Check connectivity on browse

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

@@ -1948,11 +1948,14 @@ public class FragmentMessages extends FragmentBase {
                             @Override
                             public void onError(Throwable ex) {
                                 if (getLifecycle().getCurrentState().isAtLeast(Lifecycle.State.RESUMED))
-                                    new DialogBuilderLifecycle(getContext(), getViewLifecycleOwner())
-                                            .setMessage(Helper.formatThrowable(ex))
-                                            .setPositiveButton(android.R.string.cancel, null)
-                                            .create()
-                                            .show();
+                                    if (ex instanceof IllegalArgumentException)
+                                        Snackbar.make(view, ex.getMessage(), Snackbar.LENGTH_LONG).show();
+                                    else
+                                        new DialogBuilderLifecycle(getContext(), getViewLifecycleOwner())
+                                                .setMessage(Helper.formatThrowable(ex))
+                                                .setPositiveButton(android.R.string.cancel, null)
+                                                .create()
+                                                .show();
                             }
                         });
 

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

@@ -20,6 +20,8 @@ package eu.faircode.email;
 */
 
 import android.content.Context;
+import android.net.ConnectivityManager;
+import android.net.NetworkInfo;
 
 import com.sun.mail.iap.Argument;
 import com.sun.mail.iap.Response;
@@ -154,6 +156,13 @@ public class ViewModelBrowse extends ViewModel {
             EntityAccount account = db.account().getAccount(folder.account);
 
             try {
+                // Check connectivity
+                ConnectivityManager cm = (ConnectivityManager) state.context.getSystemService(Context.CONNECTIVITY_SERVICE);
+                NetworkInfo ni = cm.getActiveNetworkInfo();
+                boolean internet = (ni != null && ni.isConnected());
+                if (!internet)
+                    throw new IllegalArgumentException(state.context.getString(R.string.title_no_internet));
+
                 Properties props = MessageHelper.getSessionProperties(account.auth_type, account.realm, account.insecure);
                 Session isession = Session.getInstance(props, null);
                 isession.setDebug(true);