[FIXED] JavaFX: How do I update a selected Item from observableArrayList, in a new Scene. Without passing the in the entire set of data backing it?

Issue

JavaFX: How do I update a selected Item from observableArrayList, in a new Scene. Without passing the in the entire set of data backing it?

I think it would make sense just to pass in the one selected item to the new window. I have unable to get the observableArrayList to reflect changes by doing this.

I have only been able to get my program to work by passing in the entire data set. Both the ArrayList backing the observableArrayList and the observableArrayList its self. Then finding the element in the ArrayList, modifying the element, re-inserting the element back into the list, and then purging and re-adding the entire ArrayList to the observableArrayList. I am sure this is not the best way to do this. Being new to Javafx I am a not sure how to make this work.

Here is a working example of how I have accomplished this to work. Hopefully, this highlights what I am doing wrong and what I need to change.

Please note: I do not want to use any static classes if possible. This is a small project that I plan to extend to a larger project and I want to avoid pitfalls of using static classes.

Please note: I am omitting posting imports. Assume I have the correct imports.

Visual reference of my example code

Directory Structure.

    --example
           main.fxml
           Main.java
           MainController.java
           modify.fxml
           ModifyController.java
           myData.java

Main.java

    public class Main extends Application {  
    @Override
    public void start(Stage primaryStage) throws Exception {

      ArrayList<myData> values = new ArrayList<>();
      values.add(new myData("1"));
      values.add(new myData("2"));
      values.add(new myData("3"));

      FXMLLoader loader = new FXMLLoader(getClass().getResource("main.fxml"));
      Parent root = loader.load();
      MainController myController = loader.getController();
      myController.initialize(values);
      primaryStage.setTitle("Hello World");
      Scene mainScene = new Scene(root);
      primaryStage.setScene(mainScene);
      myController.setMainStage(primaryStage);
      primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
      }
    }

MainController.java

    public class MainController {    
    @FXML
    private Button modifyButton;
    @FXML
    private TableView<myData> valueTable;
    @FXML
    private TableColumn valueCell;    

    private ObservableList<myData> observableDataModels;
    private ArrayList<myData> values;
    private Stage primaryStage;    

    public void initialize(ArrayList<myData> values) {
    this.values = values;
    this.observableDataModels = FXCollections.observableArrayList(values);
    this.valueCell.setCellValueFactory(new PropertyValueFactory<>("value"));
    this.valueTable.setItems(observableDataModels);
    }    

    public void setMainStage(Stage primaryStage) {
    this.primaryStage = primaryStage;
    }    

    public void onMouseClicked(MouseEvent mouseEvent) throws IOException {    

    if (!this.valueTable.getSelectionModel().getSelectedCells().isEmpty()) {
      myData selectedItem = this.valueTable.getSelectionModel().getSelectedItem();    

      FXMLLoader loader = new FXMLLoader(getClass().getResource("modify.fxml"));
      Parent root = loader.load();
      ModifyController mpc = loader.getController();
      mpc.setData(selectedItem);
      mpc.setObservableDataModels(this.observableDataModels);
      mpc.setValues(this.values);
      TextField t = mpc.getValueTxtFld();
      t.setText(selectedItem.getValue());
      mpc.setValueTxtFld(t);
      Stage modifyStage = new Stage();
      Scene modfifyPartScene = new Scene(root);
      modifyStage.setScene(modfifyPartScene);
      mpc.setCurrStage(modifyStage);
      modifyStage.show();
          }
        }
      }

ModifyController.java

public class ModifyController {

  @FXML
  private TextField valueTxtFld;
  @FXML
  private Button mdfSaveBtn;
  @FXML
  private Stage currStage;
  private myData data;
  private ObservableList<myData> observableDataModels;
  private ArrayList<myData> values;

  public void setObservableDataModels(
      ObservableList<myData> observableDataModels) {
    this.observableDataModels = observableDataModels;
  }

  public ArrayList<myData> getValues() {
    return values;
  }

  public void setValues(ArrayList<myData> values) {
    this.values = values;
  }

  public TextField getValueTxtFld() {
    return valueTxtFld;
  }

  public void setValueTxtFld(TextField valueTxtFld) {
    this.valueTxtFld = valueTxtFld;
  }

  public void setData(myData selectedItem) {
    this.data = selectedItem;
  }

  public void setCurrStage(Stage modifyStage) {
    this.currStage = modifyStage;
  }

  public void onMouseClicked(MouseEvent mouseEvent) {

    myData dataBuffer = this.data;
    int i = dataBuffer.hashCode();
    this.data.setValue(this.valueTxtFld.getText());

    int count = 0;
    for (myData d : values) {
      if (i == d.hashCode()) {
        values.remove(count);
        values.set(count, this.data);
      } else {
        count += 1;
      }
    }

    observableDataModels.removeAll(values);
    observableDataModels.addAll(values);
    this.currStage.close();


  }
}

main.fxml

<AnchorPane prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.172-ea" xmlns:fx="http://javafx.com/fxml/1" fx:controller="example.ModifyController">
   <children>
      <TextField fx:id="valueTxtFld" layoutX="193.0" layoutY="169.0" />
      <Button fx:id="mdfSaveBtn" layoutX="261.0" layoutY="219.0" mnemonicParsing="false" onMouseClicked="#onMouseClicked" text="Save" />
   </children>
</AnchorPane>

modify.fxml

<AnchorPane prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.172-ea" xmlns:fx="http://javafx.com/fxml/1" fx:controller="example.ModifyController">
   <children>
      <TextField fx:id="valueTxtFld" layoutX="193.0" layoutY="169.0" />
      <Button fx:id="mdfSaveBtn" layoutX="261.0" layoutY="219.0" mnemonicParsing="false" onMouseClicked="#onMouseClicked" text="Save" />
   </children>
</AnchorPane>

Solution

You're editing a single item. You shouldn't a list for this reason. Stage.showAndWait allows you to wait for the user to finish the input and react to it, which I strongly recommend doing.

There are several things I recomment changing in addition to this:

• Use onAction events for button clicks instead of onMouseClicked events. This way you'll also react to pressing the Enter key when the button is focused and prevents clicks with mouse buttons other than the primary one from triggering the button.
• Use the selectedItem immediately instead of the selected cells. Those 2 are independent things and a check for null isn't really any harder than calling isEmpty() on some list.
• Do not provide direct access to nodes of the scene. This just spreads the responsibility for handling the nodes across multiple classes making the code harder to maintain. Furthermore e.g. the setter for the valueTxtFld property makes the code even more confusing, since you may end up with a TextField that is not part of the scene: you could pass a different TextField than the one getValueTxtFld returns to setValueTxtFld resulting in an error that is not the simplest one to debug. If you'd simply provide access to the property you're using (the TextField.text property), this wouldn't be a problem. In this case access is not required though.

• Do not modify a list while iterating though it. You may get a ConcurrentModificationException. Also do not substitute comparing hash codes for a check for equality. This is more complex than necessary and it may fail. (Assuming your hashCode implementation is based on the String value alone there's a string for every possible int and there are strings that do don't contain int values so there must be 2 different objects with the same hashcode).
  Simply use indexOf instead:

  int index = values.indexOf(data);
  values.set(index, ...);
  

---

main.fxml

<Button fx:id="mdfSaveBtn" layoutX="261.0" layoutY="219.0" mnemonicParsing="false" onAction="#modify" text="Save" />

modify.fxml

<Button fx:id="mdfSaveBtn" layoutX="261.0" layoutY="219.0" mnemonicParsing="false" onAction="#save" text="Save" />

public class MainController {    
    ...

   // you can leave out the event parameter here, if you don't need it;
   // otherwise be sure to use a parameter of type ActionEvent    
    @FXML
    private void modify() throws IOException {
        myData data = valueTable.getSelectionModel().getSelectedItem();
        if (data != null) {
            FXMLLoader loader = new FXMLLoader(getClass().getResource("modify.fxml"));
            Parent root = loader.load();
            ModifyController mpc = loader.getController();
            mpc.setData(data);
            Stage modifyStage = new Stage();
            Scene modfifyPartScene = new Scene(root);
            modifyStage.setScene(modfifyPartScene);
            modifyStage.showAndWait();
            if (mpc.isEdited()) {
                valueTable.refresh(); // or update the table by other means
            }
        }
    }
}

public class ModifyController {

    @FXML
    private TextField valueTxtFld;
    @FXML
    private Button mdfSaveBtn;

    private myData data;

    // flag indicating, if the edit was submitted or not
    private boolean edited;

    public boolean isEdited() {
        return edited;
    }

    public void setData(myData selectedItem) {
        if (selectedItem == null) {
            throw new IllegalArgumentException();
        }
        this.data = selectedItem;
        valueTxtFld.setText(selectedItem.getValue());
        edited = false;
    }

    public void save() {
        data.setValue(valueTxtFld.getText());
        edited = true;
        mdfSaveBtn.getScene().getWindow().hide();
    }

}

Answered By - fabian