[Languages] Add new information to system language page.

- Add top Intro preference
 - Add footer preference
 - Add sub string to language picker
 - Modify title of app locale pages

Bug: 242182598 Add information to system language page.
Bug: 241600418 [Panlingual] Change strings on App languages
Test: Maunal test
Change-Id: I9bca8911e8e70c97c273294b3c9d1d73d4ea0cb2

src/com/android/settings/localepicker/LocaleDragAndDropAdapter.java

@@ -43,7 +43,6 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
 
-
 class LocaleDragAndDropAdapter
         extends RecyclerView.Adapter<LocaleDragAndDropAdapter.CustomViewHolder> {
 
@@ -154,8 +153,10 @@ class LocaleDragAndDropAdapter
         final LocaleDragCell dragCell = holder.getLocaleDragCell();
         final String label = feedItem.getFullNameNative();
         final String description = feedItem.getFullNameInUiLanguage();
+
         dragCell.setLabelAndDescription(label, description);
         dragCell.setLocalized(feedItem.isTranslated());
+        dragCell.setCurrentDefault(feedItem.getLocale().equals(Locale.getDefault()));
         dragCell.setMiniLabel(mNumberFormatter.format(i + 1));
         dragCell.setShowCheckbox(mRemoveMode);
         dragCell.setShowMiniLabel(!mRemoveMode);

src/com/android/settings/localepicker/LocaleDragCell.java

@@ -33,6 +33,7 @@ class LocaleDragCell extends RelativeLayout {
     private CheckBox mCheckbox;
     private TextView mMiniLabel;
     private TextView mLocalized;
+    private TextView mCurrentDefault;
     private ImageView mDragHandle;
 
     public LocaleDragCell(Context context, AttributeSet attrs) {
@@ -44,6 +45,7 @@ class LocaleDragCell extends RelativeLayout {
         super.onFinishInflate();
         mLabel = (TextView) findViewById(R.id.label);
         mLocalized = (TextView) findViewById(R.id.l10nWarn);
+        mCurrentDefault = (TextView) findViewById(R.id.default_locale);
         mMiniLabel = (TextView) findViewById(R.id.miniLabel);
         mCheckbox = (CheckBox) findViewById(R.id.checkbox);
         mDragHandle = (ImageView) findViewById(R.id.dragHandle);
@@ -100,6 +102,14 @@ class LocaleDragCell extends RelativeLayout {
         invalidate();
     }
 
+    /**
+     * Indicate current locale is system default.
+     */
+    public void setCurrentDefault(boolean isCurrentDefault) {
+        mCurrentDefault.setVisibility(isCurrentDefault ? VISIBLE : GONE);
+        invalidate();
+    }
+
     public ImageView getDragHandle() {
         return mDragHandle;
     }

src/com/android/settings/localepicker/LocaleHelperPreferenceController.java

@@ -0,0 +1,74 @@
+/*
+ * 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.localepicker;
+
+import android.content.Context;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.preference.PreferenceScreen;
+
+import com.android.settings.R;
+import com.android.settingslib.HelpUtils;
+import com.android.settingslib.core.AbstractPreferenceController;
+import com.android.settingslib.widget.FooterPreference;
+
+/**
+ * A controller to update current locale information of application.
+ */
+public class LocaleHelperPreferenceController extends AbstractPreferenceController {
+    private static final String TAG = LocaleHelperPreferenceController.class.getSimpleName();
+
+    private static final String KEY_FOOTER_LANGUAGE_PICKER = "footer_languages_picker";
+
+    public LocaleHelperPreferenceController(Context context) {
+        super(context);
+    }
+
+    @Override
+    public boolean isAvailable() {
+        return true;
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return KEY_FOOTER_LANGUAGE_PICKER;
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+        FooterPreference footerPreference = screen.findPreference(getPreferenceKey());
+        updateFooterPreference(footerPreference);
+    }
+
+    @VisibleForTesting
+    void updateFooterPreference(FooterPreference footerPreference) {
+        if (footerPreference != null) {
+            footerPreference.setLearnMoreAction(v -> openLocaleLearnMoreLink());
+            footerPreference.setLearnMoreText(mContext.getString(
+                    R.string.desc_locale_helper_footer_general));
+        }
+    }
+
+    private void openLocaleLearnMoreLink() {
+        mContext.startActivity(
+                HelpUtils.getHelpIntent(
+                        mContext,
+                        mContext.getString(R.string.link_locale_picker_footer_learn_more),
+                        /*backupContext=*/""));
+    }
+}

src/com/android/settings/localepicker/LocaleListEditor.java

@@ -36,6 +36,7 @@ import android.widget.TextView;
 
 import androidx.annotation.VisibleForTesting;
 import androidx.appcompat.app.AlertDialog;
+import androidx.preference.PreferenceScreen;
 import androidx.recyclerview.widget.RecyclerView;
 
 import com.android.internal.app.LocalePicker;
@@ -47,6 +48,7 @@ import com.android.settings.search.BaseSearchIndexProvider;
 import com.android.settingslib.search.SearchIndexable;
 import com.android.settingslib.search.SearchIndexableRaw;
 import com.android.settingslib.utils.StringUtil;
+import com.android.settingslib.widget.LayoutPreference;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -65,6 +67,7 @@ public class LocaleListEditor extends RestrictedSettingsFragment {
     private static final int REQUEST_LOCALE_PICKER = 0;
 
     private static final String INDEX_KEY_ADD_LANGUAGE = "add_language";
+    private static final String KEY_LANGUAGES_PICKER = "languages_picker";
 
     private LocaleDragAndDropAdapter mAdapter;
     private Menu mMenu;
@@ -73,6 +76,9 @@ public class LocaleListEditor extends RestrictedSettingsFragment {
     private boolean mShowingRemoveDialog;
     private boolean mIsUiRestricted;
 
+    private LayoutPreference mLocalePickerPreference;
+    private LocaleHelperPreferenceController mLocaleHelperPreferenceController;
+
     public LocaleListEditor() {
         super(DISALLOW_CONFIG_LOCALE);
     }
@@ -87,6 +93,14 @@ public class LocaleListEditor extends RestrictedSettingsFragment {
         super.onCreate(savedInstanceState);
         setHasOptionsMenu(true);
 
+        addPreferencesFromResource(R.xml.languages);
+        final Activity activity = getActivity();
+        activity.setTitle(R.string.language_picker_title);
+        mLocaleHelperPreferenceController = new LocaleHelperPreferenceController(activity);
+        final PreferenceScreen screen = getPreferenceScreen();
+        mLocalePickerPreference = screen.findPreference(KEY_LANGUAGES_PICKER);
+        mLocaleHelperPreferenceController.displayPreference(screen);
+
         LocaleStore.fillCache(this.getContext());
         final List<LocaleStore.LocaleInfo> feedsList = getUserLocaleList();
         mAdapter = new LocaleDragAndDropAdapter(this.getContext(), feedsList);
@@ -94,11 +108,8 @@ public class LocaleListEditor extends RestrictedSettingsFragment {
 
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstState) {
-        final View result = super.onCreateView(inflater, container, savedInstState);
-        final View myLayout = inflater.inflate(R.layout.locale_order_list, (ViewGroup) result);
-
-        configureDragAndDrop(myLayout);
-        return result;
+        configureDragAndDrop(mLocalePickerPreference);
+        return super.onCreateView(inflater, container, savedInstState);
     }
 
     @Override
@@ -288,8 +299,8 @@ public class LocaleListEditor extends RestrictedSettingsFragment {
         return result;
     }
 
-    private void configureDragAndDrop(View view) {
-        final RecyclerView list = view.findViewById(R.id.dragList);
+    private void configureDragAndDrop(LayoutPreference layout) {
+        final RecyclerView list = layout.findViewById(R.id.dragList);
         final LocaleLinearLayoutManager llm = new LocaleLinearLayoutManager(getContext(), mAdapter);
         llm.setAutoMeasureEnabled(true);
         list.setLayoutManager(llm);
@@ -298,7 +309,7 @@ public class LocaleListEditor extends RestrictedSettingsFragment {
         mAdapter.setRecyclerView(list);
         list.setAdapter(mAdapter);
 
-        mAddLanguage = view.findViewById(R.id.add_language);
+        mAddLanguage = layout.findViewById(R.id.add_language);
         mAddLanguage.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {