paintComponent how to setColor from outside

Question

I have a little problem on my project, I don't know how to handle the setColor option in this case I try to. The main Problem is that I can't give the color to the paintComponent ore I don't know how to do that. I create an object from Scatterplot (Scatterplot sp = new Scatterplot) did not work.

here is my code for the plotPanel.

public class Scatterplot extends JPanel {

    List<Double> values_x = new ArrayList<>();
    List<Double> values_y = new ArrayList<>();

    protected double maxValue_x, minValue_x, maxValue_y, minValue_y;


    public Scatterplot(List<Double> variableValues_1, List<Double> variableValues_2) {
        values_x = variableValues_1;
        maxValue_x = Collections.max(values_x);
        minValue_x = Collections.min(values_x);

        values_y = variableValues_2;
        maxValue_y = Collections.max(values_y);
        minValue_y = Collections.min(values_y);

    }



    @Override
    protected void paintComponent(Graphics g) {

        int m = 30;
        double width = getWidth();
        double height = getHeight();

        double x1 = (width-2*m) / (maxValue_x - minValue_x);
        double y1 = (height-2*m) / (maxValue_y - minValue_y);

        for (int i = 0; i < values_x.size(); i++) {
            double value_x = values_x.get(i);  
            double value_y = values_y.get(i);

            g.fillOval((int)(2*m + x1*(value_x-minValue_x)-2*m), (int)(height - (y1*(value_y-minValue_y))-2*m), 2*m, 2*m);

        }
    }      
}

The JColorChooser is implemented here:

public class GuiOptionPanel extends JPanel {


    public GuiOptionPanel(DataModel dataModel) {
        JPanel optionPanel = new JPanel(new GridLayout(7,1));

        JPanel menuPanel = new JPanel();
        JLabel menuLabel = new JLabel("Menu");
        menuLabel.setFont(menuLabel.getFont().deriveFont(Font.BOLD));
        menuPanel.add(menuLabel);
        optionPanel.add(menuPanel);

        JButton setColorButton = new JButton("Set Color");
        optionPanel.add(setColorButton);
        setColorButton.addActionListener((ActionEvent e) -> {
            JColorChooser.showDialog( null, "Color", null );
        });

        add(optionPanel);
    }
}

That is all (and some more Panels) added to a Frame:

public GuiFrame(DataModel dataModel) {
    setSize(FRAME_WIDTH, FRAME_HIGHT);
    /**
     * Create Objects
     */
    GuiInfoPanel ip = new GuiInfoPanel(dataModel);
    GuiOptionPanel op = new GuiOptionPanel(dataModel);
    JComponent sp = new Scatterplot(dataModel.getVariableValues(0), dataModel.getVariableValues(1));
    JComponent hg1 = new Histograms(dataModel.getVariableValues(0));
    JComponent hg2 = new Histograms(dataModel.getVariableValues(1));
    /**
     * Create Panels
     */
    createMainPanel();

    /**
     * Add Panels
     */
    this.add(mainPanel);
    this.add(ip, BorderLayout.SOUTH);
    menuPanel.add(op, BorderLayout.NORTH);
    scatterplotPanel.add(sp, BorderLayout.CENTER);
    histogram1.add(hg1, BorderLayout.CENTER);
    histogram2.add(hg2, BorderLayout.CENTER);
    }

The daterModel Class (This is returned by an Interface):

package dataplotproject;

import java.util.ArrayList;
import java.util.List;

public class DataModel {

    List<Variable> listOfEveryVariable = new ArrayList<>();
    String fileName = "";

    public DataModel(List<Variable> listOfEveryVariable2, String fileName2) {
        listOfEveryVariable = listOfEveryVariable2;
        fileName = fileName2;
    }

    public List<Variable> getVariables() {
        return listOfEveryVariable;
    }

    public String getFileName() {
        return fileName;
    }

    public List<String> getVariableNames() {
        List<String> names = new ArrayList<>();
        for (Variable obj : listOfEveryVariable) {
            names.add(obj.getName());
        }
        return names;
    }

    public List<Double> getVariableValues(int i){
       return listOfEveryVariable.get(i).getValueList();
    }
}

Answer 1

This is a broad question with lots of plausible answers: here's one way to do it:

1. Provide a Color instance variable in the Scatterplot (with a setter method and default color value)
2. Use (1) to set the color in Scatterplot's paintComponent method before rendering eg g.setColor(myColor);
3. Pass a reference of the Scatterplot object to GuiOptionPanel
4. In ActionListener implementation within GuiOptionPanel, the JColorChooser.showDialog method returns a Color object. Assign that to a variable. Color chosenColor = JColorChooser.showDialog( null, "Color", null );
5. Pass color from (4) to the setter method of the Scatterplot from (1) and (3)

Note that the Color returned from JColorChooser.showDialog may be null if the user cancelled - should add a conditional to make sure it is not null. You should also call repaint in the color setter method of (1) if you want the color change to take immediate affect.

Answer 2

If I understand you correctly, you probably want to do this:

@Override
protected void paintComponent(Graphics g) {
g.setColor(Color.BLACK);
[..]
}

In other words, a component is painted by its Graphics object, which handles things like color.