Context menu on TableRow<Object> does not show up on first right click - javafx

Question

So I followed this example on using context menu with TableViews from here. I noticed that using this code
row.contextMenuProperty().bind(Bindings.when(Bindings.isNotNull(row.itemProperty()))
.then(rowMenu)
.otherwise((ContextMenu)null));
does not show up on first right click on a row with values. I need to right click on that row again for the context menu to show up. I also tried this code(which is my first approach, but not using it anymore because I've read somewhere that that guide is the best/good practice for anything related about context menu and tableview), and it displays the context menu immediately
if (row.getItem() != null) {
rowMenu.show(row, event.getScreenX(), event.getScreenY());
}
else {
// do nothing
}
but my problem with this code is it throws a NullPointerException whenever i try to right click on a row that has no data.
What could I possibly do to prevent NullPointerException while having the context menu show up immediately after a right click? In my code, I also have a code that a certain menu item in the context menu will be disabled based on the property of the myObject binded to row, that's why i need the context menu to pop up right away.
I noticed this too with the first block of code. Even if the property of myObject has already changed, it still has a menu item enabled/disabled unless I right click on that row again. I hope that you could help me. Thank you!
Here is a MCVE:
public class MCVE_TableView extends Application{
#Override
public void start(Stage primaryStage) throws Exception {
BorderPane myBorderPane = new BorderPane();
TableView<People> myTable = new TableView<>();
TableColumn<People, String> nameColumn = new TableColumn<>();
TableColumn<People, Integer> ageColumn = new TableColumn<>();
ContextMenu rowMenu = new ContextMenu();
ObservableList<People> peopleList = FXCollections.observableArrayList();
peopleList.add(new People("John Doe", 23));
nameColumn.setMinWidth(100);
nameColumn.setCellValueFactory(
new PropertyValueFactory<>("Name"));
ageColumn.setMinWidth(100);
ageColumn.setCellValueFactory(
new PropertyValueFactory<>("Age"));
myTable.setItems(peopleList);
myTable.getColumns().addAll(nameColumn, ageColumn);
myTable.setRowFactory(tv -> {
TableRow<People> row = new TableRow<>();
row.setOnContextMenuRequested((event) -> {
People selectedRow = row.getItem();
rowMenu.getItems().clear();
MenuItem sampleMenuItem = new MenuItem("Sample Button");
if (selectedRow != null) {
if (selectedRow.getAge() > 100) {
sampleMenuItem.setDisable(true);
}
rowMenu.getItems().add(sampleMenuItem);
}
else {
event.consume();
}
/*if (row.getItem() != null) { // this block comment displays the context menu instantly
rowMenu.show(row, event.getScreenX(), event.getScreenY());
}
else {
// do nothing
}*/
// this requires the row to be right clicked 2 times before displaying the context menu
row.contextMenuProperty().bind(Bindings.when(Bindings.isNotNull(row.itemProperty()))
.then(rowMenu)
.otherwise((ContextMenu)null));
});
return row;
});
myBorderPane.setCenter(myTable);
Scene scene = new Scene(myBorderPane, 500, 500);
primaryStage.setTitle("MCVE");
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main (String[] args) {
launch(args);
}
}
Here is the People Class
public class People {
SimpleStringProperty name;
SimpleIntegerProperty age;
public People(String name, int age) {
this.name = new SimpleStringProperty(name);
this.age = new SimpleIntegerProperty(age);
}
public SimpleStringProperty NameProperty() {
return this.name;
}
public SimpleIntegerProperty AgeProperty() {
return this.age;
}
public String getName() {
return this.name.get();
}
public int getAge() {
return this.age.get();
}
}
Edit: MCVE added
Edit2: Updated the MCVE. Still requires to be right-clicked twice before the contextMenu pops up

Answer 1

Below's a code snippet as a quick demonstration of how-to/where-to instantiate and configure a per-row ContextMenu. It
creates a ContextMenu/MenuItem for each TableRow at the row's instantiation time
creates a conditional binding that binds the menu to the row's contextMenuProperty if not empty (just the same as you did)
configures the contextMenu in an onShowing handler, depending on the current item (note: no need for a guard against null, because the conditional binding will implicitly guarantee to not show the the menu in that case)
The snippet:
myTable.setRowFactory(tv -> {
TableRow<People> row = new TableRow<>() {
ContextMenu rowMenu = new ContextMenu();
MenuItem sampleMenuItem = new MenuItem("Sample Button");
{
rowMenu.getItems().addAll(sampleMenuItem);
contextMenuProperty()
.bind(Bindings
.when(Bindings.isNotNull(itemProperty()))
.then(rowMenu).otherwise((ContextMenu) null));
rowMenu.setOnShowing(e -> {
People selectedRow = getItem();
sampleMenuItem.setDisable(selectedRow.getAge() > 100);
});
}
};
return row;
});