在最小化/重新打開窗口後Java JFrame重新繪製

Question

我有一個使用繪製方法將車輛對象（例如車形）繪製到JFrame上的程序。然而，無論何時我點擊屏幕繪製車輛，我必須刷新窗口才能顯示，即使添加了repaint（）方法。

---

第一張圖片顯示我點擊的位置。什麼都沒發生。

最小化和打開窗口之後。

import java.awt.Graphics; 
    import java.awt.Graphics2D; 
    import java.awt.event.MouseEvent; 
    import java.awt.event.MouseListener; 
    import java.util.Iterator; 
    import java.util.LinkedList; 
    import javax.swing.JFrame; 


    /** Program specs: Draws shapes (Vehicles) that are contained within LinkedLists. 
    * When a shape is drawn over another shape it 'joins' its list. (not implemented yet, not my issue) 

    */ 

    /** 
     Creates JFrame 
    */ 
    public class FramePanel extends JFrame implements MouseListener 
    { 
     private static final int FRAME_WIDTH = 600; 
     private static final int FRAME_HEIGHT = 600; 

     Car car; // Car is a subclass of Vehicle. It only contains a draw method. 
     //Vehicle is an abstract class that only contains a draw method 

     LinkedList<LinkedList<Vehicle>> list = new LinkedList<LinkedList<Vehicle>>(); 
     LinkedList<Vehicle> temp = new LinkedList <Vehicle>(); 

     /** 
      Constructs the frame. 
     */ 
     public FramePanel() 
     { 
      addMouseListener(this); 
      setSize(FRAME_WIDTH, FRAME_HEIGHT); 

      repaint(); 
     } 


    @Override 
    public void mouseClicked(MouseEvent evt) { 

    car = new Car (evt.getX(), evt.getY()); 
    temp.add(car); //Add Vehicle to LinkedList 
    list.add(temp); //Add LinkedList to Collection of LinkedLists 

    } 

    public void mouseEntered(MouseEvent arg0) {} 
    public void mouseExited(MouseEvent arg0) {} 
    public void mousePressed(MouseEvent arg0) {} 
    public void mouseReleased(MouseEvent arg0) {} 


    public void paint(Graphics g) { 
     super.paintComponents(g) ; 
     Graphics2D g2 = (Graphics2D) g; 

     for (LinkedList<Vehicle> veh : list){ // list is collection of Linked Lists 

     Iterator<Vehicle> it = veh.iterator(); 
      while (it.hasNext()){ 
       it.next().draw(g2); 
      } 
     } 
    } 

    public static void main(String[] args) 
    { 
     JFrame frame = new FramePanel(); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.setTitle("Viewer"); 
     frame.setVisible(true);  
    } 

    } 

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注：如果我添加重繪（）語句到我的油漆（圖形G）方法該車將借鑑但將不希望閃爍/不重繪（）在構造函數中。我不想要這個。

Answer 1

在mouseClicked方法的最後一行中添加對repaint()的調用將已解決此問題。

不過，也有其他幾個要點：

• 不要延長JFrame（尤其是，不重寫的JFrame的paint方法）。相反，使用JPanel進行繪畫，並覆蓋其paintComponent方法。
• 不要讓一個頂級類實現MouseListener接口
• 不要聲明你的清單爲LinkedList，但只是作爲List（What does it mean to "program to an interface"?）
• 的GUI應該在事件派發線程創建
• 字段應該是私人（和最終，如果可能的話）

所以有些清理：

import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.event.MouseAdapter; 
import java.awt.event.MouseEvent; 
import java.util.LinkedList; 
import java.util.List; 

import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.SwingUtilities; 

public class FramePanel extends JPanel 
{ 
    public static void main(String[] args) 
    { 
     SwingUtilities.invokeLater(new Runnable() 
     { 
      @Override 
      public void run() 
      { 
       createAndShowGUI(); 
      } 
     }); 
    } 

    private static void createAndShowGUI() 
    { 
     JFrame f = new JFrame(); 
     f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

     FramePanel framePanel = new FramePanel(); 
     f.getContentPane().add(framePanel); 

     f.setSize(600,600); 
     f.setLocationRelativeTo(null); 
     f.setVisible(true); 
    } 

    private final List<List<Vehicle>> list = new LinkedList<List<Vehicle>>(); 

    /** 
     Constructs the panel. 
    */ 
    public FramePanel() 
    { 
     addMouseListener(new MouseAdapter() 
     { 
      @Override 
      public void mouseClicked(MouseEvent e) 
      { 
       addCarAt(e.getX(), e.getY()); 
      } 
     }); 
    } 

    private void addCarAt(int x, int y) 
    { 
     Car car = new Car(x, y); 
     List<Vehicle> temp = new LinkedList<Vehicle>(); 
     temp.add(car); //Add Vehicle to LinkedList 
     list.add(temp); //Add LinkedList to Collection of LinkedLists 
     repaint(); 
    } 

    @Override 
    protected void paintComponent(Graphics gr) 
    { 
     super.paintComponent(gr) ; 
     Graphics2D g = (Graphics2D)gr; 

     for (List<Vehicle> veh : list) // list is collection of Linked Lists 
     { 
      for (Vehicle v : veh) 
      { 
       v.draw(g); 
      } 
     } 
    } 
}