosition(position, pager.getId());