How can I resize the charts on a JFrame automatically?

Question

I have wrote a code that creates two scatters and two JPanels placed on a JFrame. However I could not make them fit automatically to the size of the window when it is being resized. Here is the code for one of the drawing classes:

class ALTCanvas extends JPanel{
    private static final long serialVersionUID = 1L;
    private XYSeries alts = new XYSeries("Altitude");

    public ALTCanvas() {
        final ChartPanel chartPanel = createDemoPanel();
        this.add(chartPanel, BorderLayout.CENTER);
    }

    private void update(double xnew, double ynew) {
        alts.add(new XYDataItem(xnew, ynew));
    }

    private ChartPanel createDemoPanel() {
        JFreeChart jfreechart = ChartFactory.createScatterPlot(
            "", "Time [epoch]", "Altitude [m]", createSampleData(),
            PlotOrientation.VERTICAL, false, true, false);
        XYPlot xyPlot = (XYPlot) jfreechart.getPlot();
        XYItemRenderer renderer = xyPlot.getRenderer();
        NumberAxis range = (NumberAxis) xyPlot.getRangeAxis();
        range.setTickUnit(new NumberTickUnit(0.5));
        return new ChartPanel(jfreechart){
            @Override
            public Dimension getPreferredSize() {
                return new Dimension(640, 480);
            }
        };
    }

    private XYDataset createSampleData() {
        XYSeriesCollection xySeriesCollection = new XYSeriesCollection();
        xySeriesCollection.addSeries(alts);
        return xySeriesCollection;
    }

    private String stdCalc(){
        double sum = 0, avg = 0;
        double var = 0;
        for(int i = 0; i < alts.getItemCount(); i++){
            sum += (double) alts.getY(i);
        }
        avg = sum/alts.getItemCount();
        for(int i = 0; i < alts.getItemCount(); i++){
            var += ((double)alts.getY(i) - avg)*((double)alts.getY(i) - avg);
        }
        String str = "";
        str += Math.sqrt(var);
        return str;
    }
}

Here is the code for the initialization of the graphics:

public void initGrafics() {
    // create and set up the window
    JFrame frame = new JFrame("Position / Altitude");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // set up the content pane
    Container C = frame.getContentPane();

    // create canvas objects
    PC = new POSCanvas();
    PC.setBorder(BorderFactory.createRaisedBevelBorder());
    AC = new ALTCanvas();
    AC.setBorder(BorderFactory.createRaisedBevelBorder());

    JPanel left = new JPanel();
    left.setLayout(new BoxLayout(left, BoxLayout.Y_AXIS));
    JLabel prcP = new JLabel("Precision [m]: "); JLabel acrP = new JLabel("Accuracy [m]: ");
    prcTp = new JTextField("          "); acrTp = new JTextField("          ");
    JPanel labelsP = new JPanel();
    labelsP.setLayout(new FlowLayout());
    labelsP.add(prcP); labelsP.add(prcTp); labelsP.add(acrP); labelsP.add(acrTp);
    left.add(PC); left.add(labelsP);

    JPanel right = new JPanel();
    right.setLayout(new BoxLayout(right, BoxLayout.Y_AXIS));
    JLabel stdA = new JLabel("Standard deviation [m]: "); stdTa = new JTextField("          ");
    JPanel labelsA = new JPanel();
    labelsA.setLayout(new FlowLayout());
    labelsA.add(stdA); labelsA.add(stdTa);
    right.add(AC); right.add(labelsA);

    // add objects to the pane 
    C.setLayout(new BoxLayout(C, BoxLayout.X_AXIS));
    C.add(left); C.add(right);

    //Display the window.
    frame.pack();
    frame.setVisible(true);
    frame.setLocation(500, 500);
}

Here is what it looks like after resizing:

As one can see, the charts does not fit the size of the window. Can anybody help me how to fix it? Any help would be appreciated, thank you.

Answer 1

The default layout of JPanel is FlowLayout, which "lets each component assume its natural (preferred) size," while precluding subsequent changes. The BorderLayout.CENTER parameter is meaningless in this context. Instead, add the two panels to a GridLayout(1, 0). This will place the charts side-by-side and allow them to grow and shrink as the enclosing container is resized. A complete example is cited here.