Add the preference controller to control accessibility button fade preference

* Opacity preference will be disabled when fade is disabled

Bug: 173940869
Test: atest AccessibilityButtonFadePreferenceControllerTest AccessibilityButtonOactiyPreferenceControllerTest
Change-Id: I1efd9760aa0287899cddd10ddd9a88a81ccc39ba

src/com/android/settings/accessibility/FloatingMenuFadePreferenceController.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2021 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.accessibility;
+
+import android.content.ContentResolver;
+import android.content.Context;
+import android.database.ContentObserver;
+import android.os.Handler;
+import android.os.Looper;
+import android.provider.Settings;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
+import androidx.preference.SwitchPreference;
+
+import com.android.settings.core.BasePreferenceController;
+import com.android.settingslib.core.lifecycle.LifecycleObserver;
+import com.android.settingslib.core.lifecycle.events.OnPause;
+import com.android.settingslib.core.lifecycle.events.OnResume;
+
+/** Preference controller that controls the fade switch button in accessibility button page. */
+public class FloatingMenuFadePreferenceController extends BasePreferenceController implements
+        Preference.OnPreferenceChangeListener, LifecycleObserver, OnResume, OnPause {
+
+    private static final int OFF = 0;
+    private static final int ON = 1;
+
+    private final ContentResolver mContentResolver;
+    @VisibleForTesting
+    final ContentObserver mContentObserver;
+
+    @VisibleForTesting
+    SwitchPreference mPreference;
+
+    public FloatingMenuFadePreferenceController(Context context, String preferenceKey) {
+        super(context, preferenceKey);
+        mContentResolver = context.getContentResolver();
+        mContentObserver = new ContentObserver(new Handler(Looper.getMainLooper())) {
+            @Override
+            public void onChange(boolean selfChange) {
+                updateAvailabilityStatus();
+            }
+        };
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return AccessibilityUtil.isFloatingMenuEnabled(mContext)
+                ? AVAILABLE : DISABLED_DEPENDENT_SETTING;
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+
+        mPreference = screen.findPreference(getPreferenceKey());
+    }
+
+    @Override
+    public boolean onPreferenceChange(Preference preference, Object newValue) {
+        final boolean isEnabled = (boolean) newValue;
+        putFloatingMenuFadeValue(isEnabled);
+        return true;
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        super.updateState(preference);
+        final SwitchPreference switchPreference = (SwitchPreference) preference;
+
+        switchPreference.setChecked(getFloatingMenuFadeValue() == ON);
+    }
+
+    @Override
+    public void onResume() {
+        mContentResolver.registerContentObserver(
+                Settings.Secure.getUriFor(
+                        Settings.Secure.ACCESSIBILITY_BUTTON_MODE),
+                        /* notifyForDescendants= */ false, mContentObserver);
+    }
+
+    @Override
+    public void onPause() {
+        mContentResolver.unregisterContentObserver(mContentObserver);
+    }
+
+    private void updateAvailabilityStatus() {
+        mPreference.setEnabled(AccessibilityUtil.isFloatingMenuEnabled(mContext));
+    }
+
+    private int getFloatingMenuFadeValue() {
+        return Settings.Secure.getInt(mContentResolver,
+                Settings.Secure.ACCESSIBILITY_FLOATING_MENU_FADE_ENABLED, ON);
+    }
+
+    private void putFloatingMenuFadeValue(boolean isEnabled) {
+        Settings.Secure.putInt(mContentResolver,
+                Settings.Secure.ACCESSIBILITY_FLOATING_MENU_FADE_ENABLED,
+                isEnabled ? ON : OFF);
+    }
+}