AppCompatPreferenceActivity created based on accepted answer from http://stackoverflow.com/questions/26509180/no-actionbar-in-preferenceactivity-after-upgrade-to-support-library-v21

AppCompatPreferenceActivity

package com.owncloud.android.ui.activity;



import android.app.Dialog;
import android.content.Context;
import android.content.res.Configuration;
import android.os.Build;
import android.os.Bundle;
import android.preference.Preference;
import android.preference.PreferenceActivity;
import android.preference.PreferenceScreen;
import android.support.annotation.LayoutRes;
import android.support.annotation.Nullable;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatDelegate;
import android.support.v7.widget.AppCompatCheckBox;
import android.support.v7.widget.AppCompatCheckedTextView;
import android.support.v7.widget.AppCompatEditText;
import android.support.v7.widget.AppCompatRadioButton;
import android.support.v7.widget.AppCompatSpinner;
import android.support.v7.widget.Toolbar;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.MenuInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.ListView;

import com.owncloud.android.R;

/**
 * A {@link android.preference.PreferenceActivity} which implements and proxies the necessary calls
 * to be used with AppCompat.
 * <p/>
 * This technique can be used with an {@link android.app.Activity} class, not just
 * {@link android.preference.PreferenceActivity}.
 */
public abstract class AppCompatPreferenceActivity extends PreferenceActivity {

    @Override
    public View onCreateView(String name, Context context, AttributeSet attrs) {
        // Allow super to try and create a view first
        final View result = super.onCreateView(name, context, attrs);
        if (result != null) {
            return result;
        }

        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
            // If we're running pre-L, we need to 'inject' our tint aware Views in place of the
            // standard framework versions
            switch (name) {
                case "EditText":
                    return new AppCompatEditText(this, attrs);
                case "Spinner":
                    return new AppCompatSpinner(this, attrs);
                case "CheckBox":
                    return new AppCompatCheckBox(this, attrs);
                case "RadioButton":
                    return new AppCompatRadioButton(this, attrs);
                case "CheckedTextView":
                    return new AppCompatCheckedTextView(this, attrs);
            }
        }

        return null;
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        Toolbar bar;

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
            LinearLayout root = (LinearLayout) findViewById(android.R.id.list).getParent().getParent().getParent();
            final View view = LayoutInflater.from(this).inflate(R.layout.settings_toolbar, root, false);
            bar = (Toolbar) view.findViewById(R.id.toolbar);
            root.addView(bar, 0); // insert at top
        } else {
            ViewGroup root = (ViewGroup) findViewById(android.R.id.content);
            ListView content = (ListView) root.getChildAt(0);

            root.removeAllViews();

            bar = (Toolbar) LayoutInflater.from(this).inflate(R.layout.settings_toolbar, root, false);


            int height;
            TypedValue tv = new TypedValue();
            if (getTheme().resolveAttribute(R.attr.actionBarSize, tv, true)) {
                height = TypedValue.complexToDimensionPixelSize(tv.data, getResources().getDisplayMetrics());
            }else{
                height = bar.getHeight();
            }

            content.setPadding(0, height, 0, 0);

            root.addView(content);
            root.addView(bar);
        }

        bar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });
    }

    @SuppressWarnings("deprecation")
    @Override
    public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) {
        super.onPreferenceTreeClick(preferenceScreen, preference);

        // If the user has clicked on a preference screen, set up the screen
        if (preference instanceof PreferenceScreen) {
            setUpNestedScreen((PreferenceScreen) preference);
        }

        return false;
    }

    public void setUpNestedScreen(PreferenceScreen preferenceScreen) {
        final Dialog dialog = preferenceScreen.getDialog();

        Toolbar bar;

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
            LinearLayout root = (LinearLayout) dialog.findViewById(android.R.id.list).getParent();
            bar = (Toolbar) LayoutInflater.from(this).inflate(R.layout.settings_toolbar, root, false);
            root.addView(bar, 0); // insert at top
        } else {
            ViewGroup root = (ViewGroup) dialog.findViewById(android.R.id.content);
            ListView content = (ListView) root.getChildAt(0);

            root.removeAllViews();

            bar = (Toolbar) LayoutInflater.from(this).inflate(R.layout.settings_toolbar, root, false);

            int height;
            TypedValue tv = new TypedValue();
            if (getTheme().resolveAttribute(R.attr.actionBarSize, tv, true)) {
                height = TypedValue.complexToDimensionPixelSize(tv.data, getResources().getDisplayMetrics());
            }else{
                height = bar.getHeight();
            }

            content.setPadding(0, height, 0, 0);

            root.addView(content);
            root.addView(bar);
        }

        bar.setTitle(preferenceScreen.getTitle());

        bar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dialog.dismiss();
            }
        });
    }
}

settings_toolbar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.AppBarLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?attr/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        app:navigationContentDescription="@string/abc_action_bar_up_description"
        app:navigationIcon="?attr/homeAsUpIndicator"
        app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
        app:title="@string/actionbar_settings" />
</android.support.design.widget.AppBarLayout>