Update "Allow 2G" toggle summary wording.

Update "Allow 2G" toggle summary wording to be more clear regarding
the purpose of the toggle and why it may be disabled.

Bug: b/193693810
Bug: b/196183458
Test: manual & atest -c Enable2gPreferenceControllerTest
Change-Id: Iffef8f4f44105de30392c30ffd44c1d62cd066b8

res/values/strings.xml

@@ -13642,7 +13642,10 @@
     <!-- Title for toggle if user wants to enable 2G [CHAR LIMIT=40] -->
     <string name="enable_2g_title">Allow 2G</string>
     <!-- Title for toggle if user wants to enable 2G [CHAR LIMIT=NONE] -->
-    <string name="enable_2g_summary">Use 2G cellular connections. For emergency calls, 2G is always turned on.</string>
+    <string name="enable_2g_summary">2G is less secure, but may improve your connection in some locations. For emergency calls, 2G is always allowed.</string>
+    <!-- Title for if toggle access is disabled by carrier [CHAR LIMIT=NONE] -->
+    <string name="enable_2g_summary_disabled_carrier"><xliff:g id="carrier_name_2g" example="Google Fi">%1$s</xliff:g> requires 2G to be available</string>
+
 
     <!-- Label for extra app info settings for a specific app [CHAR LIMIT=40] -->
     <string name="extra_app_info_label" translatable="false"></string>

src/com/android/settings/network/telephony/Enable2gPreferenceController.java

@@ -19,10 +19,15 @@ import android.app.settings.SettingsEnums;
 import android.content.Context;
 import android.os.PersistableBundle;
 import android.telephony.CarrierConfigManager;
+import android.telephony.SubscriptionInfo;
 import android.telephony.SubscriptionManager;
 import android.telephony.TelephonyManager;
 import android.util.Log;
 
+import androidx.preference.Preference;
+
+import com.android.settings.R;
+import com.android.settings.network.SubscriptionUtil;
 import com.android.settings.overlay.FeatureFactory;
 import com.android.settingslib.core.instrumentation.MetricsFeatureProvider;
 
@@ -41,6 +46,7 @@ public class Enable2gPreferenceController extends TelephonyTogglePreferenceContr
     private final MetricsFeatureProvider mMetricsFeatureProvider;
 
     private CarrierConfigManager mCarrierConfigManager;
+    private SubscriptionManager mSubscriptionManager;
     private TelephonyManager mTelephonyManager;
 
     /**
@@ -53,6 +59,7 @@ public class Enable2gPreferenceController extends TelephonyTogglePreferenceContr
         super(context, key);
         mCarrierConfigManager = context.getSystemService(CarrierConfigManager.class);
         mMetricsFeatureProvider = FeatureFactory.getFactory(context).getMetricsFeatureProvider();
+        mSubscriptionManager = context.getSystemService(SubscriptionManager.class);
     }
 
     /**
@@ -68,6 +75,36 @@ public class Enable2gPreferenceController extends TelephonyTogglePreferenceContr
         return this;
     }
 
+    @Override
+    public void updateState(Preference preference) {
+        super.updateState(preference);
+        if (preference == null || !SubscriptionManager.isUsableSubscriptionId(mSubId)) {
+            return;
+        }
+        final PersistableBundle carrierConfig = mCarrierConfigManager.getConfigForSubId(mSubId);
+        boolean isDisabledByCarrier =
+                carrierConfig != null
+                && carrierConfig.getBoolean(CarrierConfigManager.KEY_HIDE_ENABLE_2G);
+        preference.setEnabled(!isDisabledByCarrier);
+        String summary;
+        if (isDisabledByCarrier) {
+            summary = mContext.getString(R.string.enable_2g_summary_disabled_carrier,
+                getCarrierName());
+        } else {
+            summary = mContext.getString(R.string.enable_2g_summary);
+        }
+        preference.setSummary(summary);
+    }
+
+    private String getCarrierName() {
+        SubscriptionInfo subInfo = SubscriptionUtil.getSubById(mSubscriptionManager, mSubId);
+        if (subInfo == null) {
+            return "";
+        }
+        final String carrierName = subInfo.getCarrierName().toString();
+        return carrierName;
+    }
+
     @Override
     public int getAvailabilityStatus(int subId) {
         final PersistableBundle carrierConfig = mCarrierConfigManager.getConfigForSubId(subId);
@@ -78,7 +115,6 @@ public class Enable2gPreferenceController extends TelephonyTogglePreferenceContr
         boolean visible =
                 SubscriptionManager.isUsableSubscriptionId(subId)
                 && carrierConfig != null
-                && !carrierConfig.getBoolean(CarrierConfigManager.KEY_HIDE_ENABLE_2G)
                 && mTelephonyManager.isRadioInterfaceCapabilitySupported(
                     mTelephonyManager.CAPABILITY_USES_ALLOWED_NETWORK_TYPES_BITMASK);
         return visible ? AVAILABLE : CONDITIONALLY_UNAVAILABLE;

tests/unit/src/com/android/settings/network/telephony/Enable2gPreferenceControllerTest.java

@@ -45,12 +45,12 @@ import org.mockito.MockitoAnnotations;
 public final class Enable2gPreferenceControllerTest {
     private static final int SUB_ID = 2;
 
+    @Mock
+    private CarrierConfigManager mCarrierConfigManager;
     @Mock
     private TelephonyManager mTelephonyManager;
     @Mock
     private TelephonyManager mInvalidTelephonyManager;
-    @Mock
-    private CarrierConfigManager mCarrierConfigManager;
 
     private PersistableBundle mPersistableBundle;
     private Enable2gPreferenceController mController;