Refactor CaptionAppearanceFragment to improve maintainability (3/n)

Root cause: There is a bunch of different logic of preferences in CaptionAppearanceFragment. It’s hard to implement new features and hard to maintain and hard to be testable.
Solution: Move out color and edge preference logic of CaptionAppearanceFragment into controllers to reduce the complexity of the relationship between preference and fragment.

Bug: 197695932
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.accessibility
Change-Id: I8ed80b445a0d376a7e9dda87feda82420a78a9da

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

@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2022 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.graphics.Color;
+import android.view.accessibility.CaptioningManager.CaptionStyle;
+
+/** Provides utility methods related caption. */
+public final class CaptionUtils {
+
+    /**
+     * Unpacks the specified color value to get the color value.
+     *
+     * @param value the specified color value.
+     */
+    public static int parseColor(int value) {
+        final int colorValue;
+        if (!CaptionStyle.hasColor(value)) {
+            // "Default" color with variable alpha.
+            colorValue = CaptionStyle.COLOR_UNSPECIFIED;
+        } else if ((value >>> 24) == 0) {
+            // "None" color with variable alpha.
+            colorValue = Color.TRANSPARENT;
+        } else {
+            // Normal color.
+            colorValue = value | 0xFF000000;
+        }
+        return colorValue;
+    }
+
+    /**
+     * Unpacks the specified color value to get the opacity value.
+     *
+     * @param value the specified color value.
+     */
+    public static int parseOpacity(int value) {
+        final int opacityValue;
+        if (!CaptionStyle.hasColor(value)) {
+            // "Default" color with variable alpha.
+            opacityValue = (value & 0xFF) << 24;
+        } else if ((value >>> 24) == 0) {
+            // "None" color with variable alpha.
+            opacityValue = (value & 0xFF) << 24;
+        } else {
+            // Normal color.
+            opacityValue = value & 0xFF000000;
+        }
+
+        // Opacity value is always white.
+        return opacityValue | 0xFFFFFF;
+    }
+
+    /**
+     * Packs the specified color value and specified opacity value into merged color value.
+     *
+     * @param colorValue the color value.
+     * @param opacityValue the opacity value.
+     */
+    public static int mergeColorOpacity(int colorValue, int opacityValue) {
+        final int value;
+        // "Default" is 0x00FFFFFF or, for legacy support, 0x00000100.
+        if (!CaptionStyle.hasColor(colorValue)) {
+            // Encode "default" as 0x00FFFFaa.
+            value = 0x00FFFF00 | Color.alpha(opacityValue);
+        } else if (colorValue == Color.TRANSPARENT) {
+            // Encode "none" as 0x000000aa.
+            value = Color.alpha(opacityValue);
+        } else {
+            // Encode custom color normally.
+            value = (colorValue & 0x00FFFFFF) | (opacityValue & 0xFF000000);
+        }
+        return value;
+    }
+}