Question

我做了大约30次不同的谷歌搜索，但没有得到答案，所以我来到这里。所以我试图在屏幕上左右移动播放器的矩形（黑色方块）。当我使用常规图形时，它工作正常，但现在我使用Graphics2D，repaint（）似乎什么都不做（即当你按下左右箭头键时，矩形不会移动）。 / p>

import java.util.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JComponent;
import javax.swing.JFrame;

public class boxface extends JComponent implements KeyListener {

  private boxobj obj;

  private int x=0, y=650;

  public void keyPressed(KeyEvent e) {
    if(e.getKeyCode()== KeyEvent.VK_RIGHT)
      moveRight();
    else if(e.getKeyCode()== KeyEvent.VK_LEFT)
      moveLeft(); }
  public void keyReleased(KeyEvent e) {}
  public void keyTyped(KeyEvent e) {}

  Rectangle player = new Rectangle(x, y, 50, 50);
  Rectangle floor = new Rectangle(0, 700, 750, 700);

  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;
    g.setColor(Color.GREEN);
    g2.fill(floor);
    g.setColor(Color.BLACK);
    g2.fill(player); }

  public void moveLeft() {
    if(x > 0) {
      x -= 50;
      repaint(); }}

  public void moveRight() {
    if(x < 700) {
      x += 50;
      repaint(); }}

  public boxface(){
    this.obj=new boxobj();
    addKeyListener(this);
    setFocusable(true);
    setFocusTraversalKeysEnabled(false); }

  public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      public void run() {

        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setBounds(400, 200, 756, 779);
        f.setMinimumSize(new Dimension(756, 0));
        f.setResizable(false);
        f.getContentPane().add(new boxface());
        f.setVisible(true);

      }

    });

    final java.util.Timer tmr = new java.util.Timer();
    tmr.scheduleAtFixedRate(new TimerTask()
    {
      public void run()
      {
        System.out.println("A second has passed.");

        /* the idea is that I could make a square with random
         * dimensions (within a certain limit), so that every
         * time the timer loops, a new, random square is made.
         * I just can't seem to move the rectangles using
         * repaint(); because they're Graphics2D rectangles,
         * and I can't find a way around this.
         * 
         * An example of this can be shown if you run this
         * code; the "player" rectangle cannot be moved, even
         * though keylistener is picking up inputs and the
         * rectangle's co-ordinates are being changed. In
         * other words, repaint(); isn't doing anything. */



      }
    },0,1000);

  }//end main

}//end class

此外，＆＃34; boxobj＆＃34; class现在只是一个空类。我计划将随机矩形的初始化放在哪里。我只是把它放在这里以便于复制粘贴。

public class boxobj {

}

Answer 1

问题是您正在更新x变量，但是绘制player对象。

当您构造player（通过Rectangle player = new Rectangle(x, y, 50, 50);）时，它会在执行该行时获取x的值的副本。由于您同时声明和初始化，我们知道x为零，因此player将(0, 650, 50, 50)实例化。

稍后，用户点击右箭头键并触发事件监听器。这会将x增加到50并调用repaint，但重要的是，根本不会更新player对象。当绘画系统paintComponent调用player方法时，(0, 650, 50, 50)仍为x。

基本上y和player会记录玩家的位置，但您正在使用x对象来绘制玩家，并且这些变量不会同时更新。

纠正此问题的最佳方法是将玩家的位置存放在一个地方。您可以保留y和paintComponent并修改player方法以使用这些方法，也可以丢弃这两个变量并修改player.setLocation对象（使用{{ 1}}）。无论哪种方式都可行。

repaint（）突然不起作用

1 个答案: