如何绘制多个矩形

所以我试图制作一个简单的程序，你点击屏幕，它会创建一个块落下并与下方较大的块碰撞并坚持下去。 有点像一个简单的碰撞程序。 问题是当我创建一个块时，它先前删除了块。 我做了一个数组，但它仍然这样做。 你们有谁知道我做错了什么吗？ 我确定它是一个简单的修复。

public class Screen extends JPanel implements Runnable { public static JLabel statusbar; //displays a status bar showing what mouse movements are taking place private Image cat; //image of the cat public int xCoord ; //get the coordinates of the mouse pressed public int yCoord ; public int xCreate; public int yCreate; public Rectangle Ground; public Rectangle Block; public boolean isClicked = false; public int clickCount = 0; Rectangle blocks[] = new Rectangle[10]; int blocknum = 0; public Screen(Frame frame) { loadPic(); //calls the loadPic method above Handlerclass handler = new Handlerclass(); //creates a new class to use the mouse motion listener System.out.println("mouse works!"); addMouseListener(handler); addMouseMotionListener(handler); statusbar = new JLabel("default"); add(statusbar); } public void run(){ //this is the game run loop System.out.println("this is running"); try{ } catch(Exception e) {} //exception handling } public void loadPic(){ //loads the picture from the other project but its the same pic cat = new ImageIcon("C:\\Users\\Camtronius\\Documents\\NetBeansProjects\\Moving Block Proj\\src\\MovingBlock\\catIcon1.png").getImage(); //gets the image System.out.println("Image Loaded!"); } @Override public void paintComponent(Graphics g){ super.paintComponent(g); //paints the component, the picture, on top Graphics2D g2d = (Graphics2D) g.create(); g2d.drawImage(cat, xCoord, yCoord, null); g2d.setColor(Color.BLUE); Ground = new Rectangle(0,450,550,50); g2d.fillRect(0,450, 550, 50); for(Rectangle blocknum : blocks){ if (blocks != null) { g2d.setColor(Color.RED); g2d.fillRect(xCreate,yCreate,50,50); System.out.println(blocknum); } } //move(); } public void move(){ if(yCreate<400){ yCreate+=1; }else{ } if(Ground.intersects(blocks[blocknum])){ yCreate=400; System.out.println("contains!"); } } private class Handlerclass implements MouseListener, MouseMotionListener{ public void mouseClicked(MouseEvent event){ } public void mousePressed(MouseEvent event){ } public void mouseReleased(MouseEvent event){ if(blocknum<blocks.length){ xCreate=event.getX(); yCreate=event.getY(); blocks[blocknum] = new Rectangle(50,50, xCreate, yCreate); repaint(); } blocknum=blocknum+1; } public void mouseEntered(MouseEvent event){ } public void mouseExited(MouseEvent event){ } public void mouseDragged(MouseEvent event){ } public void mouseMoved(MouseEvent event){ statusbar.setText(String.format("Coordinates are: %d, %d", event.getX(),event.getY())); xCoord=event.getX(); yCoord=event.getY(); } } } 

Answer 1

绘画是一个破坏性的过程。 也就是说，当一个新的绘制周期运行时，应该清除Graphics上下文的先前内容……

所以，在你的paintComponent方法中，你只绘制最后一个块…

 if(isClicked = true){ blocks[blocknum] = new Rectangle(50,50, xCreate, yCreate); g2d.setColor(Color.RED); g2d.fillRect(xCreate,yCreate,50,50); System.out.println(blocknum); repaint(); // THIS IS A BAD IDEA } 

不要调用任何可能导致repaint方法。 这会让你陷入潜在的死亡循环，消耗你的CPU。

相反，你应该遍历blocks数组并绘制每个…

 for (Rectangle block : blocks) { if (block != null) { g2d.setColor(Color.RED); g2d.fill(block); } } 

在你的mouseReleased方法中，你应该添加新的矩形……

 public void mouseReleased(MouseEvent event){ blocknum=blocknum+1; if (blocknum < blocks.length) { xCreate=event.getX(); yCreate=event.getY(); blocks[blocknum] = new Rectangle(xCreate, yCreate, 50, 50); } } 

我建议你看一下自定义绘画 ， AWT中的绘画以及Swing中的Swing和Concurrency更多细节