Javafx-如何将饼图从不同的类添加到BorderPane

Question

I have two classes. A Main class and a Chart class. My Chart class extends PieChart and instantiates a Pie Chart in its constructor. My main class creates a BorderPane, I then instantiate an object of the Chart class(creating the Pie Chart) and add it to the center pane.The only problem is I don't know the exact syntax to make this work properly, specifically in the constructor of my Chart class.

I know that for example, if I was creating an HBox instead of a Pie Chart in the constructor, I could simply use this. and a number of methods. But Pie Charts have additional elements with Observable Lists so i'm not sure how to make this work? Here are my two classes below. Please help. Thank you.

MAIN CLASS

public class Main extends Application {
@Override
public void start(Stage primaryStage) {
    BorderPane border = new BorderPane();

    Chart chart = new Chart();

    border.setCenter(chart);

    Scene scene = new Scene (border, 640,680);
    primaryStage.setScene(scene);
    primaryStage.show();

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

CHART CLASS

public class Chart extends PieChart{

public Chart(){
    ObservableList<PieChart.Data>pieChart = FXCollections.observableArrayList(
            new PieChart.Data("Fruits", 75),
            new PieChart.Data("Vegetables", 25)
            );

    PieChart chart = new PieChart(pieChart);

    //What code can create the Pie Chart here? Is the solution to place the chart on it's own pane instead?
}}

Answer 1

You are probably looking for

public Chart(){
    ObservableList<PieChart.Data>pieChart = FXCollections.observableArrayList(
            new PieChart.Data("Fruits", 75),
            new PieChart.Data("Vegetables", 25)
            );
    setData(pieChart);
    // no need for this -> PieChart chart = new PieChart(pieChart);
}

or

public Chart(){
   super(FXCollections.observableArrayList(
         new PieChart.Data("Fruits", 75),
         new PieChart.Data("Vegetables", 25)
   ));
}

Edit after comment: setData(ObservableList data) is a method from PieChart class. And it will set data objects. It is just easy and convenient way to work with data in chart or any other collection powered view. (Yep, it is not chart-only style . It is pretty much the same for all JavaFX views. Chart will listen for data changes and redraw itself internaly.You just need to set data you'd like to display. In your case you have this method because your Chart extends PieChart

When you do PieChart charts = new PieChart(data); in PieChart it will call setData internaly

public PieChart(ObservableList<PieChart.Data> data){
   setData(data);
   ...
}

So that's why you have to call super(data) or setData(data) yourself in your extended class. But if you want to chage charts, you don't have to recreate whole chart every time. Can just change data with charts.setData(someData) or get data List object with charts.getData() and then change it.

For example:

PieChart charts = new PieChart();
ObservableList<PieChart.Data> pieChart = ...
charts.setData(pieChart);
// pieChart == charts.getData() // this is the same object. so
pineChart.add(new PieChart.Data("New Fruit", 75)) // will change chart

Btw, take a look at this tutorials https://docs.oracle.com/javafx/2/charts/jfxpub-charts.htm