如何在javafx栏上显示条形值

Question

从这个代码我可以生成10条现在的条形图现在我想知道如何在条形图上显示每个条形的值,如附加图像:

这是代码:

public class BarChartSample extends Application {


    @Override public void start(Stage stage) {
        stage.setTitle("Bar Chart Sample");
        final CategoryAxis xAxis = new CategoryAxis();
        final NumberAxis yAxis = new NumberAxis();
        final BarChart<String,Number> bc = 
            new BarChart<String,Number>(xAxis,yAxis);
        bc.setTitle("Country Summary");
        xAxis.setLabel("bars");       
        yAxis.setLabel("Value");

        XYChart.Series series1 = new XYChart.Series();
        series1.setName("...");       

for(int i=0;i<10;i++)
{
   //here i want to change color of bar if value of i is >5 than red if i>8 than blue 
series1.getData().add(new XYChart.Data("Value", i));

}          

}

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

Answer 1

在ChangeListener每个数据项的node属性的内部,您可以调用以下函数将标签添加到栏的顶部:

private void displayLabelForData(XYChart.Data<String, Number> data) {
  final Node node = data.getNode();
  final Text dataText = new Text(data.getYValue() + "");
  node.parentProperty().addListener(new ChangeListener<Parent>() {
    @Override public void changed(ObservableValue<? extends Parent> ov, Parent oldParent, Parent parent) {
      Group parentGroup = (Group) parent;
      parentGroup.getChildren().add(dataText);
    }
  });

  node.boundsInParentProperty().addListener(new ChangeListener<Bounds>() {
    @Override public void changed(ObservableValue<? extends Bounds> ov, Bounds oldBounds, Bounds bounds) {
      dataText.setLayoutX(
        Math.round(
          bounds.getMinX() + bounds.getWidth() / 2 - dataText.prefWidth(-1) / 2
        )
      );
      dataText.setLayoutY(
        Math.round(
          bounds.getMinY() - dataText.prefHeight(-1) * 0.5
        )
      );
    }
  });
}

该代码的工作原理是向每个条形节点的父节点添加文本标签,然后在每次调整条形大小时根据条形和文本边界动态定位文本标签.

我为此创建了一个示例解决方案.