diff --git a/app/src/main/java/eu/kanade/mangafeed/data/preference/PreferencesHelper.java b/app/src/main/java/eu/kanade/mangafeed/data/preference/PreferencesHelper.java
index 3b4d4328e..8197163f4 100644
--- a/app/src/main/java/eu/kanade/mangafeed/data/preference/PreferencesHelper.java
+++ b/app/src/main/java/eu/kanade/mangafeed/data/preference/PreferencesHelper.java
@@ -57,6 +57,14 @@ public class PreferencesHelper {
         return rxPrefs.getBoolean(getKey(R.string.pref_keep_screen_on_key), true);
     }
 
+    public Preference<Boolean> customBrightness() {
+        return rxPrefs.getBoolean(getKey(R.string.pref_custom_brightness_key), false);
+    }
+
+    public Preference<Float> customBrightnessValue() {
+        return rxPrefs.getFloat(getKey(R.string.pref_custom_brightness_value_key), 0F);
+    }
+
     public int getDefaultViewer() {
         return Integer.parseInt(prefs.getString(getKey(R.string.pref_default_viewer_key), "1"));
     }
diff --git a/app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderActivity.java b/app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderActivity.java
index a54154c76..acfa8f21e 100644
--- a/app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderActivity.java
+++ b/app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderActivity.java
@@ -36,6 +36,7 @@ import eu.kanade.mangafeed.ui.reader.viewer.webtoon.WebtoonReader;
 import eu.kanade.mangafeed.util.ToastUtil;
 import icepick.Icepick;
 import nucleus.factory.RequiresPresenter;
+import rx.Subscription;
 import rx.subscriptions.CompositeSubscription;
 
 @RequiresPresenter(ReaderPresenter.class)
@@ -52,6 +53,7 @@ public class ReaderActivity extends BaseRxActivity<ReaderPresenter> {
 
     private int uiFlags;
     private CompositeSubscription subscriptions;
+    private Subscription customBrightnessSubscription;
 
     private static final int LEFT_TO_RIGHT = 1;
     private static final int RIGHT_TO_LEFT = 2;
@@ -166,6 +168,10 @@ public class ReaderActivity extends BaseRxActivity<ReaderPresenter> {
         subscriptions.add(preferences.keepScreenOn()
                 .asObservable()
                 .subscribe(this::setKeepScreenOn));
+
+        subscriptions.add(preferences.customBrightness()
+                .asObservable()
+                .subscribe(this::setCustomBrightness));
     }
 
     private void setOrientation(boolean locked) {
@@ -205,6 +211,24 @@ public class ReaderActivity extends BaseRxActivity<ReaderPresenter> {
         }
     }
 
+    private void setCustomBrightness(boolean enabled) {
+        if (enabled) {
+            subscriptions.add(customBrightnessSubscription = preferences.customBrightnessValue()
+                    .asObservable()
+                    .subscribe(this::setCustomBrightnessValue));
+        } else {
+            if (customBrightnessSubscription != null)
+                subscriptions.remove(customBrightnessSubscription);
+            setCustomBrightnessValue(-1);
+        }
+    }
+
+    private void setCustomBrightnessValue(float value) {
+        WindowManager.LayoutParams layout = getWindow().getAttributes();
+        layout.screenBrightness = value;
+        getWindow().setAttributes(layout);
+    }
+
     private void setStatusBarVisibility(boolean hidden) {
         createUiHideFlags(hidden);
         setSystemUiVisibility();
diff --git a/app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderMenu.java b/app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderMenu.java
index 32f7f8851..fdf217454 100644
--- a/app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderMenu.java
+++ b/app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderMenu.java
@@ -40,12 +40,14 @@ public class ReaderMenu {
     @Bind(R.id.lock_orientation) ImageButton lockOrientation;
     @Bind(R.id.reader_selector) ImageButton readerSelector;
     @Bind(R.id.reader_extra_settings) ImageButton extraSettings;
+    @Bind(R.id.reader_brightness) ImageButton brightnessSettings;
 
     private ReaderActivity activity;
     private PreferencesHelper preferences;
 
     @State boolean showing;
-    private PopupWindow popupWindow;
+    private PopupWindow settingsPopup;
+    private PopupWindow brightnessPopup;
 
     private DecimalFormat decimalFormat;
 
@@ -99,7 +101,8 @@ public class ReaderMenu {
         Animation bottomMenuAnimation = AnimationUtils.loadAnimation(activity, R.anim.exit_to_bottom);
         bottomMenu.startAnimation(bottomMenuAnimation);
 
-        popupWindow.dismiss();
+        settingsPopup.dismiss();
+        brightnessPopup.dismiss();
 
         showing = false;
     }
@@ -152,14 +155,26 @@ public class ReaderMenu {
 
         // Extra settings menu
         final View popupView = activity.getLayoutInflater().inflate(R.layout.reader_popup, null);
-        popupWindow = new SettingsPopupWindow(popupView);
+        settingsPopup = new SettingsPopupWindow(popupView);
 
         extraSettings.setOnClickListener(v -> {
-            if (!popupWindow.isShowing())
-                popupWindow.showAtLocation(extraSettings,
+            if (!settingsPopup.isShowing())
+                settingsPopup.showAtLocation(extraSettings,
                         Gravity.BOTTOM | Gravity.RIGHT, 0, bottomMenu.getHeight());
             else
-                popupWindow.dismiss();
+                settingsPopup.dismiss();
+        });
+
+        // Brightness popup
+        final View brightnessView = activity.getLayoutInflater().inflate(R.layout.reader_brightness, null);
+        brightnessPopup = new BrightnessPopupWindow(brightnessView);
+
+        brightnessSettings.setOnClickListener(v -> {
+            if (!brightnessPopup.isShowing())
+                brightnessPopup.showAtLocation(brightnessSettings,
+                        Gravity.BOTTOM | Gravity.LEFT, 0, bottomMenu.getHeight());
+            else
+                brightnessPopup.dismiss();
         });
     }
 
@@ -208,7 +223,37 @@ public class ReaderMenu {
 
             keepScreenOn.setOnCheckedChangeListener((view, isChecked) ->
                     preferences.keepScreenOn().set(isChecked));
+        }
 
+    }
+
+    class BrightnessPopupWindow extends PopupWindow {
+
+        @Bind(R.id.custom_brightness) CheckBox customBrightness;
+        @Bind(R.id.brightness_seekbar) SeekBar brightnessSeekbar;
+
+        public BrightnessPopupWindow(View view) {
+            super(view, LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
+            setAnimationStyle(R.style.reader_brightness_popup_animation);
+            ButterKnife.bind(this, view);
+            initializePopupMenu();
+        }
+
+        private void initializePopupMenu() {
+            subscriptions.add(preferences.customBrightness()
+                    .asObservable()
+                    .subscribe(isEnabled -> {
+                        customBrightness.setChecked(isEnabled);
+                        brightnessSeekbar.setEnabled(isEnabled);
+                    }));
+
+            customBrightness.setOnCheckedChangeListener((view, isChecked) ->
+                    preferences.customBrightness().set(isChecked));
+
+            brightnessSeekbar.setMax(100);
+            brightnessSeekbar.setProgress(Math.round(
+                    preferences.customBrightnessValue().get() * brightnessSeekbar.getMax()));
+            brightnessSeekbar.setOnSeekBarChangeListener(new BrightnessSeekBarChangeListener());
         }
 
     }
@@ -229,6 +274,26 @@ public class ReaderMenu {
         public void onStopTrackingTouch(SeekBar seekBar) {}
     }
 
+    class BrightnessSeekBarChangeListener implements SeekBar.OnSeekBarChangeListener {
+
+        @Override
+        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
+            if (fromUser) {
+                preferences.customBrightnessValue().set((float) progress / seekBar.getMax());
+            }
+        }
+
+        @Override
+        public void onStartTrackingTouch(SeekBar seekBar) {
+
+        }
+
+        @Override
+        public void onStopTrackingTouch(SeekBar seekBar) {
+
+        }
+    }
+
     class HideMenuAnimationListener implements Animation.AnimationListener {
 
         @Override
diff --git a/app/src/main/java/eu/kanade/mangafeed/ui/reader/viewer/vertical/VerticalReader.java b/app/src/main/java/eu/kanade/mangafeed/ui/reader/viewer/vertical/VerticalReader.java
index 29ec85876..680195bc7 100644
--- a/app/src/main/java/eu/kanade/mangafeed/ui/reader/viewer/vertical/VerticalReader.java
+++ b/app/src/main/java/eu/kanade/mangafeed/ui/reader/viewer/vertical/VerticalReader.java
@@ -12,6 +12,7 @@ import eu.kanade.mangafeed.data.source.model.Page;
 import eu.kanade.mangafeed.ui.reader.ReaderActivity;
 import eu.kanade.mangafeed.ui.reader.viewer.base.BaseReader;
 import eu.kanade.mangafeed.ui.reader.viewer.common.ViewPagerReaderAdapter;
+import rx.Subscription;
 
 public class VerticalReader extends BaseReader {
 
@@ -19,11 +20,17 @@ public class VerticalReader extends BaseReader {
 
     private ViewPagerReaderAdapter adapter;
 
+    private boolean transitions;
+    private Subscription transitionsSubscription;
+
     public VerticalReader(ReaderActivity activity) {
         super(activity);
         activity.getLayoutInflater().inflate(R.layout.reader_vertical, container);
         ButterKnife.bind(this, container);
 
+        transitionsSubscription = activity.getPreferences().enableTransitions().asObservable()
+                .subscribe(value -> transitions = value);
+
         viewPager.setOffscreenPageLimit(3);
         viewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
             @Override
@@ -32,6 +39,33 @@ public class VerticalReader extends BaseReader {
                 updatePageNumber();
             }
         });
+        viewPager.setOnChapterBoundariesOutListener(new VerticalViewPager.OnChapterBoundariesOutListener() {
+            @Override
+            public void onFirstPageOutEvent() {
+                requestPreviousChapter();
+            }
+
+            @Override
+            public void onLastPageOutEvent() {
+                requestNextChapter();
+            }
+        });
+        viewPager.setOnChapterSingleTapListener(new VerticalViewPager.OnChapterSingleTapListener() {
+            @Override
+            public void onCenterTap() {
+                activity.onCenterSingleTap();
+            }
+
+            @Override
+            public void onLeftSideTap() {
+                viewPager.setCurrentItem(viewPager.getCurrentItem() - 1, transitions);
+            }
+
+            @Override
+            public void onRightSideTap() {
+                viewPager.setCurrentItem(viewPager.getCurrentItem() + 1, transitions);
+            }
+        });
     }
 
     @Override
@@ -41,7 +75,7 @@ public class VerticalReader extends BaseReader {
 
     @Override
     public void setSelectedPage(int pageNumber) {
-        viewPager.setCurrentItem(getCurrentPageIndex(pageNumber));
+        viewPager.setCurrentItem(getCurrentPageIndex(pageNumber), false);
     }
 
     @Override
@@ -53,6 +87,11 @@ public class VerticalReader extends BaseReader {
 
     @Override
     public boolean onImageTouch(MotionEvent motionEvent) {
-        return true;
+        return viewPager.onImageTouch(motionEvent);
+    }
+
+    @Override
+    public void destroy() {
+        transitionsSubscription.unsubscribe();
     }
 }
diff --git a/app/src/main/java/eu/kanade/mangafeed/ui/reader/viewer/vertical/VerticalViewPager.java b/app/src/main/java/eu/kanade/mangafeed/ui/reader/viewer/vertical/VerticalViewPager.java
index a263a867e..3d5a7afab 100644
--- a/app/src/main/java/eu/kanade/mangafeed/ui/reader/viewer/vertical/VerticalViewPager.java
+++ b/app/src/main/java/eu/kanade/mangafeed/ui/reader/viewer/vertical/VerticalViewPager.java
@@ -3,17 +3,140 @@ package eu.kanade.mangafeed.ui.reader.viewer.vertical;
 import android.content.Context;
 import android.util.AttributeSet;
 import android.view.GestureDetector;
+import android.view.MotionEvent;
 
 public class VerticalViewPager extends fr.castorflex.android.verticalviewpager.VerticalViewPager {
 
     private GestureDetector gestureDetector;
 
+    private OnChapterBoundariesOutListener mOnChapterBoundariesOutListener;
+    private OnChapterSingleTapListener mOnChapterSingleTapListener;
+
+    private static final float LEFT_REGION = 0.33f;
+    private static final float RIGHT_REGION = 0.66f;
+    private static final float SWIPE_TOLERANCE = 0.25f;
+    private float startDragY;
+
     public VerticalViewPager(Context context, AttributeSet attrs) {
         super(context, attrs);
         gestureDetector = new GestureDetector(getContext(), new ReaderViewGestureListener());
     }
 
+    @Override
+    public boolean onInterceptTouchEvent(MotionEvent ev) {
+        try {
+            gestureDetector.onTouchEvent(ev);
+
+            if ((ev.getAction() & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_DOWN) {
+                if (this.getCurrentItem() == 0 || this.getCurrentItem() == this.getAdapter().getCount() - 1) {
+                    startDragY = ev.getY();
+                }
+            }
+
+            return super.onInterceptTouchEvent(ev);
+        } catch (IllegalArgumentException e) {
+            // Do Nothing.
+        }
+
+        return false;
+    }
+
+    @Override
+    public boolean onTouchEvent(MotionEvent ev) {
+        try {
+            if (mOnChapterBoundariesOutListener != null) {
+                if (this.getCurrentItem() == 0) {
+                    if ((ev.getAction() & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_UP) {
+                        float displacement = ev.getY() - startDragY;
+
+                        if (ev.getY() > startDragY && displacement > getHeight() * SWIPE_TOLERANCE) {
+                            mOnChapterBoundariesOutListener.onFirstPageOutEvent();
+                            return true;
+                        }
+
+                        startDragY = 0;
+                    }
+                } else if (this.getCurrentItem() == this.getAdapter().getCount() - 1) {
+                    if ((ev.getAction() & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_UP) {
+                        float displacement = startDragY - ev.getY();
+
+                        if (ev.getY() < startDragY && displacement > getHeight() * SWIPE_TOLERANCE) {
+                            mOnChapterBoundariesOutListener.onLastPageOutEvent();
+                            return true;
+                        }
+
+                        startDragY = 0;
+                    }
+                }
+            }
+
+            return super.onTouchEvent(ev);
+        } catch (IllegalArgumentException e) {
+            // Do Nothing.
+        }
+
+        return false;
+    }
+
+    public boolean onImageTouch(MotionEvent event) {
+        return gestureDetector.onTouchEvent(event);
+    }
+
+    public interface OnChapterBoundariesOutListener {
+        void onFirstPageOutEvent();
+
+        void onLastPageOutEvent();
+    }
+
+    public interface OnChapterSingleTapListener {
+        void onCenterTap();
+        void onLeftSideTap();
+        void onRightSideTap();
+    }
+
+    public void setOnChapterBoundariesOutListener(OnChapterBoundariesOutListener onChapterBoundariesOutListener) {
+        mOnChapterBoundariesOutListener = onChapterBoundariesOutListener;
+    }
+
+    public void setOnChapterSingleTapListener(OnChapterSingleTapListener onChapterSingleTapListener) {
+        mOnChapterSingleTapListener = onChapterSingleTapListener;
+    }
+
     private class ReaderViewGestureListener extends GestureDetector.SimpleOnGestureListener {
-        // TODO
+
+        @Override
+        public boolean onSingleTapConfirmed(MotionEvent e) {
+            final int position = getCurrentItem();
+            final float positionX = e.getX();
+
+            if (positionX < getWidth() * LEFT_REGION) {
+                if (position != 0) {
+                    if (mOnChapterSingleTapListener != null) {
+                        mOnChapterSingleTapListener.onLeftSideTap();
+                    }
+                } else {
+                    if (mOnChapterBoundariesOutListener != null) {
+                        mOnChapterBoundariesOutListener.onFirstPageOutEvent();
+                    }
+                }
+            } else if (positionX > getWidth() * RIGHT_REGION) {
+                if (position != getAdapter().getCount() - 1) {
+                    if (mOnChapterSingleTapListener != null) {
+                        mOnChapterSingleTapListener.onRightSideTap();
+                    }
+                } else {
+                    if (mOnChapterBoundariesOutListener != null) {
+                        mOnChapterBoundariesOutListener.onLastPageOutEvent();
+                    }
+                }
+            } else {
+                if (mOnChapterSingleTapListener != null) {
+                    mOnChapterSingleTapListener.onCenterTap();
+                }
+            }
+
+            return true;
+        }
+
     }
 }
diff --git a/app/src/main/res/drawable-hdpi/ic_brightness_high.png b/app/src/main/res/drawable-hdpi/ic_brightness_high.png
new file mode 100644
index 000000000..d9276d779
Binary files /dev/null and b/app/src/main/res/drawable-hdpi/ic_brightness_high.png differ
diff --git a/app/src/main/res/drawable-ldpi/ic_brightness_high.png b/app/src/main/res/drawable-ldpi/ic_brightness_high.png
new file mode 100644
index 000000000..c2e127e65
Binary files /dev/null and b/app/src/main/res/drawable-ldpi/ic_brightness_high.png differ
diff --git a/app/src/main/res/drawable-mdpi/ic_brightness_high.png b/app/src/main/res/drawable-mdpi/ic_brightness_high.png
new file mode 100644
index 000000000..ad2327817
Binary files /dev/null and b/app/src/main/res/drawable-mdpi/ic_brightness_high.png differ
diff --git a/app/src/main/res/drawable-xhdpi/ic_brightness_high.png b/app/src/main/res/drawable-xhdpi/ic_brightness_high.png
new file mode 100644
index 000000000..77ca8377a
Binary files /dev/null and b/app/src/main/res/drawable-xhdpi/ic_brightness_high.png differ
diff --git a/app/src/main/res/drawable-xxhdpi/ic_brightness_high.png b/app/src/main/res/drawable-xxhdpi/ic_brightness_high.png
new file mode 100644
index 000000000..4da536ced
Binary files /dev/null and b/app/src/main/res/drawable-xxhdpi/ic_brightness_high.png differ
diff --git a/app/src/main/res/drawable-xxxhdpi/ic_brightness_high.png b/app/src/main/res/drawable-xxxhdpi/ic_brightness_high.png
new file mode 100644
index 000000000..6c893afc1
Binary files /dev/null and b/app/src/main/res/drawable-xxxhdpi/ic_brightness_high.png differ
diff --git a/app/src/main/res/layout/reader_brightness.xml b/app/src/main/res/layout/reader_brightness.xml
new file mode 100644
index 000000000..b25426223
--- /dev/null
+++ b/app/src/main/res/layout/reader_brightness.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:orientation="vertical"
+    android:layout_width="wrap_content"
+    android:layout_height="match_parent"
+    android:background="#333333"
+    android:paddingRight="10dp"
+    android:paddingLeft="5dp"
+    android:paddingTop="5dp"
+    android:paddingBottom="5dp">
+
+    <CheckBox
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        style="@style/grey_text"
+        android:text="@string/pref_custom_brightness"
+        android:id="@+id/custom_brightness" />
+
+    <SeekBar
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:id="@+id/brightness_seekbar" />
+</LinearLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout/reader_menu.xml b/app/src/main/res/layout/reader_menu.xml
index e4c1351c3..25c311af8 100644
--- a/app/src/main/res/layout/reader_menu.xml
+++ b/app/src/main/res/layout/reader_menu.xml
@@ -72,14 +72,16 @@
                 android:layout_width="0dp"
                 android:layout_height="match_parent"
                 android:layout_weight="1"
-                android:id="@+id/lock_orientation"
-                android:src="@drawable/ic_screen_rotation"
+                android:id="@+id/reader_brightness"
+                android:src="@drawable/ic_brightness_high"
                 android:layout_gravity="center_vertical"
                 android:background="?android:selectableItemBackground" />
             <ImageButton
                 android:layout_width="0dp"
                 android:layout_height="match_parent"
                 android:layout_weight="1"
+                android:id="@+id/lock_orientation"
+                android:src="@drawable/ic_screen_rotation"
                 android:layout_gravity="center_vertical"
                 android:background="?android:selectableItemBackground" />
             <ImageButton
diff --git a/app/src/main/res/values/keys.xml b/app/src/main/res/values/keys.xml
index a7690dc6d..e4a419841 100644
--- a/app/src/main/res/values/keys.xml
+++ b/app/src/main/res/values/keys.xml
@@ -10,6 +10,8 @@
     <string name="pref_enable_transitions_key">pref_enable_transitions_key</string>
     <string name="pref_show_page_number_key">pref_show_page_number_key</string>
     <string name="pref_keep_screen_on_key">pref_keep_screen_on_key</string>
+    <string name="pref_custom_brightness_key">pref_custom_brightness_key</string>
+    <string name="pref_custom_brightness_value_key">pref_custom_brightness_value_key</string>
 
     <string name="pref_download_directory_key">pref_download_directory_key</string>
     <string name="pref_download_threads_key">pref_download_threads_key</string>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 9d1c93f78..79b60a25c 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -28,15 +28,16 @@
 
       <!-- Reader section -->
     <string name="pref_hide_status_bar">Hide status bar</string>
+    <string name="pref_lock_orientation">Lock orientation</string>
+    <string name="pref_enable_transitions">Enable transitions</string>
+    <string name="pref_show_page_number">Show page number</string>
+    <string name="pref_custom_brightness">Use custom brightness</string>
     <string name="pref_viewer_type">Default viewer</string>
     <string name="default_viewer">Default</string>
     <string name="left_to_right_viewer">Left to right</string>
     <string name="right_to_left_viewer">Right to left</string>
     <string name="vertical_viewer">Vertical</string>
     <string name="webtoon_viewer">Webtoon (experimental)</string>
-    <string name="pref_lock_orientation">Lock orientation</string>
-    <string name="pref_enable_transitions">Enable transitions</string>
-    <string name="pref_show_page_number">Show page number</string>
 
       <!-- Downloads section -->
     <string name="pref_download_directory">Downloads directory</string>
diff --git a/app/src/main/res/values/styles.xml b/app/src/main/res/values/styles.xml
index 6297d281d..146bcf89e 100644
--- a/app/src/main/res/values/styles.xml
+++ b/app/src/main/res/values/styles.xml
@@ -103,6 +103,10 @@
         <item name="android:windowEnterAnimation">@anim/enter_from_right</item>
         <item name="android:windowExitAnimation">@anim/exit_to_right</item>
     </style>
+    <style name="reader_brightness_popup_animation">
+        <item name="android:windowEnterAnimation">@anim/enter_from_left</item>
+        <item name="android:windowExitAnimation">@anim/exit_to_left</item>
+    </style>
     <style name="grey_text">
         <item name="android:textColor">#e0e0e0</item>
     </style>
diff --git a/app/src/main/res/xml/pref_reader.xml b/app/src/main/res/xml/pref_reader.xml
index aa0da21f5..60a8e07c4 100644
--- a/app/src/main/res/xml/pref_reader.xml
+++ b/app/src/main/res/xml/pref_reader.xml
@@ -17,6 +17,10 @@
         android:key="@string/pref_show_page_number_key"
         android:defaultValue="true" />
 
+    <CheckBoxPreference android:title="@string/pref_custom_brightness"
+        android:key="@string/pref_custom_brightness_key"
+        android:defaultValue="false" />
+
     <ListPreference android:title="@string/pref_viewer_type"
         android:key="@string/pref_default_viewer_key"
         android:entries="@array/viewers"