disable export if unsaved

OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/EditKeyActivity.java

@@ -332,8 +332,12 @@ public class EditKeyActivity extends ActionBarActivity implements EditorListener
             cancelClicked();
             return true;
         case R.id.menu_key_edit_export_file:
+            if (needsSaving()) {
+                Toast.makeText(this, R.string.error_save_first, Toast.LENGTH_LONG).show();
+            } else {
                 mExportHelper.showExportKeysDialog(mDataUri, Id.type.secret_key, Constants.path.APP_DIR
                         + "/secexport.asc");
+            }
             return true;
         case R.id.menu_key_edit_delete: {
             // Message is received after key is deleted

OpenPGP-Keychain/src/main/res/values/strings.xml

@@ -286,6 +286,7 @@
     <string name="error_nfc_needed">NFC is not available on your device!</string>
     <string name="error_nothing_import">Nothing to import!</string>
     <string name="error_expiry_must_come_after_creation">expiry date must come after creation date</string>
+    <string name="error_save_first">please save the keyring first</string>
 
     <!-- progress dialogs, usually ending in '…' -->
     <string name="progress_done">done.</string>