Develop Reference

How to refresh the content of a tab in an actionBar (Android)?

Here the summary of my 'project' on Android 4.x and the problem I can't solve:
i have an actionBar with 2 tabs (i know it is deprecated):
...
Fragment fragmentTab1 = new FragmentTab1();
Fragment fragmentTab2 = new FragmentTab2();
Fragment fragmentTab3 = new FragmentTab3();
ActionBar.Tab tab1, tab2;
ActionBar actionBar = getActionBar();
tab1 = actionBar.newTab().setText("tab1");
tab2 = actionBar.newTab().setText("tab2");
tab1.setTabListener(new MyTabListener(fragmentTab1));
tab2.setTabListener(new MyTabListener(fragmentTab2));
actionBar.addTab(tab1);
actionBar.addTab(tab2);
...
I would like to change the fragment of a tab and refresh what the user sees, doing that in a method (not only when the tab is (re)selected).
It sounds simple, but impossible to find a easy way to do that.
After many fails, this is what I try (i remove the tab and add it with a new fragment):
void myMethod () {
getActionBar().removeTabAt(0);
tab1 = actionBar.newTab().setText("tab3");
tab1.setTabListener(new MyTabListener(fragmentTab3));
getActionBar().addTab(tab1, 0);
...
And then this awful thing to desesperatly try to update what is seen...
...
getActionBar().setSelectedNavigationItem(tab1.getPosition()+1);
getActionBar().setSelectedNavigationItem(tab1.getPosition());
}
Everything goes as wanted, except that the reselected tab1 is empty... :(
If I select with my finger tab2 then tab1 (so manually in place of programmaticaly), then tab1 appears as wanted...
So, how can I change programmaticaly the content of a tab and refresh what is seen in an actionBar?
Already a big thanks for your time!

You should depend on TabListener methods, don't do getActionBar().setSelectedNavigationItem(). There are good code samples on the Internet.
1) Google webpage # Creating Swipe Views with Tabs. Code snippet:
ActionBar.TabListener tabListener = new ActionBar.TabListener() {
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
// show the given tab
}
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
// hide the given tab
}
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
// probably ignore this event
}
};
Notes: Refresh your data in onTabSelected(). You may check for tags or text in tab parameter.
2) Another good link for you # Android Fragment Tabs Example. Code snippet from the link:
public class TabListener implements ActionBar.TabListener {
private Fragment fragment;
public TabListener(Fragment fragment) {
this.fragment = fragment;
}
// When a tab is tapped, the FragmentTransaction replaces
// the content of our main layout with the specified fragment;
// that's why we declared an id for the main layout.
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
ft.replace(R.id.activity_main, fragment);
}
Notes: Again, refresh your data in onTabSelected(). I have to warn you that TabListener is deprecated in the new Lollipop API.
EDIT:
Sample code to set Tabs to the correct Fragments.
// Setting tab listeners.
bmwTab.setTabListener(new TabListener(bmwFragmentTab));
toyotaTab.setTabListener(new TabListener(toyotaFragmentTab));
fordTab.setTabListener(new TabListener(fordFragmentTab));
Good luck and have fun...

Show/Hide two fragments in a single Layout [Both fragments have a Google map each]

I have an activity with a relative layout; And have two different fragments. I show one fragment and switch to the next fragment on a button click vice verse.
// When button menu is clicked
OnClickListener btnClick = new OnClickListener() {
#Override
public void onClick(View arg0) {
if(currentType==0){
InitThisFragment(1);
}else{
InitThisFragment(0);
}
}
};
public void InitThisFragment(int type){
Fragment newFragment;
if(type==0){
newFragment=new MainFragment();
}else{
newFragment=new JourneyFragment();
}
currentType=type;
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.abs_fragment_container, newFragment);
transaction.addToBackStack(null);
transaction.commit();
}
R.id.abs_fragment_container is a Relative Layout
BOTH THE FRAGMENT CONTAIN GOOGLE MAPS INSIDE THEM;
But it is not working as expected.
By default i add the first fragment [which works fine].
Then after an onClick event the 2nd fragment comes[which also works
fine]
But on my next click the app crashes;
Please help I am new to Google Maps and Fragments;

yeah of course your app crashes because the fragment with the map already exists look at this thread it helped me a lot: Duplicate ID, tag null, or parent id with another fragment for com.google.android.gms.maps.MapFragment
Especially the second answer with 41 ups is easy to understand
And yes I would have posted this one in a comment if I would have enough reputation for it!

Action bar tabs - how to retrieve value from fragments in Activity?

I've settings activity, which has 3 tabs (each tab contains fragment) + in the main activity there is also buttons row - with buttons OK, and Cancel.When I press OK, I would like to do something like this:
1) get all my custom variables from all fragments
2) save them to shared prefs
But how to get access to fragment variables? I tried this:
Adding tabs in main activity:
ActionBar.Tab tab1 = actionbar.newTab().setText(res.getString(R.string.actSettingsTab1));
tab1.setTabListener(new MyTabsListener(new Tab1Fragment(), "tab1"));
actionbar.addTab(tab1);
//...similar for all tabs
This is my tab listener:
class MyTabsListener implements ActionBar.TabListener {
private Fragment fragment;
private String tag;
public MyTabsListener(Fragment fragment, String tag) {
this.fragment = fragment;
this.tag = tag;
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
// do nothing
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
ft.replace(R.id.fragment_container, fragment, tag);
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
ft.remove(fragment);
}
}
And this is how I would like to get variables from fragments:
Tab1Fragment tab1 = (Tab1Fragment) fm.findFragmentByTag("tab1");
Tab2Fragment tab2 = (Tab1Fragment) fm.findFragmentByTag("tab2");
Tab3Fragment tab3 = (Tab1Fragment) fm.findFragmentByTag("tab3");
but it's strange - findFragmentByTag returns fragment only for selected tab, otherwise returns null. So when I have selected tab1 and press ok, findFragmentByTag return fragment for tab1, but null for others.
Maybe I'm doing something wrong, or whole my tring is goind wrong way. How to retrieve values from all fragments in parent activity and save them to shared preferences?

Separate the process into two steps:
1) Gather all settings from all the fragments in real time (i.e. as they are changed by the user). Use Listener pattern, so that fragments will expose an interface by which they will notify attached listener when user modifies any of the settings for which given fragment is responsible for. Let the activity attach itself as a listener to all fragments, and capture changes (store them in a structure that suits you).
2) Let the activity save settings using SharedPreferences when OK button is clicked. It does not have to access fragments as it always about any settings user has changed.
This way you do not have to access all the fragments at once, which is impossible if they are removed from the memory (as they are not visible anyway at a given time). Instead, you can re-assign the activity as a listener to selected fragment every time it gets selected/displayed.

I wouldn't recommend actually accessing the variables from your fragments. You could make a public method in those fragments that does the shared preferences saving that you want. Ex:
Tab1Fragment tab1 = (Tab1Fragment) fm.findFragmentByTag("tab1");
Tab2Fragment tab2 = (Tab1Fragment) fm.findFragmentByTag("tab2");
Tab3Fragment tab3 = (Tab1Fragment) fm.findFragmentByTag("tab3");
tab1.savePreferences();
tab2.savePreferences();
tab3.savePreferences();

ActionBar.Tab tab1 = actionbar.newTab().setText(res.getString(R.string.actSettingsTab1));
tab1.setTabListener(new MyTabsListener(new Tab1Fragment(), "tab1"));
actionbar.addTab(tab1);
//...similar for all tabs
this does not add your Fragment to the backstack therefore you get only the selected tab and the others are null.
I think the best you can do is iterate through the tabs of the ActionBar using getTabCount() and then you should be able to get your content with getTabAt(int index). getCustomView()

Separated Back Stacks for Tabs with Fragments in Android

Since Tab Activity is deprecated I'm trying to implement tabs with fragments. As you can see in the lots of StackOverFlow questions back stack is an issue when you work with fragments and which has its own back stack.
So the thing I'm trying to do is, there is a fragment in each tab and this fragment can call another fragment within the same tab and its also the same for the other tabs.
Since there is only one activity then there is only one back stack for whole application. So I need to create my custom back stack which is separated for each tab. It's also the same common idea in the other questions. I need to find a way to create custom back stack but I couldnt find any example to take a look.
Is there any tutorial or any example piece of code doing something similar ? Thanks in advance.

There is a backstack for the whole application, but there is also a backstack for fragments.
Perhaps have a read of this:
http://developer.android.com/guide/components/fragments.html#Transactions
When you perform a fragment transaction (add, replace or remove), you can add that transaction to the backstack.
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.fragmentContainer, fragment);
ft.addToBackStack(null);
ft.commit();
And now when you press back, the latest fragment will be 'popped' from the fragment backstack.
You could also override the onBackPressed(), and manage your fragment backstack there. (I'm currently having trouble trying to work out how to do this efficiently).
Anyway, there are several calls available from the FragmentManager to do with the backstack. The most useful to me being:
FragmentManager.getBackStackEntryCount()
and
FragmentManager.PopBackStack()

Sorry for late answer, but this might help somebody. I have added functionality like this in my project. I used fragment tabhost to add backstacks within it. Main logic will remain same in others.
Basically I took,
Stack<String> fragmentStack = new Stack<>();
boolean bBackPress = false;
String strPrevTab;
FragmentTabHost tabHost;
strPrevTab = "tag"; // Add tag for tab which is selected by default
tabHost.setOnTabChangedListener( new TabHost.OnTabChangeListener() {
#Override
public void onTabChanged( String tabId ) {
if ( !bBackPress ) {
if ( fragmentStack.contains( tabId ) ) {
fragmentStack.remove( tabId );
}
fragmentStack.push( strPrevTab );
strPrevTab = tabId;
}
}
} );
#Override
public void onBackPressed() {
if ( fragmentStack.size() == 0 ) {
finish();
} else {
strPrevTab = fragmentStack.pop();
bBackPress = true;
tabHost.setCurrentTabByTag( strPrevTab );
bBackPress = false;
}
}
Hope this helps!

Transaction between fragments only inside one ActionBar Tab

I have an app with three tabs (ActionBar Tabs), each one with one fragment at a time.
TabListener
TabsActivity
Tab1 -> ListFragment1 -> ListFragment2 -> Fragment3
Tab2 -> Tab2Fragment
Tab3 -> Tab3Fragment
The problem is when I create the FragmentTransaction (inside OnListItemClicked) from ListFragment1 to ListFragment2, the fragments inside the other tabs also change to ListFragment2.
In the end, I want to change fragments only inside on tab and preserve the state of the other tabs.
I'm already saving the state (OnSavedInstance()).
Do you know what I'm missing here?
Some of the code:
public class TabsActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tabs);
// setup Action Bar for tabs
ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// instantiate fragment for the tab
Fragment networksFragment = new NetworksFragment();
// add a new tab and set its title text and tab listener
actionBar.addTab(actionBar.newTab().setText("Tab1")
.setTabListener(new TabsListener(ListFragment1)));
// instantiate fragment for the tab
Fragment historyFragment = new HistoryFragment();
// add a new tab and set its title text and tab listener
actionBar.addTab(actionBar.newTab().setText("Tab2")
.setTabListener(new TabsListener(Tab2Fragment)));
// instantiate fragment for the tab
Fragment settingsFragment = new SettingsFragment();
// add a new tab and set its title text and tab listener
actionBar.addTab(actionBar.newTab().setText("Tab3")
.setTabListener(new TabsListener(Tab3Fragment)));
}
}
public class TabsListener implements ActionBar.TabListener {
private Fragment frag;
// Called to create an instance of the listener when adding a new tab
public TabsListener(Fragment networksFragment) {
frag = networksFragment;
}
#Override
public void onTabReselected(Tab arg0, FragmentTransaction arg1) {
// TODO Auto-generated method stub
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
ft.add(R.id.fragment_container, frag, null);
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
ft.remove(frag);
}
}
public class ListFragment1 extends ListFragment {
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
getListView().setItemChecked(position, true);
ListFragment2 fragment2 = ListFragment2.newInstance(position);
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.fragment_container, fragment2);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.addToBackStack(null);
ft.commit();
}
}

You're not missing anything (or I'm missing it too).
I searched long and hard for a way to do this "properly" but I couldn't find anything. What I ended up doing is writing my own backstack logic.
Unfortunately my employer owns my code so I can't share any of that verbatim, but here was my approach:
Create an enum with one entry for each of your tabs. Let's call it TabType.
Now create an instance variable tabStacks of type HashMap<TabType, Stack<String>>. Now you can instantiate one stack for each tab - each stack is a list of tags, as specified by Fragment.getTag(). This way you don't have to worry about storing references to Fragments and whether they're going to disappear on you when you rotate the device. Any time you need a reference to a Fragment, grab the right tag off the stack and use FragmentManager.findFragmentByTag().
Now whenever you want to push a Fragment onto a tab, generate a new tag (I used UUID.randomUUID().toString()) and use it in your call to FragmentTransaction.add(). Then push the tag on top of the stack for the currently displayed tab.
Be careful: when you want to push a new fragment on top of an old one, don't remove() the old one, since the FragmentManager will consider it gone and it will be cleaned up. Be sure to detach() it, and then attach() it later. Only use remove() when you're permanently popping a Fragment, and only use add() the first time you want to show it.
Then, you'll have to add some relatively simple logic to your TabListener. When a tab is unselected, simply peek() at its stack and detatch() the associated Fragment. When a tab is selected, peek() at the top of that stack and attach() that fragment.
Lastly, you'll have to deal with Activity lifecycle quirks (like orientation changes). Persist your Map of Stacks as well as the currently selected tab, and unpack it again in your onCreate(). (You don't get this packing and unpacking for free, but it's pretty easy to do.) Luckily your TabType enum is Serializable so it should be trivial to put into a Bundle.