如何在 Java Swing 中打开和关闭屏幕的形状

Question

好的，所以我正在尝试使用 swing 构建一个程序，其中我必须能够在屏幕的右下角绘制一个椭圆形和矩形。我目前正在尝试使用以前的程序，其中程序使用 JToggleSwitch 启动和停止一个正方形。我的问题是我如何让形状打开和关闭屏幕，因为它需要一个参数"图形 g"。这是我到目前为止的PaintPanel代码。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class PaintPanel extends JPanel
{
    private static Color[] colors =
        { Color.RED, Color.BLACK, Color.PINK, Color.ORANGE };
    private int colorNumber = 0;
    private int shape = 0;
    private int x = 0;
    private int y = 0;
    private int width = 100;
    private int height = 100;
    private int dx = 2;
    private int dy = 2;
    private String displayString = "hello";
    private boolean isStarted = true;
    public void update()
    {
        if (isStarted) 
        {
            x += dx;
            y += dy;
        }
        //dx ++;
        //dy ++;
        if (y + height > getHeight())
        {
            dy = -Math.abs(dy);
            shape++;
            colorNumber = (colorNumber+1)%colors.length;
        }
        else if (y < 0)
        {
            dy = Math.abs(dy);
            shape++;
            colorNumber = (colorNumber+1)%colors.length;
        }
        if (x + width > getWidth())
        {
            dx = -Math.abs(dx);
            shape++;
            colorNumber = (colorNumber+1)%colors.length;
        }
        else if (x < 0)
        {
            dx = Math.abs(dx);
            shape++;
            colorNumber = (colorNumber+1)%colors.length;
        }
    }
    public void changeColor()
    {
        colorNumber = (colorNumber+1) % colors.length;
    }
    public void startStop()
    {
        //if (isStarted == true) isStarted = false;
        //else isStarted = true;
        isStarted = !isStarted;
    }
    public void setDisplayText(String dt)
    {
        displayString = dt;
    }
    public void paintRectangle(Graphics g)
    {
        int w = getWidth();
        int h = getHeight();
        g.setColor(Color.PINK);
        g.fillRect(w/2, h/2, w/2, h/2);
        //g.setColor(Color.CYAN);
        //g.fillOval((5*w)/8, (5*h)/8, w/4, h/4);

    }

    public void paintComponent(Graphics g)
    {

        int w = getWidth();
        int h = getHeight();
        g.setColor(colors[colorNumber]);
        if (shape % 2 == 0) //g.fillOval(x, y, width, height);
        /*else*/ g.fillRect(x,y, width, height);

        int textx = x+width/2;
        int texty = y+height/2;
        FontMetrics fm = g.getFontMetrics();
        int texth = fm.getHeight();
        int textw = fm.stringWidth(displayString);
        textx -= textw/2;
        texty += texth/2;
        texty -= 5;     
        g.setColor(colors[(colorNumber+1)%colors.length]);
        g.drawString(displayString, textx, texty);
    }
}

这是创建窗口和面板的实际代码。这是我的主要课程。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class GuiTest extends JFrame 
    implements ActionListener
{
    private Timer frameTimer;
    private JToggleButton name;
    private JToggleButton ovalButton;
    private JToggleButton rectangle;
    //private JTextField theText;
    private PaintPanel paintPanel;
    public GuiTest()
    {
        setTitle("Servando Hernandez");
        setSize(500,500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel topPanel = new JPanel();
        topPanel.setLayout(new GridLayout(1,3));
        name = new JToggleButton("Name");
        name.addActionListener(this);
        ovalButton = new JToggleButton("Oval");
        ovalButton.addActionListener(this);
        rectangle = new JToggleButton("Rectangle");
        rectangle.addActionListener(this);
        //theText = new JTextField("HI");
        //theText.addActionListener(this);

        topPanel.add(name);
        topPanel.add(ovalButton);
        topPanel.add(rectangle);
        //topPanel.add(theText);
        Container contentPane = getContentPane();
        contentPane.setLayout(new BorderLayout());
        contentPane.add(topPanel, BorderLayout.SOUTH);
        paintPanel = new PaintPanel();
        contentPane.add(paintPanel, BorderLayout.CENTER);
        frameTimer = new Timer(50, this);
        frameTimer.start();
    }
    public void actionPerformed(ActionEvent e)
    {
        //System.out.println("Action performed");
        if (e.getSource() == name)      
        {
            paintPanel.changeColor();
        }
        else if (e.getSource() == frameTimer)
        {
            paintPanel.update();
        }
        else if (e.getSource() == ovalButton)
        {
            //System.out.println("start/stop");
            paintPanel.startStop();
        }
        else if (e.getSource() == rectangle)
        {
        }
        /*else if (e.getSource() == theText)
        {
            String text = e.getActionCommand();
            paintPanel.setDisplayText(text);
            //System.out.println(text);
        }
        */
        repaint();
    }
    public static void main(String[] args)
    {
        GuiTest gui = new GuiTest();
        gui.setVisible(true);
    }
}

Answer 1

你可以...

保持要绘制的Shape List，根据需要添加或删除它们。 然后，您将在 paintComponent 方法中循环访问列表，绘制List中的内容，并在需要更新组件时简单地调用repaint

你可以...

有一系列boolean（或其他类型的）标志，指示要绘制哪些形状。 这种修复了哪些形状可以绘制，并且实际上不允许你控制形状的z顺序。

你应该...

在执行任何自定义绘制之前调用super.paintComponent，否则每次绘制组件时都可能会产生不需要的油漆伪影。 请记住，绘制是破坏性的，当调用paintComponent时，您应该完全重新绘制组件的当前状态