Develop Reference

Android ViewPager inside Fragment loaded only once v2

My question is similtar to this:
Android ViewPager Inside Fragment Loaded Only Once
The difference is that its answer doesn't work for me.
I have 4 fragments. Inside one of these fragments there is a Fragment X with ViewPager that switch betwen two other fragments. The first time I load the FragmentX the ViewPager works fine. The problem is if I switch to one of the other 4 fragments, when I go back to the FragmentX the ViewPager has nothing inside.
Fragment X
...
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_campus, container, false);
TabLayout tabLayout = (TabLayout)view.findViewById(R.id.tab_layout);
tabLayout.addTab(tabLayout.newTab().setText("Mapa"));
tabLayout.addTab(tabLayout.newTab().setText("Eventos"));
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
vpPager = (ViewPager)view.findViewById(R.id.vpPager);
adapterViewPager = new PagerAdapter(getChildFragmentManager());
vpPager.setAdapter(adapterViewPager);
vpPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
vpPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
return view;
}
PageAdapter
public class PagerAdapter extends FragmentPagerAdapter {
private int NUM_ITEMS = 2;
public PagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
// 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:
return MapFragment.newInstance(0);
case 1:
return EventosFragment.newInstance(1);
default:
return null;
}
}
// Returns the page title for the top indicator
#Override
public CharSequence getPageTitle(int position) {
return "Page " + position;
}
}
MainActivity
public boolean onNavigationItemSelected(MenuItem item) {
int id = item.getItemId();
...
if (...) {
if (campusFragment == null) // the problem is not solved by commenting this condition
campusFragment = new CampusFragment(); // Fragment X
fragmentManager.beginTransaction().replace(R.id.content_frame, campusFragment).commit();
}
}

how not to show some tabs on tabbed activity?

I have the following activity wich show different tabs.
public class BagContent extends FragmentActivity implements ActionBar.TabListener, CosmeListener {
String[] profileTypes;
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_bag_content);
mViewPager = (ViewPager) findViewById(R.id.pager);
final ActionBar actionBar = getActionBar();
actionBar.setTitle(getString(R.string.title_activity_bag_content) + " [" + bagName + "]");
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
mSectionsPagerAdapter = new SectionsPagerAdapter(getFragmentManager());
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
actionBar.addTab(actionBar.newTab().setText(mSectionsPagerAdapter.getPageTitle(i)).setTabListener(this));
}
}
#Override
protected void onResume() {
super.onResume();
// TODO Auto-generated method stub
}
#Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
#Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
/**
* A {#link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new FormatShortFragment();
case 1:
return new FormatLongFragment();
case 2:
return new FormatPlantFragment();
}
return null;
}
#Override
public int getCount() {
// Show 3 total pages.
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_bag_content_format_short).toUpperCase(l);
case 1:
return getString(R.string.title_bag_content_format_long).toUpperCase(l);
case 2:
return getString(R.string.title_bag_content_format_plant).toUpperCase(l);
}
return null;
}
}
I have and array wiht different profile types, depending on each type i have to show some tabs or others.
Actually all tabs are been showing for every profile type. I tried to insert manually the tabs on the actionbar, but then the tabs are not showing the fragments correctly. Other problem is that navigation breaks when i go to an inexistent tab on the right edge.
I need help with this, how can I select just 1 tab for a specific profile type?
for example, how can I show just the title_bag_content_format_long and his fragment for profileTypes[1]?
Any walk aroun can be good, for example remove some tabs from some profile types or any other thing.
Thanks a lot guys, I really need help with this.
EDITED
I have made some modifications:
Added a profile type parameter to SectionsPagerAdapter constructor:
private String profileType;
public SectionsPagerAdapter(FragmentManager fm, String profileType) {
super(fm);
this.profileType = profileType;
}
Then i have modified this other methods to control the profile type:
#Override
public Fragment getItem(int position) {
if (this.profileType.equals(profileTypes[1])){
switch (position) {
case 0:
return new FormatPlantFragment();
}
} else {
switch (position) {
case 0:
return new FormatShortFragment();
case 1:
return new FormatLongFragment();
case 2:
return new FormatPlantFragment();
}
}
return null;
}
#Override
public int getCount() {
if (this.profileType.equals(profileTypes[1])){
return 1;
}
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
if (this.profileType.equals(profileTypes[1])){
switch (position) {
case 0:
return getString(R.string.title_bag_content_format_plant).toUpperCase(l);
}
} else {
switch (position) {
case 0:
return getString(R.string.title_bag_content_format_short).toUpperCase(l);
case 1:
return getString(R.string.title_bag_content_format_long).toUpperCase(l);
case 2:
return getString(R.string.title_bag_content_format_plant).toUpperCase(l);
}
}
return null;
}
This is working correctly and do the filter by profile type more versatile.
Thanks to Filpe.costa01 that gave me the push that I needed.

You're returning all the tabs because your method
#Override
public int getCount() {
// Show 3 total pages.
return 3;
}
return 3 tabs. Maybe you could use the SectionsPagerAdapter constructor to include the number of tabs you'd like, according to each profile wanted.
Something like this:
private mNumOfTabs;
public SectionsPagerAdapter(FragmentManager fm, int numberOfTabs) {
super(fm);
mNumOfTabs = numberOfTabs;
}
and you should replace your getCount() method for this one:
#Override
public int getCount() {
// Show 3 total pages.
return mNumOfTabs;
}
Organizing your profiles in an ascendant way (low profile = small number of tabs), you can use this method like it's now
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new FormatShortFragment();
case 1:
return new FormatLongFragment();
case 2:
return new FormatPlantFragment();
}
return null;
}
Otherwise, you should think about the profiles and implement a new logic to retrieve the correct tabs for each profile.

How can I set fragment Id in some of the override method of FragmentPagerAdapter?

I have a FragmentPagerAdapter, and in the fragment class I have a public method that I need to use from main activity.
In this point I don't know how to access the fragment that contains that method. Can I modify something on the class below to set id or something to fragments?
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new Fragment_1();
case 1:
return new Fragment_2();
case 2:
return new Fragment_3();
}
return null;
}
#Override
public int getCount() {
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.fg_1).toUpperCase(l);
case 1:
return getString(R.string.fg_2).toUpperCase(l);
case 2:
return getString(R.string.fg_3).toUpperCase(l);
}
}
return null;
}
}
How can I set a Fragment id, or Fragment tag or something to acces the fragment later?
Any other way to access fragment methods could be good.
EDITED WITH MORE INFORMATION:
I'm really lost with this. But, I have a ViewPager too, these fragments are associated to actionBar Tabs.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener(){
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
actionBar.addTab(actionBar.newTab().setText(mSectionsPagerAdapter.getPageTitle(i)).setTabListener(this));
}
Is there any way to communicate with the fragments?

Like so :
switch (position) {
case 0:
Fragment f = new Fragment_1();
f.setId(...);
return f;
case 1:
...
}
This assumes you have a setId method in your fragment.
What I do however is define a static string TAG per fragment, I can then access it with Fragment_1.TAG.

viewPager adapter null pointer exception

I got an error while setting adapter, i only have one folder for layouts
and to tabs fragments on activity_main , i have searched in many websites but no results. Please help!
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
context = this;
mTitle = getTitle();
navMenuTitle = getResources().getStringArray(R.array.titles);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter); //Null Pointer Exception
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
getSupportActionBar().setTitle(navMenuTitle[position]);
}
});
this is the SectionAdapter
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
switch(position){
case 0:
return MainGenFragment.newInstance(position + 1);
case 1:
return new FragmentMyPwd();
}
return null;
}
#Override
public int getCount() {
// Show 3 total pages. Now Changed to 2.
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
//case 2:
//return getString(R.string.title_section3).toUpperCase(l);
}
return null;
}
}

You need to add setContentView(R.layout.yourlayout) in onCreate(). Without that, mViewPager will be null because it is not found with findViewById().

Navigating between Fragments while using a ViewPager

I've looked at so many questions here that I don't even know exactly what I'm looking for.
I have a simple app that uses a ViewPager. It has 3 tabs and there is a fragment for each tab. The first fragment contains a ListView. I want to be able to click on an element in the ListView and have that bring me to a different fragment.
So basically I want to remove the fragment that contained the ListView once an element is clicked and add in a new fragment. I've tried to do this in a few different ways with none working.
The last thing I tried was to edit the TabsPageAdapter once an element was clicked which pretty much works except when I press the back button it exits the app. Also it doesn't seem like the cleanest way of doing this.
TabsPagerAdapter
public class TabsPagerAdapter extends FragmentStatePagerAdapter {
SherlockFragment mf;
TalkingPointsFragment tpf;
ContactFragment gf;
int mode = 0;
public TabsPagerAdapter(FragmentManager fm) {
super(fm);
mf = new CanvassFragment();
tpf = new TalkingPointsFragment();
gf = new ContactFragment();
}
public TabsPagerAdapter(FragmentManager fm, int mode)
{
super(fm);
if(mode == 0)
{
mf = new CanvassFragment();
tpf = new TalkingPointsFragment();
gf = new ContactFragment();
}
else if(mode == 1)
{
mf = new ContactFragment();
tpf = new TalkingPointsFragment();
gf = new ContactFragment();
}
}
#Override
public SherlockFragment getItem(int index) {
switch (index) {
case 0:
return mf;
case 1:
return tpf;
case 2:
return gf;
}
return null;
}
#Override
public int getCount() {
// get item count - equal to number of tabs
return 3;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object)
{
}
}
The onclick code:
ViewPager viewp = (ViewPager) getActivity().findViewById(R.id.pager);
TabsPagerAdapter mAdapter = new TabsPagerAdapter(getActivity().getSupportFragmentManager(),1);
viewp.setAdapter(mAdapter);
mAdapter.notifyDataSetChanged();
layout_main.xml
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:actionBarTabStyle="#drawable/actionbar_tab_indicator">

I FragmentStatePagerAdapter too and when a user selects map from the ActionBar, I add the GoogleMapsFragment on top of the FragmentStatePagerAdapter:
// create a new map
mapsFragment = GoogleMapFragment.newInstance();
// Then we add it using a FragmentTransaction.
FragmentTransaction fragmentTransaction = getSupportFragmentManager()
.beginTransaction();
fragmentTransaction.add(android.R.id.content, mapsFragment,
FRAGMENT_MAP_TAG);
fragmentTransaction.commit();
For your case you would probably need to add it to the backstack too, which I have not because in my app the user has to navigate back using the ActionBar.
Thought this approach could work for you too when a user selects an item from your list.
Of course this has the disadvantage of not being able to use the FragmentStatePagerAdapter until the user navigates back. So I am not sure wether that would be acceptable for your app.

Ok, so this took a bit more code that I imagined. Hope you get the idea:
public class MainClass extends FragmentActivity implements CanvassCallback {
// save a single reference to ViewPager and TabsPagerAdapter
private ViewPager mViewPager;
private TabsPagerAdapter mAdapter;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.mViewPager = (ViewPager) findViewById(R.id.pager);
this.mAdapter = new TabsPagerAdapter(getSupportFragmentManager(), this);
mViewPager.setAdapter(mAdapter);
...
}
// from the CanvassCallback interface
public void itemSelected() {
mAdapter.canvassSelected();
mAdapter.notifyDataSetChanged();
}
#Override
public void onBackPressed() {
if (mViewPager.getCurrentItem() == 0 && mAdapter.isCanvassSelected() {
mAdapter.canvassSelected();
mAdapter.notifyDataSetChanged();
}
else {
super.onBackPressed();
}
}
}
Mockup of your CanvassFragment showing the callback
public class CanvassFragment extends SherlockFragment {
public interface CanvassCallback {
public void itemSelected();
}
private CanvassCallback canvassCallback;
public void setCanvassCallback(CanvassCallback canvassCallback) {
this.canvassCallback = canvassCallback;
}
...
// The onClick of your item
private void onClick() {
// notify your activity that an item was selected
canvassCallback.itemSelected();
}
}
The registeredFragments are not strictly needed but I think it provides some value if your need to call methoods on your Fragment from activity.
public class TabsPagerAdapter extends FragmentStatePagerAdapter {
// see upvoted answer from http://stackoverflow.com/questions/8785221/retrieve-a-fragment-from-a-viewpager
SparseArray<Fragment> registeredFragments = new SparseArray<Fragment>();
private boolean canvassSelected = false;
private CanvassCallback canvassCallback;
public TabsPagerAdapter(FragmentManager fm, CanvassCallback canvassCallback) {
super(fm);
this.canvassCallback = canvassCallback;
}
public void canvassSelected() {
canvassSelected = !canvassSelected;
}
public boolean isCanvassSelected() {
return canvassSelected;
}
#Override
public SherlockFragment getItem(int index) {
switch (index) {
case 0:
if (canvassSelected)
return new ContactFragment();
CanvassFragment canvassFragment = new CanvassFragment();
// this ensures that your Activity gets notified when an item is clicked
canvassFragment.setCanvassCallback(canvassCallback);
return canvassFragment;
case 1:
return new TalkingPointsFragment();
case 2:
return new ContactFragment();
}
return null;
}
#Override
public int getCount() {
// get item count - equal to number of tabs
return 3;
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
Log.d(TAG, "instantiateItem " + position);
Fragment fragment = (Fragment) super.instantiateItem(container, position);
registeredFragments.put(position, fragment);
return fragment;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
Log.d(TAG, "destroyItem " + position);
registeredFragments.remove(position);
super.destroyItem(container, position, object);
}
}