Java-如何使文本显示在您单击的位置？

Question

我创建了一个Jframe，该Jframe根据您单击的位置显示X和Y值。 Jframe为300x100px。

现在，当我单击Jframe内部时，我确实会得到正确的x和y点，但文本在Jframe上以随机斑点出现。我希望文字出现在用户点击何处而不是在随机点中出现的，因为它经常出现在框架之外。.我在代码中做错了什么？

************************************************************/

import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.event.MouseInputListener;

public class Proj06Runner {
    public static void main(String[] args) {
            System.out.println("NAME"); //replace with name 

        //creating jframe
        JFrame main = new JFrame("NAME"); //replace with name       

        //set size of frame
        main.setSize(300, 100);

        //creating lable
        JLabel j1 = new JLabel("");
        j1.setForeground(Color.RED);
        //make frmae visible
        main.setVisible(true);
        //addding mouselistner to frame
        main.addMouseListener(new MouseInputListener() {

            @Override
            public void mouseClicked(MouseEvent e) {
                String output = "x=" + e.getX() + ",y=" + e.getY();

                //add label to text which is shown
                j1.setText(output);
                Dimension size=j1.getPreferredSize();

                j1.setBounds(e.getX(),e.getY(),size.width,size.height);
                main.add(j1);
            }
            //MouseInputListner is interface so that we have to implement all methods
            @Override
            public void mousePressed(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mouseReleased(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mouseEntered(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mouseExited(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mouseDragged(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mouseMoved(MouseEvent e) {
                // TODO Auto-generated method stub

            }

        });
        //make progrma terminate after clicking close button
        main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

Answer 1

这是因为布局。布局经理用于自动确定容器中组件的布局。如果要将组件放在特定的坐标位置，则根本不应使用布局管理器。

将Jframe的布局设置为null。

main.setLayout(null);

Answer 2

您可以...

使用基于自定义绘画的解决方案，例如...

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;

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

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private List<Point> points = new ArrayList<>(8);

        public TestPane() {
            addMouseListener(new MouseAdapter() {
                @Override
                public void mouseClicked(MouseEvent e) {
                    points.add(e.getPoint());
                    repaint();
                }
            });
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(300, 100);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            FontMetrics fm = g2d.getFontMetrics();
            for (Point p : points) {
                g2d.drawString("x = " + p.x + ",y = " + p.y, p.x, p.y + fm.getAscent());
            }
            g2d.dispose();
        }

    }
}

请参阅 aw和摇摆和执行自定义绘画
有关更多详细信息，

您可以...

使用自定义布局管理器...

import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.LayoutManager2;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

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

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {
        private List<Point> points = new ArrayList<>(8);

        public TestPane() {
            setLayout(new PointLayoutManager());
            addMouseListener(new MouseAdapter() {
                @Override
                public void mouseClicked(MouseEvent e) {
                    add(new JLabel("x=" + e.getX() + ",y=" + e.getY()), e.getPoint());
                    repaint();
                    revalidate();
                }
            });
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(300, 100);
        }
    }

    public class PointLayoutManager implements LayoutManager2 {

        private Map<Component, Point> points = new HashMap<>();

        @Override
        public void addLayoutComponent(Component comp, Object constraints) {
            if (constraints instanceof Point) {
                points.put(comp, (Point)constraints);
            }
        }

        @Override
        public Dimension maximumLayoutSize(Container target) {
            return preferredLayoutSize(target);
        }

        @Override
        public float getLayoutAlignmentX(Container target) {
            return 0.5f;
        }

        @Override
        public float getLayoutAlignmentY(Container target) {
            return 0.5f;
        }

        @Override
        public void invalidateLayout(Container target) {
        }

        @Override
        public void addLayoutComponent(String name, Component comp) {
        }

        @Override
        public void removeLayoutComponent(Component comp) {
            points.remove(comp);
        }

        @Override
        public Dimension preferredLayoutSize(Container parent) {
            int maxX = 0;
            int maxY = 0;
            for (Component comp : parent.getComponents()) {
                Dimension size = comp.getPreferredSize();
                maxX = Math.max(comp.getX() + size.width, maxX);
                maxY = Math.max(comp.getY() + size.height, maxY);
            }

            return new Dimension(maxX, maxY);
        }

        @Override
        public Dimension minimumLayoutSize(Container parent) {
            return preferredLayoutSize(parent);
        }

        @Override
        public void layoutContainer(Container parent) {
            for (Component comp : parent.getComponents()) {
                Point p = points.get(comp);
                if (p == null) {
                    // This will deliberatly hide the component
                    comp.setSize(0, 0);
                    continue;
                }
                Dimension size = comp.getPreferredSize();
                comp.setBounds(new Rectangle(p, size));
            }
        }

    }
}

这将与其他组件效果很好，并且您可以将组件包装在jscrollpane中，并免费获取可解开的窗口。

当您认为不需要布局经理时，99.9％的时间，您错了，其他0.1％的时间，您需要一个自定义布局管理器