I'm having difficulty in setting smooth scroll for Fragments inside ViewPager, nested in another Fragment which acts as their parent.
I set up this method :
public void scrollToTop()
{
this.recyclerView.smoothScrollToPosition(0);
}
For Fragments not in a ViewPager, but I don't know how to get the reference of Fragments inside a ViewPager.
I did
BottomLobiFragment activeLobi = (BottomLobiFragment)getSupportFragmentManager().findFragmentByTag(utilities.lobbyTag);
to get the parent Fragment.
Code for a ViewPager (The rest are almost identical, difference is only at number of item, and constructor)
public class LobbyPagerAdapter extends FragmentStatePagerAdapter {
public LobbyPagerAdapter (FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int pos) {
switch(pos) {
case 0: return Friends.newInstance("Friends, Instance 1");
// case 1: return Photo.newInstance("Photo, Instance 1");
// case 2: return Activities.newInstance("Activities, Instance 1");
default: return Friends.newInstance("Friends, Default");
}
}
#Override
public CharSequence getPageTitle(int position) {
return CONTENT[position % CONTENT.length];
}
#Override
public int getCount() {
//return 3;
return CONTENT.length;
}
private class setAdapterTask extends AsyncTask<Void,Void,Void> {
protected Void doInBackground(Void... params) {
return null;
}
#Override
protected void onPostExecute(Void result) {
}
}
}
Note : Every adapter is located inside the parent Fragment
First modify your Adapter to this
public class LobbyPagerAdapter extends FragmentStatePagerAdapter {
private ArrayList<Fragment> mFragments = new ArrayList<>();
public LobbyPagerAdapter (FragmentManager fm) {
super(fm);
mFragments.add(Friends.newInstance("Friends, Instance 1"));
mFragments.add(Photo.newInstance("Photo, Instance 1"));
mFragments.add(Activities.newInstance("Activities, Instance 1"));
}
#Override
public Fragment getItem(int pos) {
return mFragments.get(pos);
}
#Override
public CharSequence getPageTitle(int position) {
return CONTENT[position % CONTENT.length];
}
#Override
public int getCount() {
//return 3;
return CONTENT.length;
}
private class setAdapterTask extends AsyncTask<Void,Void,Void> {
protected Void doInBackground(Void... params) {
return null;
}
#Override
protected void onPostExecute(Void result) {
}
}
}
Now in your fragment or activity which is holding the ViewPager & the adapter instance, you can simply do like adapter.getItem(1); example :
//Suppose your LobbyPagerAdapter instance looks like this in your code
LobbyPagerAdapter adapter = new LobbyPagerAdapter(getFragmentManager());
// And now you want to get the fragment at second position in your tab
Photo photoFragmentObject = (Photo)adapter.getItem(1);
// And now you want to get the fragment at first position in your tab
Friends friendsFragmentObject = (Friends)adapter.getItem(0);
Related
Here's the inner class that contains fragments and changes fragment views on swipe. This class is defined in an Activity.
private class ViewPagerAdapter extends FragmentPagerAdapter {
private int count;
ViewPagerAdapter(FragmentManager fm, int count) {
super(fm);
this.count = count;
}
#Override
public Fragment getItem(int position) {
switch(position) {
case 0:
return new FriendsListFragment();
case 1:
Bundle bundle = new Bundle();
bundle.putString(Keys.TAG, ChatListFragment.class.getSimpleName());
ChatListFragment chatListFragment = new ChatListFragment();
chatListFragment.setArguments(bundle);
return chatListFragment;
case 2:
return new MoreFragment();
default:
return null;
}
}
#Override
public int getCount() {
return count;
}
}
Here I would like to add a code that sets tags to each fragment, so that I can recognize which fragment I'm at.
I searched quite much, and I haven't found a proper answer for this question, so please help.
You can override the setPrimaryItem method of your FragmentPagerAdapter.
private class ViewPagerAdapter extends FragmentPagerAdapter {
protected int currentPosition = -1;
protected Fragment currentFragment;
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// ....
}
#Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
super.setPrimaryItem(container, position, object);
this.currentPosition = position;
if (object instanceof Fragment) {
this.currentFragment = (Fragment) object;
}
}
public int getCurrentPosition() {
return currentPosition;
}
public Fragment getCurrentFragment() {
return currentFragment;
}
}
Just use getCurrentPosition or getCurrentFragment methods to get information about current Fragment.
I have implemented the first row of tab.
Inside that tab i have another set of Tabs.
Specifically two more tabs.
Please refer to these images.
The Picture above is the dog tab is selected.
The picture above is I want to select the Cat tab.
But unfortunately, the tab is not sliding properly.
its like its just a slowly scrolling.
but it should be on just one slide it should be on the cat tab.
My First layer of tab is inside Fragment.
The second row of tab is also in Fragment.
public class AdapterFragmentPagerItem extends FragmentStatePagerAdapter {
String[] pageTitle={"Do's","Dont's","First Aid"};
public AdapterFragmentPagerItem(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch(position){
case 0:
return new FragmentDo();
case 1:
return new FragmentDonts();
case 2:
return new FragmentFirstAid();
}
return null;
}
#Override
public int getCount() {
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
return pageTitle[position];
}
}
The above code is for the first image.
public class AdapterFragmentDos extends FragmentStatePagerAdapter {
String[] pageTitle = {"Dog", "Cat"};
public AdapterFragmentDos(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
if(position==0){
return new FragmentDonts();
}else{
return new FragmentFirstAid();
}
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
return pageTitle[position];
}
}
And this is for the second image.
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());
I am using FragmentPagerAdapter that contains two Fragments. Two Fragments extends from AbstractFragment which extends Fragment. I am not able to get the page title of the fragment when its created because the title is pass as an argument to the fragment:
FragmentActivity's inner Class:
ArrayList<AbstractFragment> fragments = new ArrayList<AbstractFragment >();
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return fragments.get(position);
}
#Override
public int getCount() {
return fragments.size();
}
#Override
public CharSequence getPageTitle(int position) {
return fragments.get(position).getTitle();
}
}
AbstractFragment :
protected Bundle data;
protected String title;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
data=this.getArguments();
numberSetData=data.getParcelableArrayList(KEY_CHART_DATA);
title=data.getString(KEY_CHART_TITLE);
//Title should is determined here.
}
public abstract String getTitle();
ConcreteFragment:
#Override
public String getTitle(){
return title;
}
The problem solves if I swipe to the next fragment , title will appear but not when its created. Any advice?
You are calling getTitle at a point where onCreate has not yet been called for that Fragment. A known workaround for this would be to check if onCreate has been called, and if not then return data.getString(KEY_CHART_TITLE).
public String getTitle()
{
if( title == null )
{
title = getArguments().getString(KEY_CHART_TITLE);
}
return title;
}
I'm making an adroid application with viewpager and fragments. I want to make an option to add or remove fragment pages to the pager dynamically. I have a custom FragmentPagerAdapter:
public class MyAdapter extends FragmentPagerAdapter implements TitleProvider{
protected final List<PageFragment> fragments;
/**
* #param fm
* #param fragments
*/
public MyAdapter(FragmentManager fm, List<PageFragment> fragments) {
super(fm);
this.fragments = fragments;
}
public void addItem(PageFragment f){
fragments.add(f);
notifyDataSetChanged();
}
public void addItem(int pos, PageFragment f){
for(int i=0;i<fragments.size();i++){
if(i>=pos){
getSupportFragmentManager().beginTransaction().remove(getSupportFragmentManager().findFragmentByTag(getFragmentTag(i))).commit();
}
}
fragments.add(pos,f);
notifyDataSetChanged();
pager.setAdapter(this);
pager.setCurrentItem(pos);
}
public void removeItem(int pos){
getSupportFragmentManager().beginTransaction().remove(getSupportFragmentManager().findFragmentByTag(getFragmentTag(pos))).commit();
for(int i=0;i<fragments.size();i++){
if(i>pos){
getSupportFragmentManager().beginTransaction().remove(getSupportFragmentManager().findFragmentByTag(getFragmentTag(i))).commit();
}
}
fragments.remove(pos);
notifyDataSetChanged();
pager.setAdapter(this);
if(pos<fragments.size()){
pager.setCurrentItem(pos);
}else{
pager.setCurrentItem(pos-1);
}
}
#Override
public Fragment getItem(int position) {
return fragments.get(position).toFragment();
}
#Override
public int getCount() {
return fragments.size();
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
private String getFragmentTag(int pos){
return "android:switcher:"+R.id.pager+":"+pos;
}
public String getTitle(int position) {
String name = fragments.get(position).getName();
if(name.equals(""))
return "- "+position+" -";
return name;
}
}
I can remove any fragment except the 0. when I try to remove it I got a NullPointerException on the notifyDataSetChanged(); or on the pager.setAdapter(this); if i comment out the notify.
I also got a NullPointerException when I try to insert a new page. When I add the new page to the end of the list it's working fine.
I even tried to readd the fragments in the insert with this after the fragments.add(pos,f)
for(int i=0;i<fragments.size();i++){
if(i>=pos){
getSupportFragmentManager().beginTransaction().add(fragments.get(i).toFragment(),getFragmentTag(i-1)).commit();
}
}
if I use getFragmentTag(i-1) I got nullpointer again. With using just i I got illegalstateexception because can not modify fragment's tag. With beginTransaction().add(pager.getId,fragments.get(i).toFragment()) it is still nullpointer...
My question is: what am I doing wrong, and how can it be done properly? (and maybe: from where notyfyDataSetChanged() get the data when causes nullpointerexception?)
This is what I used to get around the problem with fragments being tagged when instantiated and the fact that previously tagged fragments cannot change position within the ViewPager when trying to add or remove pages, i.e. getting the exception:
java.lang.IllegalStateException: Can't change tag of fragment
MyFragment{4055f558 id=0x7f050034 android:switcher:2131034164:3}: was
android:switcher:2131034164:3 now android:switcher:2131034164:4
This adapter is created with a list of all pages upfront and you can then use setEnabled(int position, boolean enabled) to disable or enable certain pages which hides or shows these pages in the ViewPager.
It works by maintaining an internal list of all fragments but exposing to the ViewPager and mapping the positions of enabled fragments only.
public class DynamicFragmentPagerAdapter extends FragmentPagerAdapter {
public final ArrayList<Fragment> screens = new ArrayList<Fragment>();
private Context context;
private List<AtomicBoolean> flags = new ArrayList<AtomicBoolean>();
public DynamicFragmentPagerAdapter(FragmentManager fm, Context context, List<Class<?>> screens) {
super(fm);
this.context = context;
for(Class<?> screen : screens)
addScreen(screen, null);
notifyDataSetChanged();
}
public DynamicFragmentPagerAdapter(FragmentManager fm, Context context, Map<Class<?>, Bundle> screens) {
super(fm);
this.context = context;
for(Class<?> screen : screens.keySet())
addScreen(screen, screens.get(screen));
notifyDataSetChanged();
}
private void addScreen(Class<?> clazz, Bundle args) {
screens.add(Fragment.instantiate(context, clazz.getName(), args));
flags.add(new AtomicBoolean(true));
}
public boolean isEnabled(int position) {
return flags.get(position).get();
}
public void setEnabled(int position, boolean enabled) {
AtomicBoolean flag = flags.get(position);
if(flag.get() != enabled) {
flag.set(enabled);
notifyDataSetChanged();
}
}
#Override
public int getCount() {
int n = 0;
for(AtomicBoolean flag : flags) {
if(flag.get())
n++;
}
return n;
}
#Override
public Fragment getItem(int position) {
return screens.get(position);
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE; // To make notifyDataSetChanged() do something
}
#Override
public void notifyDataSetChanged() {
try {
super.notifyDataSetChanged();
} catch (Exception e) {
Log.w("", e);
}
}
private List<Fragment> getEnabledScreens() {
List<Fragment> res = new ArrayList<Fragment>();
for(int n = 0; n < screens.size(); n++) {
if(flags.get(n).get())
res.add(screens.get(n));
}
return res;
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
// We map the requested position to the position as per our screens array list
Fragment fragment = getEnabledScreens().get(position);
int internalPosition = screens.indexOf(fragment);
return super.instantiateItem(container, internalPosition);
}
#Override
public CharSequence getPageTitle(int position) {
Fragment fragment = getEnabledScreens().get(position);
if(fragment instanceof TitledFragment)
return ((TitledFragment)fragment).getTitle(context);
return super.getPageTitle(position);
}
public static interface TitledFragment {
public String getTitle(Context context);
}
}
I have a solution that works with a non-fragment based adapter. Take a look at my post and see if it helps.
I can remove any fragment except the 0.
For me it works if just use a >= condition whitin the removeItem's for-loop:
if (i >= pos){
fm.beginTransaction().remove(fragments.get(i).getFragment()).commit();
}