Fix dark theme and battery saver interaction

In settings we weren't properly taking into account battery saver
enabled dark theme. This CL makes it so that when battery saver
on we disable the toggle until battery saver is off since
you can't change dark theme in battery saver. Additionally it
adds a message indicating why the toggle was disabled so the
user doesn't get confused.

Test: robotests
Bug: 131913864
Change-Id: I855e429a666098c837650852d1e1355477afa13d

src/com/android/settings/display/DarkUIPreferenceController.java

@@ -17,27 +17,53 @@
 package com.android.settings.display;
 
 import android.app.UiModeManager;
+import android.content.BroadcastReceiver;
 import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.os.PowerManager;
 import android.provider.Settings;
 
 import androidx.annotation.VisibleForTesting;
 import androidx.fragment.app.Fragment;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
+import androidx.preference.SwitchPreference;
 
+import com.android.settings.R;
 import com.android.settings.core.TogglePreferenceController;
+import com.android.settingslib.core.lifecycle.LifecycleObserver;
+import com.android.settingslib.core.lifecycle.events.OnStart;
+import com.android.settingslib.core.lifecycle.events.OnStop;
 
-public class DarkUIPreferenceController extends TogglePreferenceController {
+public class DarkUIPreferenceController extends TogglePreferenceController implements
+        LifecycleObserver, OnStart, OnStop {
 
     public static final String DARK_MODE_PREFS = "dark_mode_prefs";
     public static final String PREF_DARK_MODE_DIALOG_SEEN = "dark_mode_dialog_seen";
     public static final int DIALOG_SEEN = 1;
+
+    @VisibleForTesting
+    SwitchPreference mPreference;
+
     private UiModeManager mUiModeManager;
+    private PowerManager mPowerManager;
     private Context mContext;
+
     private Fragment mFragment;
 
+    private BroadcastReceiver mReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            updateEnabledStateIfNeeded();
+        }
+    };
+
     public DarkUIPreferenceController(Context context, String key) {
         super(context, key);
         mContext = context;
         mUiModeManager = context.getSystemService(UiModeManager.class);
+        mPowerManager = context.getSystemService(PowerManager.class);
     }
 
     @Override
@@ -45,6 +71,18 @@ public class DarkUIPreferenceController extends TogglePreferenceController {
         return mUiModeManager.getNightMode() == UiModeManager.MODE_NIGHT_YES;
     }
 
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+        mPreference = screen.findPreference(getPreferenceKey());
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        super.updateState(preference);
+        updateEnabledStateIfNeeded();
+    }
+
     @Override
     public boolean setChecked(boolean isChecked) {
         final boolean dialogSeen =
@@ -67,6 +105,29 @@ public class DarkUIPreferenceController extends TogglePreferenceController {
         }
     }
 
+    @VisibleForTesting
+    void updateEnabledStateIfNeeded() {
+        if (mPreference == null) {
+            return;
+        }
+        boolean isBatterySaver = isPowerSaveMode();
+        mPreference.setEnabled(!isBatterySaver);
+        if (isBatterySaver) {
+            int stringId = mUiModeManager.getNightMode() == UiModeManager.MODE_NIGHT_YES
+                    ? R.string.dark_ui_mode_disabled_summary_dark_theme_on
+                    : R.string.dark_ui_mode_disabled_summary_dark_theme_off;
+            mPreference.setSummary(mContext.getString(stringId));
+        } else {
+            mPreference.setSummary(null);
+        }
+    }
+
+    @VisibleForTesting
+    boolean isPowerSaveMode() {
+        return mPowerManager.isPowerSaveMode();
+    }
+
+
     @VisibleForTesting
     void setUiModeManager(UiModeManager uiModeManager) {
         mUiModeManager = uiModeManager;
@@ -76,6 +137,17 @@ public class DarkUIPreferenceController extends TogglePreferenceController {
         mFragment = fragment;
     }
 
+    @Override
+    public void onStart() {
+        mContext.registerReceiver(mReceiver,
+                new IntentFilter(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED));
+    }
+
+    @Override
+    public void onStop() {
+        mContext.unregisterReceiver(mReceiver);
+    }
+
     @Override
     public int getAvailabilityStatus() {
         return AVAILABLE;