I have a simple app that has two fragments and when in landscape mode, both fragments are shown side by side and in portrait I show Fragment A and then if they select an option, start an Activity that shows Fragment B. My problem is when I am in Portrait mode and showing Fragment B, if the user selects a menu option I want to refresh or redraw the View that is associated with Fragment B and can’t understand how to make this work. I tried the getView method and getLayoutInflater method but the screen doesn’t change because I think I am creating a new view. I also tried to get a reference to Fragment A thinking I could call its routine to build a new fragment and replace Fragment B but can’t get a reference to it because it is not being displayed. What I really need to do is just force the onCreateView method to be called again to inflate the new view but I have tried several methods to try to do this but can’t get the onCreateView to be called again. Any thoughts on how to this?
You will want to perform a FragmentTransaction and use the replace() method
This shouldn't be too hard to do, but the answer will depend on where your Menu is located (i.e. is your onOptionsItemSelected() call back inside your parent Activity or is it in either Fragment A/B?).
Suppose for simplicity's sake, your menu implementation and onOptionsItemSelected() is in the parent activity, and you want to reshape the fragments in the event that menu_option1 is chosen. It would look something like this:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
//...
switch (item.getItemId()) {
case R.id.menu_option1:
//do something
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment newFragment = new YourFragmentClass();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.your_fragment_id, newFragment);
transaction.addToBackStack(null);
transaction.commit();
return true;
case R.id.menu_option2:
//do something else;
return true;
default:
return super.onOptionsItemSelected(item);
}
}
Alternatively, if your menu is a child of one of your Fragments (which it should be for the sake of more reusable code), then one method is to require that host Activity to implement an interface defined by the Fragment, that can be used as a call back.
And in the onOptionsItemSelected() callback inside your fragment class, you simply make a call to this callback method.
Although it sounds like a mouthful, you only really need to do a couple of things. Pretend that this is your Fragment class
public static class FragmentA extends ListFragment {
OnSelectedListener mListener;
// Container Activity must implement this interface
public interface OnSelectedListener {
public void onSelected();
}
...
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
//This is to ensure that the Activity has implemented the interface we set up above
try {
mListener = (OnSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString() + " must implement OnSelectedListener");
}
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
//...
switch (item.getItemId()) {
case R.id.menu_option1:
//do something
getActivity().onSelected();
return true;
case R.id.menu_option2:
//do something else;
return true;
default:
return super.onOptionsItemSelected(item);
}
}
...
}
Then in the Activity, you would see something like:
public class MainActivity extends Activity implements FragmentA.onSelectedListener{
...
public void onSelected(){
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment newFragment = new YourFragmentClass();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.your_fragment_id, newFragment);
transaction.addToBackStack(null);
transaction.commit();
}
}
if the user selects a menu option I want to refresh or redraw the View that is associated with Fragment B and can’t understand how to make this work
In onOptionsItemSelected(), have the activity call a method on the fragment that causes it to update its widgets with the new content. Or, have the activity execute a FragmentTransaction to replace the fragment (if the fragment was originally set up via a FragmentTransaction).
Related
Problem 1
I have a Navigation Drawer and most of my fragment transactions happens from here.
So say I have 4 Items in my drawer and I am doing the transaction from all of them. So if I am at the fragment [A] and now I click on the fragment [B], I need to come back to the previous fragment i.e. [A]. But if I keep clicking on the Item B of the navigation drawer that opens the fragment [B], I keep adding it to the backstack and when I press the back button, I am still at the same fragment.
Problem 2
How do I achieve the Clear Top behavior that is used for the intents for the fragments. As intents have the power to clear the activities from the stack from the top only, I want to achieve the same behavior.
Problem 1 & 2 solution Idea:
Create an Interface say FragmentInstanceHandler
public interface FragmentInstanceHandler {
public void openFragment(Fragment fragment, String fragmentTag);
}
Create a BaseFragment like below and extend this to all your Fragment classes:
public BaseFragment extends Fragment {
public FragmentInstanceHandler fragmentInstanceHandler;
public void setFragmentInstanceHandler(FragmentInstanceHandler fragmentInstanceHandler) {
this.fragmentInstanceHandler = fragmentInstanceHandler;
}
}
Implement the FragmentInstanceHandler interface to the Activity in which you are going to open all the Fragments. Let's say Activity is MainActivity:
public MainActivity extends Activity implements FragmentInstanceHandler {
private BaseFragment currentFragment;
#Override
public void openFragment(BaseFragment fragment, String fragmentTag) {
FragmentManager fragmentManager = getSupportFragmentManager();
Fragment oldFragmentInstance = fragmentManager .findFragmentByTag(fragmentTag);
boolean fragmentPopped = fragmentManager.popBackStackImmediate (fragmentTag, 0);
if (!fragmentPopped && oldFragmentInstance == null) {
fragment.setFragmentInstanceHandler(this);
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.container, fragment, fragmentTag);
fragmentTransaction.addToBackStack(fragmentTag);
fragmentTransaction.commit();
currentFragment = fragment;
} else if(fragmentPopped ){
currentFragment = oldFragmentInstance;
}
if(mDrawerLayout!= null)
mDrawerLayout.closeDrawers();
}
}
Now whenever you want to open a new Fragment even from any other Fragment you can call method like below, It is advised to provide new tag if you want to have new instance of same Fragment:
fragmentInstanceHandler.openFragment(new MyFragment(), "FragmentNewInstance");
You can tweak FragmentInstanceHandlerto add your own method to replace the current Fragment instead of adding. Above solution just gives you an idea how you can acheive your solution by putting and mananging all your code from one place.
I have done many programs, where I have implemented multiple Fragments inside a Single Activity, but not when using Single Activity to host multiple Fragments as Tabs and then on Tap show another Fragments...
Using MaterialViewPager library, in which I am calling different different Fragments to show views in their respective Tabs.
Like For the First Tab, I am using two Fragments, where
In First Fragment, I am using RecyclerView... to show list of Menus.
And in Second Fragment, I am using RecyclerView... to show list of Items under particular Menu.
So here my question is How to call Fragment from Fragment.
mRecyclerView.addOnItemTouchListener(new RecyclerItemClickListener(getActivity(), mRecyclerView ,new RecyclerItemClickListener.OnItemClickListener() {
#Override
public void onItemClick(View view, int position) {
Value value = valueList.get(position);
List<Learning> learning = value.getLearning();
// using when putting "item" data into same recyclerview
// but on back press just exiting, not showing list of Menus again
/**
learningAdapter = new LearningAdapter(learning, R.layout.card_learning, getActivity());
mRecyclerView.setAdapter(learningAdapter);
**/
ItemFragment fragment = new ItemFragment();
replaceFragment(fragment);
}
Method replaceFragment
public void replaceFragment(Fragment someFragment) {
FragmentTransaction transaction = getFragmentManager().beginTransaction();
// using Fragment not Activity, so where can I use frame_container in xml
transaction.replace(R.id.frame_container, someFragment);
transaction.addToBackStack(null);
transaction.commit();
}
you can have a callback interface that is implemented by the activity which hosts these two fragments. Fragment A will use the call back to notify the activity to replace A with fragment B. Depending on your need, you can pass parameters across through the callback method itself.
Your callback interface:
public interface YourCallback {
public void methodWhichReplacesFragmentAwithB(params...);
}
Your Activity hosting fragments:
public class YourActivity extends ... implements YourCallback {
..
..
#Override
public void methodWhichReplacesFragmentAwithB(params...) {
//insert replace fragment code here
}
}
Your fragment will have a callback object, YourCallback callbackObj;. This callback object can be initialised using the activity (pass as this from activity) itself since the activity has the implementation of the interface. Now, you can use
callbackObj.methodWhichReplacesFragmentAwithB(actual_params...);
to replace the fragment. This callback interface can be exploited for other communications to parent Activity as well as other fragment hosted in that activity.
To replace fragment,
FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frame_container, someFragment).addToBackStack("null").commit();
You can try this:
YourFragment fragment = new YourFragment();
FragmentTransaction transaction = ((AppCompatActivity) mContext).getSupportFragmentManager()
.beginTransaction();
transaction.replace(R.id.frame, fragment);
transaction.addToBackStack(null);
transaction.commit();
There is One option which i have been using from long time before. I will added the solution with clear example.
So you want to pass the value from fragment A to fragment B
So, here what you want to do is, you have pass the value through the activity.
1) you pass the value from fragment A to activity
2) then activity to fragment B
Step 1: first create an Interface Like below in fragment A
public interface HomePage {
void onHomeButtonsClicked(String clickedButton);
}
public void setOnHomeButtonClicked(HomePage homePage) {
this.homePage = homePage;
}
Step 2: then create the instance like below in Activity. where fragment created in PagerAdapter
((FragmentA) fragment).setOnHomeButtonClicked(new FragmentA.HomePage() {
#Override
public void onHomeButtonsClicked(String buttonClicked) {
pageSelected.onHomeButtonsClicked(selectedPage);
}
}
});
Step 3: then create the interface in Activity like below.
public interface PageSelected {
void onHomeButtonsClicked(String clickedButton);
}
public void setOnHomeButtonClicked(PageSelected pageSelected) {
this.pageSelected = pageSelected;
}
step 3: then add the following method in fragment B in onCreateView or onResume()
((MainActivity) getActivity()).setOnHomeButtonClicked(new MainActivity.PageSelected() {
#Override
public void onHomeButtonsClicked(String clickedButton) {
//fragment B received the value here
}
});
Step 5: finally add the line in fragment A in button click or where you want to pass the value.
homePage.onHomeButtonsClicked("Some String , by this code it is in String. you can change in your own data type");
You can rise your question if you face any difficulties.
I added a menu with some actions, which are handled in MainActivity as well. For example after firing the 'Logout' menu action, MainActivity method 'onOptionsMenuSelected()' want to forward to LoginFragment. Unfortunately the text elements of the former fragments are still showing up, altough I am calling replace() of FragmentTransaction to change the relevant fragment to show in my forwardToLoginFragment() method. What needs to be done to hide old fragments and their content successfully?
Moreover, sometimes my app stops, because FragmentManager tries to add a fragment to the activity more than once. This results in an app crash. How to manage the fragments wisely to prevent this issue as well?
Excerpts of my MainActivity class:
private void forwardToLoginFragment(){
LoginFragment loginFragment = (LoginFragment) getFragmentManager().findFragmentByTag(LoginFragment.LOGIN_FRAGMENT_TAG);
FragmentTransaction ft = getFragmentManager().beginTransaction();
if (loginFragment == null){
loginFragment = new LoginFragment();
ft.add(R.id.container, loginFragment, LoginFragment.LOGIN_FRAGMENT_TAG);
} else {
ft.replace(R.id.container, loginFragment);
}
ft.commit();
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()){
...
case R.id.menu_main_signout:
Toast.makeText(this, "Signing out ...", Toast.LENGTH_SHORT).show();
setSignedIn(false);
forwardToLoginFragment();
return true;
...
default:
return super.onOptionsItemSelected(item);
}
}
I have an Android activity that holds and manages six fragments, is fragment is a step in a flow, some of the fragments are replaced and some of them are added.
The Activity just uses a Framelayout as the container for the fragments as follows:
<FrameLayout
android:id="#+id/content"
android:layout_below="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="match_parent" />
Then the flow of the fragments is like this:
//Activity starts, add first Fragment
fragmentManager.beginTransaction().replace(R.id.content, FirstFragment.newInstance(listOfItems)).commit();
then
//User pressed button, activity got callback from first fragment
FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.replace(R.id.content, fragment2);
transaction.addToBackStack("frag2");
transaction.commit();
then
//Another callback from Frag2, perform the add of frag 3
FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.add(R.id.content, fragment3);
transaction.addToBackStack("frag3");
transaction.commit();
And so on....
I also manage the back stack from the Activity like this:
//Controlling the back stack when the user selects the soft back button in the toolbar
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
if (fragmentManager.getBackStackEntryCount() == 0) {
super.onBackPressed();
overridePendingTransition(R.anim.no_change, R.anim.slide_down);
} else {
if(!BaseFragment.handleBackPressed(getSupportFragmentManager())){
super.onBackPressed();
Fragment fragment = fragmentManager.getFragments()
.get(fragmentManager.getBackStackEntryCount());
fragment.onResume(); //Make sure the fragment that is currently at the top of the stack calls its onResume method
}
}
return true;
}
return super.onOptionsItemSelected(item);
}
//Controlling the back stack when the user selects the "hardware" back button
#Override
public void onBackPressed() {
if (fragmentManager.getBackStackEntryCount() == 0) {
super.onBackPressed();
overridePendingTransition(R.anim.no_change, R.anim.slide_down);
} else {
if(!BaseFragment.handleBackPressed(getSupportFragmentManager())){
super.onBackPressed();
Fragment fragment = fragmentManager.getFragments()
.get(fragmentManager.getBackStackEntryCount());
fragment.onResume(); //Make sure the fragment that is currently at the top of the stack calls its onResume method
}
}
}
My problem is that I open the app and go to this Activity which loads the fragments and then go through the flow to a certain stage ( I haven't narrowed it down yet) then I press the home button and blank my screen. Now after a certain amount of time when I open the app again it opens on the fragment I left but everything seems to be messed up, when I press back it seems to pop the wrong fragment and the UI becomes mixed up with the different fragments.
My guess is that when I open the app again the Activity onResume or the Fragment onResume or some lifecycle event is being called that I am not handling correctly?
So I was wondering is there best practices, guidelines or patterns that should be adhered to when using a Fragment pattern like I am doing so?
Since you have so many fragments in one activity, and they use the same container, that means all fragments are in the same place, and only one fragment will show at a time.
So why don't you use ViewPager and let FragmentPagerAdapter manager these fragments? In this way, you do not need to manager fragment lifecycle by yourself, you just need to override FragmentPagerAdapter methods:
to create fragment instance by getItem,
to update fragment by getItemPosition and Adapter.notifyDataSetChanged(),
to show selected fragment by mViewPager.setCurrentItem(i)
Code snippets, detail refer to https://github.com/li2/Update_Replace_Fragment_In_ViewPager/
private FragmentPagerAdapter mViewPagerAdapter = new FragmentPagerAdapter(getSupportFragmentManager()) {
#Override
public int getCount() {
return PAGE_COUNT;
}
// Return the Fragment associated with a specified position.
#Override
public Fragment getItem(int position) {
Log.d(TAG, "getItem(" + position + ")");
if (position == 0) {
return Page0Fragment.newInstance(mDate);
} else if (position == 1) {
return Page1Fragment.newInstance(mContent);
}
return null;
}
#Override
// To update fragment in ViewPager, we should override getItemPosition() method,
// in this method, we call the fragment's public updating method.
public int getItemPosition(Object object) {
Log.d(TAG, "getItemPosition(" + object.getClass().getSimpleName() + ")");
if (object instanceof Page0Fragment) {
((Page0Fragment) object).updateDate(mDate);
} else if (object instanceof Page1Fragment) {
((Page1Fragment) object).updateContent(mContent);
}
return super.getItemPosition(object);
};
};
As title says, do anyone know a way how to implement OnBackPressed functionality, just like in Activity, but in Fragment View?
It does not work when I use onKey, onKeyDown or onBackPressed in Fragment - app is closing. I would like to execute specific code when back button is pressed, because in one of fragments I have ListView, which is filled with data depending on user actions.
So when back is pressed I would like to modify values of variables ("categories" and "part"), to fill ListView with specific data (so modify some values because user clicked something, and refresh this ListView), giving a feeling that user is going back (from parts, to categories and to close the app).
But as I mentioned, when I use onKey, onKeyDown or onBackPressed, app is closing... For instance when I include in my Fragment class:
public void onBackPressed() {
Toast.makeText(getActivity(), "AAAA", Toast.LENGTH_LONG).show();
}
Toast does not appear. With "onKeyDown" and "onKey" - the same situation... What am I doing wrong here, any ideas?
To answer your very first sentance:
as title says, do anyone know a way how to implement OnBackPressed
functionality, just like in Activity, but in Fragment View?
To make the back-button work with fragments you have to add them to the backstack. That should trigger the function you want.
// Create new fragment and transaction
Fragment newFragment = new ExampleFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();
Finally, got it.
I had to, in my "ActionBarActivity" from method "onNavigationDrawerItemSelected" move declaration of "Fragment newFragment" to outside of this method, to make it available in whole class. Then I had to include "OnBackPressed" in my "ActionBarActivity" like this:
#Override
public void onBackPressed() {
if (!newFragment.onBackPressed()) {
super.onBackPressed();
}
}
And finally, in my Fragment I included also onBackPressed:
public boolean onBackPressed() {
if (part != -1) {
part = -1;
toAdd = "" + category + "_";
updateList();
return true;
}
return false;
}
And it works just like I wanted. When I push back, and when variable "part" in my Fragment is not -1, then it is executing operations defined above, returning true to "ActionBarActivity" so the app is not closing. But when, in my Fragment, variable is -1, then onBackPressed app is going back to main view, and again when user is pushing back, app is closing. That's what I wanted!
Thank You all for the help!
#Override
public void onBackPressed() {
super.onBackPressed();
Intent register = new Intent(PollCreateCommunities_Activity.this, PollActivity.class);
startActivity(register);
finish();
}
public boolean onOptionsItemSelected(MenuItem menuItem) {
switch (menuItem.getItemId()) {
case android.R.id.home:
Intent register = new Intent(PollCreateCommunities_Activity.this, PollActivity.class);
startActivity(register);
return true;
}
return (super.onOptionsItemSelected(menuItem));
}