I have FragmentTabHost with children tabs (Fragment)
public void onCreate(Bundle savedInstanceState) {
...
mTabHost.addTab(newTabSpec, MainTab.class, new Bundle())
...
}
How i can call public method from my MainTab (or other tab)?
public class MainTab extends Fragment {
public void showNews() {
...
}
}
and vice versa
how i can call any method from FragmentTabHost inside it children tab (Fragment).
Another words, i need know how get link to any children Fragment than is tab in FragmentTabController. How i can get object "MainTab" inside TabHos?
For example in iOS i cat get first viewcontroller from children tab like this:
UINavigationController *navController = [appDelegate.tabController.viewControllers objectAtIndex: 1]
Is there a similar method in android?
O'k. I was wrong in concept when try get reference to any fragment or view from another. In android i should use events instead.
Related
Problem:
I am currently running into a problem where my app is trying to load too many fragments when it opens for the first time.
I have BottomNavigationView with ViewPager that loads 4 fragments - each one of the Fragment contains TabLayout with ViewPager to load at least 2 more fragments.
As you can imagine, that is a lot of UI rendering (10+ fragments) - especially when some of these fragments contain heavy components such as calendar, bar graphs, etc.
Currently proposed solution:
Control the UI loading when the fragment is required - so until the user goes to that fragment for the first time, there is no reason to load it.
It seems like it's definitely possible as many apps, including the Play Store, are doing it. Please see the example here
In the video example above - the UI component(s) are being loaded AFTER the navigation to the tab is completed. It even has an embedded loading symbol.
1) I am trying to figure out how to do exactly that - at what point would I know that this fragment UI need to be created vs it already is created?
2) Also, what is the fragment lifecycle callback where I would start the UI create process? onResume() means UI is visible to the user so loading the UI there will be laggy and delayed.
Hope this is clear enough.
EDIT:
I'm already using the FragmentStatePagerAdapter as ViewPager adapter. I noticed that the super(fm) method in the constructor is deprecated now:
ViewPagerAdapter(FragmentManager fm) {
super(fm); // this is deprecated
}
So I changed that to:
ViewPagerAdapter(FragmentManager fm) {
super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
}
BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT: Indicates that only the current fragment will be in the Lifecycle.State.RESUMED state. All other Fragments are capped at Lifecycle.State.STARTED.
This seems useful as the onResume() of the Fragment will only be called when the Fragment is visible to the user. Can I use this indication somehow to load the UI then?
The reason your app loads multiple Fragments at the startup is most probably, you're initializing them all at once. Instead, you can initialize them when you need them. Then use show\ hide to attach\ detach from window without re-inflating whole layout.
Simple explanation: You'll create your Fragment once user clicks on BottomNavigationView's item. On clicked item, you'll check if Fragment is not created and not added, then create it and add. If it's already created then use show() method to show already available Fragment and use hide() to hide all other fragments of BottomNavigationView.
As per your case show()/hide is better than add()/replace because as you said you don't want to re-inflate the Fragment when you want show them
public class MainActivity extends AppCompatActivity{
FragmentOne frg1;
FragmentTwo frg2;
#Override
public boolean onNavigationItemSelected(MenuItem item){
switch(item.getId()){
case R.id.fragment_one:
if (frg2 != null && frg2.isAdded(){
fragmentManager.beginTransaction().hide(frg2).commit();
}
if(frg1 != null && !frg1.isAdded){
frg1 = new FragmenOne();
fragmentManager.beginTransaction().add(R.id.container, frg1).commit();
}else if (frg1 != null && frg1.isAdded) {
fragmentManager.beginTransaction().show(frg1).commit();
}
return true;
case R.id.fragment_two:
// Reverse of what you did for FragmentOne
return true;
}
}
}
And for your ViewPager as you can see from the example you're referring to; PlayStore is using setOffscreenPageLimit. This will let you choose how many Views should be kept alive, otherwise will be destroyed and created from start passing through all lifecycle events of the Fragment (in case view is Fragment). In PlayStore app's case that's probably 4-5 that why it started loading again when you re-selected "editor's choice" tab. If you do the following only selected and neighboring (one in the right) Fragments will be alive other Fragments outside screen will be destroyed.
public class FragmentOne extends Fragment{
ViewPager viewPager;
#Override
public void onCreateView(){
viewPager = .... // Initialize
viewpAger.setOffscreenPageLimit(1); // This will keep only 2 Fragments "alive"
}
}
Answer to both questions
If you use show/hide you won't need to know when to inflate your view. It will be handled automatically and won't be laggy since it's just attaching/detaching views not inflating.
It depends upon how you initialize your fragment in your activity. May be you are initializing all your fragment in onCreate method of your activity instead of that you can initialize it when BottomNavigation item is selected like below :
Fragment one,two,three,four;
#Override
public boolean onNavigationItemSelected(MenuItem item){
Fragment fragment;
switch(item.getId()){
case R.id.menu_one:{
if(one==null)
one = Fragment()
fragment = one;
break;
}
case R.id.menu_two:{
if(two==null)
two = Fragment()
fragment = two;
break;
}
}
getFragmentManager().beginTransaction().replace(fragment).commit();
}
To decide how many page is load in you view pager at one time you can use :
setOffscreenPageLimit.
viewPager.setOffscreenPageLimit(number)
To get the resume and pause functionality on fragments you can take an example from this link.
Please try this.
i was worked with the same kind of the Application, There were multiple tabs and also Tabs have multiple inner tabs.
i was used the concept of ViewPager method, In which there is one method of onPageSelected() for that method we were getting the page position.
By the Use of this position we are checking the current Fragment and called their custom method that we created inside that fragment like onPageSelected() defined inside that fragment.
With this custom method onPageSelected() inside the Fragment we checked that weather the list are available or not if list have data then we are not making the call of Api otherwise we are calling the Api and loading that list.
I think you have same kind of requirement to follow if your Tabs have inner Tab or viewpager you can follow same concept inside of that so if your current fragment of viewpager method onpageSelected called at that time your viewpager fragment initialized.
you have to call just initialization like data binding or view initialization need to be called in onCreate() method and other list attachment and api call to be managed by the custom method onPageSelected that will be called based on ViewPager onPageSelected.
let me Know if you need any help for same.
You can try to have Fragments with FrameLayouts only in ViewPager. The actual Fragments could be added to FrameLayout in onResume() (after checking if this Fragment isn't already attached). It should work if BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT works as expected.
I would recommend you use BottomNavigationView.setOnNavigationItemSelectedListener to toggle between the fragment UI whenever it is needed.
navigationView.setOnNavigationItemSelectedListener(item -> {
switch(item.getItemId()) {
case R.id.item1:
// you can replace the code findFragmentById() with findFragmentByTag("dashboard");
// if you only have one framelayout to hold the fragment
fragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
if (fragment == null) {
fragment = new ExampleFragment();
// if the fragment is identified by tag, add another
// argument to this method:
// replace(R.id.fragment_container, fragment, "dashboard")
getSupportFragmentManager().begintransaction()
.replace(R.id.fragment_container, fragment)
.commit();
}
break;
}
}
The idea is simple, when the user swipes or selects a different tab, the fragment that was visible is replaced by the new fragment.
Just load fragments one by one. Create the main fragment layout with many placeholders and stubs and then just load them in the order you like.
Use FragmentTransaction.replace() from the main fragment after it loads.
Have you tried the setUserVisibleHint() method of a fragment
override fun setUserVisibleHint(isVisibleToUser: Boolean) {
super.setUserVisibleHint(isVisibleToUser)
if(isVisibleToUser){
// Do you stuff here
}
}
This will only get called when a fragment is visible to the user
How about you maintain just one ViewPager? Sounds crazy? In that case, you just change the dataset of PagerAdapter when you switch between the bottom tabs. Let's see how you can accomplish this,
As you mentioned, you have 4 fragments, which are assigned to each individual tabs of the bottom navigation view. Each performs some redundant work i.e. holding a viewPager with tab layout and setting the same kind of adapters. So, if we can combine these 4 redundant tasks into one then we will be able to get rid of 4 fragments. And as there will be just one viewPager with one single adapter then we will be able to reduce the fragment loading count from ~10 to 2 if we set offScreenPageLimit to 1. Let's see some example,
activity.xml should look like
<LinearLayout>
<TabLayout />
<ViewPager />
<BottomNavigationView />
</LinearLayout>
It's optional but I would recommend to create a base PagerFragment abstract class with abstract method getTabTitle()
public abstract class PagerFragment extends Fragment {
public abstract String getTabTitle();
}
Now it's time to make our PagerAdapter class
public class SectionsPagerAdapter extends FragmentStatePagerAdapter {
public Map<Integer, List<PagerFragment>> map = ...; // If you are concerned about memory then I could recommend to store DataObject instead of PagerFragment and instantiate fragment on demand using that data.
public int currentTabId = R.id.first_bottom_tab_id;
private List<PagerFragment> getCurrentFragments() {
return map.get(currentTabId);
}
public void setCurrentTabId(int tabId) {
this.currentTabId = tabId;
}
public SectionsPagerAdapter(FragmentManager manager) {
super(manager);
}
#Override
public Fragment getItem(int position) {
return getCurrentFragments().get(position);
}
#Override
public int getCount() {
return getCurrentFragments().size();
}
#Override
public int getItemPosition(#NonNull Object object) {
return POSITION_NONE;
}
#Override
public CharSequence getPageTitle(int position) {
return getCurrentFragments().get(position).getTabTitle();
}
}
And finally, in Activity
SectionsPagerAdapter pagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(pagerAdapter);
viewPager.setOffscreenPageLimit(1);
viewPagerTab.setViewPager(viewPager);
bottomNavigationView.setOnNavigationItemSelectedListener(menuItem -> {
pagerAdapter.setCurrentTabId(menuItem.getItemId())
pagerAdapter.notifyDataSetChanged();
viewPagerTab.setViewPager(viewPager);
}
This is the basic idea. You can mix some of your own ideas with it to make a wonderful result. Let me know if it is useful?
UPDATE
Answer to your questions,
I think with my solution you can achieve exactly the same behavior of the video as I already did it in a project. In my solution, if you set offset page limit to 1 then only adjacent fragment's is created in advance. So, fragment creation will be handled by adapter and viewpager you don't need to worry about it.
In my above solution, you should create UI in onCreateView().
I have a ViewPager using a FragmentPagerAdapter for displaying three tabs, each represented by its ow fragment. One of these fragments contains a list, that should be updated on switching / swiping to that tab. But I don't find any way to make it happen. I tried using the onResume method, but the fragments seem not to be paused and resumed on tab change. I also tried using ViewPager.OnPageChangeListener in my MainActivity:
#Override
public void onPageSelected(int position)
{
FragmentRefreshInterface currentFragment = (FragmentRefreshInterface) mSectionsPagerAdapter.getItem(position);
currentFragment.onRefreshed();
}
And in the fragment I use the following:
#Override
public void onRefreshed()
{
List<Record> records = mRecordingService.getRecords();
mRecordAdapter.clear();
mRecordAdapter.add(record);
}
But using this code I can't access my RecordingService class that is used to provide the database functions (because mRecordingService seems to be null). I initialize it in the fragment like this:
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
mRecordingService = new RecordingService(getContext());
}
Using the onPageChangeListener is the correct way to do it. I believe the reason why your code is not working, is because you are calling getItem on your pager adapter: getItem() actually returns a new instance of the fragment. In order to get the current instance, you use instantiateItem() (which returns a reference to the fragment actually being used).
Change your code to look something like this:
#Override
public void onPageSelected(int position)
{
FragmentRefreshInterface currentFragment = (FragmentRefreshInterface) mSectionsPagerAdapter.instantiateItem(viewPager,position);
currentFragment.onRefreshed();
}
And it should work.
I suggest that the code you have in onRefreshed() go in onResume() instead. Fragment doesn't have an onRefreshed() method. You must be implementing another interface that declares this method.
Since you are storing data in a database, you should be use a CursorAdapter or subclass such as SimpleCursorAdapter. If you do this correctly, the ListView will automatically update when you add a record to the database. Then the service can add records without needing to access the service from the fragment.
In your MainActivity:
private FirstFragment firstFragment;
private WantedFragment wantedFragment;
private ThirdFragment thirdfragment;
In getItem
switch(postition){
//return first, wanted, third fragments depending on position
}
onPageSelected:
if(position == 1) // position of the wanted fragment
wantedfragment.onRefreshed()
I have a MainActivity, Contains TabLayout having two fragments FA, FB
The First Fragment FA having another Tablayout contains 2 fragments FAA, FAB
I have a button inside FAA, i want when i click on it, it send me to FB which already inside the parent TabLayout
I tried many solutions but it didn't help, any suggestions?
#OnClick(R.id.frag_timeline_fab_faa)
public void goToFBFromFAA(View view) {
// Code shoud be here
}
The way to do this is through interfaces.Here is a similar question I found
In fragment FAA:
public interface OnFragmentInteractionListener {
void onFragmentInteraction(Param param);
}
Then in your parent fragment you need to implement that interface:
public class FA extends Fragment implements
FAA.OnFragmentInteractionListener {
#Override
public void onFragmentInteraction(Param param) {
//Your code here
}
}
I have added a horizontal scroll view and in the layout I have added reference to two fragments such that both the fragments are visible in the scroll.
the problem is when I enter values in the left layout I want the value to be displayed in the right layout.
I am using an interface for the same, but its not working. as in I keep getting null pointer exception for the same.. How to get around this??
this is the main class fragment
public static SliderRightAdapter sliderRightAdapterFragment; <-- this calls the second layout
#Override
public View onCreateView(LayoutInflater inflater,
#Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
// TODO Auto-generated method stub
View view = inflater.inflate(R.layout.f_pp, container, false);
sliderRightAdapterFragment = (SliderRightAdapter) getActivity()
.getSupportFragmentManager().findFragmentById(
R.id.secondary_sliderProduct_description);
return view;
}
.
.
.
.
this is where i am getting null pointer exception on sliderRightAdapterfragment
interfaceObject.onButtonClick(CGS, sliderRightAdapterFragment);
and this is where it is initialized...
sliderRightAdapterFragment = PDFinterface.sliderRightAdapterFragment;
From what I'm seeing, you're letting the fragments communicate directly with each other.
I'd recommend against it, since this can quickly lead to maintaining unused references, as fragments can have quite diverse lifecycles. The idea behind fragments is to have small segments of functionality which can communicate with their parent some information.
I think a better way to approach would be to use the parent activity as a form of 'manager' between these two fragments.
Instead of maintaining a static reference to the other fragment, store a normal reference to the activity, preferably in the form of a listener interface the activity implements. Then you'd use the findFragmentById/Tag to notify the other fragment of the change. All in all, this would look something like this:
Fragment:
public interface ActivityListener {
void onText(String text);
}
private ActivityListener listener;
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
if(activity instanceof ActivityListener) {
listener = (ActivityListener) activity;
}
// else some error
}
#Override
public void onDetach(Activity activity) {
// to make absolutely sure you don't maintain a reference to a killed activity
listener = null;
}
Activity:
#Override
public void onText(String text) {
Fragment frag = getSupportFragmentManager.findFragmentById(<someId>);
// notify with text information
}
Something like this should work fine.
I currently have a viewpageindicator with three tab 1,2 and 3.
The problem is when i swipe to tab 2, the onActivityCreated from fragment 3 is being called.
At my tab 3 fragment, i will call a asyntask onActivityCreated , therefore when fragment 2 is being switched, it will load a asyntask.
By default, ViewPagers load one Fragment on either side of the current Fragment. To know when a Fragment is in the centre, you could use the onPageChangeListener of the ViewPager in combination with an interface implemented by every Fragment subclass.
public interface FragmentChangeListener
{
void onCentered();
}
Implement this interface in every Fragment
public class CustomFragment extends Fragment implements FragmentChangeListener
{
....
#Override
public void onCentered()
{
//Show alertDialog and start asyncTask
}
}
In your Activity class:
ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener()
{
#Override
public void onPageSelected(int position)
{
FragmentChangeListener listener = (FragmentChangeListener) //cast fragment at this position to FragmentChangeListener
listener.onCentered();
}
}
I think your best option is to determine if the fragment is visible or not to decide whether you should show your dialog box or not. You can get an idea of how to do that here: How to determine when Fragment becomes visible in ViewPager
It's possible you should consider redesigning this interaction, the viewpager was designed to easily swipe between views and poping up dialog boxes could prove to be a confusing interaction.