更改图表颜色

Question

我测试了这个css代码来改变图表颜色,但是当我运行代码时我得到了NPE:

public class MainApp extends Application {

    @Override public void start(Stage stage) {
        stage.setTitle("Line Chart Sample");
        //defining the axes
        final NumberAxis xAxis = new NumberAxis();
        final NumberAxis yAxis = new NumberAxis();
        xAxis.setLabel("Number of Month");
        //creating the chart
        final LineChart<Number,Number> lineChart = new LineChart<>(xAxis,yAxis);


        // Look up first series fill
        Node node = lineChart.lookup(".default-color0.chart-series-area-fill");
        // Set the first series fill to translucent pale green
        node.setStyle("-fx-fill: linear-gradient(#f2f2f2, #d4d4d4);"
            + "  -fx-background-insets: 0 0 -1 0, 0, 1, 2;"
            + "  -fx-background-radius: 3px, 3px, 2px, 1px;");

        Node nodew = lineChart.lookup(".chart-series-area-line");
        // Set the first series fill to translucent pale green
        nodew.setStyle("-fx-stroke: #989898; -fx-stroke-width: 1px; ");



        lineChart.setTitle("Stock Monitoring, 2010");
        //defining a series
        XYChart.Series series = new XYChart.Series();
        series.setName("My portfolio");
        //populating the series with data
        series.getData().add(new XYChart.Data(1, 23));
        series.getData().add(new XYChart.Data(2, 14));
        series.getData().add(new XYChart.Data(3, 15));
        series.getData().add(new XYChart.Data(4, 24));
        series.getData().add(new XYChart.Data(5, 34));
        series.getData().add(new XYChart.Data(6, 36));
        series.getData().add(new XYChart.Data(7, 22));
        series.getData().add(new XYChart.Data(8, 45));
        series.getData().add(new XYChart.Data(9, 43));
        series.getData().add(new XYChart.Data(10, 17));
        series.getData().add(new XYChart.Data(11, 29));
        series.getData().add(new XYChart.Data(12, 25));

        Scene scene  = new Scene(lineChart,800,600);
        lineChart.getData().add(series);

        stage.setScene(scene);
        stage.show();
    }

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

}

这一行是问题所在:

node.setStyle("-fx-fill: linear-gradient(#f2f2f2, #d4d4d4);".........);

你能告诉我怎么解决这个问题吗？这个css代码在AreaChart中使用.现在我想在LineChart中使用它.

PS

我也从这个例子中尝试了这个css:

http://docs.oracle.com/javafx/2/charts/css-styles.htm

Node node = lineChart.lookup(".default-color0.chart-series-line");
        // Set the first series fill to translucent pale green
        node.setStyle("-fx-stroke: #e9967a;");

但我再次获得NPE.

Answer 1

1. 请确保参考css文档,了解您正在使用的节点类型,以查看它支持的样式类.
2. 在将css样式应用于节点之前,查找通常不可用.这至少意味着它必须被渲染到屏幕上,但似乎有时需要另一帧或两帧.因此,如果您想使用查找,则必须在调用后调用它stage.show();,有时您需要采取进一步的步骤以便稍后调用它.
3. 更好的方法是使用外部样式表.请参阅教程:还有一个样式图表的特定页面.

更新(其他想法):

在Java 8中(也许在JavaFX 2.2中:我没有caspian.css的副本方便),所有与数据相关的颜色都是根据查找颜色 CHART_COLOR_1来定义的CHART_COLOR_8.这给了一个很好的单线来设置颜色,至少:

lineChart.setStyle("CHART_COLOR_1: #e9967a;");