Keep previous label in QLineEdit for label

labelme/app.py

@@ -681,8 +681,8 @@ class MainWindow(QMainWindow, WindowMixin):
 
         position MUST be in global coordinates.
         """
-        text = ''
         items = self.uniqLabelList.selectedItems()
+        text = None
         if items:
             text = items[0].text()
         text = self.labelDialog.popUp(text)

labelme/labelDialog.py

@@ -109,14 +109,14 @@ class LabelDialog(QDialog):
             self.edit.setText(self.edit.text().trimmed())
 
     def popUp(self, text=None, move=True):
-        if text is None:
-            text = ''
-        self.edit.setText(text)
-        self.edit.setSelection(0, len(text))
-        items = self.labelList.findItems(text, Qt.MatchFixedString)
-        if items:
-            assert len(items) == 1
-            self.labelList.setCurrentItem(items[0])
+        # if text is None, the previous label in self.edit is kept
+        if text is not None:
+            self.edit.setText(text)
+            self.edit.setSelection(0, len(text))
+            items = self.labelList.findItems(text, Qt.MatchFixedString)
+            if items:
+                assert len(items) == 1
+                self.labelList.setCurrentItem(items[0])
         self.edit.setFocus(Qt.PopupFocusReason)
         if move:
             self.move(QCursor.pos())