調用Java的更新後的塗料圖形

Question

問題：

的W，A，S每個按鍵後或D的用戶x和y應該改變和廣場上吸引到x和y的含義圖形不更新。我的問題是你如何更新它？我曾嘗試在任何地方以各種可能的方式使用重繪，並開始認爲這不是問題。有人能告訴我我做錯了什麼或者如何解決問題。我對Java很新，所以如果我做了一個非常簡單的錯誤，請原諒我。

代碼：

import java.awt.*; 
import java.awt.event.KeyEvent; 
import java.awt.event.KeyListener; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
public class KeyPressDrawing extends JFrame implements KeyListener{ 
    // define variables 
    public static int user_x = 50; 
    public static int user_y = 50; 

    // init 
    public KeyPressDrawing(String s){ 
     super(s); 
     JPanel area = new JPanel(); 
     add(area); 
     setSize(800, 800); 
     setVisible(true); 
     addKeyListener(this); 
     setResizable(false); 
    } 

    // draw 
    public void paint(Graphics g) { 
     g.setColor (Color.black); 
     // x position, y position, width length, height length 
     g.fillRect(KeyPressDrawing.user_x, KeyPressDrawing.user_y, 50, 50); 
     repaint(); 
} 

    // check and change 

    public void keyTyped(KeyEvent e) {} 


    public void keyPressed(KeyEvent e) {} 


    public void keyReleased(KeyEvent e) { 
     if (e.getKeyCode() == KeyEvent.VK_W) { 
      System.out.println("Up"); 
      KeyPress.user_y -= 20; 

     } 
     if (e.getKeyCode() == KeyEvent.VK_A) { 
      System.out.println("Left"); 
      KeyPress.user_x -= 20; 

     } 
     if (e.getKeyCode() == KeyEvent.VK_S) { 
      System.out.println("Down"); 
      KeyPress.user_y += 20; 

     } 
     if (e.getKeyCode() == KeyEvent.VK_D) { 
      System.out.println("Right"); 
      KeyPress.user_x += 20; 
      } 
     } 

    public static void main(String[] args){ 
     new KeyPressDrawing("Control Panel"); 
    } 
} 

Answer 1

有幾個與你的代碼的問題。首先，您將Janel作爲JFrame中的主窗口部件放置，但是您會覆蓋JFrame本身的paint方法，並且不會將調用委託給超類，因此不會呈現您的JPanel。你可能想要做的是將矩形的繪圖移動到JPanel子類中，該子類是框架的主子部件。然後，在您的keyReleased方法中，您將調用子控件的重繪爲方法。在每次釋放鑰匙之後，子面板將被告知需要重新繪製。刪除JFrame的paint方法並使用默認值。

import java.awt.*; 
import javax.swing.*; 
import java.awt.event.*; 
import java.awt.geom.Ellipse2D; 


public class Sample extends JFrame implements KeyListener { 
    public int user_x; 
    public int user_y; 
    public Canvas canvas; 

    class Canvas extends JPanel{ 
    public Canvas() { 
     setSize(getPreferredSize()); 
     Canvas.this.setBackground(Color.white); 
     user_x = 10; 
     user_y = 10; 
    } 

    @Override 
    public final Dimension getPreferredSize() { 
     return new Dimension(600, 600); 
    } 

    @Override 
    public final void paintComponent(final Graphics g) { 
     super.paintComponent(g); 
     Graphics2D g2d = (Graphics2D) g; 
     Ellipse2D circle = new Ellipse2D.Double(0d, 0d, 100d, 100d); 
     g2d.setColor(Color.red); 
     g2d.translate(user_x, user_y); 
     g2d.draw(circle); 
     g2d.fill(circle); 
    } 
    } 

    public Sample() { 
    super("Sample"); 
    setSize(300, 300); 
    addWindowListener(new WindowAdapter() { 
     public void windowClosing(WindowEvent e) {System.exit(0);} 
     public void windowOpened(WindowEvent e) {} 
    }); 
    canvas = new Canvas(); 
    getContentPane().add(canvas); 
    addKeyListener(this); 
    } 


// Implementation of java.awt.event.KeyListener 

    public final void keyTyped(final KeyEvent keyEvent) { 

    } 

    public final void keyPressed(final KeyEvent keyEvent) { 

    } 

    public final void keyReleased(final KeyEvent e) { 
    if (e.getKeyCode() == KeyEvent.VK_W) { 
     System.out.println("Up"); 
     user_y -= 20; 
    } 
    if (e.getKeyCode() == KeyEvent.VK_A) { 
     System.out.println("Left"); 
     user_x -= 20; 
    } 
    if (e.getKeyCode() == KeyEvent.VK_S) { 
     System.out.println("Down"); 
     user_y += 20; 
    } 
    if (e.getKeyCode() == KeyEvent.VK_D) { 
     System.out.println("Right"); 
     user_x += 20; 
    } 
    //either canvas.repaint or just repaint for the frame will work here 
    repaint(); 
    } 

    public static final void main(final String[] args) { 

    Sample f = new Sample(); 
    f.setVisible(true); 
    } 

} // Sample