I have two fragments sitting side by side in the same activity. When I touch a button in the right fragment (fragment B), I need a TextView in the left fragment to update (fragment A). I have looked all over for the best way to do this, but nothing seems to work for my needs. Could someone possibly give me an example of how I would code this? Fragment A is set through the XML layout, and fragment B gets loaded programmatically into a container. I have tried accomplishing this by using a method in fragment A to update the text, and calling on that method from a method in the parent activity. I then call on the method in the parent activity from fragment B.
This is the code in fragment B that declares the interface and calls a method in the interface
AttackCards attackCards;
public interface AttackCards {
public void deckSize();
}
public void onAttach(DeckBuilder deckBuilder) {
super.onAttach(deckBuilder);
attackCards = (AttackCards) deckBuilder;
}
attackCards.deckSize(); //this is in my onclick methods
This is the code in the activity that implements the interface and calls the method in fragment A
public class DeckBuilder extends Activity implements AttackCards{
public void deckSize() {
DeckBuilderFragment deckBuilderFragment = (DeckBuilderFragment)getFragmentManager().
findFragmentById(R.id.deckbuilder_fragment);
deckBuilderFragment.deckSize();
}
This is the method in fragment A that appends the textview with the contents of a shared preferences value
public void deckSize() {
deckSize = (TextView) getView().findViewById(R.id.decksize);
final SharedPreferences defaultDeck = getActivity()
.getSharedPreferences("defaultDeck", Context.MODE_PRIVATE);
deckSize.setText(String.valueOf(defaultDeck.getInt("decksize", 0)));
}
Sadly this attempt simply brings me a nullpointer when touching a button. I am getting a null pointer at
attackCards.deckSize(); //this is in my onclick methods
Could someone please help me out with an example of how to do this correctly?
One fragment should not communicate to another fragment directly. It should do so through attached activity. The detail explanation with code example is available here
Android Developer site
Declare an interface in Fragment B, and implement the interface in the activity. Call the interface through callback in Fragment B when button is clicked. You can have a public function in Fragment A to update the TextView, so activity directly call the function to update the text.
You can define an interface in Fragment B and implement it on the MainActivity. Then on the callback method (onClickOnB in this case) set the text on the TextView. You should obtain a reference of the TextView in the Activity's onCreate() after setContentView(). This works because Fragment A is static. Otherwise, you can create a public method inside Fragment A so you can set the text from inside the callback by getting a reference of Fragment A and calling such method.
Fragment B
public class FragmentB extends Fragment implements onClickListener{
ClickOnB listener;
public void setOnFragmentBClickListener(ClickOnB listener){
this.listener = listener;
}
#Override
public void onClick(View v){
//stringMessage is a `String` you will pass to `Fragment` A to update its `TextView`
listener.onClickOnB(stringMessage);
}
interface ClickOnB{
public void onClickOnB(String message);
}
}
MainActivity
public class MainActivity extends Activity implements ClickOnB{
#Override
protected onCreate(Bundle savedInstanceState){
//Get a reference of `Fragment` B somewhere in your code after you added it dynamically and set the listener.
((FragmentB)getFragmentManager().findFragmentByTag("FragmentB")).setOnFragmentBClickListener(this);
}
#Override
public void onClickOnB(String message){
//Set the text to the `TextView` here (I am assuming you get a reference of the `TextView` in onCreate() after inflating your layout.
mTextView.setText(message);
}
}
Related
I have two fragments, A and B let's say, where B contains a list. I would like to add a listener on Fragment B that notifies Fragment A of the chosen list item. I couldn't figure out how to initialize the listener in Fragment B since it is bad practice to pass arguments in fragment's constructors.
NOTE: Fragment B is contained inside Fragment A. i.e. I have a FrameLayout in Fragment A; and Fragment B covers that FrameLayout.
Any idea how I could do that?
If you're saying that Fragment B is a child fragment of Fragment A (that is, you've added it to Fragment A using Fragment A's getChildFragmentManager()), then you can use the same approach that you use for Activity interfaces, but using getParentFragment() instead of getActivity().
For example:
Fragment B:
#Override
public void onAttach(Context context) {
MyInterface myInterface = (MyInterface) getParentFragment();
}
Assuming that Fragment A implements MyInterface.
One convenience method we've used to avoid having to know whether a Fragment is hosted by another Fragment or an Activity is something like:
public static <T> getInterface(Class<T> interfaceClass, Fragment thisFragment) {
final Fragment parent = thisFragment.getParentFragment();
if (parent != null && interfaceClass.isAssignableFrom(parent)) {
return interfaceClass.cast(parent);
}
final Activity activity = thisFragment.getActivity();
if (activity != null && interfaceClass.isAssignableFrom(activity)) {
return interfaceClass.cast(activity);
}
return null;
}
Then you can just use:
MyInterface myInterface = getInterface(MyInterface.class, this);
and it doesn't matter whether Fragment B is hosted as a child Fragment or in an Activity directly.
A better approach for this situation, since what you want to do is communication between fragments, is to use an interface. You want to notify A when B has changed. This should be done through the parent activity. Here is the android documentation on the topic: https://developer.android.com/training/basics/fragments/communicating.html.
The gist of it is that you want to define an interface with a method called OnItemSelected (you can name it whatever you want). In B, you want a reference to this interface. When an item is selected, call your new OnItemSelected method. Implement this interface in the parent activity of the two fragments. In the implementation, you can put whatever code you want to modify A.
An example
CommunicationInterface
public interface CommunicationInterface {
public void onItemSelected(int position);
}
FragmentB
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
CommunicationInterface myInterface = (CommunicationInterface) getActivity();
// What ever else you want here
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
// Send the event to the host activity
myInterface.onItemSelected(position);
}
MainActivity
public class MainActivity extends FragmentActivity implements CommunicationInterface {
// What ever other code you have
#Override
public void onItemSelected(int position) {
FragmentA fragA = (FragmentA)
getSupportFragmentManager().findFragmentById(R.id.fragment_a);
// Code to interact with Fragment A
}
Checkout the contract pattern https://gist.github.com/JakeWharton/2621173
If you are using multiple fragment, you dont have do it for every fragment, just add it to your BaseActivity if you have one.
This example shows the communication between activity and fragment. But for nested fragment you can replace the acitivy with getParentFragment();
I have two static fragments in same activity, in "fragmentA" i have a customized list, when an item is clicked must to appear a detail in "fragmentB", detail appear only when i change screen orientation, no automatically. I use this code in main activity for refresh but application restart(detail appear).
finish();
startActivity(getIntent());
Someone knows a better way to make appear detail automatically in "fragmentB" when i clicked some item from "fragmentA", always using two static fragments in same activity.
Don't use static references to hold a Fragment, it's a really bad practice.
Don't store the Context in a static reference. Or you could will leak memory.
Instead, implement an Interface:
//FragmentActivityTest
public class FragmentActivityTest extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FragmentB fragmentB = new FragmentB();
FragmentA fragmentA = new FragmentA();
fragmentA.setFragmentBHandler(fragmentB);
//Perform transactions etc
}
}
//FragmentA
public class FragmentA extends Fragment {
private FragmentBHandler _handler;
public void setFragmentBHandler(FragmentBHandler handler) {
_handler = handler;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
((ListView) getView().findViewById(R.id.list_view)).setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
_handler.updateDetail();
}
});
}
}
//FragmentB
public class FragmentB extends Fragment implements FragmentBHandler {
#Override
public void updateDetail() {
//do your work
}
}
You should use an event bus like greenrobot or otto. FragmentB subscribe to an event, and FragmentA post that event. When you click on an item, you'll send an event, and the subscriber will execute your action (show details).
Without showing code, I can only guess your current implementation.
The proper way to communicate between fragments is
Pass data to the parent activity from Fragment A on item click,
Activity passes this data to fragment B by finding the fragment in fragment manager and call a method in fragment B,
That method in fragment B should determine if it should populate the detail.
I have ActivityA which contains FragmentA inside it. How to access the TextView in the activity from the Fragment.
Override onViewCreated() method inside your Fragment class and use the Fragment View to declare the TextView:
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ActivityA.text_view= (TextView) view.findViewById(R.id.text_view); // your TextView must be declared as (public static TextView text_view) in the Activity
// now access the TextView as you want
}
The easiest way is to create a getter method inside your Mainactivity that returns your textview and access it by casting your fragment's activity to your Mainactivity.
So in your Mainactivity,
public AppCompatTextView getMyTextView(){
return myTextView;
}
And in your Fragment
((MainActivity)getActivity()).getMyTextView()
And do whatever you please with it.
You can either use callbacks or make your fragment as an inner class.
For callbacks you need to implements some interface in your activity let say you want to update your TextView and in the onAttach method of the fragment you can then use the reference of that interface to communicate with the activity.
sample:
in activity:
public class Question implements MyInterFace
in fragment:
#Override
public void onAttach(Activity activity) {
// TODO Auto-generated method stub
youInterfaceObject = (MyInterFace)activity;
super.onAttach(activity);
}
For inner class it is just easy just create a global variable of the TextView in your activity and call it from the inner class.
May not work for views, but give it a try:
((MainActivity) getActivity()).textViewName;
i got a problem while working with fragments, in the first fragment i got a textview, ie:
<EditText
android:id="#+id/LeyOrdenanza"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="#dimen/dpde10"
android:ems="10"
android:hint="Ley / Ordenanza"
android:textColor="#color/cafeoscuro"
android:textColorHint="#color/cafeclaro"
android:textSize="#dimen/legra25" />
the user puts a value, then i change of fragmet, in the new fragment i got a button that calls a function in the class that contains the fragments like this :
EditText LeyOrdenanzav = (EditText) findViewById(R.id.LeyOrdenanza);
LeyOrdenanza = LeyOrdenanzav.getText().toString();
but i get null, when i put the button with the function on the same fragment, everything works like a charm, but i need to change that button to the second fragment, thats when it stops working, any suggestions?...
Hi i hope i got your question right,
in order to send data between fragments you need to create an interface communicator as follows, I'll suggest to make a new class so not to confuse yourself.
public interface Communicator {
public void getData(String data);
}
Have your MainActivity Implement Communicator as follows.
public class MainActivity extends ActionBarActivity implements Communicator
after implementing the communicator add the umimplemented method which is getData in the form String in your Case.
this method will work as a hub between the two fragments.
Create an Instance of the Communicator in the fragment where you get the String from the TextView
Communicator communicator = (Communicator) getActivity();
Now Pass the String Like this communicator.getData(StringtToPass);
Initialize an instance of the Fragment in the method using Fragment Manger
FragmentManager fragmentManager = getFragmentManager(); fragmentTwo fragmentTwo = (fragmentTwo) fragmentManager.findFragmentById(R.id.fragmentTwo);
On the Other fragment create a method similar to this
public void setData(String string) {
textView.setText(stringPassed);
}
After you initialize the Fragment in the MainActivity you can pass the data this way.
fragmentTwo.setData(StringToPass);
Hope this will help a little.
How can I communicate a listview of a ListFragment after an event of a Fragment inside another Fragment?
In the ListFragment (fragment A) I have a method to refresh the ListView. But also, I need to refresh it after a click of a Button inside a Fragment, wich is child of another Fragment (fragment b)
Its like Fragment A (listFragment) | Fragment B (detailview)
(fragment C - child fragment of B)
How can I do it?
You can access another Fragment by its tag:
// find your fragment
YourFragment f = (YourFragment) getSupportFragmentManager().findFragmentByTag("yourFragTag");
// update the list view
f.updateListView();
The tag of your Fragment is set when it is attached to a container layout:
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction().replace(R.id.frameBuy, YourFragment.newInstance(), "yourFragTag").commit();
So when you click your Button, find the Fragment you want to refresh by its tag, and then call your refresh method.
IF you are using a ViewPager, this is how to get the Fragments tag:
/**
* Gets the fragment tag of a fragment at a specific position in the viewpager.
*
* #param pos the pos
* #return the fragment tag
*/
public String getFragmentTag(int pos){
return "android:switcher:"+R.id.yourViewPagerId+":"+pos;
}
You can do it with a few simple steps:
Create a listener interface for component to listen to the button click event from FragmentC. For example:
public interface FragmentCButtonListener {
public void onButtonClicked();
}
Add a method in FragmentC to allow listener registration. FragmentC will keep track of the listener, and call the listener callback as soon as the button is clicked. For example:
public class FragmentC extends Fragment {
FragmentCButtonListener myListener;
public void registerListener (FragmentCButtonListener listener) {
myListener = listener;
}
}
FragmentA should implement FragmentCButtonListener interface, register itself as a listener to FragmentC, and refresh the list view when it receives the callback from FragmentC. For example:
public class FragmentC extends Fragment implements FragementCButtonListener {
FragmentC fragmentC;
public void onCreate() {
fragment = new FragmentC();
fragment.registerListener (this);
}
public void onButtonClicked() {
//refresh the list view
}
}
Please note, I assume the FragmentA has a reference to FragmentC in the sample. If not, just make sure the container class of all fragments registers itself as the listener of FragmentC. The container class can as FragmentA to update listview once it receives callback from FragmentC.
follow these steps
We have two fragments called AddFragmentand ListFragment, and upon adding an item on first fragment you want the updated list be shown on list fragment (what sort of sorcery is this!!!).
Step 1 create the listener interface on class level of AddFragment with a method that is going to be implemented by the other guy (ListFragment ) and create Interface type variable
public class AddFragment extends Fragment{
//listener varriable
//listener
public interface OnCategoryAddedListener{
public void refreshList();
}
private static OnCategoryAddedListener meAddListener;
}
Step 2 create register method on class level of the same AddFragment class and set listenter variable
public class AddFragment extends Fragment{
public void registerListener(OnCategoryAddedListener listener)
{
meAddListener = listener;
}
}
Step 3 upon any event cud be button click or yelling at ur application(that is considered rude event in android :-) ) check for listener object meAddListener variable and call the interface,
in a Shakespeare’s nutshell it means “for thou who implement ye interface and brought the method within ur class shelter, I shall give u my utmost privilege and blessing to …. ”
Step 4 On ListFragment implement the AddFragment’s interface,no turning back just go implement its method. Within that method u just call abracadabra to repopulate ur list or any sort of updatable android view object… and ur done
public class ListFragment extends Fragment implements AddFragment.OnCattegoryAddedListener{
//refer to AddFragment
AddFragment addFragment;
//once the fragment is within the memory scope u instantiate AddFragment
//and register listener with AddFragment context which inherently implement OnCategoryAddedListener
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
categoryAddFragment = new CategoryAddFragment();
categoryAddFragment.registerListener(this);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
fillList();
}
public void fillList() {
ArrayAdapter<String> catArrayAdapter = new ArrayAdapter<>(context,android.R.layout.simple_list_item_1,getItems());
setListAdapter(catArrayAdapter);
}
//le interface method u can count on to refresh ur list content
public void refreshList(){
fillList();
}
check this out for a little more
enjoy the java magic