问题描述
- 在一个面板上交替显示红色的圆和绿色的圆
- import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.WindowConstants;public class ShiYan04 {
public static void main(String args[])
{
Ckou ck=new Ckou();
}}
class Ckou extends JFrame
{
public Ckou()
{
JFrame jframe=new JFrame(""变色圆"");
Container container=jframe.getContentPane();
jframe.setBackground(Color.BLUE);
jframe.setSize(600400);
jframe.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
jframe.setVisible(true);Drawt dt=new Drawt(); container.add(dt); JButton button=new JButton(""开始""); button.setSize(30 30); container.add(button); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { T2 t2=new T2(dt); Thread tt2=new Thread(t2); T1 t1=new T1(dtt2); Thread tt1=new Thread(t1); tt1.start(); tt2.start(); try { Thread.sleep(100000); } catch(Exception e3) {} } } );}class T1 implements Runnable{ Drawt t; T2 a; public T1(Drawt tT2 a) { this.t=t; this.a=a; } public void run() { while(true) { System.out.println(""现在显示绿色""); a.stop=true; t.i=1; t.repaint(); try { Thread.sleep(3000); } catch(Exception e1) {} a.stop=false; try { Thread.sleep(3000); } catch(Exception e1) {} } }}class T2 implements Runnable{ volatile boolean stop = true; Drawt t; public T2(Drawt t) { this.t=t; } public void run() { while(!stop) { System.out.println(""现在显示红色""); t.i=2; try { Thread.sleep(3000); } catch(Exception e2) {} } }}class Drawt extends JPanel{ int i=0; public Drawt() {} public void paint(Graphics g) { if(i==1) { g.setColor(Color.green); g.drawOval(10010070 70); } else if(i==2) { g.setColor(Color.red); g.drawOval(15015070 70); } }}}
首先他一直输出的是绿色的圆，
然后就是由于加上主线程main的睡眠，我的圆显示不出来
解决方案
你的代码存在的问题：
1）你的T2线程的while循环第一次执行就跳出了，导致红色线程一下就结束了。应该也是跟T1一样用while(true)内部操作时根据i的值绘图。
2）Button的宽度太小了，导致看不到文本值。
3）绘制圆形是两个不一样的圆形，所以看不到交替效果。
4）main线程sleep时间太长了，可以改小一点。
修正你的代码如下：
import java.awt.Color;import java.awt.Container;import java.awt.Graphics;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.WindowConstants;public class ShiYan04 { public static void main(String args[]) { Ckou ck = new Ckou(); }}class Ckou extends JFrame { public Ckou() { JFrame jframe = new JFrame(""变色圆""); Container container = jframe.getContentPane(); jframe.setBackground(Color.BLUE); jframe.setSize(600 400); jframe.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); jframe.setVisible(true); Drawt dt = new Drawt(); container.add(dt); JButton button = new JButton(""开始""); button.setSize(100 30); container.add(button); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { T2 t2 = new T2(dt); Thread tt2 = new Thread(t2); T1 t1 = new T1(dt t2); Thread tt1 = new Thread(t1); tt1.start(); tt2.start(); try { Thread.sleep(100000); } catch (Exception e3) { } } }); } class T1 implements Runnable { Drawt t; T2 a; public T1(Drawt t T2 a) { this.t = t; this.a = a; } public void run() { while (true) { System.out.println(""现在显示绿色""); a.stop = true; t.i = 1; t.repaint(); try { Thread.sleep(3000); } catch (Exception e1) { } a.stop = false; try { Thread.sleep(3000); } catch (Exception e1) { } } } } class T2 implements Runnable { volatile boolean stop = true; Drawt t; public T2(Drawt t) { this.t = t; } public void run() { while (true) { System.out.println(""stop :""+stop); System.out.println(""现在显示红色""); t.i = 2; try { Thread.sleep(3000); } catch (Exception e2) { } } } } class Drawt extends JPanel { int i = 0; public Drawt() { } public void paint(Graphics g) { System.out.println(""paint i:""+i); if (i == 1) { g.setColor(Color.green); g.drawOval(150 150 70 70); } else if (i == 2) { g.setColor(Color.red); g.drawOval(150 150 70 70); }else{ g.setColor(Color.ORANGE); g.drawOval(150 150 70 70); } } }}测试OK。可以优化的是paint方法的g.drawOval代码放在外面，只在if分支中设置颜色，添加一个初始默认颜色。
public void paint(Graphics g) { System.out.println(""paint i:""+i); if (i == 1) { g.setColor(Color.green); } else if (i == 2) { g.setColor(Color.red); }else{ g.setColor(Color.ORANGE); } g.drawOval(150 150 70 70); }时间： 2024-08-29 01:35:31