利用Swing在窗体上绘制线条与文字（二）——绘制简单形状

清疚 2024-04-18 23:30 63阅读 0赞

# 效果 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNTc2MDI4_size_16_color_FFFFFF_t_70]

# 代码： #

TestFrame.java:

package Test;
    
    
    import javax.swing.*;
    import java.awt.*;
    
    public class TestFrame extends JFrame {
        
        public TestFrame(){
        
              setLayout(new GridLayout(2,3,5,5));
              add(new FigurePanel(FigurePanel.LINE));
              add(new FigurePanel(FigurePanel.RECTANGLE));
              add(new FigurePanel(FigurePanel.ROUND_RECTANGLE));
              add(new FigurePanel(FigurePanel.OVAL));
              add(new FigurePanel(FigurePanel.RECTANGLE,true));
              add(new FigurePanel(FigurePanel.ROUND_RECTANGLE,true));
    
    
        }
    
        public static void main(String[] args) {
        
            TestFrame frame=new TestFrame();
            frame.setTitle("TestFigurePanel");
            frame.setSize(400,200);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        }
    }

FigurePanel.java:

package Test;
    
    import javax.swing.*;
    import java.awt.*;
    
    public class FigurePanel extends JPanel {
        
        public static final int LINE=1;
        public static final int RECTANGLE=2;
        public static final int ROUND_RECTANGLE=3;
        public static final int OVAL=4;
    
        public int getType() {
        
            return type;
        }
    
        public void setType(int type) {
        
            this.type = type;
            repaint();
        }
    
        private int type=1;
    
        public boolean isFilled() {
        
            return filled;
        }
    
        public void setFilled(boolean filled) {
        
            this.filled = filled;
            repaint();
        }
    
        private boolean filled=false;
    
        public FigurePanel(){
        
    
        }
        public FigurePanel(int type){
        
            this.type=type;
        }
        public FigurePanel(int type,boolean filled){
        
            this.type=type;
            this.filled=filled;
        }
        protected void paintComponent(Graphics g){
        
            super.paintComponent(g);
            int width=getWidth();
            int height=getHeight();
    
            switch(type){
        
                case LINE:
                    g.setColor(Color.BLACK);
                    g.drawLine(10,10,width-10,height-10);
                    g.drawLine(width-10,10,10,height-10);
                    break;
                case RECTANGLE:
                    g.setColor(Color.BLUE);
                    if(filled)
                        g.fillRect((int)(0.1*width),(int)(0.1*height),
                                (int)(0.8*width),(int)(0.8*height));
                    else
                        g.drawRect((int)(0.1*width),(int)(0.1*height),
                                (int)(0.8*width),(int)(0.8*height));
                    break;
                case ROUND_RECTANGLE:
                    g.setColor(Color.RED);
                    if(filled)
                        g.fillRoundRect((int)(0.1*width),(int)(0.1*height),
                                (int)(0.8*width),(int)(0.8*height),20,20);
                    else
                        g.drawRoundRect((int)(0.1*width),(int)(0.1*height),
                                (int)(0.8*width),(int)(0.8*height),20,20);
                    break;
                case OVAL:
                    g.setColor(Color.BLACK);
                    if(filled)
                        g.fillOval((int)(0.1*width),(int)(0.1*height),(int)(0.8*width),(int)(0.8*height));
                    else
                        g.drawOval((int)(0.1*width),(int)(0.1*height),(int)(0.8*width),(int)(0.8*height));
    
            }
        }
        public Dimension getPreferredSize(){
        
            return new Dimension(80,80);
        }
    }

# 讲解： #

add(new FigurePanel(FigurePanel.LINE));

这里面的FigurePanel.LINE在FigurePanel类里面已经定义了若干个常量。

public static final int LINE=1;
       public static final int RECTANGLE=2;
       public static final int ROUND_RECTANGLE=3;
       public static final int OVAL=4;

方便下面的case选择。

在FigurePanel类里面，有两个私有成员，一个是type，一个是filled，type就是上面定义的四个常量，取值范围是1~4的整数，filled是一个boolean类型成员，即是否填充。

给成员变量填上getter和setter方法。

switch(type)

开始选择要绘制的图像的类型，在case里面，如果选择的未填充的图形，那么会采用draw\_type来绘制图形。

case LINE:
                g.setColor(Color.BLACK);
                g.drawLine(10,10,width-10,height-10);
                g.drawLine(width-10,10,10,height-10);
                break;

例如选择绘制直线，这里会绘制一个交错的直线。颜色是随意的，这里的width和height就是

public static void main(String[] args) {
        TestFrame frame=new TestFrame();
        frame.setTitle("TestFigurePanel");
        frame.setSize(400,200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

里面的高和宽。

case OVAL:
                g.setColor(Color.BLACK);
                if(filled)
                    g.fillOval((int)(0.1*width),(int)(0.1*height),(int)(0.8*width),(int)(0.8*height));
                else
                    g.drawOval((int)(0.1*width),(int)(0.1*height),(int)(0.8*width),(int)(0.8*height));

如果想要绘制椭圆，首先会判断是否填充，如果是填充的，就会调用fill\_type来绘制，反之调用draw\_oval绘制一个空心的。

repaint();

repaint这个方法是在Component类里面定义的，调用repaint方法会导致paintComponent方法被调用，即刷新视图。一般情况下，如果要显示新的东西，就要调用这个方法。

public Dimension getPreferredSize(){
        return new Dimension(80,80);
    }

Dimension类是封装单个对象中组件的宽度和高度

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