调整JFrame大小后更新JFreeChart / JPanel

Posted 2021-04-03

我正在尝试使用JFileChooser来选择一个excel文件，然后由JFreeChart显示。我首先在构造函数中选择带有classLoader的默认文件，然后使用JFileChooser更新我的图形。问题是当我选择一个文件时，我显示图形的面板不会更新，除非我调整框架大小。

public class MyFrame extends JFrame 
{
    private static final long serialVersionUID = 1L;

    MyFrame() throws BiffException, IOException
    {
        this.setSize(1500,1000);
        this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);

        graphpanel = new Graph();
        menu = new MenuBar(graphPanel);
        this.add(graphPanel);

        this.add(menu, BorderLayout.PAGE_START);
    }


    public static void main(String[] args) throws BiffException, IOException 
    {
        MyFrame idFrame = new MyFrame();
        idFrame.setVisible(true);
    }


    Graph graphPanel;
    MenuBar menu;

}

public class Graph extends JPanel
{

    Graph() throws BiffException, IOException
    {
        ClassLoader classLoader = getClass().getClassLoader();
        file = new File(classLoader.getResource("zeszyt.xls").getFile());


        FileInputStream f = new FileInputStream(file);
        Workbook w = Workbook.getWorkbook(f);
        Sheet s = w.getSheet("Sheet1");

        XYDataset dataset = createDataset(s);
        JFreeChart chart = ChartFactory.createXYLineChart("title","x", "y",dataset,PlotOrientation.VERTICAL,true, true, false);
        ChartPanel panel = new ChartPanel(chart);

        this.add(panel); 
        this.setLayout(new GridLayout(1,1));
    }

    private XYDataset createDataset(Sheet s) 
      {
        XYSeriesCollection dataset = new XYSeriesCollection();

        XYSeries series = new XYSeries("y = x^2");
        for(int i=1; i<39; i++)
        {
            series.add(Double.parseDouble(s.getCell(0,i).getContents()),Double.parseDouble(s.getCell(1,i).getContents()));
        }
        dataset.addSeries(series);

        return dataset;
      }

    public void setFile(File file) throws BiffException, IOException
    {
        this.file = file;
        FileInputStream f = new FileInputStream(file);
        Workbook w = Workbook.getWorkbook(f);
        Sheet s = w.getSheet("Sheet2");

        XYDataset dataset = createDataset(s);
        JFreeChart chart = ChartFactory.createXYLineChart("title here","x", "y",dataset,PlotOrientation.VERTICAL,true, true, false);
        ChartPanel panel = new ChartPanel(chart);

        this.removeAll();
        this.add(panel); 
        this.setLayout(new GridLayout(1,1));
        this.setBackground(Color.RED);
    }
    File file;
}

public class MenuBar extends JMenuBar 
{
    public MenuBar(Graph graphPanel) 
    {
        menu1 = new JMenu("Plik");

        JMenuItem menu1Item = new JMenuItem("Open file...");
        this.add(menu1);
        menu1.add(menu1Item);

        menu1Item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent arg0)
            {
                int returnValue = jfc.showOpenDialog(null);
                if (returnValue == JFileChooser.APPROVE_OPTION) 
                {
                    file = jfc.getSelectedFile();
                    try {
                        graphPanel.setFile(file);
                    } catch (BiffException | IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        });


    }
    JMenu menu1;
    JMenuItem menu1Item;

    JFileChooser jfc = new JFileChooser(FileSystemView.getFileSystemView().getHomeDirectory());
    File file;

}

答案

除非我调整框架大小，否则显示图形的面板不会更新。

创建时组件的默认大小为（0,0），因此无需绘制任何内容。在添加所有组件之后，您需要调用面板的布局管理器）以为每个组件提供大小/位置。

因此，在向可见GUI添加组件时，基本代码为：

panel.add(...);
panel.revalidate(); // invoke the layout manager
panel.repaint(); // make sure panel is repainted.