Java图形没有画任何东西

Question

The program draws a bunch of rectangles for a bar graph. I know the bar class works perfectly fine because I've got it working before adding in the graph panel class. I was drawing straight onto the frame instead of the graph panel. I assume its a problem in the way my set visible methods are called as it was pointed out to me before. I tried looking into it but I've had no luck after playing around and reading documentation.

     import java.awt.Color;
    import java.util.ArrayList;
    import java.util.Random;
    import javax.swing.JFrame;
    import javax.swing.JPanel;
    import java.awt.Graphics;
    import java.awt.Graphics2D;
    import java.awt.Rectangle;
    import java.util.concurrent.Semaphore;

@SuppressWarnings("serial")
public class GraphPanel extends JPanel {

    private ArrayList<Bar> graphBars;
    private int nBars;

    public GraphPanel(int nBars, JFrame mainFrame) {
        this.setSize(400, 400);
        this.graphBars = new ArrayList<Bar>(nBars);
        this.nBars = nBars;
        this.initBars(mainFrame.getWidth());
        for(Bar b: this.graphBars) {
            this.add(b);
        }

    }

    private void initBars(int frameW) {
        Random random = new Random();
        float hue; 
        Color color; 
        int barPadding = frameW/this.nBars;
        for(int i = 0; i < this.nBars; i++) {
            hue = random.nextFloat();
            color = Color.getHSBColor(hue, 0.9f, 1.0f);
            this.graphBars.add(new Bar(i*barPadding + 30, 350, color));
        }
    }

    public ArrayList<Bar> getBarList() {
        return this.graphBars;
    }
}






@SuppressWarnings("serial")
public class Bar extends JPanel implements Runnable {

    int height = 0;
    Color barColor;
    Rectangle bar;
    private final int WIDTH = 20;
    Thread bartender;
    private Semaphore s;

    public Bar(int x, int y, Color barColor) {
        this.barColor= barColor;
        this.bar = new Rectangle(x, y, this.WIDTH, this.height);
        this.bartender= new Thread(this);
        this.s = new Semaphore(1);
    }

    public boolean setNewHeight(int h) {
        try {
            this.s.acquire();
            this.height = h;
            this.s.release();
            return true;
        } catch (InterruptedException e) {
            e.printStackTrace();
            return false;
        }
    }

    @SuppressWarnings("deprecation")
    public void update() {
        if (this.bar.height < this.height) {
            bar.reshape(this.bar.x, --this.bar.y, this.bar.width, ++this.bar.height);
        } else {
            bar.reshape(this.bar.x, ++this.bar.y, this.bar.width, --this.bar.height);
        }
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g.create();
        g2d.setColor(this.barColor);
        g2d.fill(this.bar);
    }

    @SuppressWarnings("deprecation")
    public void callBarTender() {
        this.bartender.resume();
    }

    @SuppressWarnings("deprecation")
    @Override
    public void run() {
        System.out.println("sdf");
        while(true) {
            if (this.bar.height < this.height) {
                for(int i = this.bar.height; i<this.height; i++ ) {
                    try {
                        update();
                        repaint();
                        Thread.sleep(15);
                    } catch(Exception e) {
                        System.out.println(e);
                    }
                }
            } else if (this.height < this.bar.height) {
                for(int i = this.bar.height; i>this.height; i-- ) {
                    try {
                        update();
                        repaint();
                        Thread.sleep(15);
                    } catch(Exception e) {
                        System.out.println(e);
                    }
                }
            }
            this.bartender.suspend();
        }
    }

}



 public static void main(String[] args) {
            JFrame frame = new JFrame();
            frame.setSize(400, 400);
            frame.setResizable(false);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            GraphPanel gPane = new GraphPanel(3, frame);
            frame.add(gPane);

            gPane.getBarList().get(0).setVisible(true);
            gPane.getBarList().get(1).setVisible(true);
            gPane.getBarList().get(2).setVisible(true);
            gPane.setVisible(true);
            frame.setVisible(true);

            gPane.getBarList().get(0).setNewHeight(100);
            gPane.getBarList().get(1).setNewHeight(100);
            gPane.getBarList().get(2).setNewHeight(100);

            gPane.getBarList().get(0).bartender.start();
            gPane.getBarList().get(1).bartender.start();
            gPane.getBarList().get(2).bartender.start();
    }

Answer 1

• You should override getPreferredSize of your GraphPanel to ensure that they are laid out correctly
• The x/y positions you are passing to the Bar class are irrelevant, as this is causing your Rectangle to paint outside of the visible context of the Bar pane. Painting is done from within the context of the component (0x0 been the top/left corner of the component)
• The use of Rectangle or the way you are using it, is actually causing issues. It's impossible to know exactly how big you component will be until it's layed or painted
• There is a reason why resume and suspend are deprecated, this could cause no end of "weird" (and wonderful) issues
• Take a look at Laying Out Components Within a Container for why you're bars aren't been updated correctly and why the x/y coordinates are pointless
• Take a look at How to use Swing Timers for an alternative to your use of Thread

Possibly, something more like...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame();
                frame.setSize(400, 400);
                //      frame.setResizable(false);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                GraphPanel gPane = new GraphPanel(3, frame);
                frame.add(gPane);

                gPane.getBarList().get(1).setFill(false);

                gPane.getBarList().get(0).start();
                gPane.getBarList().get(1).start();
                gPane.getBarList().get(2).start();

                frame.setVisible(true);

            }
        });
    }

    public class GraphPanel extends JPanel {

        private ArrayList<Bar> graphBars;
        private int nBars;

        public GraphPanel(int nBars, JFrame mainFrame) {
            this.graphBars = new ArrayList<Bar>(nBars);
            this.nBars = nBars;
            this.initBars(mainFrame.getWidth());
            for (Bar b : this.graphBars) {
                this.add(b);
            }

        }

        private void initBars(int frameW) {
            Random random = new Random();
            float hue;
            Color color;
            for (int i = 0; i < this.nBars; i++) {
                hue = random.nextFloat();
                color = Color.getHSBColor(hue, 0.9f, 1.0f);
                this.graphBars.add(new Bar(color));
            }
        }

        public ArrayList<Bar> getBarList() {
            return this.graphBars;
        }
    }

    @SuppressWarnings("serial")
    public class Bar extends JPanel {

        private Color barColor;
        private boolean fill = true;

        private float fillAmount = 0;
        private float delta = 0.01f;

        private Timer timer;
        private Rectangle bar;

        public Bar(Color barColor) {
            bar = new Rectangle();
            setBorder(new LineBorder(Color.RED));
            this.barColor = barColor;
            timer = new Timer(15, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    fillAmount += isFill() ? delta : -delta;
                    //                  System.out.println(fillAmount);
                    if (fillAmount < 0) {
                        fillAmount = 0;
                        ((Timer) e.getSource()).stop();
                    } else if (fillAmount > 1.0f) {
                        fillAmount = 1f;
                        ((Timer) e.getSource()).stop();
                    }
                    repaint();
                }
            });
        }

        public void start() {
            timer.start();
        }

        public void stop() {
            timer.stop();
        }

        public void setFill(boolean fill) {
            this.fill = fill;
            if (!timer.isRunning()) {
                if (fill && fillAmount == 1) {
                    fillAmount = 0;
                } else if (!fill && fillAmount == 0) {
                    fillAmount = 1;
                }
            }
        }

        public boolean isFill() {
            return fill;
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(20, 100);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(this.barColor);
            int height = Math.round(getHeight() * fillAmount);
            bar.setSize(getWidth(), height);
            bar.setLocation(0, getHeight() - height);
            g2d.fill(bar);
            g2d.dispose();
        }

    }
}