I'm trying to work out a way to get the currently displayed fragment on a Android app I'm working on. I have a Startup View that loads fragments, what I need to do is display a popup message when the user taps the back button but only when the using is tapping the back button from a certain fragement. For example:
Fragment A > Nav to.. > Fragment B > Nav to... > Fragment C
If the user clicks the back button from fragment C then nothing is displayed and the user goes back to fragment B as expected. But when the user click back on fragment B a popup is displayed asking the user to confirm that action before being allowed to continue back to fragment A, I hope that makes sense.
I know about the OnBackPressed() which I can override on a view but I cant touch that in a fragment. Any pointers would be appreciated.
Hi when you add a new transaction replace use a key TAG
var ft = FragmentManager.BeginTransaction();
ft.Replace(Resource.Id.details, details, "FRAGMENT1");
and if you need to check if the specify fragment is visible
Fragment myFragment = (Fragment)FragmentManager.FindFragmentByTag("FRAGMENT1");
if (myFragment.IsVisible){
//your code here
}
or if you need to get and check all of fragments inside the fragment manager you can use this
var fragmentsarray = FragmentManager.Fragments;
foreach(var fragment in fragmentsarray)
{
if (fragment.IsVisible) {
//put the code to use and get the tag to identify the current Fragment
string tag = fragment.Tag;
}
}
if need more specify Fragments info you can check the Android Docs here http://developer.android.com/reference/android/app/Fragment.html
Hope it helps you
Related
I have an app with a main activity which loads a navigation drawer, and a pair of fragments that load in that activity ...
In the navigation drawer I have 4 options A, B, C and D ... the first one loads FragmentA on my activity and the last 3 load FragmentB ..
FragmentA displays a list of elements and, upon selecting one of these elements FragmentB is used to load its content... I want to change the home (hamburger/drawer) icon on FragmentB for the up icon when initiating from FragmentA (and change the corresponding behavior to make a popstack on select).. I have no problem with this using setDisplayHomeAsUpEnabled(true), but since all this is occurring inside one activity if I then select one other option (say B) from the navigation drawer the up icon will still be showing (it its also showing on the popped fragment)...
if I use setDisplayHomeAsUpEnabled(false) all this do is hide the home/up button from the toolbar, I need to recover the home button and make sure this will be shown when FragmentB is initiated from the drawer menu ...
Does this problem ring a bell to anyone? or am I just using fragments the wrong way? .. any advice will be appreciated
EDIT
this is more or less what I have in code
In Main Activity .. as the onNavigationItemSelected(MenuItem item) for the drawer I have a something like this ...
switch(optionNumber) {
case 0:
fragment = FragmentA.newInstance(optionNumber);
break;
default:
fragment = FragmentB.newInstance(optionNumber);
break;
}
Fragment frag = fragmentManager.findFragmentByTag("current_fragment");
if (frag != null && frag.getClass() == FolderFragment.class){
((FolderFragment)frag).resetScroll();
}
fragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
fragmentManager.beginTransaction().replace(R.id.content, fragment, "current_fragment").commit();
which selects the fragment to load according to the option selected..
In FragmentA I'm calling FragmentB with this ..
FragmentB fFragment = FragmentB.newInstance(position);
Bundle args = new Bundle();
args.putString("filter", "something"); fFragment.setArguments(args);
mActivity.getSupportFragmentManager().beginTransaction()
.replace(R.id.flContent, fFragment, "current_fragment")
.addToBackStack(null)
.commit();
Preserving the fragment in the stack
And in fragmentB inside onResume() function I got something like...
String filter = getArguments().getString("filter", null);
if (type != null) {
mActivity.setTitle(title);
mActivity.getSupportActionBar().setDisplayShowHomeEnabled(true);
}else {
/*mActivity.getSupportActionBar().setDisplayHomeAsUpEnabled(false);
mActivity.getSupportActionBar().setDisplayShowHomeEnabled(true);
mActivity.getSupportActionBar().setHomeButtonEnabled(true);
mActivity.getSupportActionBar().setIcon(R.mipmap.ic_menu);*/
}
So When I'm creating fragmentB I check for arguments and see if it comes from fragmentA or not ( I could also check the fragmentmanager backstack and see if there's something)... there I just change the drawer icon with setDisplayShowHomeEnabled(true) ... leaving the back arrow, if I return to FragmentA (via onBackPressed()) FragmentA shows the arrow and I need it to show the original drawer icon ... the same happens if I select an option from the drawer menu ...
Does this gives more clarity to my issue ?... I have some commented code there because it doesn't work .. if I activate the line with setDisplayHomeAsUpEnabled(false).. the icon just disappears from the activity (which is the intended result of the function as far as I know)...
After a while I finally found this post
Switching between Android Navigation Drawer image and Up caret when using fragments
I guess that when involving a Drawer in the interface you might need to handle this issue with that component... this post gave me the answer.
Particular notice to the last comment by Wolfram Rittmeyer
My Application has one Activity with a layout (FrameLayout) for many fragments.
At the start of the Application it displays a list of Places (PlacesFragment).
When a Place is clicked, a Fragment that displays a list of cams (CamFragment) is added. Inside this fragment there is also a button "info".
When the user press the "info" button a new fragment (InfoPlaceFragment) that displays information about the place, is added.
Here is a graphical explanation:
I want to be able to go back to "CamFragment(B)" from "InfoPlaceFragment(C)", and to go back to "PlacesFragment(A)" from "CamFragment(B)".
One Question:
1) Is it possible to realize this or an alternative solution is better?
------- EDIT -------
SOLUTION:
In the "MainActivity.java":
onPlaceParse() // This method is called when the data from the server is received:
// Here I create the "PlaceFragment"
fManager = getSupportFragmentManager();
fragmentPlaces = new PlacesFragment();
fManager.beginTransaction()
.replace(R.id.fragment_list_container, fragmentPlaces)
.commit();
onResortSelected // This method is called when the resort is selected
fragmentCams = new CamsFragment();
fManager.beginTransaction()
.replace(R.id.fragment_list_container, fragmentCams)
.addToBackStack(null)
.commit();
onButtonInfoSelected // This method is called when the btn info is selected
fragmentInfo = new InfoResortFragment();
fManager = getSupportFragmentManager();
fManager.beginTransaction()
.replace(R.id.fragment_list_container, fragmentInfo, "Info")
.addToBackStack(null)
.commit();
When you press the back button, if you are in the "Info Fragment" it returns to "PlaceFragment" and if you are in the "CamsFragment" it returns to "PlacesFragment".
This is possible, you need to call addToBackStack(null) in the fragment transactions.
Reference: Providing Proper Back Navigation
When you create your FragmentTransaction that will add/remove/replace (or whatever pattern you are using) the Fragments, just make sure to call addToBackStack(). Then, when the user presses the back button, the system will automatically cycle back through the entries added to the back stack, in reverse order from how they were originally added. No additional work is required on your part! :)
In my application I have two fragments A and B. A fragment contains Google map and listview inside on it B fragment Google map only.
I want open B fragment from A fragment but when I press back button it has to go to A fragment without loading data.
public void addPage(final DefaultFragment pDefaultFragment, final boolean isAddToBackStack){
FragmentTransaction transaction = mFragmentManager.beginTransaction();
transaction.add(R.id.content_frame, pDefaultFragment);
//transaction.replace(R.id.content_frame, pDefaultFragment);
if (isAddToBackStack) transaction.addToBackStack(null);
transaction.commitAllowingStateLoss();
}
I use this code for adding fragment
Bframent b = new Bfragment();
addPage(b,true);
I know differences between transaction. add and transaction.replace. My problem is when I use transaction.add A fragment's map doesn't destroy it stays above of B fragment's map when pressing button. But when use transaction.replace after press back button data loads again.
So could anyone tell me what should I do to Press back button without to load data without any problem on view also.
On back press just provide your fragment null;
I am a new Android developer.
In iOS, there is a class called UINavigationController by which I can push a new viewController to stack and go back to the previous view by pushing the "back" button.
[self pushViewController: myViewController animated:YES]
As far as I know, the instance of UINavigationController has a property to hold the controllers. Therefore, all the attributes in each of the controllers are saved as well in the stack.
I am wondering if the Android can do something similar.
Now I have two fragments to simulate the split view as iOS.
I subclass ListFragment to represent the `lsit view* in the left side and the other fragment to represent the item detail in the right side.
When user taps one of the items in the list view it will go to another list.
SecondFragment newFragment = new SecondFragment();
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
transaction.replace(R.id.fragment_container, newFragment);
transaction
.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
getActionBar().setTitle("new items");
transaction.commit();
getActionBar().setDisplayHomeAsUpEnabled(true);
invalidateOptionsMenu();
However, I want to go back to the previous view by clicking the back button.
I realize that I should add the code as follow:
transaction.addToBackStack(null);
However, my application exits after I tap the back button.
If I want to go back, I have to make another Fragment transaction. The problem is, I want to save the content as item list in the ListFragment other than saving it to the MainActivity. It is much easier for me to retrieve the previous list view content from stack.
Is there any way in Android can do something similar in iOS as UINavigationController?
Scenario what i'm trying to achieve:
Loading activity with two frame containers (for list of items and for details).
At the app launch time add listFragment in listFrame and some initial infoFragment in detailsFrame containers.
Navigating through list items without adding each detail transaction to back stack (want to keep only infoFragment in stack).
As soon as user hit back button (navigate back) he falls back to intial infoFragment what was added in launch time.
If sequential back navigation fallows then apps exit.
My code:
protected override void OnCreate(Bundle savedInstanceState)
{
...
var listFrag = new ListFragment();
var infoFrag = new InfoFragment();
var trans = FragmentManager.BeginTransaction();
trans.Add(Resource.Id.listFrame, listFrag);
trans.Add(Resource.Id.detailsFrame, infoFrag);
trans.Commit();
...
}
public void OnItemSelected(int id)
{
var detailsFrag = DetailFragment.NewInstance(id);
var trans = FragmentManager.BeginTransaction();
trans.Replace(Resource.Id.detailsFrame, detailsFrag);
if (FragmentManager.BackStackEntryCount == 0)
{
trans.AddToBackStack(null);
}
trans.Commit();
}
My problem:
After back button has been hit, infoFrag is overlapped with previous detailFrag! Why?
You can do this:
if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
getSupportFragmentManager().popBackStack(getSupportFragmentManager().getBackStackEntryAt(0).getId(), getSupportFragmentManager().POP_BACK_STACK_INCLUSIVE);
} else {
super.onBackPressed();}
In your activity, so you to keep first fragment.
You shouldn't have, in your first fragment, the addToBackStack. But, in the rest, yes.
Very nice explanation by Budius. I read his advice and implemented similar navigation, which I would like to share with others.
Instead of replacing fragments like this:
Transaction.remove(detail1).add(detail2)
Transaction.remove(detail2).add(detail3)
Transaction.remove(detail3).add(detail4)
I added a fragment container layout in the activity layout file. It can be either LinearLayout, RelativeLayot or FrameLayout etc.. So in the activity on create I had this:
transaction.replace(R.id.HomeInputFragment, mainHomeFragment).commit();
mainHomeFragment is the fragment I want to get back to when pressing the back button, like infoFrag. Then, before EVERY NEXT transaction I put:
fragmentManager.popBackStackImmediate();
transaction.replace(R.id.HomeInputFragment, frag2).addToBackStack(null).commit();
or
fragmentManager.popBackStackImmediate();
transaction.replace(R.id.HomeInputFragment, frag3).addToBackStack(null).commit();
That way you don't have to keep track of which fragment is currenty showing.
The problem is that the transaction that you're backing from have two steps:
remove infoFrag
add detailsFrag (that is the first1 detail container that was added)
(we know that because the documentation This is essentially the same as calling remove(Fragment) for all currently added fragments that were added with the same containerViewId and then add(int, Fragment, String) with the same arguments given here. )
So whenever the system is reverting that one transaction is reverting exactly those 2 steps, and it say nothing about the last detailFrag that was added to it, so it doesn't do anything with it.
There're two possible work arounds I can think on your case:
Keep a reference on your activity to the last detailsFrag used and use the BackStackChange listener to whenever the value change from 1 to 0 (you'll have to keep track of previous values) you also remove that one remaining fragment
on every click listener you'll have to popBackStackImmediatly() (to remove the previous transaction) and addToBackStack() on all transactions. On this workaround you can also use some setCustomAnimation magic to make sure it all looks nice on the screen (e.g. use a alpha animation from 0 to 0 duration 1 to avoid previous fragment appearing and disappearing again.
ps. I agree that the fragment manager/transaction should be a bit more clever to the way it handles back stack on .replace() actions, but that's the way it does it.
edit:
what is happening is like this (I'm adding numbers to the details to make it more clear).
Remember that .replace() = .remove().add()
Transaction.remove(info).add(detail1).addToBackStack(null) // 1st time
Transaction.remove(detail1).add(detail2) // 2nd time
Transaction.remove(detail2).add(detail3) // 3rd time
Transaction.remove(detail3).add(detail4) // 4th time
so now we have detail4 on the layout:
< Press back button >
System pops the back stack and find the following back entry to be reversed
remove(info).add(detail1);
so the system makes that transaction backward.
tries to remove detail1 (is not there, so it ignores)
re-add(info) // OVERLAP !!!
so the problem is that the system doesn't realise that there's a detail4 and that the transaction was .replace() that it was supposed to replace whatever is in there.
You could just override onBackPressed and commit a transaction to the initial fragment.
I'm guessing but:
You've added the transaction to replace infoFrag with 1st detailsFrag into the backstack.
But then you replace 1st detailsFrag with 2nd detailsFrag.
At this point when you click back, the fragment manager cannot cleanly replace 1st detailsFrag with infoFrag as 1st detailsFrag has already been removed and replaced.
Whether the overlapping behaviour is expected or not I don't know.
I would suggest debugging the Android core code to see what it is doing.
I'm not sure whether you can achieve without say overriding Activity::onBackPressed() and doing the pops yourself having added all transactions to the backstack.