How do you show a DialogPreference

• Here is a random layout called some_layout.xml:

  <?xml version="1.0" encoding="utf-8"?>
  <androidx.constraintlayout.widget.ConstraintLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"">
  
      <!-- Some views in here -->
  
  </androidx.constraintlayout.widget.ConstraintLayout>
  

• Here is a class SomeDialog.java that extends DialogPreference:

  import android.content.Context;
  
  import androidx.preference.DialogPreference;
  
  public class SomeDialog extends DialogPreference {
  
  
      public SomeDialog(Context context) {
          super(context);
      }
  
      @Override
      public int getDialogLayoutResource() {
          return R.layout.some_layout;
      }
  }
  

• And here's the preference screen:

  <?xml version="1.0" encoding="utf-8"?>
  <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
  
      <android.example.perappbrightness.SomeDialog
              android:title="@string/rate_app"
              android:summary="@string/rate_summary"
              android:key="rate_app"/>
  
  </PreferenceScreen>
  

Relevant part of crash error. The line at which MainActivty crashes is PreferenceManager.setDefaultValues(this, R.xml.preferences, false);:

java.lang.RuntimeException: Unable to start activity ComponentInfo{android.example.perappbrightness/android.example.perappbrightness.MainActivity}: android.view.InflateException: Binary XML file line #36: Error inflating class android.example.perappbrightness.SomeDialog
    Caused by: android.view.InflateException: Binary XML file line #36: Error inflating class android.example.perappbrightness.SomeDialog
android.example.perappbrightness.MainActivity.onCreate(MainActivity.java:72)

SettingsActivity.java is an untouched. It's from the template of Android Studio.

What am I doing wrong?

First, you need to add more constructors to SomeDialog. The Context constructor is not enough since the Preference will be inflated from xml. Having the following three constructors is usually sufficient:

public SomeDialog(Context context) {
    super(context);
}

public SomeDialog(Context context, AttributeSet attrs) {
    super(context, attrs);
}

public SomeDialog(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
}

In addition to that, the SettingsFragment in your SettingsActivity needs to implement onDisplayPreferenceDialog(Preference preference) to show a custom dialog for the custom Preference.

public static class SettingsFragment extends PreferenceFragmentCompat {
    @Override
    public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
        setPreferencesFromResource(R.xml.root_preferences, rootKey);
    }

    @Override
    public void onDisplayPreferenceDialog(Preference preference) {
        if (preference instanceof SomeDialog) {
            MyDialogFragment dialogFragment = new MyDialogFragment();
            Bundle b = new Bundle();
            b.putString(MyDialogFragment.KEY, preference.getKey());
            b.putInt(MyDialogFragment.KEY_LAYOUT_RES_ID,  ((SomeDialog) preference).getDialogLayoutResource());

            dialogFragment.setArguments(b);
            dialogFragment.setTargetFragment(this, 0);
            dialogFragment.show(getFragmentManager(), null);
        } else super.onDisplayPreferenceDialog(preference);
    }
}

And, last not least, you also have to provide the custom dialog itself. This is done via a class extending DialogFragment.

My very simple DialogFragment has a TextView inside a FrameLayout, just to show it works

MyDialogFragment code:

public class MyDialogFragment extends DialogFragment {

    public static final String KEY = "key";
    public static final String KEY_LAYOUT_RES_ID = "resid";


    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
                return inflater.inflate(requireArguments().getInt(KEY_LAYOUT_RES_ID), container, false);

    }


    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        TextView textView = view.findViewById(R.id.textView);
        textView.setText(requireArguments().getString(KEY));
    }
}