java-主要方法和关键侦听器
作者：互联网
谁能告诉我为什么这个程序说我缺少一种主要方法？我在此代码的底部.
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
public class Collision extends JFrame
{
final int WIDTH = 900, HEIGHT = 650;
double p1Speed = .5, p2Speed = .5;
//these are the ints that represent directions
final int UP = 0, RIGHT = 1, DOWN = 2, LEFT = 3;
//these will keep track of the players directions(default = up)
int p1Direction = UP;
int p2Direction = UP;
Rectangle left = new Rectangle(0,0,WIDTH/9,HEIGHT);
Rectangle right = new Rectangle((WIDTH/9)*8,0,WIDTH/9,HEIGHT);
Rectangle top = new Rectangle(0,0,WIDTH,HEIGHT/9);
Rectangle bottom = new Rectangle(0,(HEIGHT/9)*8, WIDTH,HEIGHT/9);
Rectangle center = new Rectangle((int)((WIDTH/9)* 2.5),(int)((HEIGHT/9)*2.5),(int)
((WIDTH/9)*5),(HEIGHT/9)*4);
Rectangle obstacle = new Rectangle(WIDTH/2,(int)((HEIGHT/9)*7),WIDTH/10,HEIGHT/9);
Rectangle obstacle2 = new Rectangle(WIDTH/3,(int)((HEIGHT/9)*5),WIDTH/10,HEIGHT/4);
Rectangle obstacle3 = new Rectangle(2*(WIDTH/3),(int)
((HEIGHT/9)*5),WIDTH/10,HEIGHT/4);
Rectangle obstacle4 = new Rectangle(WIDTH/3,HEIGHT/9,WIDTH/30,HEIGHT/9);
Rectangle obstacle5 = new Rectangle(WIDTH/2,(int)((HEIGHT/9)*1.5),WIDTH/30,HEIGHT/4);
Rectangle finish = new Rectangle(WIDTH/9,(HEIGHT/2)-HEIGHT/9,(int)
((WIDTH/9)*1.5),HEIGHT/70);
Rectangle p1 = new Rectangle(WIDTH/9,HEIGHT/2, WIDTH/30,WIDTH/30);
Rectangle p2 = new Rectangle(((WIDTH/9)+((int)((WIDTH/9)*1.5)/2)),(HEIGHT/2)+
(HEIGHT/10),WIDTH/30,WIDTH/30);
public Collision()
{
//the following code creates the JFrame
super("Radical Racing");
setSize(WIDTH,HEIGHT);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
//start the inner class (which works on it's own because it is a thread)
Move1 m1 = new Move1();
Move2 m2 = new Move2();
m1.start();
m2.start();
}
public void paint(Graphics g)
{
super.paint(g);
//draw the bckround for the racetrack
g.setColor(Color.DARK_GRAY);
g.fillRect(0,0,WIDTH,HEIGHT);
//When we drawthe border will be green
g.setColor(Color.GREEN);
//the following rectangle is the start line for the outer player
Rectangle lineO = new
Rectangle(WIDTH/9,HEIGHT/2,(int)((WIDTH/9)*1.5)/2,HEIGHT/140);
//the following rctangle is the start line for the inner player
Rectangle lineI = new
Rectangle(((WIDTH/9)+((int)((WIDTH/9)*1.5)/2)),(HEIGHT/2)+(HEIGHT/10),
(int)((WIDTH/9)*1.5)/2,HEIGHT/140);
//now using the rectangles, draw it
g.fillRect(left.x,left.y,left.width,left.height);
g.fillRect(right.x,right.y,right.width,right.height);
g.fillRect(top.x,top.y,top.width,top.height);
g.fillRect(bottom.x,bottom.y,bottom.width,bottom.height);
g.fillRect(center.x,center.y,center.width,center.height);
g.fillRect(obstacle.x,obstacle.y,obstacle.width,obstacle.height);
g.fillRect(obstacle2.x,obstacle2.y,obstacle2.width,obstacle2.height);
g.fillRect(obstacle3.x,obstacle3.y,obstacle3.width,obstacle3.height);
g.fillRect(obstacle4.x,obstacle4.y,obstacle4.width,obstacle4.height);
g.fillRect(obstacle5.x,obstacle5.y,obstacle5.width,obstacle5.height);
//set the starting line color
g.setColor(Color.WHITE);
//the draw the starting line
g.fillRect(lineO.x,lineO.y,lineO.width,lineO.height);
g.fillRect(lineI.x,lineI.y,lineI.width,lineI.height);
//set the color of the finish line to yellow
g.setColor(Color.YELLOW);
g.fillRect(finish.x,finish.y,finish.width,finish.height);
//set the color to blue for p1
g.setColor(Color.BLUE);
//now draw the actual player
g.fill3DRect(p1.x,p1.y,p1.width,p1.height,true);
//set the color to red for p2
g.setColor(Color.red);
//now draw the actual player
g.fill3DRect(p2.x,p2.y,p2.width,p2.height,true);
}
private class Move1 extends Thread implements KeyListener
{
public void run()
{
//add the code to make the KeyListener "wake up"
addKeyListener(this);
//now, put the code should all be in an infinite loop, so the process repeats.
while(true)
{
try
{
//first refresh the screen:
repaint();
//check to see if the car hits the outside of the walls.
//If so make it slow it's speed by setting it's speed to .4.
if(p1.intersects(left) || p1.intersects(right) ||
p1.intersects(top) || p1.intersects(bottom) ||
p1.intersects(obstacle) || p1.intersects(obstacle2) ||
p1.intersects(p2) || p1.intersects(obstacle3) ||
p1.intersects(obstacle4) || p1.intersects(obstacle5))
{
p1Speed = -4;
}
if(p1.intersects(center))
{
p1Speed = -2.5;
}
//increase speed a bit
if(p1Speed<=5)
p1Speed+=.2;
//these will move the player based on direction
if(p1Direction == UP)
{
p1.y-=(int)p1Speed;
}
if(p1Direction ==DOWN)
{
p1.y+=(int)p1Speed;
}
if(p1Direction == LEFT)
{
p1.x-=(int)p1Speed;
}
if(p1Direction == RIGHT)
{
p1.x+=(int)p1Speed;
}
//This delays the refresh rate
Thread.sleep(75);
}
catch(Exception e)
{//if there is an exception (an error), exit the loop
break;
}
}
}
//You must also implement this method from Key Listener
public void keyPressed(KeyEvent event)
{
}
//You must also implement this method from key listener
public void keyReleased(KeyEvent event)
{
}
//You must also implement this method from key listener
public void keyTyped(KeyEvent event)
{
if(event.getKeyChar()=='a')
{
p1Direction = LEFT;
}
if(event.getKeyChar()=='s')
{
p1Direction = DOWN;
}
if(event.getKeyChar()=='d')
{
p1Direction = RIGHT;
}
if(event.getKeyChar()=='w')
{
p1Direction = UP;
}
}
}
private class Move2 extends Thread implements KeyListener
{
public void run()
{
//add the code to make the key listener wake up
addKeyListener(this);
//now this should all be in an infinite loop so that the process repeats
while(true)
{
try
{
//first refresh the screen
repaint();
//check to see if the car hits the outside walls.
//if so make it slow its speed by setting it's speed to -4.
if(p2.intersects(left) || p2.intersects(right) ||
p2.intersects(top) || p2.intersects(bottom) ||
p2.intersects(obstacle) || p2.intersects(obstacle2) ||
p1.intersects(p2))
{
p2Speed = -4;
}
if(p2.intersects(center))
{
p2Speed = -2.5;
}
//increase speed a bit
if(p2Speed<=5)
p2Speed = .2;
//these will move the player based off direction
if(p2Direction == UP)
{
p2.y-=(int)p2Speed;
}
if(p2Direction ==DOWN)
{
p2.y+=(int)p2Speed;
}
if(p2Direction == LEFT)
{
p2.x-=(int)p2Speed;
}
if(p2Direction == LEFT)
{
p2.x+=(int)p2Speed;
}
//this delays the refresh rate:
Thread.sleep(75);
}
catch(Exception e)
{
//if there is an exception, exit the loop.
break;
}
}
}
//you must also implement this method from key listener
public void keyPressed(KeyEvent event)
{
}
public void keyReleased(KeyEvent event)
{
}
public void keyTyped(KeyEvent event)
{
if(event.getKeyChar()=='j')
{
p2Direction = LEFT;
}
if(event.getKeyChar()=='k')
{
p2Direction = DOWN;
}
if(event.getKeyChar()=='l')
{
p2Direction = RIGHT;
}
if(event.getKeyChar()=='i')
{
p2Direction = UP;
}
}
//This starts the program by calling the constructor:
public static void main(String [] args)
{
new Collision();
}
}
解决方法:
仅当侦听的组件具有焦点时,KeyListener才起作用,并且KeyListener经常失败,因为事实并非如此.因此,要做的一件事就是测试这一点,如果组件失去了焦点,则需要做一些事情来纠正这一点.
话虽如此,但我不得不问您使用的是哪本书,因为通常来说,您要避免将KeyListeners与Swing应用程序结合使用,而使用Key Bindings.另外,通常不建议直接在JFrame中绘制,因此您可能希望使用其他书籍.
标签：keylistener,swing,key-bindings,main-method,java 来源： https://codeday.me/bug/20191201/2079648.html