feature JabRef#6189 popOver implemented

- popover implemented and located above assigned button
- ready to display relevant information once implemented

src/main/java/org/jabref/gui/fieldeditors/JournalEditor.fxml

@@ -17,7 +17,8 @@
             <Tooltip text="%Switches between full and abbreviated journal name if the journal name is known."/>
         </tooltip>
     </Button>
-    <Button onAction="#getJournalStatistics"
+    <Button fx:id="journalStatisticsButton"
+            onAction="#getJournalStatistics"
             styleClass="icon-button">
         <graphic>
             <JabRefIconView glyph="VIEW_JOURNAL_STATISTICS"/>

src/main/java/org/jabref/gui/fieldeditors/JournalEditor.java

@@ -2,6 +2,7 @@
 
 import javafx.fxml.FXML;
 import javafx.scene.Parent;
+import javafx.scene.control.Button;
 import javafx.scene.layout.HBox;
 
 import org.jabref.gui.autocompleter.AutoCompletionTextInputBinding;
@@ -19,6 +20,7 @@ public class JournalEditor extends HBox implements FieldEditorFX {
 
     @FXML private JournalEditorViewModel viewModel;
     @FXML private EditorTextField textField;
+    @FXML private Button journalStatisticsButton;
 
     public JournalEditor(Field field,
                          JournalAbbreviationRepository journalAbbreviationRepository,
@@ -60,6 +62,6 @@ private void toggleAbbreviation() {
 
     @FXML
     private void getJournalStatistics() {
-        viewModel.getJournalStatistics();
+        viewModel.getJournalStatistics(journalStatisticsButton);
     }
 }

src/main/java/org/jabref/gui/fieldeditors/JournalEditorPopOver.java

@@ -0,0 +1,24 @@
+package org.jabref.gui.fieldeditors;
+
+import javafx.scene.control.Button;
+import javafx.scene.control.Label;
+import javafx.scene.layout.VBox;
+
+import org.controlsfx.control.PopOver;
+
+public class JournalEditorPopOver {
+
+    public void openPopOver(Button journalStatisticsButton) {
+
+        Label text1 = new Label("This is a text field");
+        Label text2 = new Label("This is another textfield");
+        Label text3 = new Label("Lorem ipsum dolor sit amet");
+        VBox vBox = new VBox(text1, text2, text3);
+        PopOver popOver = new PopOver(vBox);
+
+        popOver.setArrowLocation(PopOver.ArrowLocation.BOTTOM_CENTER);
+
+        popOver.show(journalStatisticsButton, 0);
+
+    }
+}

src/main/java/org/jabref/gui/fieldeditors/JournalEditorViewModel.java

@@ -2,6 +2,8 @@
 
 import java.util.Optional;
 
+import javafx.scene.control.Button;
+
 import org.jabref.gui.autocompleter.SuggestionProvider;
 import org.jabref.logic.integrity.FieldCheckers;
 import org.jabref.logic.journals.JournalAbbreviationRepository;
@@ -33,7 +35,9 @@ public void toggleAbbreviation() {
         }
     }
 
-    public void getJournalStatistics() {
-        System.out.println("hello world");
+    public void getJournalStatistics(Button journalStatisticsButton) {
+        JournalEditorPopOver popOver = new JournalEditorPopOver();
+        popOver.openPopOver(journalStatisticsButton);
+
     }
 }