Develop Reference

Fragments stacking on each other

I have a problem with fragments. In my xml file I have a fragment already set there, I want with the click of a button replace it with another fragment. So with my code I can replace the fragment with the one that I want on the click of the button, but the first fragment wont disappear, so I can still see it under my second fragment, the code it's this:
public class MainActivity extends AppCompatActivity {
FragmentManager fragmentManager;
Button button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.fragment,new BlankFragment2());
fragmentTransaction.addToBackStack(null).commit();
}
});
}
}

Set a background color of the root layout of the second fragment and put clickable and focusable true in xml file. It will make disappear of the first fragment and also disable the clicks of first fragment when showing another fragment.

Remove addToBackStack(null).
That stores the Fragment and keeps it attached so that calling popBackStack() will remove the top Fragment and replace it with the previous.

correctly implementing addToBackStack will help in this case and many other
addToBackStack takes an argument which is called task record TAG , To perform a transaction later on , you can use this tag to remove back stack up to a point
For more understanding read
https://medium.com/#bherbst/managing-the-fragment-back-stack-373e87e4ff62

How to perform event on next Fragment of viewpager?

Suppose I am having 5 fragments in viewpager. Lets say Fragment A, B, C, D, E.
I have a button on fragment A to go to fragment B. When I press this button, viewpager scrolls to fragment B. Somehow I controlled the duration of fragment A to B. Now the thing is, I have an scrollable container in Fragment B. I want to scroll that container during the Scroll between A to B happens. Now its scrolling after I am going from Fragment A to B. I want this happen between this transition.
Inside first fragment:
#Override
public void onClick(View view) {
if(view.getId() == bottomLayout.getId())
{
MainActivity.pager.setCurrentItem(1);
}
}
It will change my pager position 0 to 1. Now when its changing. I controlled the scroll speed of viewpager. On top of second fragment, I have a ScrollView, I need to perform scroll on this scrollview as fragment is changing,not after its changed.

To animate the view of the FragmentB, you need to tell it to start animation as soon as you call viewPager.setCurrentItem().
Inside FragmentA's click listener, you will ask the parent Activity to change the ViewPager item (see Communicating with the Activity to know how this should be done) :
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
activityCallback.setViewPagerItem(POSITION_OF_FRAGMENT_B);
}
});
In your Activity in which the ViewPager resides, you will write:
public void setViewPagerItem(int position) {
viewPager.setCurrentItem(position);
// following asks the fragmentB to start its animation on its view.
if (position == POSITION_OF_FRAGMENT_B) {
fragmentB.startYourAnimation();
}
}
In FragmentB, you add a method:
public void startYourAnimation() {
// write your code to animate your ListView or whatever you want to
// animate inside the FragmentB
}
Notes:
Unless you've called viewPager.setOffscreenPageLimit(), an instance of FragmentB will already exist if you're doing it from FragmentA or FragmentC,
a Fragment should not communicate with other fragments directly, instead they should use their parent Activity as a middle person. See Communicating with Other Fragments.

No it is not possible to do so because any scrollable view like listview or recyclerview, the items are created only when it is visible to user and only when scrolled, so if that fragment is not visible, you cannot scroll any of its child scrollable view.

Handling the backstack with fragments containing tabs

I'm trying to create an Android application which contains a single activity with a container and a navigation drawer. The initialy empty container loads fragments which has a ViewPager inside a tab layout in which I load a frgment with a FragmentTransaction:
public static void replaceFragmentInContainer(FragmentManager fragmentManager, Fragment fragmentToShow,
boolean addToBackStack)
{
FragmentTransaction transaction = fragmentManager.beginTransaction();
if (addToBackStack)
{
transaction.addToBackStack(null);
}
transaction.replace(R.id.container, fragmentToShow);
transaction.commit();
}
I'm using v4 fragments with a v7 ActionBar in a v7 ActionBarActivity.
Every loaded fragment is a fragment which only loads tabs with other fragments which they hold the actual usability. An example of such tab loading fragment:
public class MainFragment extends TabsFragment
{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
super.onCreateView(inflater, container, savedInstanceState);
View contentView = inflater.inflate(R.layout.fragment_main, container, false);
initTabsLayout(savedInstanceState, contentView, R.id.pager);
addTab("tabspectag1", "", R.drawable.draw1, Fragment1.class, null);
addTab("tabspectag2", "", R.drawable.draw2, Fragment2.class, null);
addTab("tabspectag3", "", R.drawable.draw3, Fragment3.class, null);
return contentView;
}
The problem I'm facing is with the backstack. When a fragment is added to the backstack and I press the back button, the app does go back to the previous fragment like I want to and I see the tabs layout itself, but the content of the tabs is empty like there was nothing loaded to that tab. When it happens, I manage to reload the tab's content only when choosing that screen again with the navigational drawer.
I've tried overriding the onBackPressed in the activity:
#Override
public void onBackPressed()
{
if (getFragmentManager().getBackStackEntryCount() > 0)
{
getFragmentManager().popBackStack();
} else
{
super.onBackPressed();
}
}
but that like I said, it's like I'm getting back to the previous fragment but the tab inside that fragment is not repainting the fragment it had.
What can be done to solve this issue?
Since I DO see the tabs layout of the original fragment in the backstack but not the fragment inside the tab, is it possible I just need to somehow refresh the tab content meaning repaint it? If I can do such a thing then how can I do it?

You didn't post the entire code but, bear in mind that when using fragments inside fragments, the outer fragment should use the childfragmentmanager instead of the regular fragment manager.
If you have an Activity, then you have a fragment that has a Viewpager and inside that viewpager the views are fragments, those outer fragments must use their own childfragmentmanager instead of the activities fragmentmanager.
Activity uses getFragmentManager() to instantiate and show new fragments. Fragments use getChildFragmentManager() to instantiate and show new inner fragments. (fragments inside fragments).
If you always use the same fragmentmanager to handle the transactions the behaviour will be unpredictable.
Your Viewpager should have an TabsAdapter associated that extends from FragmentStatePagerAdapter to show new fragments(and uses the getChildFragmentManager from the fragment instead of the activity).

swap between grid and list fragments

The main section of my screen layout shows a set of items. The use can choose if a grid or a list should be shown. Therefore I implemented two fragements (for list and grid) that are then shown inside the placeholder (main section of the main layout).
But now I wonder how to reuse the fragements in order to have the last scrolling position etc. If I remember the fragment in a private field instead of re-creating it, then the view remains empty.
Any idea?
public void onShowGrid(View view) {
// how to re-use instead of re-create
fragmentGrid = new PreviewGridFragment();
this.getFragmentManager().beginTransaction()
.replace(R.id.preview_fragment, fragmentGrid)
.addToBackStack(null).commit();
}
public void onShowList(View view) {
// how to re-use instead of re-create
fragmentList = new PreviewListFragment();
this.getFragmentManager().beginTransaction()
.replace(R.id.preview_fragment, fragmentList)
.addToBackStack(null).commit();
}

I think it is not a good idea to save your fragments in private fields because it consumes memory and you do not need to do it, better idea is creating static field in each fragment and save the last position in that then when you create your new fragment scroll to that position.

Android Open Fragment over ViewPager

I'm new to android programming and I'm trying to make an app that uses tabs in a viewpager from one main fragmentactivity.
The viewpager and tabs work fine but I want to have an options menu that when an item is selected, opens a completely new fragment, but I don't seem to be able to remove the view pager. I would like to just be able to put the new fragment over the viewpager on the main screen but trying to do that with a fragmenttransaction doesn't seem to work
Any ideas?
Thank you for your time

Ensure that:
1) your Fragment (e.g.: ViewPagerFragment1), which will be selected by the viewpager, has a FrameLayout as root layout with the id "container" e.g:
<FrameLayout
android:layout_height="fill_parent"
android:layout_width="fill_parent"
android:id="#+id/container"
xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout.... and so on
</FrameLayout>
2) Inside the ViewPagerFragment1 class, you have to replace/add the new fragment to the FrameLayout after an action has been triggered. E.g.:
#Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.selection:
// Create new fragment and transaction
NewFragment newFragment = new NewFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.container, newFragment, "NewFragment");
transaction.addToBackStack(null);
transaction.commit();
break;
default:
break;
}
}

Well, you will be adding the Fragment to some FrameLayout using the ID of the FrameLayout I assume. Just make sure the FrameLayout you are adding the Fragment to is on top of the ViewPager.
For example if both the ViewPager and FrameLayout are in a RelativeLayout container then make sure the FrameLayout is declared below the ViewPager in the XML. This will stack the FragmeLayout on top of the ViewPager. When the Fragment is added to the FrameLayout it will be drawn on top.