java中GUI基础

 

使用gui创建一个窗口：

public class TestApp {
    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            JFrame frame = new JFrame("Welcome");
            frame.setSize(500, 500);
            frame.setResizable(false);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
        });
    }
}

创建一个窗口和面板：

public class AlgoFrame extends JFrame{

    private int canvasWidth;
    private int canvasHeight;

    public AlgoFrame(String title, int canvasWidth, int canvasHeight){

        super(title);

        this.canvasWidth = canvasWidth;
        this.canvasHeight = canvasHeight;

        //setSize(canvasWidth, canvasHeight);
        AlgoCanvas canvas = new AlgoCanvas();
        // canvas.setPreferredSize(new Dimension(canvasWidth,canvasHeight));
        setContentPane(canvas);
        pack();

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);

        setVisible(true);

        // System.out.println(getContentPane().getBounds());
    }

    public AlgoFrame(String title){

        this(title, 1024, 768);
    }

   
    private class AlgoCanvas extends JPanel{

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            g.drawOval(50, 50, 300, 300);
        }

        @Override
        public Dimension getPreferredSize(){
            return new Dimension(canvasWidth, canvasHeight);
        }
    }
}

Graphics2D 进行画图操作：

private class AlgoCanvas extends JPanel {

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            // g.drawOval(50, 50, 300, 300);

            Graphics2D g2d = (Graphics2D) g;

            int strokeWidth = 5;
            g2d.setStroke(new BasicStroke(strokeWidth, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));//设置线条宽度

            g2d.setColor(Color.RED);//设置颜色，直到下次颜色改变
            Ellipse2D circle = new Ellipse2D.Double(50, 50, 300, 300);
            g2d.draw(circle);

            g2d.setColor(Color.BLUE);
            Ellipse2D circle2 = new Ellipse2D.Double(50, 50, 300, 300);
            g2d.fill(circle2);
        }

通过指定圆心、半径来绘制圆形：

public class AlgoVisHelper {

    private AlgoVisHelper() {
    }

    public static void strokeCircle(Graphics2D g, int x, int y, int r) {

        Ellipse2D circle = new Ellipse2D.Double(x - r, y - r, 2 * r, 2 * r);
        g.draw(circle);
    }

    public static void fillCircle(Graphics2D g, int x, int y, int r) {

        Ellipse2D circle = new Ellipse2D.Double(x - r, y - r, 2 * r, 2 * r);
        g.fill(circle);
    }

    public static void setColor(Graphics2D g, Color color) {
        g.setColor(color);
    }

    public static void setStrokeWidth(Graphics2D g, int w) {
        int strokeWidth = w;
        /**
         * 第一个参数：线条宽度
         * 第二个参数：线条末端的形状  原点
         * 第三个参数：折点的形状  平滑的圆形
         */
        g.setStroke(new BasicStroke(strokeWidth, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));
    }
}

 

private class AlgoCanvas extends JPanel {

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            // g.drawOval(50, 50, 300, 300);

            Graphics2D g2d = (Graphics2D) g;

            // 抗锯齿
            RenderingHints hints = new RenderingHints(
                                            RenderingHints.KEY_ANTIALIASING,
                                            RenderingHints.VALUE_ANTIALIAS_ON);
            g2d.addRenderingHints(hints);

            // 具体绘制
            AlgoVisHelper.setColor(g2d, Color.BLUE);
            AlgoVisHelper.fillCircle(g2d, width/2,height/2,200);

            AlgoVisHelper.setStrokeWidth(g2d,5);
            AlgoVisHelper.setColor(g2d, Color.RED);
            AlgoVisHelper.strokeCircle(g2d, width/2,height/2,200);
        }
｝

 

 

 public AlgoCanvas(){
            // 双缓存
            super(true);
}