技術標籤：Java

繪製如下形式的一個二叉樹

package text8;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.FileOutputStream;
import java.io.IOException;
 
public class Drawing {
    // 以下是常量
    private static final String PATH = "tree.png";
    // 畫板長度
    private
 
 static final int WIDTH = 800;
    // 畫板寬度
    private static final int HEIGHT = 500;
    // 圓形半徑
    private static final int OVAL_RADIUS = 15;
    // 字型大小
    private static final int FONT_SIZE = 15;
    // 根據字型位數，選擇字型偏移量
    private static final int offset_1 = 12;
    private static final int offset_2 = 9;
    private
 
 static final int offset_3 = 4;
    //畫連線時的偏移量
    private static final int LINE_OFFSET = 3;
    //字型格式
    private static final String FONT_STYLE = "宋體";
    //圖片格式
    private static final String IMAGE_STYLE = "PNG";
    //寫數字時用到的偏移量
    private static final int FONT_OFFSET = 1;
    //父圓形與子圓形之間的偏移量
 

    private static final int OVAL_OFFSET = 10;
    //root結點的y座標
    private static final int ROOT_Y = 50;
    //圖形快取區
    private BufferedImage bi;
    //畫圖筆
    private Graphics2D g2;
 
    //以下是變數
    // 當前圓位置和值
    private int my_x;
    private int my_y;
    private char val;
 
    // 當前字型位置
    private int my_font_x;
    private int my_font_y;
 
 
    private void initSettings(){
        //得到圖片緩衝區
        bi = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
        //得到繪製環境(這張圖片的筆)
        g2 = (Graphics2D) bi.getGraphics();
        g2.fillRect(0,0,WIDTH,HEIGHT);
        g2.setBackground(Color.WHITE);
        g2.setColor(Color.BLACK);
        g2.setFont(new Font(FONT_STYLE,Font.PLAIN,FONT_SIZE));
    }
    private void closeSettings() throws IOException {
        ImageIO.write(bi,IMAGE_STYLE,new FileOutputStream(PATH));
    }
 
    public static class DrawNode{
        protected char val;
        protected DrawNode left;
        protected DrawNode right;
        public DrawNode() {}
        public DrawNode(char val) {
            this.val = val;
        }
        public DrawNode(char val, DrawNode left, DrawNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }
 
    /**
     * 畫一個圓，包括數字
     */
    private void drawOval(){
        g2.drawOval(my_x,my_y,OVAL_RADIUS*2,OVAL_RADIUS*2);
        my_font_y = my_y+OVAL_RADIUS+FONT_SIZE/2-FONT_OFFSET;
        switch (String.valueOf(val).length()){
            case 1: my_font_x = my_x+offset_1;break;
            case 2: my_font_x = my_x+offset_2;break;
            case 3: my_font_x = my_x+offset_3;break;
            default: System.out.println("值為"+String.valueOf(val).length()+"位數，不支援！");
        }
        g2.drawString(String.valueOf(val),my_font_x,my_font_y);
    }
 
    /**
     * 畫連線
     * @param isLeft 父結點與子結點的關係
     * @param parent_x 父結點的x座標
     * @param parent_y 父結點的y座標
     */
    private void drawLine(boolean isLeft,int parent_x,int parent_y){
        int parent_point_x;
        int parent_point_y;
        int my_point_x;
        int my_point_y;
        if(isLeft){
            parent_point_x = parent_x+OVAL_RADIUS/2-LINE_OFFSET;
            parent_point_y = parent_y+(3*OVAL_RADIUS)/2+LINE_OFFSET;
            my_point_x = my_x+(3*OVAL_RADIUS)/2+LINE_OFFSET;
            my_point_y = my_y+OVAL_RADIUS/2-LINE_OFFSET;
        }else{
            parent_point_x = parent_x+(3*OVAL_RADIUS)/2+LINE_OFFSET;
            parent_point_y = parent_y+(3*OVAL_RADIUS)/2+LINE_OFFSET;
            my_point_x = my_x+OVAL_RADIUS/2-LINE_OFFSET;
            my_point_y = my_y+OVAL_RADIUS/2-LINE_OFFSET;
        }
        g2.drawLine(parent_point_x,parent_point_y,my_point_x,my_point_y);
    }
 
    /**
     * 一邊中序遍歷一邊畫圖
     * @param node
     */
    private void firstTraverseAndDraw(DrawNode parentNode,DrawNode node,boolean isLeft,int parent_x,int parent_y){
        if(node == null){
            return;
        }
        //只畫當前結點，而不畫父結點。但是要根據父結點與當前結點的關係，確定當前結點的位置，並將連線畫出來
        val = node.val;
        if(parentNode == null){
            my_x = WIDTH/2 - OVAL_RADIUS;
            my_y = ROOT_Y;
        }else{
            my_y = parent_y+2*OVAL_RADIUS+OVAL_OFFSET;
            if(isLeft){
                my_x = parent_x-2*OVAL_RADIUS-OVAL_OFFSET;
            }else{
                my_x = parent_x+2*OVAL_RADIUS+OVAL_OFFSET;
            }
            drawLine(isLeft,parent_x,parent_y);
        }
        drawOval();
 
        // 遞迴畫出左子樹和右子樹
        parent_x = my_x;
        parent_y = my_y;
        firstTraverseAndDraw(node,node.left,true,parent_x,parent_y);
        firstTraverseAndDraw(node,node.right,false,parent_x,parent_y);
    }
 
    public DrawNode build(){
        
        // 此處輸入樹上的點
        
        return a;
    }
    public void drawEntrance(DrawNode drawNode) throws IOException {
        initSettings();
        firstTraverseAndDraw(null,drawNode,true,0,0);
        closeSettings();
    }
 
    public static void main(String[] args) throws IOException {
        Drawing d = new Drawing();
        //先構建一顆二叉樹
        DrawNode root = d.build();
        //呼叫入口方法畫圖
        d.drawEntrance(root);
    }
 
}