在Java中制作绘画应用程序的更简单方法? [英] Easier way to make a paint application in java?

问题描述

所以基本上，我有几天前在工作的一些代码，类似于Paint，它可以让您使用鼠标在屏幕上进行绘制.我有点偶然发现了这个属性，我意识到它的效率很低，我想知道是否有更实用的方法可以做到这一点.确实没有任何理由要提供我的所有代码，但这是重要的部分

So basically I have some code I was working on a couple of days ago that is kind of like Paint, which allows you to essentially draw on the screen using the mouse. I kind of discovered this property by accident, and I realized that it is really inefficient and i'm wondering if there is a more practical way to do this. There isn't really any reason to give all of my code, but here are the important parts

private static void createAndShowGui() {
    SimpleDraw mainPanel = new SimpleDraw();
    MenuBar.createMenuBar();
    JLabel label = new JLabel();
    label.setText("Drawing prototype 0.0.1");
     // label.setHorizontalTextPosition(JLabel.NORTH);
    label.setFont(new Font("Serif", Font.BOLD, 20));
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(mainPanel);
    frame.pack();
    frame.setLocationByPlatform(true);
    frame.getContentPane().setLayout(new BoxLayout(frame.getContentPane(),BoxLayout.PAGE_AXIS));
    frame.setVisible(true);
    frame.setJMenuBar(MenuBar.getMenuBar());
    frame.setBackground(Color.WHITE);
    frame.add(label);

上面的代码块设置了jframe(窗口)

The code block above sets up the jframe (the window)

 @Override
    public void mouseDragged(MouseEvent e)
    {
    // These console outputs are just so that I know what is happening
        System.out.println("Event: MOUSE_DRAG");
        System.out.println(e.getX());
        System.out.println(e.getY());
        System.out.println(e.getComponent());
        System.out.println(e.getWhen());
        System.out.println(e.getButton());
         MOUSE_X = e.getX() - 5;  //-5 so that the cursor represents the center of the square, not the top left corner.
         MOUSE_Y = e.getY() - 5;  //^
         rect = new Rectangle(MOUSE_X, MOUSE_Y, 10, 10 ); //This doesn't ever come into action.
         repaint();  

     }

上面的代码几乎只设置了MOUSE_X和MOUSE_Y变量以及repaint()；方法

The code above pretty much just sets the MOUSE_X and MOUSE_Y variables and the repaint(); method

@Override
    protected void paintComponent(Graphics g) {

    Graphics2D g2 = (Graphics2D) g;
    if (rect != null) {

        if (!colorChoice.equals("Default"))
        {
            g2.setColor(Color.BLACK);
        }

        switch(colorChoice) {

        case "GRAY":
            g2.setColor(Color.GRAY);
            break;
        case "CYAN":
            g2.setColor(Color.CYAN);
            break;
        case "BLUE":
            g2.setColor(Color.BLUE);
            break;
        case "RED":
            g2.setColor(Color.RED);
            break;
        case "PINK":
            g2.setColor(Color.PINK);
            break;
        case "YELLOW":
            g2.setColor(Color.YELLOW);
            break;
        case "GREEN":
            g2.setColor(Color.GREEN);
            break;
        case "PURPLE":
            g2.setColor(Color.MAGENTA);
            break;
        case "RESET":
            g2.setColor(Color.WHITE);
        case "WHITE":
            g2.setColor(Color.WHITE);

        }





        g2.fillRect(MOUSE_X, MOUSE_Y, 15, 15); 

        if (colorChoice.equals("RESET")) 
        resetColorOnCursor(); 

        }
    }

    public static void clearBoard()
    {
    tempColor = colorChoice;
    setColorChoice("RESET");
    frame.repaint();




    }


    public static void resetColorOnCursor()
    {
    setColorChoice(tempColor);
    }

这是我偶然遇到的东西.当我发现这一点时，我试图做的基本上是在您移动鼠标时使光标跟随一个正方形.但是我忘记键入代码部分paintComponent(g);，这会将程序变成了我最初想要的东西.从本质上讲，这是我清理董事会的方式的底部.我100％确信这不是清除/重置这样的框架的正确方法，但是我找不到其他方法.如果有人有任何技巧或更好的方法来正确地完成此操作，我将不胜感激.谢谢！ :D

This is the thing I came across accidentally. What I was trying to do when I found this out was basically make a square follow your cursor whenever you moved your mouse. But I forgot to type the code part paintComponent(g);, which turns this program into the thing that I originally intended. The bottom parts of this are essentially how I would clear the board. I'm 100% sure that this isn't the proper way to clear/reset a frame like this, but I couldn't find another way. If anyone has any tips or better methods to use to do this properly I would be very appreciative. Thanks! :D

推荐答案

您当前的方法基本上是通过不调用super.paintComponent来打破绘画链的要求. paintComponent方法执行一系列操作，这些操作您没有接手，可能会导致一些非常怪异的绘画瑕疵，难以一致地复制.

You're current approach is basically breaking the requirements of the paint chain, by not calling super.paintComponent. The paintComponent method does a set of operations, which you are not taking over and which could result in some very weird paint artifacts which are difficult to replicate consistently.

Graphics是共享资源，因此用于绘制其他控件的Graphics上下文将与用于绘制组件的上下文相同，除非您事先清理"了上下文，否则先前保留在上下文中的内容将保留下来(这就是为什么您当前编码似乎"可以正常工作的原因.)

Graphics is a shared resource, so the Graphics context which was used to paint some other control will be the same which is used to paint your component, unless you are "cleaning" the context before hand, what was previously painted to the context will remain (which is why you code currently "seems" to work).

相反，应该使用MouseListener定义锚点，该锚点表示按下鼠标的点，然后使用MouseMotionListener定义选择区域的范围，例如...

Instead, you should use a MouseListener to define a anchor point, which represents the point at which the mouse was pressed and then use the MouseMotionListener to define the extent of the selection area, for example...

import java.awt.AlphaComposite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class SelectExample {

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

    public SelectExample() {
        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("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private Rectangle selection;

        public TestPane() {
            MouseAdapter ma = new MouseAdapter() {

                private Point clickPoint;

                @Override
                public void mousePressed(MouseEvent e) {
                    clickPoint = e.getPoint();
                    selection = null;
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    Point dragPoint = e.getPoint();
                    int x = Math.min(clickPoint.x, dragPoint.x);
                    int y = Math.min(clickPoint.y, dragPoint.y);

                    int width = Math.max(clickPoint.x, dragPoint.x) - x;
                    int height = Math.max(clickPoint.y, dragPoint.y) - y;

                    if (selection == null) {
                        selection = new Rectangle(x, y, width, height);
                    } else {
                        selection.setBounds(x, y, width, height);
                    }
                    repaint();
                }

                @Override
                public void mouseReleased(MouseEvent e) {
                    selection = null;
                    repaint();
                }

            };

            addMouseListener(ma);
            addMouseMotionListener(ma);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (selection != null) {
                g.setColor(UIManager.getColor("List.selectionBackground"));
                Graphics2D g2d = (Graphics2D) g.create();
                g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
                g2d.fill(selection);
                g2d.dispose();
                g2d = (Graphics2D) g.create();
                g2d.draw(selection);
                g2d.dispose();
            }
        }

    }

}

仅突出显示如果您继续违反paintComponent方法的要求会遇到的问题，这就是当我不致电super.paintComponent

Just to highlight the issue you will face if you continue to violate the requirements of the paintComponent method, this is what happens when I don't call super.paintComponent

我只是在JFrame上添加了两个JButton(所以甚至没有直接添加到面板上). paintComponent做了一系列重要的工作，而您却忽略了这些工作，这会引起更多的问题.

I simply added two JButton's to the JFrame (so not even directly to the panel). paintComponent does a series of important jobs, which you neglected to perform, which is going to cause more problems and issues.

自由形式的线实际上是一种错觉，它是在一系列点之间绘制的一系列(小)线，其原因是因为MouseListener不会报告鼠标移动的每个位置，具体取决于鼠标移动的速度，您可能会收到很多回拨或一些回拨.

A free form line is actually a illusion, it's a series of (small) lines drawn between a series of points, the reason for this is because the MouseListener won't report every mouse position it moves across, depending on the speed the mouse is moved, you might get lots of call backs or a few.

因此，我们将点存储在List中，并在它们之间绘制线，而不是仅绘制点，例如...

So, instead of drawing to just draw the points, we store the points in a List and draw lines between them, for example...

import java.awt.AlphaComposite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
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.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class FreeFormLines {

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

    public FreeFormLines() {
        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("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private List<List<Point>> points;

        public TestPane() {
            points = new ArrayList<>(25);
            MouseAdapter ma = new MouseAdapter() {

                private List<Point> currentPath;

                @Override
                public void mousePressed(MouseEvent e) {
                    currentPath = new ArrayList<>(25);
                    currentPath.add(e.getPoint());

                    points.add(currentPath);
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    Point dragPoint = e.getPoint();
                    currentPath.add(dragPoint);
                    repaint();
                }

                @Override
                public void mouseReleased(MouseEvent e) {
                    currentPath = null;
                }

            };

            addMouseListener(ma);
            addMouseMotionListener(ma);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            for (List<Point> path : points) {
                Point from = null;
                for (Point p : path) {
                    if (from != null) {
                        g2d.drawLine(from.x, from.y, p.x, p.y);
                    }
                    from = p;
                }
            }
            g2d.dispose();
        }

    }

}

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