问题
I'm working on a JavaFX program that can display different grocery items as a BarChart. My code structure uses an initial loading class, GroceryGrapher.java, a controller, GroceryGrapherController.java, and an .fxml file, GroceryGrapher.fxml.
I'm relatively new to JavaFX and I've tried different approaches to creating and displaying my BarChart. For the most part I've resolved issues and can load the chart with its data and components, but my issue is that the chart won't display / update after the program has started. The BarChart is part of an AnchorPane (which all comes under a StackPane) in my FXML file, and I've tried to update it after initialization since it starts out blank but it remains blank.
The BarChart is part of the AnchorPane, which also has a MenuBar. My goal was to be able to update different parts of the BarChart via the MenuBar. When I load the program, the MenuBar and empty BarChart are loaded:
This is how I initialize my BarChart and its data:
public class GroceryGrapherController implements Initializable {
@FXML
private AnchorPane anchorPane = new AnchorPane();
@FXML
private NumberAxis xAxis = new NumberAxis();
@FXML
private CategoryAxis yAxis = new CategoryAxis();
@FXML
private BarChart<Number, String> groceryBarChart;
@FXML
//private Stage stage;
Parent root;
@Override
public void initialize(URL location, ResourceBundle resources) {
groceryBarChart = new BarChart<Number, String>(xAxis, yAxis);
groceryBarChart.setTitle("Horizontal Grocery List");
xAxis.setLabel("Number");
xAxis.setTickLabelRotation(90);
yAxis.setLabel("Grocery Type");
// Populate BarChart
XYChart.Series<Number, String> series1 = new XYChart.Series<>();
series1.setName("Chocolates");
series1.getData().add(new XYChart.Data<Number, String>(25601.34, "Reese"));
series1.getData().add(new XYChart.Data<Number, String>(20148.82, "Cadbury"));
series1.getData().add(new XYChart.Data<Number, String>(10000, "Mars"));
series1.getData().add(new XYChart.Data<Number, String>(35407.15, "Snickers"));
series1.getData().add(new XYChart.Data<Number, String>(12000, "Lindt"));
XYChart.Series<Number, String> series2 = new XYChart.Series<>();
series2.setName("Vegetables");
series2.getData().add(new XYChart.Data<Number, String>(57401.85, "Cabbage"));
series2.getData().add(new XYChart.Data<Number, String>(41941.19, "Lettuce"));
series2.getData().add(new XYChart.Data<Number, String>(45263.37, "Tomato"));
series2.getData().add(new XYChart.Data<Number, String>(117320.16, "Eggplant"));
series2.getData().add(new XYChart.Data<Number, String>(14845.27, "Beetroot"));
XYChart.Series<Number, String> series3 = new XYChart.Series<>();
series3.setName("Drinks");
series3.getData().add(new XYChart.Data<Number, String>(45000.65, "Water"));
series3.getData().add(new XYChart.Data<Number, String>(44835.76, "Coke"));
series3.getData().add(new XYChart.Data<Number, String>(18722.18, "Sprite"));
series3.getData().add(new XYChart.Data<Number, String>(17557.31, "Mountain Dew"));
series3.getData().add(new XYChart.Data<Number, String>(92633.68, "Beer"));
// Need to do this because of a bug with CategoryAxis... manually set categories
yAxis.setCategories(FXCollections.observableArrayList("Reese", "Cadbury", "Mars", "Snickers", "Lindt", "Cabbage", "Lettuce",
"Tomato", "Eggplant", "Beetroot", "Water", "Coke", "Sprite", "Mountain Dew", "Beer"));
groceryBarChart.getData().addAll(series1, series2, series3);
}
Now, I have an item:
In my MenuBar to load the BarChart (since it initially appears empty), which utilizes the a method I created, loadGraph. I've tried different methods to get my updated BarChart to show up with no major success. My initial idea was to use setScene in the loadGraph method to set the scene to the BarChart, as shown in this example.
Stage stage = (Stage) anchorPane.getScene().getWindow();
stage.setScene(new Scene(groceryBarChart, 800, 600));
While that did work, it naturally replaced the scene to solely consist of the BarChart, removing my MenuBar and previous GUI:
I saw this question which had a similar issue (I think) but I wasn't really sure how to apply it to my program. I got this code:
try {
FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("GroceryGrapher.fxml"));
root = (Parent) fxmlLoader.load();
GroceryGrapherController ggController = fxmlLoader.getController();
} catch (Exception e) {
e.printStackTrace();
}
I copied over my initialization from the initialize method to a new method and tried calling it with ggController but it didn't change anything. I also tried creating a new method, updateData:
@FXML
private void updateData() {
Platform.runLater(() -> {
groceryBarChart.setTitle("Horizontal Grocery List");
});
}
I tried calling it with ggController in the loadGraph method but my BarChart still didn't change.
I know I'm doing something wrong, but I'm not very familiar with the BarChart class and JavaFX in too much depth, so I figured I would come here to ask for help. I need to update the existing BarChart in my GUI so that my data can load without replacing the entire scene, in order for the MenuBar to remain visible in the scene able to perform functions. How would I go about altering the BarChart component part of my AnchorPane, updating the data as necessary, without completely replacing the scene as I did previously?
Thank you very much and sorry if this question is bad or my coding practices are wrong. All feedback would be much appreciated!
EDIT Just in case it might help, here is my FXML code for the BarChart.
<BarChart fx:id="groceryBarChart" layoutY="31.0" prefHeight="566.0" prefWidth="802.0">
<xAxis>
<CategoryAxis fx:id="yAxis" side="BOTTOM" />
</xAxis>
<yAxis>
<NumberAxis side="LEFT" fx:id="xAxis" />
</yAxis>
</BarChart>
回答1:
Most of the problems seem to be resolved, so I'll comment on this part only:
Ohh, I see. I increased the height and it seems to be thicker, thank you for your comment, that's very interesting behavior from the library. So I shouldn't use the approach I'm using?
Well, it depends. There is no other way to treat each data series as a separate list of categories in BarChart (at least, I'm not aware of any), so if you want to have groups of categories, each group with its own color, you'll have to use the same method as in your example.
The alternatives are to write your own implementation of bar chart layoutPlotChildren() method which will show only one bar per category (the only one if there are no two data series that contain the same category), or to find another chart library with those features. Of couse, you can always choose to show your data in different format (one data series for each month).
If you plan to use your original method, you'll have to adjust vertical position of bars (to center them again), and you'll have to fix bar height problem too:
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.chart.*;
import java.net.URL;
import java.util.ResourceBundle;
public class GroceryGrapherController implements Initializable {
@FXML
private NumberAxis xAxis;
@FXML
private CategoryAxis yAxis;
@FXML
private BarChart<Number, String> groceryBarChart;
//the height of one bar in the chart (if it can fit category area); you can pick another value
private final double barHeight = 10;
@Override
public void initialize(URL location, ResourceBundle resources) {
groceryBarChart.setTitle("Horizontal Grocery List");
//there's only one bar per category, so remove the gap (don't edit this, it's used in calculations)
groceryBarChart.setBarGap(0);
//gap between categories; you can pick another value
groceryBarChart.setCategoryGap(5);
//there're some bugs with the chart layout not updating when this is enabled, so disable it
groceryBarChart.setAnimated(false);
xAxis.setLabel("Number");
xAxis.setTickLabelRotation(90);
yAxis.setLabel("Grocery Type");
//if category height changes (ex. when you resize the chart), bar positions and height need to be recalculated
yAxis.categorySpacingProperty().addListener((observable, oldValue, newValue) ->
recalculateBarPositionsAndHeight()
);
//your original data
// Populate BarChart
final XYChart.Series<Number, String> series1 = new XYChart.Series<>();
series1.setName("Chocolates");
series1.getData().addAll(
new XYChart.Data<>(25601.34, "Reese"),
new XYChart.Data<>(20148.82, "Cadbury"),
new XYChart.Data<>(10000, "Mars"),
new XYChart.Data<>(35407.15, "Snickers"),
new XYChart.Data<>(12000, "Lindt")
);
final XYChart.Series<Number, String> series2 = new XYChart.Series<>();
series2.setName("Vegetables");
series2.getData().addAll(
new XYChart.Data<>(57401.85, "Cabbage"),
new XYChart.Data<>(41941.19, "Lettuce"),
new XYChart.Data<>(45263.37, "Tomato"),
new XYChart.Data<>(117320.16, "Eggplant"),
new XYChart.Data<>(14845.27, "Beetroot")
);
final XYChart.Series<Number, String> series3 = new XYChart.Series<>();
series3.setName("Drinks");
series3.getData().addAll(
new XYChart.Data<>(45000.65, "Water"),
new XYChart.Data<>(44835.76, "Coke"),
new XYChart.Data<>(18722.18, "Sprite"),
new XYChart.Data<>(17557.31, "Mountain Dew"),
new XYChart.Data<>(92633.68, "Beer")
);
groceryBarChart.getData().addAll(series1, series2, series3);
}
private void recalculateBarPositionsAndHeight() {
final int seriesCount = groceryBarChart.getData().size();
final double categoryHeight = yAxis.getCategorySpacing() - groceryBarChart.getCategoryGap();
final double originalBarHeight = categoryHeight / seriesCount;
final double barTranslateY = originalBarHeight * (seriesCount - 1) / 2;
//find the (bar) node associated with each series data and adjust its size and position
groceryBarChart.getData().forEach(numberStringSeries ->
numberStringSeries.getData().forEach(numberStringData -> {
Node node = numberStringData.getNode();
//calculate the vertical scaling of the node, so that its height matches "barHeight"
//or maximum height available if it's too big
double scaleY = Math.min(barHeight, categoryHeight) / originalBarHeight;
node.setScaleY(scaleY);
//translate the node vertically to center it around the category label
node.setTranslateY(barTranslateY);
})
);
}
}
I chose fixed bar height, but you don't need to (in which case you'll have to edit recalculateBarPositionsAndHeight method to use originalBarHeight).
来源：https://stackoverflow.com/questions/54566993/reload-and-display-blank-javafx-barchart-after-launching-the-program