java - 绘制边界矩形以选择要记录的区域

Question

如何在屏幕上绘制那个半透明的矩形？这不可能，JFrame因为 JFrame 在右上角有通常的关闭、最小化、最大化选项。
如果它确实是一个挥杆能力，它是如何凭空抽出来的？无需将其插入JFrame任何内容？请告诉我它是什么以及如何实现它...

Answer 1

想到的直接想法是使用java.awt.Robot捕获屏幕截图，将其绘制到无框窗口。从那里你可以简单地在它上面画一个矩形

更新了示例

...花了一些时间...

public class SelectionRectangle {

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

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

                JFrame frame = new JFrame("Test");
                frame.setUndecorated(true);
                frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new BackgroundPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public class BackgroundPane extends JPanel {

        private BufferedImage background;
        private Point mouseAnchor;
        private Point dragPoint;

        private SelectionPane selectionPane;

        public BackgroundPane() {
            selectionPane = new SelectionPane();
            try {
                Robot bot = new Robot();
                background = bot.createScreenCapture(getScreenViewableBounds());
            } catch (AWTException ex) {
                Logger.getLogger(SelectionRectangle.class.getName()).log(Level.SEVERE, null, ex);
            }

            selectionPane = new SelectionPane();
            setLayout(null);
            add(selectionPane);

            MouseAdapter adapter = new MouseAdapter() {
                @Override
                public void mousePressed(MouseEvent e) {
                    mouseAnchor = e.getPoint();
                    dragPoint = null;
                    selectionPane.setLocation(mouseAnchor);
                    selectionPane.setSize(0, 0);
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    dragPoint = e.getPoint();
                    int width = dragPoint.x - mouseAnchor.x;
                    int height = dragPoint.y - mouseAnchor.y;

                    int x = mouseAnchor.x;
                    int y = mouseAnchor.y;

                    if (width < 0) {
                        x = dragPoint.x;
                        width *= -1;
                    }
                    if (height < 0) {
                        y = dragPoint.y;
                        height *= -1;
                    }
                    selectionPane.setBounds(x, y, width, height);
                    selectionPane.revalidate();
                    repaint();
                }

            };
            addMouseListener(adapter);
            addMouseMotionListener(adapter);

        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.drawImage(background, 0, 0, this);
            g2d.dispose();
        }

    }

    public class SelectionPane extends JPanel {

        private JButton button;
        private JLabel label;

        public SelectionPane() {
            button = new JButton("Close");
            setOpaque(false);

            label = new JLabel("Rectangle");
            label.setOpaque(true);
            label.setBorder(new EmptyBorder(4, 4, 4, 4));
            label.setBackground(Color.GRAY);
            label.setForeground(Color.WHITE);
            setLayout(new GridBagLayout());

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            add(label, gbc);

            gbc.gridy++;
            add(button, gbc);

            button.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    SwingUtilities.getWindowAncestor(SelectionPane.this).dispose();
                }
            });

            addComponentListener(new ComponentAdapter() {
                @Override
                public void componentResized(ComponentEvent e) {
                    label.setText("Rectangle " + getX() + "x" + getY() + "x" + getWidth() + "x" + getHeight());
                }
            });

        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(new Color(128, 128, 128, 64));
            g2d.fillRect(0, 0, getWidth(), getHeight());

            float dash1[] = {10.0f};
            BasicStroke dashed =
                            new BasicStroke(3.0f,
                            BasicStroke.CAP_BUTT,
                            BasicStroke.JOIN_MITER,
                            10.0f, dash1, 0.0f);
            g2d.setColor(Color.BLACK);
            g2d.setStroke(dashed);
            g2d.drawRect(0, 0, getWidth() - 3, getHeight() - 3);
            g2d.dispose();
        }

    }

    public static Rectangle getScreenViewableBounds() {
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice gd = ge.getDefaultScreenDevice();

        return getScreenViewableBounds(gd);
    }

    public static Rectangle getScreenViewableBounds(GraphicsDevice gd) {
        Rectangle bounds = new Rectangle(0, 0, 0, 0);
        if (gd != null) {
            GraphicsConfiguration gc = gd.getDefaultConfiguration();
            bounds = gc.getBounds();

            Insets insets = Toolkit.getDefaultToolkit().getScreenInsets(gc);

            bounds.x += insets.left;
            bounds.y += insets.top;
            bounds.width -= (insets.left + insets.right);
            bounds.height -= (insets.top + insets.bottom);
        }
        return bounds;
    }
}

使用 SnipIt 示例更新

有些人建议使用放置在屏幕顶部的透明窗口，这实际上是行不通的，因为透明窗口实际上不会响应鼠标点击，除非它们有要在上面绘制的东西以允许鼠标事件被困。

还建议您使用 Window 作为选择机制，这是一个有效的答案，但是，我（个人）会发现这是一个不合适的解决方案，因为您希望用户只需单击并拖动选择矩形（恕我直言）。

另一种方法是使用类似 SnipIt 的东西。

public class SnipIt {

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

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

                JFrame frame = new JFrame();
                frame.setUndecorated(true);
                // This works differently under Java 6
                frame.setBackground(new Color(0, 0, 0, 0));
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new SnipItPane());
                frame.setBounds(getVirtualBounds());
                frame.setVisible(true);
            }
        });
    }

    public class SnipItPane extends JPanel {

        private Point mouseAnchor;
        private Point dragPoint;

        private SelectionPane selectionPane;

        public SnipItPane() {
            setOpaque(false);
            setLayout(null);
            selectionPane = new SelectionPane();
            add(selectionPane);
            MouseAdapter adapter = new MouseAdapter() {
                @Override
                public void mousePressed(MouseEvent e) {
                    mouseAnchor = e.getPoint();
                    dragPoint = null;
                    selectionPane.setLocation(mouseAnchor);
                    selectionPane.setSize(0, 0);
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    dragPoint = e.getPoint();
                    int width = dragPoint.x - mouseAnchor.x;
                    int height = dragPoint.y - mouseAnchor.y;

                    int x = mouseAnchor.x;
                    int y = mouseAnchor.y;

                    if (width < 0) {
                        x = dragPoint.x;
                        width *= -1;
                    }
                    if (height < 0) {
                        y = dragPoint.y;
                        height *= -1;
                    }
                    selectionPane.setBounds(x, y, width, height);
                    selectionPane.revalidate();
                    repaint();
                }
            };
            addMouseListener(adapter);
            addMouseMotionListener(adapter);
        }

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

            Graphics2D g2d = (Graphics2D) g.create();

            Rectangle bounds = new Rectangle(0, 0, getWidth(), getHeight());
            Area area = new Area(bounds);
            area.subtract(new Area(selectionPane.getBounds()));

            g2d.setColor(new Color(192, 192, 192, 64));
            g2d.fill(area);

        }
    }

    public class SelectionPane extends JPanel {

        private JButton button;
        private JLabel label;

        public SelectionPane() {
            button = new JButton("Close");
            setOpaque(false);

            label = new JLabel("Rectangle");
            label.setOpaque(true);
            label.setBorder(new EmptyBorder(4, 4, 4, 4));
            label.setBackground(Color.GRAY);
            label.setForeground(Color.WHITE);
            setLayout(new GridBagLayout());

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            add(label, gbc);

            gbc.gridy++;
            add(button, gbc);

            button.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    SwingUtilities.getWindowAncestor(SelectionPane.this).dispose();
                }
            });

            addComponentListener(new ComponentAdapter() {
                @Override
                public void componentResized(ComponentEvent e) {
                    label.setText("Rectangle " + getX() + "x" + getY() + "x" + getWidth() + "x" + getHeight());
                }
            });

        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            // I've chosen NOT to fill this selection rectangle, so that
            // it now appears as if you're "cutting" away the selection
//            g2d.setColor(new Color(128, 128, 128, 64));
//            g2d.fillRect(0, 0, getWidth(), getHeight());

            float dash1[] = {10.0f};
            BasicStroke dashed =
                    new BasicStroke(3.0f,
                    BasicStroke.CAP_BUTT,
                    BasicStroke.JOIN_MITER,
                    10.0f, dash1, 0.0f);
            g2d.setColor(Color.BLACK);
            g2d.setStroke(dashed);
            g2d.drawRect(0, 0, getWidth() - 3, getHeight() - 3);
            g2d.dispose();
        }
    }

    public static Rectangle getVirtualBounds() {

        Rectangle bounds = new Rectangle(0, 0, 0, 0);

        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice lstGDs[] = ge.getScreenDevices();
        for (GraphicsDevice gd : lstGDs) {

            bounds.add(gd.getDefaultConfiguration().getBounds());

        }

        return bounds;

    }
}

Answer 2

将多显示器支持更新为来自@MadProgrammer 的示例答案。

没有ExtendedState(JFrame.MAXIMIZED_BOTH)和pack()

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

            JFrame frame = new JFrame("Test");
            frame.setUndecorated(true);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setLayout(new BorderLayout());
            frame.add(new BackgroundPane());

            frame.setResizable( false );
            frame.setBounds( getScreenViewableBounds() );

            frame.setVisible(true);
        }

    });
}

---

public static Rectangle getScreenViewableBounds() {
    GraphicsDevice[] devices = GraphicsEnvironment.getLocalGraphicsEnvironment().getScreenDevices();
    int minx = Integer.MAX_VALUE;
    int miny = Integer.MAX_VALUE;
    int maxx = Integer.MIN_VALUE;
    int maxy = Integer.MIN_VALUE;
    for( GraphicsDevice device : devices ) {
        for( GraphicsConfiguration config : device.getConfigurations() ) {
            Rectangle bounds = config.getBounds();
            minx = Math.min( minx, bounds.x );
            miny = Math.min( miny, bounds.y );
            maxx = Math.max( maxx, bounds.x + bounds.width );
            maxy = Math.max( maxy, bounds.y + bounds.height );
        }
    }
    return new Rectangle( new Point(minx, miny), new Dimension(maxx - minx, maxy - miny) );
}

Answer 3

您可以使用透明、未装饰的框架来创建基本边框。

public class ScreenRectangle extends JFrame {

    public ScreenRectangle() {
        this.setUndecorated(true);
        this.setBackground(new Color(0, 0, 0, 0.25F));
        // opacity ranges 0.0-1.0 and is the fourth paramater
        this.add(new DrawPanel());
    }

    private class DrawPanel extends JPanel {

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawRect(0, 0, this.getWidth(), this.getHeight());
            // any other drawing
        } 
    }
}

框架也setOpaque可能需要处理，或者面板尺寸可能需要处理，但这是它的总体思路。