Add progressive disclsoure

- Add a ProgressiveDisclosureMixin that contains all logic for collapse
  preference list when it's too long
- Refactored PreferenceController's updateState to take a preference
  instead of PreferenceScreen, because with progressive disclosure the
  preference can either be in screen or the mixin. DashboardFragment is
  responsible finding the preference before passing it to controller.

Bug: 32255863
Test: RunSettingsRoboTests

Change-Id: I6713abd61c954ce12732902e5b3ca4d4c0b1563e

src/com/android/settings/dashboard/DashboardFragment.java

@@ -52,12 +52,14 @@ import java.util.Set;
 public abstract class DashboardFragment extends SettingsPreferenceFragment
         implements SettingsDrawerActivity.CategoryListener, Indexable,
         SummaryLoader.SummaryConsumer {
+    private static final String TAG = "DashboardFragment";
 
     private final Map<Class, PreferenceController> mPreferenceControllers =
             new ArrayMap<>();
     private final Set<String> mDashboardTilePrefKeys = new ArraySet<>();
     private DashboardDividerDecoration mDividerDecoration;
 
+    protected ProgressiveDisclosureMixin mProgressiveDisclosureMixin;
     protected DashboardFeatureProvider mDashboardFeatureProvider;
     private boolean mListeningToCategoryChange;
     private SummaryLoader mSummaryLoader;
@@ -67,6 +69,8 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
         super.onAttach(context);
         mDashboardFeatureProvider =
                 FeatureFactory.getFactory(context).getDashboardFeatureProvider(context);
+        mProgressiveDisclosureMixin = new ProgressiveDisclosureMixin(context, this);
+        getLifecycle().addObserver(mProgressiveDisclosureMixin);
 
         final List<PreferenceController> controllers = getPreferenceControllers(context);
         if (controllers == null) {
@@ -160,6 +164,18 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
         }
     }
 
+    @Override
+    public Preference findPreference(CharSequence key) {
+        Preference preference = super.findPreference(key);
+        if (preference == null && mProgressiveDisclosureMixin != null) {
+            preference = mProgressiveDisclosureMixin.findPreference(key);
+        }
+        if (preference == null) {
+            Log.d(TAG, "Cannot find preference with key " + key);
+        }
+        return preference;
+    }
+
     protected <T extends PreferenceController> T getPreferenceController(Class<T> clazz) {
         PreferenceController controller = mPreferenceControllers.get(clazz);
         return (T) controller;
@@ -259,7 +275,19 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
             // (larger value has higher priority). However pref order defines smaller value has
             // higher priority.
             pref.setOrder(-tile.priority);
-            screen.addPreference(pref);
+
+            // Either add to screen, or to collapsed list.
+            if (mProgressiveDisclosureMixin.isCollapsed()) {
+                // Already collapsed, add to collapsed list.
+                mProgressiveDisclosureMixin.addToCollapsedList(pref);
+            } else if (mProgressiveDisclosureMixin.shouldCollapse(screen)) {
+                // About to have too many tiles on scree, collapse and add pref to collapsed list.
+                mProgressiveDisclosureMixin.collapse(screen);
+                mProgressiveDisclosureMixin.addToCollapsedList(pref);
+            } else {
+                // No need to collapse, add to screen directly.
+                screen.addPreference(pref);
+            }
         }
     }
 
@@ -278,9 +306,15 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
      */
     private void updatePreferenceStates() {
         Collection<PreferenceController> controllers = mPreferenceControllers.values();
-        final PreferenceScreen screen = getPreferenceScreen();
         for (PreferenceController controller : controllers) {
-            controller.updateState(screen);
+            final String key = controller.getPreferenceKey();
+
+            final Preference preference = findPreference(key);
+            if (preference == null) {
+                Log.d(TAG, "Cannot find preference with key " + key);
+                continue;
+            }
+            controller.updateState(preference);
         }
     }
 
@@ -302,15 +336,20 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
      */
     private void refreshAllPreferences(final String TAG) {
         // First remove old preferences.
-        final PreferenceScreen screen = getPreferenceScreen();
-        if (screen != null) {
-            screen.removeAll();
+        if (getPreferenceScreen() != null) {
+            // Intentionally do not cache PreferenceScreen because it will be recreated later.
+            getPreferenceScreen().removeAll();
         }
 
         // Add resource based tiles.
         displayResourceTiles();
 
         refreshDashboardTiles(TAG);
+
+        if (!mProgressiveDisclosureMixin.isCollapsed()
+                && mProgressiveDisclosureMixin.shouldCollapse(getPreferenceScreen())) {
+            mProgressiveDisclosureMixin.collapse(getPreferenceScreen());
+        }
     }
 
     /**
@@ -319,10 +358,13 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
     private void refreshDashboardTiles(final String TAG) {
         final PreferenceScreen screen = getPreferenceScreen();
         for (String key : mDashboardTilePrefKeys) {
+            // Remove tiles from screen
             final Preference pref = screen.findPreference(key);
             if (pref != null) {
                 screen.removePreference(pref);
             }
+            // Also remove tile from collapsed set
+            mProgressiveDisclosureMixin.removePreference(screen, key);
         }
         mDashboardTilePrefKeys.clear();
         displayDashboardTiles(TAG, getPreferenceScreen());