问题
Question: How does one create a callback from a DialogFragment to another Fragment. In my case, the Activity involved should be completely unaware of the DialogFragment.
Consider I have
public class MyFragment extends Fragment implements OnClickListener
Then at some point I could do
DialogFragment dialogFrag = MyDialogFragment.newInstance(this);
dialogFrag.show(getFragmentManager, null);
Where MyDialogFragment looks like
protected OnClickListener listener;
public static DialogFragment newInstance(OnClickListener listener) {
DialogFragment fragment = new DialogFragment();
fragment.listener = listener;
return fragment;
}
But there is no guarantee that the listener will be around if the DialogFragment pauses and resumes through its lifecycle. The only guarantees in a Fragment are those passed in through a Bundle via setArguments and getArguments.
There is a way to reference the activity if it should be the listener:
public Dialog onCreateDialog(Bundle bundle) {
OnClickListener listener = (OnClickListener) getActivity();
....
return new AlertDialog.Builder(getActivity())
........
.setAdapter(adapter, listener)
.create();
}
But I don\'t want the Activity to listen for events, I need a Fragment. Really, it could be any Java object that implements OnClickListener.
Consider the concrete example of a Fragment that presents an AlertDialog via DialogFragment. It has Yes/No buttons. How can I send these button presses back to the Fragment that created it?
回答1:
Activity involved is completely unaware of the DialogFragment.
Fragment class:
public class MyFragment extends Fragment {
int mStackLevel = 0;
public static final int DIALOG_FRAGMENT = 1;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState != null) {
mStackLevel = savedInstanceState.getInt("level");
}
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("level", mStackLevel);
}
void showDialog(int type) {
mStackLevel++;
FragmentTransaction ft = getActivity().getFragmentManager().beginTransaction();
Fragment prev = getActivity().getFragmentManager().findFragmentByTag("dialog");
if (prev != null) {
ft.remove(prev);
}
ft.addToBackStack(null);
switch (type) {
case DIALOG_FRAGMENT:
DialogFragment dialogFrag = MyDialogFragment.newInstance(123);
dialogFrag.setTargetFragment(this, DIALOG_FRAGMENT);
dialogFrag.show(getFragmentManager().beginTransaction(), "dialog");
break;
}
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
switch(requestCode) {
case DIALOG_FRAGMENT:
if (resultCode == Activity.RESULT_OK) {
// After Ok code.
} else if (resultCode == Activity.RESULT_CANCELED){
// After Cancel code.
}
break;
}
}
}
}
DialogFragment class:
public class MyDialogFragment extends DialogFragment {
public static MyDialogFragment newInstance(int num){
MyDialogFragment dialogFragment = new MyDialogFragment();
Bundle bundle = new Bundle();
bundle.putInt("num", num);
dialogFragment.setArguments(bundle);
return dialogFragment;
}
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
return new AlertDialog.Builder(getActivity())
.setTitle(R.string.ERROR)
.setIcon(android.R.drawable.ic_dialog_alert)
.setPositiveButton(R.string.ok_button,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
getTargetFragment().onActivityResult(getTargetRequestCode(), Activity.RESULT_OK, getActivity().getIntent());
}
}
)
.setNegativeButton(R.string.cancel_button, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
getTargetFragment().onActivityResult(getTargetRequestCode(), Activity.RESULT_CANCELED, getActivity().getIntent());
}
})
.create();
}
}
回答2:
TargetFragment solution doesn't seem the best option for dialog fragments because it may create IllegalStateException after application get destroyed and recreated. In this case FragmentManager couldn't find the target fragment and you will get an IllegalStateException with a message like this:
"Fragment no longer exists for key android:target_state: index 1"
It seems like Fragment#setTargetFragment() is not meant for communication between a child and parent Fragment, but rather for communication between sibling-Fragments.
So alternative way is to create dialog fragments like this by using the ChildFragmentManager of the parent fragment, rather then using the activities FragmentManager:
dialogFragment.show(ParentFragment.this.getChildFragmentManager(), "dialog_fragment");
And by using an Interface, in onCreate method of the DialogFragment you can get the parent fragment:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
try {
callback = (Callback) getParentFragment();
} catch (ClassCastException e) {
throw new ClassCastException("Calling fragment must implement Callback interface");
}
}
Only thing left is to call your callback method after these steps.
For more information about the issue, you can check out the link: https://code.google.com/p/android/issues/detail?id=54520
回答3:
Maybe a bit late, but may help other people with the same question like I did.
You can use setTargetFragment on Dialog before showing, and in dialog you can call getTargetFragment to get the reference.
回答4:
I followed this simple steps to do this stuff.
- Create interface like
DialogFragmentCallbackInterfacewith some method likecallBackMethod(Object data). Which you would calling to pass data. - Now you can implement
DialogFragmentCallbackInterfaceinterface in your fragment likeMyFragment implements DialogFragmentCallbackInterface At time of
DialogFragmentcreation set your invoking fragmentMyFragmentas target fragment who createdDialogFragmentusemyDialogFragment.setTargetFragment(this, 0)check setTargetFragment (Fragment fragment, int requestCode)MyDialogFragment dialogFrag = new MyDialogFragment(); dialogFrag.setTargetFragment(this, 1);Get your target fragment object into your
DialogFragmentby callinggetTargetFragment()and cast it toDialogFragmentCallbackInterface.Now you can use this interface to send data to your fragment.DialogFragmentCallbackInterface callback = (DialogFragmentCallbackInterface) getTargetFragment(); callback.callBackMethod(Object data);That's it all done! just make sure you have implemented this interface in your fragment.
回答5:
The Communicating with Other Fragments guide says the Fragments should communicate through the associated Activity.
Often you will want one Fragment to communicate with another, for example to change the content based on a user event. All Fragment-to-Fragment communication is done through the associated Activity. Two Fragments should never communicate directly.
回答6:
You should define an interface in your fragment class and implement that interface in its parent activity. The details are outlined here http://developer.android.com/guide/components/fragments.html#EventCallbacks . The code would look similar to:
Fragment:
public static class FragmentA extends DialogFragment {
OnArticleSelectedListener mListener;
// Container Activity must implement this interface
public interface OnArticleSelectedListener {
public void onArticleSelected(Uri articleUri);
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mListener = (OnArticleSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString() + " must implement OnArticleSelectedListener");
}
}
}
Activity:
public class MyActivity extends Activity implements OnArticleSelectedListener{
...
@Override
public void onArticleSelected(Uri articleUri){
}
...
}
回答7:
I was facing a similar problem. The solution that I found out was :
Declare an interface in your DialogFragment just like James McCracken has explained above.
Implement the interface in your activity (not fragment! That is not a good practice).
From the callback method in your activity, call a required public function in your fragment which does the job that you want to do.
Thus, it becomes a two-step process : DialogFragment -> Activity and then Activity -> Fragment
回答8:
The correct way of setting a listener to a fragment is by setting it when it is attached. The problem I had was that onAttachFragment() was never called. After some investigation I realised that I had been using getFragmentManager instead of getChildFragmentManager
Here is how I do it:
MyDialogFragment dialogFragment = MyDialogFragment.newInstance("title", "body");
dialogFragment.show(getChildFragmentManager(), "SOME_DIALOG");
Attach it in onAttachFragment:
@Override
public void onAttachFragment(Fragment childFragment) {
super.onAttachFragment(childFragment);
if (childFragment instanceof MyDialogFragment) {
MyDialogFragment dialog = (MyDialogFragment) childFragment;
dialog.setListener(new MyDialogFragment.Listener() {
@Override
public void buttonClicked() {
}
});
}
}
回答9:
I am getting result to Fragment DashboardLiveWall(calling fragment) from Fragment LiveWallFilterFragment(receiving fragment) Like this...
LiveWallFilterFragment filterFragment = LiveWallFilterFragment.newInstance(DashboardLiveWall.this ,"");
getActivity().getSupportFragmentManager().beginTransaction().
add(R.id.frame_container, filterFragment).addToBackStack("").commit();
where
public static LiveWallFilterFragment newInstance(Fragment targetFragment,String anyDummyData) {
LiveWallFilterFragment fragment = new LiveWallFilterFragment();
Bundle args = new Bundle();
args.putString("dummyKey",anyDummyData);
fragment.setArguments(args);
if(targetFragment != null)
fragment.setTargetFragment(targetFragment, KeyConst.LIVE_WALL_FILTER_RESULT);
return fragment;
}
setResult back to calling fragment like
private void setResult(boolean flag) {
if (getTargetFragment() != null) {
Bundle bundle = new Bundle();
bundle.putBoolean("isWorkDone", flag);
Intent mIntent = new Intent();
mIntent.putExtras(bundle);
getTargetFragment().onActivityResult(getTargetRequestCode(),
Activity.RESULT_OK, mIntent);
}
}
onActivityResult
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == Activity.RESULT_OK) {
if (requestCode == KeyConst.LIVE_WALL_FILTER_RESULT) {
Bundle bundle = data.getExtras();
if (bundle != null) {
boolean isReset = bundle.getBoolean("isWorkDone");
if (isReset) {
} else {
}
}
}
}
}
回答10:
Updated:
I made a library based on my gist code that generates those casting for you by using @CallbackFragment and @Callback.
https://github.com/zeroarst/callbackfragment.
And the example give you the example that send a callback from a fragment to another fragment.
Old answer:
I made a BaseCallbackFragment and annotation @FragmentCallback. It currently extends Fragment, you can change it to DialogFragment and will work. It checks the implementations with the following order: getTargetFragment() > getParentFragment() > context (activity).
Then you just need to extend it and declare your interfaces in your fragment and give it the annotation, and the base fragment will do the rest. The annotation also has a parameter mandatory for you to determine whether you want to force the fragment to implement the callback.
public class EchoFragment extends BaseCallbackFragment {
private FragmentInteractionListener mListener;
@FragmentCallback
public interface FragmentInteractionListener {
void onEcho(EchoFragment fragment, String echo);
}
}
https://gist.github.com/zeroarst/3b3f32092d58698a4568cdb0919c9a93
回答11:
According to the official documentation:
Fragment#setTargetFragment
Optional target for this fragment. This may be used, for example, if this fragment is being started by another, and when done wants to give a result back to the first. The target set here is retained across instances via FragmentManager#putFragment.
Fragment#getTargetFragment
Return the target fragment set by setTargetFragment(Fragment, int).
So you can do this:
// In your fragment
public class MyFragment extends Fragment implements OnClickListener {
private void showDialog() {
DialogFragment dialogFrag = MyDialogFragment.newInstance(this);
// Add this
dialogFrag.setTargetFragment(this, 0);
dialogFrag.show(getFragmentManager, null);
}
...
}
// then
public class MyialogFragment extends DialogFragment {
@Override
public void onAttach(Context context) {
super.onAttach(context);
// Then get it
Fragment fragment = getTargetFragment();
if (fragment instanceof OnClickListener) {
listener = (OnClickListener) fragment;
} else {
throw new RuntimeException("you must implement OnClickListener");
}
}
...
}
回答12:
I solved this in an elegant way with RxAndroid. Receive an observer in the constructor of the DialogFragment and suscribe to observable and push the value when the callback being called. Then, in your Fragment create an inner class of the Observer, create an instance and pass it in the constructor of the DialogFragment. I used WeakReference in the observer to avoid memory leaks. Here is the code:
BaseDialogFragment.java
import java.lang.ref.WeakReference;
import io.reactivex.Observer;
public class BaseDialogFragment<O> extends DialogFragment {
protected WeakReference<Observer<O>> observerRef;
protected BaseDialogFragment(Observer<O> observer) {
this.observerRef = new WeakReference<>(observer);
}
protected Observer<O> getObserver() {
return observerRef.get();
}
}
DatePickerFragment.java
public class DatePickerFragment extends BaseDialogFragment<Integer>
implements DatePickerDialog.OnDateSetListener {
public DatePickerFragment(Observer<Integer> observer) {
super(observer);
}
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// Use the current date as the default date in the picker
final Calendar c = Calendar.getInstance();
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH);
int day = c.get(Calendar.DAY_OF_MONTH);
// Create a new instance of DatePickerDialog and return it
return new DatePickerDialog(getActivity(), this, year, month, day);
}
@Override
public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) {
if (getObserver() != null) {
Observable.just(month).subscribe(getObserver());
}
}
}
MyFragment.java
//Show the dialog fragment when the button is clicked
@OnClick(R.id.btn_date)
void onDateClick() {
DialogFragment newFragment = new DatePickerFragment(new OnDateSelectedObserver());
newFragment.show(getFragmentManager(), "datePicker");
}
//Observer inner class
private class OnDateSelectedObserver implements Observer<Integer> {
@Override
public void onSubscribe(Disposable d) {
}
@Override
public void onNext(Integer integer) {
//Here you invoke the logic
}
@Override
public void onError(Throwable e) {
}
@Override
public void onComplete() {
}
}
You can see the source code here: https://github.com/andresuarezz26/carpoolingapp
来源：https://stackoverflow.com/questions/13733304/callback-to-a-fragment-from-a-dialogfragment