Add a helper class for filtering available subscriptions

In several places implementing the new changes for better UX with
multiple mobile subscriptions, we need a bit of code that filters the
results coming from the SubscriptionManager. This CL adds that common
code in a util class that will be used in later CLs.

Bug: 116349402
Test: RunSettingsRoboTests
Change-Id: Ie9376629604ac2c4a2f15123edc380c5999f2f83

src/com/android/settings/network/SubscriptionUtil.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2018 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.network;
+
+import android.telephony.SubscriptionInfo;
+import android.telephony.SubscriptionManager;
+import android.text.TextUtils;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+public class SubscriptionUtil {
+    public static List<SubscriptionInfo> getAvailableSubscriptions(SubscriptionManager manager) {
+        List<SubscriptionInfo> subscriptions = manager.getAvailableSubscriptionInfoList();
+        if (subscriptions == null) {
+            subscriptions = new ArrayList<>();
+        }
+        // With some carriers such as Google Fi which provide a sort of virtual service that spans
+        // across multiple underlying networks, we end up with subscription entries for the
+        // underlying networks that need to be hidden from the user in the UI.
+        for (Iterator<SubscriptionInfo> iter = subscriptions.iterator(); iter.hasNext(); ) {
+            SubscriptionInfo info = iter.next();
+            if (TextUtils.isEmpty(info.getMncString())) {
+                iter.remove();
+            }
+        }
+        return subscriptions;
+    }
+}