Show topology pane in per-display fragment

Some changes made to the UI, i.e. presence or absence of items, based on
feedback. There is some ambiguity because we are not fully v2 yet, hence
this change.

When all external displays are attached after opening the fragment, we
now show no preference items, whereas before we showed the pane with
built-in display options.

If only one external display is attached, we skip the "display list"
version of the fragment, and instead show the pane and other v2 items in
the per-display fragment.

If 2 or more external displays are attached, we do not show the pane
after selecting a display, which makes the rotation/resolution items
easier to find. I tried to get scrollToPreference to work but could not,
and it could be a little disorienting anyway.

To help manage the growing number of setOrder calls, keep the order
values as well as other pref data in a single spot. This also reduces
the amount of boilerplate around constants needed and makes uniform how
multiple preferences are built.

Flag: com.android.settings.flags.display_topology_pane_in_display_list
Bug: b/366056922
Bug: b/394361999
Test: TODO
Change-Id: Iaa33f6d9220a1658a372c0432fe159a69dbb88a5

src/com/android/settings/connecteddevice/display/DisplayTopology.kt

@@ -159,8 +159,6 @@ class TopologyScale(
     }
 }
 
-const val TOPOLOGY_PREFERENCE_KEY = "display_topology_preference"
-
 /** Represents a draggable block in the topology pane. */
 class DisplayBlock(context : Context) : Button(context) {
     @VisibleForTesting var mSelectedImage: Drawable = ColorDrawable(Color.BLACK)
@@ -240,7 +238,6 @@ class DisplayTopologyPreference(context : Context)
         // Prevent highlight when hovering with mouse.
         isSelectable = false
 
-        key = TOPOLOGY_PREFERENCE_KEY
         isPersistent = false
 
         injector = Injector(context)

src/com/android/settings/connecteddevice/display/ExternalDisplayPreferenceFragment.java

@@ -64,33 +64,69 @@ import java.util.List;
  * The Settings screen for External Displays configuration and connection management.
  */
 public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmentBase {
+    @VisibleForTesting enum PrefBasics {
+        DISPLAY_TOPOLOGY(10, "display_topology_preference", null),
+        MIRROR(20, "mirror_preference", null),
+
+        // If shown, use toggle should be before other per-display settings.
+        EXTERNAL_DISPLAY_USE(30, "external_display_use_preference",
+                R.string.external_display_use_title),
+
+        ILLUSTRATION(35, "external_display_illustration", null),
+
+        // If shown, external display size is before other per-display settings.
+        EXTERNAL_DISPLAY_SIZE(40, "external_display_size", R.string.screen_zoom_title),
+        EXTERNAL_DISPLAY_ROTATION(50, "external_display_rotation",
+                R.string.external_display_rotation),
+        EXTERNAL_DISPLAY_RESOLUTION(60, "external_display_resolution",
+                R.string.external_display_resolution_settings_title),
+
+        // Built-in display link is after per-display settings.
+        BUILTIN_DISPLAY_LIST(70, "builtin_display_list_preference",
+                R.string.builtin_display_settings_category),
+
+        DISPLAYS_LIST(80, "displays_list_preference", null),
+
+        // If shown, footer should appear below everything.
+        FOOTER(90, "footer_preference", null);
+
+
+        PrefBasics(int order, String key, @Nullable Integer titleResource) {
+            this.order = order;
+            this.key = key;
+            this.titleResource = titleResource;
+        }
+
+        // Fields must be public to make the linter happy.
+        public final int order;
+        public final String key;
+        @Nullable public final Integer titleResource;
+
+        void apply(Preference preference) {
+            if (order != -1) {
+                preference.setOrder(order);
+            }
+            if (titleResource != null) {
+                preference.setTitle(titleResource);
+            }
+            preference.setKey(key);
+            preference.setPersistent(false);
+        }
+    }
+
     static final int EXTERNAL_DISPLAY_SETTINGS_RESOURCE = R.xml.external_display_settings;
-    static final String DISPLAYS_LIST_PREFERENCE_KEY = "displays_list_preference";
-    static final String BUILTIN_DISPLAY_LIST_PREFERENCE_KEY = "builtin_display_list_preference";
-    static final String EXTERNAL_DISPLAY_USE_PREFERENCE_KEY = "external_display_use_preference";
-    static final String EXTERNAL_DISPLAY_ROTATION_KEY = "external_display_rotation";
-    static final String EXTERNAL_DISPLAY_RESOLUTION_PREFERENCE_KEY = "external_display_resolution";
-    static final String EXTERNAL_DISPLAY_SIZE_PREFERENCE_KEY = "external_display_size";
     static final int EXTERNAL_DISPLAY_CHANGE_RESOLUTION_FOOTER_RESOURCE =
             R.string.external_display_change_resolution_footer_title;
     static final int EXTERNAL_DISPLAY_LANDSCAPE_DRAWABLE =
             R.drawable.external_display_mirror_landscape;
     static final int EXTERNAL_DISPLAY_TITLE_RESOURCE =
             R.string.external_display_settings_title;
-    static final int EXTERNAL_DISPLAY_USE_TITLE_RESOURCE =
-            R.string.external_display_use_title;
     static final int EXTERNAL_DISPLAY_NOT_FOUND_FOOTER_RESOURCE =
             R.string.external_display_not_found_footer_title;
     static final int EXTERNAL_DISPLAY_PORTRAIT_DRAWABLE =
             R.drawable.external_display_mirror_portrait;
-    static final int EXTERNAL_DISPLAY_ROTATION_TITLE_RESOURCE =
-            R.string.external_display_rotation;
-    static final int EXTERNAL_DISPLAY_RESOLUTION_TITLE_RESOURCE =
-            R.string.external_display_resolution_settings_title;
-    static final int EXTERNAL_DISPLAY_SIZE_TITLE_RESOURCE = R.string.screen_zoom_title;
     static final int EXTERNAL_DISPLAY_SIZE_SUMMARY_RESOURCE = R.string.screen_zoom_short_summary;
-    static final int BUILTIN_DISPLAY_SETTINGS_CATEGORY_RESOURCE =
+
-            R.string.builtin_display_settings_category;
     @VisibleForTesting
     static final String PREVIOUSLY_SHOWN_LIST_KEY = "mPreviouslyShownListOfDisplays";
     private boolean mStarted;
@@ -253,9 +289,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     ListPreference getRotationPreference(@NonNull Context context) {
         if (mRotationPref == null) {
             mRotationPref = new ListPreference(context);
-            mRotationPref.setPersistent(false);
+            PrefBasics.EXTERNAL_DISPLAY_ROTATION.apply(mRotationPref);
-            mRotationPref.setKey(EXTERNAL_DISPLAY_ROTATION_KEY);
-            mRotationPref.setTitle(EXTERNAL_DISPLAY_ROTATION_TITLE_RESOURCE);
         }
         return mRotationPref;
     }
@@ -265,9 +299,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     Preference getResolutionPreference(@NonNull Context context) {
         if (mResolutionPreference == null) {
             mResolutionPreference = new Preference(context);
-            mResolutionPreference.setPersistent(false);
+            PrefBasics.EXTERNAL_DISPLAY_RESOLUTION.apply(mResolutionPreference);
-            mResolutionPreference.setKey(EXTERNAL_DISPLAY_RESOLUTION_PREFERENCE_KEY);
-            mResolutionPreference.setTitle(EXTERNAL_DISPLAY_RESOLUTION_TITLE_RESOURCE);
         }
         return mResolutionPreference;
     }
@@ -277,9 +309,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     MainSwitchPreference getUseDisplayPreference(@NonNull Context context) {
         if (mUseDisplayPref == null) {
             mUseDisplayPref = new MainSwitchPreference(context);
-            mUseDisplayPref.setPersistent(false);
+            PrefBasics.EXTERNAL_DISPLAY_USE.apply(mUseDisplayPref);
-            mUseDisplayPref.setKey(EXTERNAL_DISPLAY_USE_PREFERENCE_KEY);
-            mUseDisplayPref.setTitle(EXTERNAL_DISPLAY_USE_TITLE_RESOURCE);
         }
         return mUseDisplayPref;
     }
@@ -289,8 +319,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     IllustrationPreference getIllustrationPreference(@NonNull Context context) {
         if (mImagePreference == null) {
             mImagePreference = new IllustrationPreference(context);
-            mImagePreference.setPersistent(false);
+            PrefBasics.ILLUSTRATION.apply(mImagePreference);
-            mImagePreference.setKey("external_display_illustration");
         }
         return mImagePreference;
     }
@@ -308,9 +337,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     private PreferenceCategory getDisplaysListPreference(@NonNull Context context) {
         if (mDisplaysPreference == null) {
             mDisplaysPreference = new PreferenceCategory(context);
-            mDisplaysPreference.setPersistent(false);
+            PrefBasics.DISPLAYS_LIST.apply(mDisplaysPreference);
-            mDisplaysPreference.setOrder(40);
-            mDisplaysPreference.setKey(DISPLAYS_LIST_PREFERENCE_KEY);
         }
         return mDisplaysPreference;
     }
@@ -319,10 +346,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     private PreferenceCategory getBuiltinDisplayListPreference(@NonNull Context context) {
         if (mBuiltinDisplayPreference == null) {
             mBuiltinDisplayPreference = new PreferenceCategory(context);
-            mBuiltinDisplayPreference.setPersistent(false);
+            PrefBasics.BUILTIN_DISPLAY_LIST.apply(mBuiltinDisplayPreference);
-            mBuiltinDisplayPreference.setOrder(30);
-            mBuiltinDisplayPreference.setKey(BUILTIN_DISPLAY_LIST_PREFERENCE_KEY);
-            mBuiltinDisplayPreference.setTitle(BUILTIN_DISPLAY_SETTINGS_CATEGORY_RESOURCE);
         }
         return mBuiltinDisplayPreference;
     }
@@ -338,7 +362,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     @NonNull Preference getDisplayTopologyPreference(@NonNull Context context) {
         if (mDisplayTopologyPreference == null) {
             mDisplayTopologyPreference = new DisplayTopologyPreference(context);
-            mDisplayTopologyPreference.setOrder(10);
+            PrefBasics.DISPLAY_TOPOLOGY.apply(mDisplayTopologyPreference);
         }
         return mDisplayTopologyPreference;
     }
@@ -346,7 +370,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     @NonNull Preference getMirrorPreference(@NonNull Context context) {
         if (mMirrorPreference == null) {
             mMirrorPreference = new MirrorPreference(context);
-            mMirrorPreference.setOrder(20);
+            PrefBasics.MIRROR.apply(mMirrorPreference);
         }
         return mMirrorPreference;
     }
@@ -386,16 +410,18 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
 
     private void updateScreenForDisplayId(final int displayId,
             @NonNull final PrefRefresh screen, @NonNull Context context) {
-        final boolean forceShowList = displayId == INVALID_DISPLAY
-                && isTopologyPaneEnabled(mInjector);
         final var displaysToShow = externalDisplaysToShow(displayId);
 
-        if (!forceShowList && displaysToShow.isEmpty() && displayId == INVALID_DISPLAY) {
+        if (displaysToShow.isEmpty() && displayId == INVALID_DISPLAY) {
             showTextWhenNoDisplaysToShow(screen, context);
-        } else if (!forceShowList && displaysToShow.size() == 1
+        } else if (displaysToShow.size() == 1
                 && ((displayId == INVALID_DISPLAY && !mPreviouslyShownListOfDisplays)
                         || displaysToShow.get(0).getDisplayId() == displayId)) {
             showDisplaySettings(displaysToShow.get(0), screen, context);
+            if (displayId == INVALID_DISPLAY && isTopologyPaneEnabled(mInjector)) {
+                // Only show the topology pane if the user did not arrive via the displays list.
+                maybeAddV2Components(context, screen);
+            }
         } else if (displayId == INVALID_DISPLAY) {
             // If ever shown a list of displays - keep showing it for consistency after
             // disconnecting one of the displays, and only one display is left.
@@ -446,21 +472,30 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
         screen.addPreference(updateResolutionPreference(context, display));
         screen.addPreference(updateRotationPreference(context, display, displayRotation));
         if (isResolutionSettingEnabled(mInjector)) {
-            screen.addPreference(updateFooterPreference(context,
+            // Do not show the footer about changing resolution affecting apps. This is not in the
-                    EXTERNAL_DISPLAY_CHANGE_RESOLUTION_FOOTER_RESOURCE));
+            // UX design for v2, and there is no good place to put it, since (a) if it is on the
+            // bottom of the screen, the external resolution setting must be below the built-in
+            // display options for the per-display fragment, which is too hidden for the per-display
+            // fragment, or (b) the footer is above the Built-in display settings, rather than the
+            // bottom of the screen, which contradicts the visual style and purpose of the
+            // FooterPreference class, or (c) we must hide the built-in display settings, which is
+            // inconsistent with the topology pane, which shows that display.
+            // TODO(b/352648432): probably remove footer once the pane and rest of v2 UI is in
+            // place.
+            if (!isTopologyPaneEnabled(mInjector)) {
+                screen.addPreference(updateFooterPreference(context,
+                        EXTERNAL_DISPLAY_CHANGE_RESOLUTION_FOOTER_RESOURCE));
+            }
         }
         if (isDisplaySizeSettingEnabled(mInjector)) {
             screen.addPreference(updateSizePreference(context));
         }
     }
 
-    private void showDisplaysList(@NonNull List<Display> displaysToShow,
+    private void maybeAddV2Components(Context context, PrefRefresh screen) {
-                                  @NonNull PrefRefresh screen, @NonNull Context context) {
         if (isTopologyPaneEnabled(mInjector)) {
             screen.addPreference(getDisplayTopologyPreference(context));
-            if (!displaysToShow.isEmpty()) {
+            screen.addPreference(getMirrorPreference(context));
-                screen.addPreference(getMirrorPreference(context));
-            }
 
             // If topology is shown, we also show a preference for the built-in display for
             // consistency with the topology.
@@ -468,7 +503,11 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
             screen.addPreference(builtinCategory);
             builtinCategory.addPreference(getBuiltinDisplaySizeAndTextPreference(context));
         }
+    }
 
+    private void showDisplaysList(@NonNull List<Display> displaysToShow,
+                                  @NonNull PrefRefresh screen, @NonNull Context context) {
+        maybeAddV2Components(context, screen);
         var displayGroupPref = getDisplaysListPreference(context);
         if (!displaysToShow.isEmpty()) {
             screen.addPreference(displayGroupPref);
@@ -501,8 +540,9 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
             groupCleanable.addPreference(category);
 
             var prefItem = new DisplayPreference(context, display);
-            prefItem.setTitle(context.getString(EXTERNAL_DISPLAY_RESOLUTION_TITLE_RESOURCE)
+            prefItem.setTitle(
-                    + " | " + context.getString(EXTERNAL_DISPLAY_ROTATION_TITLE_RESOURCE));
+                    context.getString(PrefBasics.EXTERNAL_DISPLAY_RESOLUTION.titleResource) + " | "
+                    + context.getString(PrefBasics.EXTERNAL_DISPLAY_ROTATION.titleResource));
             prefItem.setKey(itemKey);
 
             category.addPreference(prefItem);
@@ -577,6 +617,7 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
     private Preference updateFooterPreference(@NonNull final Context context, final int title) {
         var pref = getFooterPreference(context);
         pref.setTitle(title);
+        PrefBasics.FOOTER.apply(pref);
         return pref;
     }
 
@@ -625,10 +666,8 @@ public class ExternalDisplayPreferenceFragment extends SettingsPreferenceFragmen
 
     private Preference updateSizePreference(@NonNull final Context context) {
         var pref = (Preference) getSizePreference(context);
-        pref.setKey(EXTERNAL_DISPLAY_SIZE_PREFERENCE_KEY);
+        PrefBasics.EXTERNAL_DISPLAY_SIZE.apply(pref);
         pref.setSummary(EXTERNAL_DISPLAY_SIZE_SUMMARY_RESOURCE);
-        pref.setPersistent(false);
-        pref.setTitle(EXTERNAL_DISPLAY_SIZE_TITLE_RESOURCE);
         pref.setOnPreferenceClickListener(
                 (Preference p) -> {
                     writePreferenceClickMetric(p);

src/com/android/settings/connecteddevice/display/Mirroring.kt

@@ -23,8 +23,6 @@ import androidx.preference.SwitchPreferenceCompat
 
 import com.android.settings.R
 
-const val MIRROR_PREFERENCE_KEY = "mirror_builtin_display"
-
 /**
  * A switch preference which is backed by the MIRROR_BUILT_IN_DISPLAY global setting.
  */
@@ -32,7 +30,6 @@ class MirrorPreference(context: Context): SwitchPreferenceCompat(context) {
     init {
         setTitle(R.string.external_display_mirroring_title)
 
-        key = MIRROR_PREFERENCE_KEY
         isPersistent = false
     }
 

tests/unit/src/com/android/settings/connecteddevice/display/ExternalDisplayPreferenceFragmentTest.java

@@ -17,19 +17,10 @@ package com.android.settings.connecteddevice.display;
 
 import static android.view.Display.INVALID_DISPLAY;
 
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.DISPLAYS_LIST_PREFERENCE_KEY;
 import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_CHANGE_RESOLUTION_FOOTER_RESOURCE;
 import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_NOT_FOUND_FOOTER_RESOURCE;
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_RESOLUTION_PREFERENCE_KEY;
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_RESOLUTION_TITLE_RESOURCE;
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_ROTATION_KEY;
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_ROTATION_TITLE_RESOURCE;
 import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_SETTINGS_RESOURCE;
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_SIZE_PREFERENCE_KEY;
 import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_SIZE_SUMMARY_RESOURCE;
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_SIZE_TITLE_RESOURCE;
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_USE_PREFERENCE_KEY;
-import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.EXTERNAL_DISPLAY_USE_TITLE_RESOURCE;
 import static com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.PREVIOUSLY_SHOWN_LIST_KEY;
 import static com.android.settings.flags.Flags.FLAG_DISPLAY_SIZE_CONNECTED_DISPLAY_SETTING;
 import static com.android.settings.flags.Flags.FLAG_DISPLAY_TOPOLOGY_PANE_IN_DISPLAY_LIST;
@@ -61,6 +52,7 @@ import androidx.test.annotation.UiThreadTest;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 
 import com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.DisplayPreference;
+import com.android.settings.connecteddevice.display.ExternalDisplayPreferenceFragment.PrefBasics;
 import com.android.settingslib.widget.FooterPreference;
 import com.android.settingslib.widget.MainSwitchPreference;
 
@@ -97,23 +89,22 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         fragment.onSaveInstanceStateCallback(outState);
         assertThat(outState.getBoolean(PREVIOUSLY_SHOWN_LIST_KEY)).isFalse();
         assertThat(mHandler.getPendingMessages().size()).isEqualTo(1);
-        PreferenceCategory pref = mPreferenceScreen.findPreference(DISPLAYS_LIST_PREFERENCE_KEY);
+        PreferenceCategory pref = mPreferenceScreen.findPreference(PrefBasics.DISPLAYS_LIST.key);
         assertThat(pref).isNull();
         verify(mMockedInjector, never()).getAllDisplays();
         mHandler.flush();
         assertThat(mHandler.getPendingMessages().size()).isEqualTo(0);
         verify(mMockedInjector).getAllDisplays();
-        pref = mPreferenceScreen.findPreference(DISPLAYS_LIST_PREFERENCE_KEY);
+        pref = mPreferenceScreen.findPreference(PrefBasics.DISPLAYS_LIST.key);
         assertThat(pref).isNotNull();
         assertThat(pref.getPreferenceCount()).isEqualTo(2);
         fragment.onSaveInstanceStateCallback(outState);
         assertThat(outState.getBoolean(PREVIOUSLY_SHOWN_LIST_KEY)).isTrue();
 
-        pref = mPreferenceScreen.findPreference(DisplayTopologyKt.TOPOLOGY_PREFERENCE_KEY);
+        pref = mPreferenceScreen.findPreference(PrefBasics.DISPLAY_TOPOLOGY.key);
         assertThat(pref).isNull();
 
-        pref = mPreferenceScreen.findPreference(
+        pref = mPreferenceScreen.findPreference(PrefBasics.BUILTIN_DISPLAY_LIST.key);
-                ExternalDisplayPreferenceFragment.BUILTIN_DISPLAY_LIST_PREFERENCE_KEY);
         assertThat(pref).isNull();
     }
 
@@ -126,56 +117,51 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         doReturn(new Display[] {mDisplays[1]}).when(mMockedInjector).getAllDisplays();
         mHandler.flush();
 
-        var pref = mPreferenceScreen.findPreference(DisplayTopologyKt.TOPOLOGY_PREFERENCE_KEY);
+        var pref = mPreferenceScreen.findPreference(PrefBasics.DISPLAY_TOPOLOGY.key);
         assertThat(pref).isNotNull();
-        pref = mPreferenceScreen.findPreference(MirroringKt.MIRROR_PREFERENCE_KEY);
+        pref = mPreferenceScreen.findPreference(PrefBasics.MIRROR.key);
         assertThat(pref).isNotNull();
 
-        PreferenceCategory listPref =
+        pref = mPreferenceScreen.findPreference(PrefBasics.DISPLAYS_LIST.key);
-                mPreferenceScreen.findPreference(DISPLAYS_LIST_PREFERENCE_KEY);
-        assertThat(listPref).isNotNull();
-        assertThat(listPref.getPreferenceCount()).isEqualTo(1);
-
-        listPref = mPreferenceScreen.findPreference(
-                ExternalDisplayPreferenceFragment.BUILTIN_DISPLAY_LIST_PREFERENCE_KEY);
-        assertThat(listPref).isNotNull();
-        assertThat(listPref.getPreferenceCount()).isEqualTo(1);
-    }
-
-    @Test
-    @UiThreadTest
-    public void testShowDisplayListWithPane_NoExternalDisplays() {
-        mFlags.setFlag(FLAG_DISPLAY_TOPOLOGY_PANE_IN_DISPLAY_LIST, true);
-
-        initFragment();
-        doReturn(new Display[0]).when(mMockedInjector).getAllDisplays();
-        mHandler.flush();
-
-        var pref = mPreferenceScreen.findPreference(DisplayTopologyKt.TOPOLOGY_PREFERENCE_KEY);
-        assertThat(pref).isNotNull();
-        pref = mPreferenceScreen.findPreference(MirroringKt.MIRROR_PREFERENCE_KEY);
         assertThat(pref).isNull();
 
         PreferenceCategory listPref =
-                mPreferenceScreen.findPreference(DISPLAYS_LIST_PREFERENCE_KEY);
+                mPreferenceScreen.findPreference(PrefBasics.BUILTIN_DISPLAY_LIST.key);
-        assertThat(listPref).isNull();
-
-        listPref = mPreferenceScreen.findPreference(
-                ExternalDisplayPreferenceFragment.BUILTIN_DISPLAY_LIST_PREFERENCE_KEY);
-        assertThat(listPref).isNotNull();
-        assertThat(listPref.getPreferenceCount()).isEqualTo(1);
         var builtinPref = listPref.getPreference(0);
         assertThat(builtinPref.getOnPreferenceClickListener().onPreferenceClick(builtinPref))
                 .isTrue();
         assertThat(mLaunchedBuiltinSettings).isTrue();
     }
 
+    @Test
+    @UiThreadTest
+    public void testDontShowDisplayListOrPane_NoExternalDisplays() {
+        mFlags.setFlag(FLAG_DISPLAY_TOPOLOGY_PANE_IN_DISPLAY_LIST, true);
+
+        initFragment();
+        doReturn(new Display[0]).when(mMockedInjector).getAllDisplays();
+        mHandler.flush();
+
+        // When no external display is attached, interactive preferences are omitted.
+        var pref = mPreferenceScreen.findPreference(PrefBasics.DISPLAY_TOPOLOGY.key);
+        assertThat(pref).isNull();
+        pref = mPreferenceScreen.findPreference(PrefBasics.MIRROR.key);
+        assertThat(pref).isNull();
+
+        PreferenceCategory listPref =
+                mPreferenceScreen.findPreference(PrefBasics.DISPLAYS_LIST.key);
+        assertThat(listPref).isNull();
+
+        listPref = mPreferenceScreen.findPreference(PrefBasics.BUILTIN_DISPLAY_LIST.key);
+        assertThat(listPref).isNull();
+    }
+
     @Test
     @UiThreadTest
     public void testLaunchDisplaySettingFromList() {
         initFragment();
         mHandler.flush();
-        PreferenceCategory pref = mPreferenceScreen.findPreference(DISPLAYS_LIST_PREFERENCE_KEY);
+        PreferenceCategory pref = mPreferenceScreen.findPreference(PrefBasics.DISPLAYS_LIST.key);
         assertThat(pref).isNotNull();
         var display1Category = (PreferenceCategory) pref.getPreference(0);
         var display1Pref = (DisplayPreference) display1Category.getPreference(0);
@@ -204,7 +190,7 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         // Only one display available
         doReturn(new Display[] {mDisplays[1]}).when(mMockedInjector).getAllDisplays();
         mHandler.flush();
-        PreferenceCategory pref = mPreferenceScreen.findPreference(DISPLAYS_LIST_PREFERENCE_KEY);
+        PreferenceCategory pref = mPreferenceScreen.findPreference(PrefBasics.DISPLAYS_LIST.key);
         assertThat(pref).isNotNull();
         assertThat(pref.getPreferenceCount()).isEqualTo(1);
     }
@@ -219,15 +205,15 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         // Init
         initFragment();
         mHandler.flush();
-        PreferenceCategory list = mPreferenceScreen.findPreference(DISPLAYS_LIST_PREFERENCE_KEY);
+        PreferenceCategory list = mPreferenceScreen.findPreference(PrefBasics.DISPLAYS_LIST.key);
         assertThat(list).isNull();
-        var pref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_RESOLUTION_PREFERENCE_KEY);
+        var pref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_RESOLUTION.key);
         assertThat(pref).isNotNull();
-        pref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_ROTATION_KEY);
+        pref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_ROTATION.key);
         assertThat(pref).isNotNull();
         var footerPref = (FooterPreference) mPreferenceScreen.findPreference(KEY_FOOTER);
         assertThat(footerPref).isNotNull();
-        var sizePref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_SIZE_PREFERENCE_KEY);
+        var sizePref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_SIZE.key);
         assertThat(sizePref).isNull();
         verify(footerPref).setTitle(EXTERNAL_DISPLAY_CHANGE_RESOLUTION_FOOTER_RESOURCE);
     }
@@ -241,15 +227,15 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         // Init
         initFragment();
         mHandler.flush();
-        PreferenceCategory list = mPreferenceScreen.findPreference(DISPLAYS_LIST_PREFERENCE_KEY);
+        PreferenceCategory list = mPreferenceScreen.findPreference(PrefBasics.DISPLAYS_LIST.key);
         assertThat(list).isNull();
-        var pref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_RESOLUTION_PREFERENCE_KEY);
+        var pref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_RESOLUTION.key);
         assertThat(pref).isNotNull();
-        pref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_ROTATION_KEY);
+        pref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_ROTATION.key);
         assertThat(pref).isNotNull();
         var footerPref = (FooterPreference) mPreferenceScreen.findPreference(KEY_FOOTER);
         assertThat(footerPref).isNotNull();
-        var sizePref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_SIZE_PREFERENCE_KEY);
+        var sizePref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_SIZE.key);
         assertThat(sizePref).isNotNull();
         verify(footerPref).setTitle(EXTERNAL_DISPLAY_CHANGE_RESOLUTION_FOOTER_RESOURCE);
     }
@@ -263,13 +249,13 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         verify(mMockedInjector, never()).getDisplay(anyInt());
         mHandler.flush();
         verify(mMockedInjector).getDisplay(mDisplayIdArg);
-        var pref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_RESOLUTION_PREFERENCE_KEY);
+        var pref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_RESOLUTION.key);
         assertThat(pref).isNotNull();
-        pref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_ROTATION_KEY);
+        pref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_ROTATION.key);
         assertThat(pref).isNotNull();
         var footerPref = (FooterPreference) mPreferenceScreen.findPreference(KEY_FOOTER);
         assertThat(footerPref).isNotNull();
-        var sizePref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_SIZE_PREFERENCE_KEY);
+        var sizePref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_SIZE.key);
         assertThat(sizePref).isNotNull();
         verify(footerPref).setTitle(EXTERNAL_DISPLAY_CHANGE_RESOLUTION_FOOTER_RESOURCE);
     }
@@ -283,20 +269,20 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         mHandler.flush();
         verify(mMockedInjector).getDisplay(mDisplayIdArg);
         var mainPref = (MainSwitchPreference) mPreferenceScreen.findPreference(
-                EXTERNAL_DISPLAY_USE_PREFERENCE_KEY);
+                PrefBasics.EXTERNAL_DISPLAY_USE.key);
         assertThat(mainPref).isNotNull();
         assertThat("" + mainPref.getTitle()).isEqualTo(
-                getText(EXTERNAL_DISPLAY_USE_TITLE_RESOURCE));
+                getText(PrefBasics.EXTERNAL_DISPLAY_USE.titleResource));
         assertThat(mainPref.isChecked()).isFalse();
         assertThat(mainPref.isEnabled()).isTrue();
         assertThat(mainPref.getOnPreferenceChangeListener()).isNotNull();
-        var pref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_RESOLUTION_PREFERENCE_KEY);
+        var pref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_RESOLUTION.key);
         assertThat(pref).isNull();
-        pref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_ROTATION_KEY);
+        pref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_ROTATION.key);
         assertThat(pref).isNull();
         var footerPref = (FooterPreference) mPreferenceScreen.findPreference(KEY_FOOTER);
         assertThat(footerPref).isNull();
-        var sizePref = mPreferenceScreen.findPreference(EXTERNAL_DISPLAY_SIZE_PREFERENCE_KEY);
+        var sizePref = mPreferenceScreen.findPreference(PrefBasics.EXTERNAL_DISPLAY_SIZE.key);
         assertThat(sizePref).isNull();
     }
 
@@ -307,10 +293,10 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         initFragment();
         mHandler.flush();
         var mainPref = (MainSwitchPreference) mPreferenceScreen.findPreference(
-                EXTERNAL_DISPLAY_USE_PREFERENCE_KEY);
+                PrefBasics.EXTERNAL_DISPLAY_USE.key);
         assertThat(mainPref).isNotNull();
         assertThat("" + mainPref.getTitle()).isEqualTo(
-                getText(EXTERNAL_DISPLAY_USE_TITLE_RESOURCE));
+                getText(PrefBasics.EXTERNAL_DISPLAY_USE.titleResource));
         assertThat(mainPref.isChecked()).isFalse();
         assertThat(mainPref.isEnabled()).isFalse();
         assertThat(mainPref.getOnPreferenceChangeListener()).isNull();
@@ -327,9 +313,9 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         var fragment = initFragment();
         mHandler.flush();
         var pref = fragment.getRotationPreference(mContext);
-        assertThat(pref.getKey()).isEqualTo(EXTERNAL_DISPLAY_ROTATION_KEY);
+        assertThat(pref.getKey()).isEqualTo(PrefBasics.EXTERNAL_DISPLAY_ROTATION.key);
         assertThat("" + pref.getTitle()).isEqualTo(
-                getText(EXTERNAL_DISPLAY_ROTATION_TITLE_RESOURCE));
+                getText(PrefBasics.EXTERNAL_DISPLAY_ROTATION.titleResource));
         assertThat(pref.getEntries().length).isEqualTo(4);
         assertThat(pref.getEntryValues().length).isEqualTo(4);
         assertThat(pref.getEntryValues()[0].toString()).isEqualTo("0");
@@ -359,9 +345,9 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         var fragment = initFragment();
         mHandler.flush();
         var pref = fragment.getResolutionPreference(mContext);
-        assertThat(pref.getKey()).isEqualTo(EXTERNAL_DISPLAY_RESOLUTION_PREFERENCE_KEY);
+        assertThat(pref.getKey()).isEqualTo(PrefBasics.EXTERNAL_DISPLAY_RESOLUTION.key);
         assertThat("" + pref.getTitle()).isEqualTo(
-                getText(EXTERNAL_DISPLAY_RESOLUTION_TITLE_RESOURCE));
+                getText(PrefBasics.EXTERNAL_DISPLAY_RESOLUTION.titleResource));
         assertThat("" + pref.getSummary()).isEqualTo("1920 x 1080");
         assertThat(pref.isEnabled()).isTrue();
         assertThat(pref.getOnPreferenceClickListener()).isNotNull();
@@ -378,8 +364,9 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         var fragment = initFragment();
         mHandler.flush();
         var pref = fragment.getSizePreference(mContext);
-        assertThat(pref.getKey()).isEqualTo(EXTERNAL_DISPLAY_SIZE_PREFERENCE_KEY);
+        assertThat(pref.getKey()).isEqualTo(PrefBasics.EXTERNAL_DISPLAY_SIZE.key);
-        assertThat("" + pref.getTitle()).isEqualTo(getText(EXTERNAL_DISPLAY_SIZE_TITLE_RESOURCE));
+        assertThat("" + pref.getTitle())
+                .isEqualTo(getText(PrefBasics.EXTERNAL_DISPLAY_SIZE.titleResource));
         assertThat("" + pref.getSummary())
                 .isEqualTo(getText(EXTERNAL_DISPLAY_SIZE_SUMMARY_RESOURCE));
         assertThat(pref.isEnabled()).isTrue();
@@ -398,8 +385,9 @@ public class ExternalDisplayPreferenceFragmentTest extends ExternalDisplayTestBa
         var fragment = initFragment();
         mHandler.flush();
         var pref = fragment.getUseDisplayPreference(mContext);
-        assertThat(pref.getKey()).isEqualTo(EXTERNAL_DISPLAY_USE_PREFERENCE_KEY);
+        assertThat(pref.getKey()).isEqualTo(PrefBasics.EXTERNAL_DISPLAY_USE.key);
-        assertThat("" + pref.getTitle()).isEqualTo(getText(EXTERNAL_DISPLAY_USE_TITLE_RESOURCE));
+        assertThat("" + pref.getTitle())
+                .isEqualTo(getText(PrefBasics.EXTERNAL_DISPLAY_USE.titleResource));
         assertThat(pref.isEnabled()).isTrue();
         assertThat(pref.isChecked()).isTrue();
         assertThat(pref.getOnPreferenceChangeListener()).isNotNull();