• JAVA学习第十一课：java绘图

    1、前提知识

    • 布局：Layout
    • 什么是布局？界面元素的排布和变化规律
    • 案例：计算器
    • 开发布局，用到Java中的哪个包？
      • java.awt
      • 文档浏览

    2、案例引入：界面上放10个按钮

    import javax.swing.*;
import java.awt.*;
class LayoutTest1 extends JFrame{
	private JPanel jpl = new JPanel();
	public LayoutTest1(){
		FlowLayout fl = new FlowLayout(FlowLayout.LEFT, 20, 50);
		jpl.setLayout(fl);
		JButton[] bts = new JButton[10];
		for(int i=0; i<10; i++){
			bts[i] = new JButton("按钮"+i);
			jpl.add(bts[i]);
		}
		
		this.add(jpl);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setSize(800,600);
		this.setVisible(true);
	}
	public static void main (String[] args) {
		new LayoutTest1();
	}
}

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    3、布局方式1：流式布局（FlowLayout）

    • 从左到右，从上到下排布；JPanel默认是这种布局方式
    • 该布局由java.awt.FlowLoyout管理；通过容器的setLayout函数可以设置

    4、布局方式2：网格布局（GridLayout）

    • 将容器分为多行多列；例如计算器中的数字面板
    • 案例：界面上放置24个按钮，6行，4列
    • 案例：界面上添加一个国际象棋棋盘，8*8，黑白交错
    package frame;


import javax.swing.*;
import java.awt.*;
class Test extends JFrame{
	private JPanel jpl = new JPanel();
	public Test(){
		jpl.setLayout(new GridLayout(6,4,5,5));
		JButton[] bts = new JButton[24];
		for(int i=0; i<24; i++){
			bts[i] = new JButton("按钮"+i);
			jpl.add(bts[i]);
		}
		
		this.add(jpl);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setSize(800,600);
		this.setVisible(true);
	}
	public static void main (String[] args) {
		new Test();
	}
}

	



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package frame;

import javax.swing.*;
import java.awt.*;
class Test extends JFrame{
	private JPanel jpl = new JPanel();
	public  Test(){
		jpl.setLayout(new GridLayout(8,8));		
		JPanel[][] pls = new JPanel[8][8];		
		for(int i=0; i<8; i++){
			for(int j=0; j<8; j++){
				pls[i][j] = new JPanel();
				if((i+j)%2==0){
					pls[i][j].setBackground(Color.white);
				}else{
					pls[i][j].setBackground(Color.black);					
				}
				jpl.add(pls[i][j]);
			}	
		}
		
		this.add(jpl);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setSize(800,600);
		this.setVisible(true);
	}
	public static void main (String[] args) {
		new Test();
	}
}

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    5、布局方式3：边界布局（BorderLayout）

    • 将容器分为东西南北中五个位置；上北下南左西右东
    
import javax.swing.*;
import java.awt.*;
class LayoutTest1 extends JFrame{
	private JPanel jpl = new JPanel();
	public LayoutTest1(){
		jpl.setLayout(new BorderLayout());
		jpl.add(new JButton("按钮东"), BorderLayout.EAST);	
		jpl.add(new JButton("按钮西"), BorderLayout.WEST);	
		jpl.add(new JButton("按钮南"), BorderLayout.SOUTH);	
		jpl.add(new JButton("按钮北"), BorderLayout.NORTH);	
		jpl.add(new JButton("按钮中"), BorderLayout.CENTER);		
		
		this.add(jpl);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setSize(800,600);
		this.setVisible(true);
	}
	public static void main (String[] args) {
		new LayoutTest1();
	}
}

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    6、布局方式4：空布局（万能布局）

    • 将容器的Layout设置为null，然后用坐标来确定容器中的元素位置
    
import javax.swing.*;
import java.awt.*;
class LayoutTest1 extends JFrame{
	private JPanel jpl = new JPanel();
	public LayoutTest1(){
		jpl.setLayout(null);
		JButton jbt = new JButton("按钮");
		jbt.setLocation(300,200);
		jbt.setSize(200,400);		
		jpl.add(jbt);
			
		
		this.add(jpl);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setSize(800,600);
		this.setVisible(true);
	}
	public static void main (String[] args) {
		new LayoutTest1();
	}
}

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    ——————习题——————

    1、界面上一副图片，鼠标进入图片，图片自动避开到另一个地方

    import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class LayoutTest1 extends JFrame implements MouseListener{
	private JPanel jpl = new JPanel();
	private Icon    ico = new ImageIcon("img.jpg");
	private JLabel jlb = new JLabel(ico);
	public LayoutTest1(){
		jlb.addMouseListener(this);
		jpl.setLayout(null);
		jlb.setLocation(300,200);
		jlb.setSize(ico.getIconWidth(),ico.getIconHeight());				
		jpl.add(jlb);   this.add(jpl);		
    	this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setSize(800,600);
		this.setVisible(true);
	}
	public void mouseClicked(MouseEvent e) {}
	public void mouseEntered(MouseEvent e) {
		int X = (int)(Math.random() * 800);
		int Y = (int)(Math.random() * 600);
		jlb.setLocation(X,Y);
	}
	public void mouseExited(MouseEvent e) {}
	public void mousePressed(MouseEvent e){} 
	public void mouseReleased(MouseEvent e){} 

	public static void main (String[] args) {
		new LayoutTest1();
	}
}

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    2、界面上一副图片，鼠标可以将图片从一个地方拖到另一个地方

    import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class LayoutTest1 extends JFrame implements MouseMotionListener {
	private JPanel jpl = new JPanel();
	private Icon    ico = new ImageIcon("img.jpg");
	private JLabel jlb = new JLabel(ico);
	public LayoutTest1(){
		this.addMouseMotionListener(this);
		jpl.setLayout(null);
		jlb.setLocation(300,200);
		jlb.setSize(ico.getIconWidth(),ico.getIconHeight());				
		jpl.add(jlb);   this.add(jpl);		
    	this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setSize(800,600);
		this.setVisible(true);
	}
	public void mouseDragged(MouseEvent e){
		int X = e.getX();		int Y = e.getY();
		jlb.setLocation(X,Y);		
	}
	public void mouseMoved(MouseEvent e){}
	public static void main (String[] args) {
		new LayoutTest1();
	}
}

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    3、界面上一副图片，通过键盘上下左右键控制其移动
    KeyListener

    import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class LayoutTest1 extends JFrame implements KeyListener {
	private JPanel jpl = new JPanel();
	private Icon    ico = new ImageIcon("img.jpg");
	private JLabel jlb = new JLabel(ico);
	public LayoutTest1(){
		this.addKeyListener(this);
		jpl.setLayout(null);
		jlb.setLocation(300,200);
		jlb.setSize(ico.getIconWidth(),ico.getIconHeight());				
		jpl.add(jlb);   this.add(jpl);		
    	this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setSize(800,600);
		this.setVisible(true);
	}
	public void keyPressed(KeyEvent e) {	
		int code = e.getKeyCode();
		int X = jlb.getX();  int Y = jlb.getY();
		if(code==KeyEvent.VK_UP){
			Y-=ico.getIconHeight();
		}else if(code==KeyEvent.VK_DOWN){
			Y+=ico.getIconHeight();
		}else if(code==KeyEvent.VK_LEFT){
			X-=ico.getIconWidth();
		}else if(code==KeyEvent.VK_RIGHT){
			X+=ico.getIconWidth();
		}
		jlb.setLocation(X,Y);
	}
	public void keyReleased(KeyEvent e) {}
	public void keyTyped(KeyEvent e) {}
	public static void main (String[] args) {
		new LayoutTest1();
	}
}

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    7、绘图的前提

    • 画架：JFrame
    • 画布：JPanel
    • 画笔：？？
    • 现场编程案例：在界面上放置一个画布
    • 基本结构：编写画布（JPanel子类），放置在JFrame上
    import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel{
	public void paint(Graphics g){
		System.out.println("Hello");
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}



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    8、画笔

    • JPanel有一个paint函数，函数中包含画笔
    • public void paint(Graphics g)
      • 该函数中的参数，可以当成画笔使用
      • 该函数在界面刷新时自动调用
      • 绘图功能，写在paint函数中，用Graphics作为画笔
    • Graphics有drawXXX和fillXXX函数绘图；setColor函数设置颜色
      • 案例：界面上绘制椭圆和线段，用不同颜色
    import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel{
	public void paint(Graphics g){
		g.setColor(Color.red);
		g.drawLine(100,100,200,300);
		g.setColor(Color.blue);
		g.fillOval(100,200,200,100);
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}


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    9、界面手工刷新：调用paint

    • 用画布的repaint函数调用paint
    • 案例：界面上不断出现随机位置，随机颜色，随机大小的椭圆
    import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel implements Runnable{
	public MyCanvas(){
		new Thread(this).start();
	}
	public void paint(Graphics g){
		Graphics2D g2d = (Graphics2D)g;
		g2d.setColor(new Color((int)(Math.random()*256), (int)(Math.random()*256), (int)(Math.random()*256)));
		int X = (int)(Math.random()*this.getWidth());
		int Y = (int)(Math.random()*this.getHeight());
		int W = (int)(Math.random()*100);
		int H = (int)(Math.random()*100);		
		g2d.fillOval(X,Y,W,H);
	}
	public void run(){
		while(true){
			try {	Thread.sleep(100); } catch(Exception ex){}
			this.repaint();
		}
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}


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    10、画笔Graphics升级版：Graphics2D

    • 可以将Graphics对象直接转成Graphics2D使用
    import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel implements Runnable{
	public MyCanvas(){
		new Thread(this).start();
	}
	public void paint(Graphics g){
		Graphics2D g2d = (Graphics2D)g;
		g2d.setStroke(new BasicStroke(10));
		g2d.setColor(new Color((int)(Math.random()*256), (int)(Math.random()*256), (int)(Math.random()*256)));
		int X = (int)(Math.random()*this.getWidth());
		int Y = (int)(Math.random()*this.getHeight());
		int W = (int)(Math.random()*100);
		int H = (int)(Math.random()*100);
		g2d.drawOval(X,Y,W,H);
	}
	public void run(){
		while(true){
			try {	Thread.sleep(100); } catch(Exception ex){}
			this.repaint();
		}
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}


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    11、绘制图像

    • 使用画笔的drawImage函数
    • 案例：将img.jpg绘制在界面上
    
import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel  {
	Image img  = Toolkit.getDefaultToolkit().createImage("img.jpg");
	public void paint(Graphics g){	
		g.drawImage(img,100,100,this);	
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}


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    • 直接绘制图像
      • drawImage(Image img,int x,int y, ImageObserver observer)
    • 案例：将img.jpg缩放绘制在界面上
    import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel  {
	Image img  = Toolkit.getDefaultToolkit().createImage("img.jpg");
	public void paint(Graphics g){	
		g.drawImage(img,100,100,this);
		g.drawImage(img,500,500, 200, 200, this);
			
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}


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    • 缩放绘制图像

      • drawImage(Image img,int x,int y, int width,
        int height,ImageObserver observer)

      • 案例：图像自动在界面上放大

    import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel implements Runnable {
	int W = 0;
	int H = 0;
	Image img  = Toolkit.getDefaultToolkit().createImage("img.jpg");
	MyCanvas(){
		new Thread(this).start();
	}
	public void paint(Graphics g){	
		g.drawImage(img,100,100, W, H, this);			
	}
	public void run(){
		while(true){
			W+=10; H+=8;
			repaint();
			try{  Thread.sleep(100); } catch(Exception e){}
		}
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}


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    • 裁剪绘制图像
      • drawImage(Image img,int dx1,int dy1,
        int dx2, int dy2,
        int sx1, int sy1,
        int sx2, int sy2,
        ImageObserver observer)
      • 案例：将图像的下半部分绘制在界面，充满界面
    import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel   {
	Image img  = Toolkit.getDefaultToolkit().createImage("img.jpg");
	public void paint(Graphics g){	
		g.drawImage(img,0,0, this.getWidth(), this.getHeight(),
		                           0, img.getHeight(this)/2, img.getWidth(this),img.getHeight(this) ,
		                           this);			
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}


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    • 旋转绘制图像
      • 旋转绘制，实际上是画布旋转
      • 使用Graphics2D的rotate函数
        • rotate(double theta, double x, double y)
        • 绕圆心旋转某弧度
    
import javax.swing.*;
import java.awt.*;
class MyCanvas extends JPanel  {
	Image img  = Toolkit.getDefaultToolkit().createImage("img.jpg");
	public void paint(Graphics g){	
		Graphics2D g2d = (Graphics2D)g;
		g2d.rotate(Math.PI/4, 100+img.getWidth(this)/2,100+img.getHeight(this)/2);
		g.drawImage(img,100,100,this);			
	}
}

class PaintTest  extends JFrame{
	MyCanvas mc = new MyCanvas();
	public PaintTest(){
		this.add(mc);
		this.setSize(800,600);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setVisible(true);
	}
	public static void main(String[] args)    {
		new PaintTest();
	}
}


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  • 原文地址：https://blog.csdn.net/weixin_62529383/article/details/127837624