Skip downloading messages when roaming

app/src/main/java/eu/faircode/email/Core.java

@@ -1417,6 +1417,9 @@ class Core {
             Context context,
             EntityFolder folder, IMAPFolder ifolder,
             IMAPMessage imessage, long id, State state) throws MessagingException, IOException {
+        if (state.getNetworkState().isRoaming())
+            return;
+
         DB db = DB.getInstance(context);
         EntityMessage message = db.message().getMessage(id);
         if (message == null)

app/src/main/java/eu/faircode/email/FragmentOptions.java

@@ -68,6 +68,7 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
     private TextView tvScheduleEnd;
 
     private TextView tvConnectionType;
+    private TextView tvConnectionRoaming;
     private SwitchCompat swMetered;
     private Spinner spDownload;
 
@@ -151,6 +152,7 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
         tvScheduleEnd = view.findViewById(R.id.tvScheduleEnd);
 
         tvConnectionType = view.findViewById(R.id.tvConnectionType);
+        tvConnectionRoaming = view.findViewById(R.id.tvConnectionRoaming);
         swMetered = view.findViewById(R.id.swMetered);
         spDownload = view.findViewById(R.id.spDownload);
 
@@ -789,6 +791,7 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
 
                     tvConnectionType.setText(networkState.isUnmetered() ? R.string.title_legend_unmetered : R.string.title_legend_metered);
                     tvConnectionType.setVisibility(networkState.isConnected() ? View.VISIBLE : View.GONE);
+                    tvConnectionRoaming.setVisibility(networkState.isRoaming() ? View.VISIBLE : View.GONE);
                 }
             }
         });

app/src/main/java/eu/faircode/email/Helper.java

@@ -780,6 +780,7 @@ public class Helper {
         private Boolean connected = null;
         private Boolean suitable = null;
         private Boolean unmetered = null;
+        private Boolean roaming = null;
 
         boolean isConnected() {
             return (connected != null && connected);
@@ -793,6 +794,10 @@ public class Helper {
             return (unmetered != null && unmetered);
         }
 
+        boolean isRoaming() {
+            return (roaming != null && roaming);
+        }
+
         public void update(NetworkState newState) {
             connected = newState.connected;
             unmetered = newState.unmetered;
@@ -809,6 +814,23 @@ public class Helper {
         state.connected = (isMetered != null);
         state.unmetered = (isMetered != null && !isMetered);
         state.suitable = (isMetered != null && (metered || !isMetered));
+
+        if (state.connected) {
+            ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
+            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
+                NetworkInfo ani = cm.getActiveNetworkInfo();
+                if (ani != null)
+                    state.roaming = ani.isRoaming();
+            } else {
+                Network active = cm.getActiveNetwork();
+                if (active != null) {
+                    NetworkCapabilities caps = cm.getNetworkCapabilities(active);
+                    if (caps != null)
+                        state.roaming = !caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_ROAMING);
+                }
+            }
+        }
+
         return state;
     }
 

app/src/main/res/layout/fragment_options.xml

@@ -149,6 +149,19 @@
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/vSeparatorConnection" />
 
+        <TextView
+            android:id="@+id/tvConnectionRoaming"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="12dp"
+            android:layout_marginEnd="60dp"
+            android:text="@string/title_legend_roaming"
+            android:textAppearance="@style/TextAppearance.AppCompat.Small"
+            android:textStyle="italic"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/tvConnectionType" />
+
         <androidx.appcompat.widget.SwitchCompat
             android:id="@+id/swMetered"
             android:layout_width="match_parent"
@@ -158,7 +171,7 @@
             android:layout_marginEnd="12dp"
             android:text="@string/title_advanced_metered"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/tvConnectionType"
+            app:layout_constraintTop_toBottomOf="@id/tvConnectionRoaming"
             app:switchPadding="12dp" />
 
         <TextView

app/src/main/res/values/strings.xml

@@ -550,6 +550,7 @@
 
     <string name="title_legend_metered">Connection is metered</string>
     <string name="title_legend_unmetered">Connection is unmetered</string>
+    <string name="title_legend_roaming">Roaming</string>
 
     <string name="title_legend_expander">Expander</string>
     <string name="title_legend_avatar">Avatar</string>