Support the rich content for accessibility service (1/n)

Goal: 1. let third party developer can use html text that include from their local image file and
         animated image instead of only plain text to rich their content.
      2. Avoid malicious links made by third party developer

Action: 1. Add html, static text, and animated image preferences.
        2. Add android:AnimatedImageDrawable, and android:htmlDescription attributes.
        3. Fine-tune interface and integration
        4. Add custom tag filter

Bug: 136292241
Test: Maunal & make RunSettingsRoboTests
Change-Id: I82cd5319efb7faa1ff7e8354a279828fce5135b8

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

@@ -0,0 +1,139 @@
+/*
+ * 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.accessibility;
+
+import android.content.Context;
+import android.text.Html;
+import android.text.TextUtils;
+import android.widget.TextView;
+
+import androidx.preference.PreferenceViewHolder;
+
+import java.util.List;
+import java.util.regex.Pattern;
+
+/**
+ * A custom {@link android.widget.TextView} preference that shows html text with a custom tag
+ * filter.
+ */
+public final class HtmlTextPreference extends StaticTextPreference {
+
+    private boolean mDividerAllowedAbove = false;
+    private int mFlag = Html.FROM_HTML_MODE_COMPACT;
+    private Html.ImageGetter mImageGetter;
+    private Html.TagHandler mTagHandler;
+    private List<String> mUnsupportedTagList;
+
+    HtmlTextPreference(Context context) {
+        super(context);
+    }
+
+    @Override
+    public void onBindViewHolder(PreferenceViewHolder holder) {
+        super.onBindViewHolder(holder);
+        holder.setDividerAllowedAbove(mDividerAllowedAbove);
+
+        final TextView summaryView = holder.itemView.findViewById(android.R.id.summary);
+        if (summaryView != null && !TextUtils.isEmpty(getSummary())) {
+            final String filteredText = getFilteredText(getSummary().toString());
+            summaryView.setText(Html.fromHtml(filteredText, mFlag, mImageGetter, mTagHandler));
+        }
+    }
+
+    /**
+     * Sets divider whether to show in preference above.
+     *
+     * @param allowed true will be drawn on above this item
+     */
+    public void setDividerAllowedAbove(boolean allowed) {
+        if (allowed != mDividerAllowedAbove) {
+            mDividerAllowedAbove = allowed;
+            notifyChanged();
+        }
+    }
+
+    /**
+     * Sets the flag to which text format to be applied.
+     *
+     * @param flag to indicate that html text format
+     */
+    public void setFlag(int flag) {
+        if (flag != mFlag) {
+            mFlag = flag;
+            notifyChanged();
+        }
+    }
+
+    /**
+     * Sets image getter and help to load corresponding images when parsing.
+     *
+     * @param imageGetter to load image by image tag content
+     */
+    public void setImageGetter(Html.ImageGetter imageGetter) {
+        if (imageGetter != null && !imageGetter.equals(mImageGetter)) {
+            mImageGetter = imageGetter;
+            notifyChanged();
+        }
+    }
+
+    /**
+     * Sets tag handler to handle the unsupported tags.
+     *
+     * @param tagHandler the handler for unhandled tags
+     */
+    public void setTagHandler(Html.TagHandler tagHandler) {
+        if (tagHandler != null && !tagHandler.equals(mTagHandler)) {
+            mTagHandler = tagHandler;
+            notifyChanged();
+        }
+    }
+
+    /**
+     * Sets unsupported tag list, the text will be filtered though this list in advanced.
+     *
+     * @param unsupportedTagList the list of unsupported tags
+     */
+    public void setUnsupportedTagList(List<String> unsupportedTagList) {
+        if (unsupportedTagList != null && !unsupportedTagList.equals(mUnsupportedTagList)) {
+            mUnsupportedTagList = unsupportedTagList;
+            notifyChanged();
+        }
+    }
+
+    private String getFilteredText(String text) {
+        if (mUnsupportedTagList == null) {
+            return text;
+        }
+
+        int i = 1;
+        for (String tag : mUnsupportedTagList) {
+            if (!TextUtils.isEmpty(text)) {
+                final String index = String.valueOf(i++);
+                final String targetStart1 = "(?i)<" + tag + " ";
+                final String targetStart2 = "(?i)<" + tag + ">";
+                final String replacementStart1 = "<unsupportedtag" + index + " ";
+                final String replacementStart2 = "<unsupportedtag" + index + ">";
+                final String targetEnd = "(?i)</" + tag + ">";
+                final String replacementEnd = "</unsupportedtag" + index + ">";
+                text = Pattern.compile(targetStart1).matcher(text).replaceAll(replacementStart1);
+                text = Pattern.compile(targetStart2).matcher(text).replaceAll(replacementStart2);
+                text = Pattern.compile(targetEnd).matcher(text).replaceAll(replacementEnd);
+            }
+        }
+        return text;
+    }
+}