java中,用Graphics 在canvas画图,图形一伞就没有,奖励分数20!

[小码哥的进阶]

import java.awt.*;
import javax.swing.JFrame;

public class TestCirCles {
	public static void main(String[] args) {
		// Circle.drawCircle(100, 100, 50);
		// System.out.println("hello world");
		// Parts.drawCircle(100, 100, 50);

		MyCanvas ca = new MyCanvas();
		ca.paint();

	}
}

class MyCanvas  {
	static Graphics g1;
	static JFrame f;
	static Image imag;
	static {
		f = new JFrame("画图演示");
		// 创建一个区域
		Canvas canvas = new Canvas();
		f.add(canvas);
		f.setSize(400, 400);
		f.setBackground(Color.white);
		f.setVisible(true);
		//imag = f.createImage(400,300);
		//g1 = imag .getGraphics();
		// 要先让组件显示后，才会返回Graphics对象，否则会返回null
		g1=canvas.getGraphics();
		f.setDefaultCloseOperation(3);
	}
	int x = 100, y = 100, r = 100, n = 100;
	int x0 = 10, y0 = 10;

	/**
	 * 画圆 知识点:引入 double数据类型
	 */
	public void paint() {
		for (int i = 0; i <= 360; i = i + 360 / n) {
			// 数据类型double
			double cs = Math.cos(i);
			double ss = Math.sin(i);
			x0 = (int) (x + r * cs);
			y0 = (int) (y + r * ss);
			g1.drawString("*", x0, y0);
		}
	}
}

另一个代码也是这种情况

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;

import javax.swing.JFrame;

public class Circle extends JFrame {

	private static final long serialVersionUID = -2420677068593785097L;
	public static final int WIDTH = 800;
	public static final int HEIGHT = 600;
	// static MyPanel panel = new MyPanel();
	static Graphics g;
	static JFrame f;
	static {
		f = new JFrame("画图演示");
		// 创建一个区域
		Canvas canvas = new Canvas();
		f.add(canvas);
		f.setSize(400, 400);
		f.setBackground(Color.white);
		f.setVisible(true);
		// 要先让组件显示后，才会返回Graphics对象，否则会返回null
		g = canvas.getGraphics();
	}

	public static void drawCircle(double pointX, double pointY, float radius) {
		Graphics2D g2 = (Graphics2D) g;
		radius = 100;
		g.setColor(Color.RED);
		Ellipse2D circle = new Ellipse2D.Double();
		circle.setFrameFromCenter(pointX, pointY, pointX + radius, pointY
				+ radius);
		g2.fill(circle);

	}

}

[小码哥的进阶]

好像说用双缓冲技术,不好使啊,不太会用 /**双缓冲画布*/ private Image memoryImage; /**双缓冲画笔*/ private Graphics memoryGraphics; //重新开辟一块内存区域，用于存放叠加后的图片 this.memoryImage = this.createImage(900,700); //从双缓冲画布当中得到双缓冲画笔,这样通过双缓冲画笔绘制的图片就会叠加在双缓冲画布中 this.memoryGraphics = this.memoryImage.getGraphics(); //绘制文字 this.memoryGraphics.drawString("分数:"+pointer, 100, 57); //绘制图片 this.memoryGraphics.drawImage(hartNumImg,50,80,30,25,this);

[grapepaul]

标题改成 献上XX分数，会有更多人来回答你的问题。 ps. 20太少了