java - 图形绘制图像双陆棋游戏

Question

这可能是一个愚蠢的问题，但我只是一个初学者，所以怜悯我的灵魂:)。所以我的问题是我有一个名为游戏页面的类，它是显示所有游戏的 IFrame。在它里面我有一个名为 Board 的类，其中包含一张板子的图片，它可以很好地使用:

public void paintComponent(Graphics page)
{
  super.paintComponent(page);
  page.drawImage(image, 0, 0, null);
}

图像是我得到的板的图像，如下所示:

image = ImageIO.read(new File("pics/board.png"));

好的，效果很好。所以在板子里面我也有一个“Slot”类型的二维数组，Slot是我编写的另一个类，它有一个WhitePiece堆栈或BlackPiece堆栈这些是我编写的代表棋盘上黑色或白色棋子的类。

因此，在 Board 类中，有一个名为“reset board”的方法，它将其组织到双陆棋的起始位置，以便初始化所有插槽。

现在黑白片在图像类型中得到了一张图片，我得到的是这样的: pic = ImageIO.read(new File("pics/whitePiece.png"));

现在的问题是当我在重置板内调用 Slot 类中的 drawSlot 方法时我认为它无法获取图片。我这样调用它:首先我调用drawBoard: 绘图板(板)；

然后这是绘图板:

  public void drawBoard(Slot[][] board) throws IOException{
   for(int i=0;i<2;i++){
    for(int j=0;j<12;j++){
        board[i][j].drawSlot(getGraphics());
    }
   }
  }

这是有问题的方法:drawSlot:

  public void drawSlot(Graphics g) throws IOException{    
  if(type == SlotType.empty){ 
      System.out.println("no type selected slot is empty Slot  Number"+slotNumber);
  }else
      if(type == SlotType.white){
        if(!wPieces.isEmpty()){
        Image pic = wPieces.pop().getPic();
        wPieces.push(new WhitePiece());
        if(slotNumber <= 11){
          for(int i=0;i<piecesAmount;i++){
            g.drawImage(pic, 5, i*30, null);
          }
        }
        else{
            for(int i=0;i<piecesAmount;i++){
                g.drawImage(pic, 5,300-(i*30), null);
            }
       }
        }else{
            System.out.println("Slot Stack is Empty Slot #"+slotNumber);
        }
      }else
      {
          if(!bPieces.isEmpty()){
          Image pic = bPieces.pop().getPic();
          bPieces.push(new BlackPiece());
          if(slotNumber<=11){
             for(int i=0;i<piecesAmount;i++){
                g.drawImage(pic, 5, i*30, 30, 30, null);
            }
          }else{
              for(int i=0;i<piecesAmount;i++){
                    g.drawImage(pic, 5, 300-(i*30), 30, 30, null);
              }  
          }
    }
          else{
      System.out.println("Slot Stack is empty Slot #"+slotNumber);
   }
}

 }

这是我得到的错误:(我认为这表明我获取图片的方式不好。)

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Try1.Slot.drawSlot(Slot.java:122)
at Try1.Board.drawBoard(Board.java:128)
at Try1.Board.resetBoard(Board.java:122)
at Try1.GamePage.<init>(GamePage.java:98)
at Try1.StartPage.startGame(StartPage.java:67)
at Try1.StartPage$eventHandler.actionPerformed(StartPage.java:49)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

我很想知道我做错了什么。谢谢大家，我知道这是一篇很长的文章，你真的必须投入其中但我是初学者，需要帮助:)。

Answer 1

不要在 swing 组件上使用 getGraphics()。在 paintComponent() 中绘制插槽。

public void paintComponent(Graphics page) {
    super.paintComponent(page);
    page.drawImage(image, 0, 0, null);
    drawBoard(page, board);
}

并修改drawBoard()以使用传递的图形对象:

public void drawBoard(Graphics g, Slot[][] board) {
   for(int i=0;i<2;i++) {
       for(int j=0;j<12;j++){
           board[i][j].drawSlot(g);
       }
   }
}

然后当棋盘发生变化时调用repaint()。