Display: make Colors settings entry preference reactive

Added `display_color_mode` listener to Colors preference. As a result,
it becomes reactive and updates its color mode value summary.

Flag: EXEMPT minor change
Bug: 397659800
Test: changed color mode using `adb` commands and verify that Colors
summary reacts and print correct color mode

Change-Id: I963768e3dbb43b547ec53e6445b2791ec0f57cff

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

@@ -14,15 +14,37 @@
 package com.android.settings.display;
 
 import android.content.Context;
+import android.database.ContentObserver;
 import android.hardware.display.ColorDisplayManager;
+import android.net.Uri;
+import android.os.Handler;
+import android.os.Looper;
+import android.provider.Settings;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleObserver;
+import androidx.lifecycle.OnLifecycleEvent;
 import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
 
 import com.android.settings.core.BasePreferenceController;
 
-public class ColorModePreferenceController extends BasePreferenceController {
+public class ColorModePreferenceController extends BasePreferenceController
+        implements LifecycleObserver {
+
+    private Preference mPreference;
+
+    private final ContentObserver mContentObserver = new ContentObserver(
+            new Handler(Looper.getMainLooper())) {
+        @Override
+        public void onChange(boolean selfChange, @Nullable Uri uri) {
+            if (mPreference != null) {
+                updateState(mPreference);
+            }
+        }
+    };
 
     public ColorModePreferenceController(@NonNull Context context, @NonNull String key) {
         super(context, key);
@@ -36,11 +58,32 @@ public class ColorModePreferenceController extends BasePreferenceController {
                 AVAILABLE : DISABLED_FOR_USER;
     }
 
+    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
+    public void onResume() {
+        mContext.getContentResolver().registerContentObserver(
+                Settings.System.getUriFor(Settings.System.DISPLAY_COLOR_MODE),
+                /* notifyForDescendants= */ false,
+                mContentObserver);
+    }
+
+    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
+    public void onPause() {
+        mContext.getContentResolver().unregisterContentObserver(mContentObserver);
+    }
+
     @Override
     public CharSequence getSummary() {
         return getColorModeName();
     }
 
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+        mPreference = screen.findPreference(getPreferenceKey());
+        if (mPreference != null) {
+            updateState(mPreference);
+        }
+    }
+
     @Override
     public void updateState(@Nullable Preference preference) {
         if (preference == null) {

tests/robotests/src/com/android/settings/display/colors/ColorModePreferenceControllerTest.kt

@@ -15,10 +15,15 @@
  */
 package com.android.settings.display
 
+import android.content.ContentResolver
 import android.content.Context
+import android.database.ContentObserver
 import android.hardware.display.ColorDisplayManager
+import android.provider.Settings
 
 import androidx.preference.Preference
+import androidx.preference.PreferenceScreen
+import androidx.preference.PreferenceManager
 import androidx.test.core.app.ApplicationProvider
 
 import com.android.settingslib.testutils.shadow.ShadowColorDisplayManager
@@ -31,22 +36,34 @@ import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner
 import org.robolectric.annotation.Config
 import org.robolectric.shadow.api.Shadow
+import org.robolectric.shadows.ShadowContentResolver
 
 @RunWith(RobolectricTestRunner::class)
-@Config(shadows = [ShadowColorDisplayManager::class])
+@Config(shadows = [ShadowColorDisplayManager::class, ShadowContentResolver::class])
 class ColorModePreferenceControllerTest {
     private lateinit var context: Context
     private lateinit var preference: Preference
     private lateinit var controller: ColorModePreferenceController
     private lateinit var shadowColorDisplayManager: ShadowColorDisplayManager
+    private lateinit var shadowContentResolver: ShadowContentResolver
 
     @Before
     fun setup() {
         context = ApplicationProvider.getApplicationContext()
+
         controller = ColorModePreferenceController(context, "test")
         preference = Preference(context)
+        val preferenceManager = PreferenceManager(context)
+        val preferenceScreen = preferenceManager.createPreferenceScreen(context)
+        preference.setKey(controller.getPreferenceKey());
+        preferenceScreen.addPreference(preference)
+
         shadowColorDisplayManager = Shadow.extract(
-            context.getSystemService(ColorDisplayManager::class.java));
+            context.getSystemService(ColorDisplayManager::class.java))
+        val contentResolver = context.getContentResolver();
+        shadowContentResolver = Shadow.extract(contentResolver)
+
+        controller.displayPreference(preferenceScreen)
     }
 
     @Test
@@ -80,4 +97,43 @@ class ColorModePreferenceControllerTest {
         val naturalColorModeName = context.getString(R.string.color_mode_option_natural)
         assertThat(preference.summary.toString()).isEqualTo(naturalColorModeName)
     }
+
+    @Test
+    fun onResume_verifyRegisterColorModeObserver() {
+        controller.onResume()
+        assertThat(shadowContentResolver.getContentObservers(
+            Settings.System.getUriFor(Settings.System.DISPLAY_COLOR_MODE)))
+            .hasSize(1)
+    }
+
+    @Test
+    fun onPause_verifyUnregisterColorModeObserver() {
+        controller.onResume()
+        controller.onPause()
+        assertThat(shadowContentResolver.getContentObservers(
+            Settings.System.getUriFor(Settings.System.DISPLAY_COLOR_MODE)))
+            .isEmpty()
+    }
+
+    @Test
+    fun contentObserver_onChange_updatesPreferenceSummary() {
+        controller.onResume()
+        assertThat(shadowContentResolver.getContentObservers(
+            Settings.System.getUriFor(Settings.System.DISPLAY_COLOR_MODE)))
+            .hasSize(1)
+
+        shadowColorDisplayManager.setColorMode(ColorDisplayManager.COLOR_MODE_NATURAL)
+        triggerOnChangeListener()
+        assertThat(preference.summary).isEqualTo(context.getString(R.string.color_mode_option_natural))
+
+        shadowColorDisplayManager.setColorMode(ColorDisplayManager.COLOR_MODE_AUTOMATIC)
+        triggerOnChangeListener()
+        assertThat(preference.summary).isEqualTo(context.getString(R.string.color_mode_option_automatic))
+    }
+
+    private fun triggerOnChangeListener() {
+        shadowContentResolver.getContentObservers(
+            Settings.System.getUriFor(Settings.System.DISPLAY_COLOR_MODE))
+            .forEach {it.onChange(false, null)};
+    }
 }