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

res/values/strings.xml

@@ -10056,6 +10056,12 @@
     <!-- [CHAR LIMIT=60] Name of setting that changes the UI to dark -->
     <string name="dark_ui_mode">Dark Theme</string>
 
+    <!-- [CHAR LIMIT=60] Summary string on dark theme explaining why the toggle is disabled while the setting is still on-->
+    <string name="dark_ui_mode_disabled_summary_dark_theme_on">On / Temporarily disabled due to Battery Saver</string>
+
+    <!-- [CHAR LIMIT=60] Summary string on dark theme explaining why the toggle is disabled while the setting is off-->
+    <string name="dark_ui_mode_disabled_summary_dark_theme_off">Temporarily turned on due to Battery Saver</string>
+
     <!-- [CHAR_LIMIT=NONE] Summary that is shown in the footer when dark mode is selected -->
     <string name="dark_ui_settings_dark_summary">Supported apps will also switch to dark theme</string>
 

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;

tests/robotests/src/com/android/settings/display/DarkUIPreferenceControllerTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package com.android.settings.display;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.content.Context;
+import android.os.Handler;
+import android.os.IPowerManager;
+import android.os.PowerManager;
+
+import androidx.fragment.app.Fragment;
+import androidx.preference.PreferenceScreen;
+import androidx.preference.SwitchPreference;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
+
+@RunWith(RobolectricTestRunner.class)
+public class DarkUIPreferenceControllerTest {
+
+    private DarkUIPreferenceController mController;
+    private Context mContext;
+    @Mock
+    private Fragment mFragment;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mContext = spy(RuntimeEnvironment.application);
+        mController = spy(new DarkUIPreferenceController(mContext, "dark_ui_mode"));
+        mController.setParentFragment(mFragment);
+        mController.mPreference = new SwitchPreference(mContext);
+        mController.onStart();
+    }
+
+    @Test
+    public void batterySaverToggles_disabledStateUpdates() {
+        doReturn(true).when(mController).isPowerSaveMode();
+        mController.updateEnabledStateIfNeeded();
+        assertThat(mController.mPreference.isEnabled()).isFalse();
+
+        doReturn(false).when(mController).isPowerSaveMode();
+        mController.updateEnabledStateIfNeeded();
+        assertThat(mController.mPreference.isEnabled()).isTrue();
+
+        doReturn(true).when(mController).isPowerSaveMode();
+        mController.updateEnabledStateIfNeeded();
+        assertThat(mController.mPreference.isEnabled()).isFalse();
+    }
+}