Update accesibility button to suuport accessibility gesutre

1. Add gesture preference controller for gesture navigation
2. Auto update the preview illustarion when screen reader is on
3. Auto update accessibility button title for system navigation

Bug: 190563948
Test: make RunSettingsRoboTests ROBOTEST_FILTER=AccessibilityButtonGesturePreferenceControllerTest ROBOTEST_FILTER=AccessibilityButtonPreviewPreferenceControllerTest ROBOTEST_FILTER=AccessibilityLayerDrawableTest ROBOTEST_FILTER=AccessibilityPreferenceControllerTest ROBOTEST_FILTER=AccessibilityButtonFooterPreferenceControllerTest
Change-Id: Ifa98fc029430d86d3143133b3203b239340f2e41

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

@@ -0,0 +1,133 @@
+/*
+ * 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.Context;
+import android.graphics.drawable.Drawable;
+import android.graphics.drawable.LayerDrawable;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
+
+import com.android.settings.R;
+
+import java.util.Objects;
+
+/** LayerDrawable that contains device icon as background and given icon as foreground. */
+public class AccessibilityLayerDrawable extends LayerDrawable {
+
+    private AccessibilityLayerDrawableState mState;
+
+    /**
+     * Creates a new layer drawable with the list of specified layers.
+     *
+     * @param layers a list of drawables to use as layers in this new drawable,
+     *               must be non-null
+     */
+    private AccessibilityLayerDrawable(@NonNull Drawable[] layers) {
+        super(layers);
+    }
+
+    /**
+     * Create the {@link LayerDrawable} that contains device icon as background and given menu icon
+     * with given {@code opacity} value as foreground.
+     *
+     * @param context the valid context used to get the icon
+     * @param resId the resource ID of the given icon
+     * @param opacity the opacity to apply to the given icon
+     * @return the drawable that combines the device icon and the given icon
+     */
+    public static AccessibilityLayerDrawable createLayerDrawable(Context context, int resId,
+            int opacity) {
+        final Drawable bg = context.getDrawable(R.drawable.accessibility_button_preview_base);
+        final AccessibilityLayerDrawable basicDrawable = new AccessibilityLayerDrawable(
+                new Drawable[]{bg, null});
+
+        basicDrawable.updateLayerDrawable(context, resId, opacity);
+        return basicDrawable;
+    }
+
+    /**
+     * Update the drawable  with given {@code resId} drawable and {@code opacity}(alpha)
+     * value at index 1 layer.
+     *
+     * @param context the valid context used to get the icon
+     * @param resId the resource ID of the given icon
+     * @param opacity the opacity to apply to the given icon
+     */
+    public void updateLayerDrawable(Context context, int resId, int opacity) {
+        final Drawable icon = context.getDrawable(resId);
+        icon.setAlpha(opacity);
+        this.setDrawable(/* index= */ 1, icon);
+        this.setConstantState(context, resId, opacity);
+    }
+
+    @Override
+    public ConstantState getConstantState() {
+        return mState;
+    }
+
+    /** Stores the constant state and data to the given drawable. */
+    private void setConstantState(Context context, int resId, int opacity) {
+        mState = new AccessibilityLayerDrawableState(context, resId, opacity);
+    }
+
+    /** {@link ConstantState} to store the data of {@link AccessibilityLayerDrawable}. */
+    @VisibleForTesting
+    static class AccessibilityLayerDrawableState extends ConstantState {
+
+        private final Context mContext;
+        private final int mResId;
+        private final int mOpacity;
+
+        AccessibilityLayerDrawableState(Context context, int resId, int opacity) {
+            mContext = context;
+            mResId = resId;
+            mOpacity = opacity;
+        }
+
+        @NonNull
+        @Override
+        public Drawable newDrawable() {
+            return createLayerDrawable(mContext, mResId, mOpacity);
+        }
+
+        @Override
+        public int getChangingConfigurations() {
+            return 0;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) {
+                return true;
+            }
+            if (o == null || getClass() != o.getClass()) {
+                return false;
+            }
+            final AccessibilityLayerDrawableState that = (AccessibilityLayerDrawableState) o;
+            return mResId == that.mResId
+                    && mOpacity == that.mOpacity
+                    && Objects.equals(mContext, that.mContext);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(mContext, mResId, mOpacity);
+        }
+    }
+}