InstantiationException on Orientation Change when DialogFragment is on the top

Question

I have a DialogFragment defined as inner class in my Fragment class. On Orientation Change even the following exception is poped up:

 Caused by: android.app.Fragment$InstantiationException: Unable to instantiate fragment my.package.fragments.ImportFragment$FailedImportDialog: make sure class name exists, is public, and has an empty constructor that is public
        at android.app.Fragment.instantiate(Fragment.java:585)
        at android.app.FragmentState.instantiate(Fragment.java:96)
        at android.app.FragmentManagerImpl.restoreAllState(FragmentManager.java:1682)
        at android.app.Activity.onCreate(Activity.java:861)
        at my.package.activities.ImportActivity.onCreate(ImportActivity.java:8)
        at android.app.Activity.performCreate(Activity.java:4465)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
        ... 12 more
        Caused by: java.lang.InstantiationException: can't instantiate class my.package.fragments.ImportFragment$FailedImportDialog; no empty constructor
        at java.lang.Class.newInstanceImpl(Native Method)
        at java.lang.Class.newInstance(Class.java:1319)
        at android.app.Fragment.instantiate(Fragment.java:574)

But I do have public constructor:

class FailedImportDialog extends DialogFragment {

        private EditText edtPassword;
        private Button button;

        public FailedImportDialog() { // Here it is!
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.another_password_dialog, container, false);
            edtPassword = (EditText) v.findViewById(R.id.another_password_dialog_et_password);

            getDialog().setTitle(R.string.failed_to_decrypt);

            Button button = (Button) v.findViewById(R.id.another_password_dialog_btn_ok);
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {

            });

            return v;

    }
}

Here is xml:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:orientation="vertical"
              android:padding="10dp">

    <TextView android:id="@+id/another_password_dialog_tv_text"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:text="@string/what_password_did_you_use">
    </TextView>

    <EditText android:id="@+id/another_password_dialog_et_password"
              android:layout_height="wrap_content"
              android:layout_width="match_parent"
              android:inputType="textPassword">
        <requestFocus>
        </requestFocus>
    </EditText>

    <Button android:id="@+id/another_password_dialog_btn_ok"
            android:layout_height="wrap_content"
            android:layout_width="match_parent"
            android:text="OK">
    </Button>

</LinearLayout>

Do you guys know why this exception happens? Thank you!

UPDATE: If I move a class to a separate file there is no such an exception, everything goes smoothly. So the question is - why this exception happens when DialogFragment is an inner class?

Answer 1

try making the inner class static:

public static class FailedImportDialog extends DialogFragment 

I will post more explanation about this in a while. In the meantime, try this and let me know if it works.

Answer 2

Calling setRetainInstance(true) will cause the FragmentManager to save your actual Fragment instance. Instead of destroying and recreating the Fragment, it will just pass the same one along to the new Activity.