我正在为我的第一年学位写一个突破性游戏，我刚刚重新实现了项目，这意味着我之前尝试过的方法现在已经多余了。所以我试图删除它，我得到了这个：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at breakout.ViewBreakout.display(ViewBreakout.java:106)
at breakout.ViewBreakout.drawActualPicture(ViewBreakout.java:69)
at breakout.ViewBreakout.drawPicture(ViewBreakout.java:161)
at breakout.ViewBreakout.paint(ViewBreakout.java:147)
at javax.swing.RepaintManager$3.run(RepaintManager.java:819)
at javax.swing.RepaintManager$3.run(RepaintManager.java:796)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:769)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:718)
at javax.swing.RepaintManager.access$1100(RepaintManager.java:62)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1677)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
这是我的代码，项目位置位是多余的
package breakout;
import java.util.Observable;
import static breakout.Global.*;
/**
* Model of the game of breakout
* The active object ActiveModel does the work of moving the ball
*/
public class ModelBreakout extends Observable
{
private GameObject ball; // The ball
private GameObject bricks[]; // The bricks
private GameObject bat; // The bat
private GameObject item[]; // The item
private int itemLocations[]; //Item location
private ModelActivePart am = new ModelActivePart( this );
private Thread activeModel = new Thread( am );
private int score = 0;
public void createGameObjects()
{
ball = new GameObject(ModelActivePart.randomRange(10, W -10), H/2, BALL_SIZE, BALL_SIZE, Colour.RED );
bat = new GameObject(W/2, H - BRICK_HEIGHT*4, BRICK_WIDTH*3,
BRICK_HEIGHT, Colour.GRAY);
item = new GameObject[100];
bricks = new GameObject[BRICKS];
int[] itemLocations = new int[100];
for(int i = 1; i < BRICKS + 1; i++)
{
if(i <= 10)
{
bricks[i - 1] = new GameObject((i*BRICK_WIDTH - 40) + i * 7, 100, BRICK_WIDTH,
BRICK_HEIGHT, Colour.BLUE);
if(itemLocations[0] == i - 1)
{
item[0] = new GameObject(((i*BRICK_WIDTH - 40) + i * 7) + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[1] == i - 1)
{
item[1] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[2] == i - 1)
{
item[2] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[3] == i - 1)
{
item[3] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
}
else if (i > 10 && i <= 20)
{
bricks[i - 1] = new GameObject(((i - 10)*BRICK_WIDTH - 40) + (i - 10) * 7, 150, BRICK_WIDTH,
BRICK_HEIGHT, Colour.RED);
if(itemLocations[0] == i - 1)
{
item[0] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[1] == i - 1)
{
item[1] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[2] == i - 1)
{
item[2] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[3] == i - 1)
{
item[3] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
}
else
{
bricks[i - 1] = new GameObject(((i - 20)*BRICK_WIDTH - 40) + (i - 20) * 7, 200, BRICK_WIDTH,
BRICK_HEIGHT, Colour.GRAY);
if(itemLocations[0] == i - 1)
{
item[0] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[1] == i - 1)
{
item[1] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[2] == i - 1)
{
item[2] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
if(itemLocations[3] == i - 1)
{enter code here
item[3] = new GameObject((i*BRICK_WIDTH - 40) + i * 7 + BRICK_WIDTH/2, 100, BRICK_WIDTH/3,
BRICK_HEIGHT/2, Colour.GRAY);
}
}
}
// *[1]**********************************************************
// * Fill in code to place the bricks on the board DONE *
// **************************************************************
}
public void startGame() { activeModel.start(); }
public GameObject getBall() { return ball; }
public GameObject[] getBricks() { return bricks; }
public GameObject[] getItem() { return item; }
public int getItemLoc( int index ) { return itemLocations[index]; }
public GameObject getBat() { return bat; }
public void addToScore( int n ) { score += n; }
public int getScore() { return score; }
public void stopGame() { }
/**
* Move the bat dist pixels. (-dist) => left or (+dist) => right
* @param dist - Distance to move
*/
public void moveBat( float dist )
{
// *[2]**********************************************************************
// * Fill in code to prevent the bat being moved off the screen Done *
// **************************************************************************
float BatX = bat.getX();
if ( BatX == 5 && dist == -5)
{
bat.moveX(0);
}
else if (BatX + (BRICK_WIDTH*3) == W - 5 && dist == 5)
{
bat.moveX(0);
}
else
{
Debug.trace( "Model: Move bat = %6.2f", dist );
bat.moveX(dist);
//modelChanged();
}
}
/**
* Model has changed so notify observers so that they
* can redraw the current state of the game
*/
public void modelChanged()
{
setChanged(); notifyObservers();
}
}
对于可怕格式化的代码感到抱歉..
这是我的观点突破代码：
package breakout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.util.Observable;
import java.util.Observer;
import javax.swing.JFrame;
import static breakout.Global.*;
/**
* Displays a graphical view of the game of breakout
* Uses Garphics2D would need to be re-implemented for Android
*/
public class ViewBreakout extends JFrame implements Observer
{
private ControllerBreakout controller;
private GameObject ball; // The ball
private GameObject[] bricks; // The bricks
private GameObject bat; // The bat
private GameObject[] item; // The item
private int score = 0; // The score
private int frames = 0;
public ViewBreakout()
{
setSize( W, H ); // Size of window
addKeyListener( new Transaction() ); // Called when key press
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
/**
* Code called to draw the current state of the game
* Uses draw: Draw a shape
* fill: Fill the shape
* setPaint: Colour used
* drawString: Write string on display
* @param g Graphics context to use
*/
public void drawActualPicture( Graphics2D g )
{
frames++;
// White background
g.setPaint( Color.white );
g.fill( new Rectangle2D.Float( 0, 0, W, H ) );
Font font = new Font("Monospaced",Font.BOLD,24);
g.setFont( font );
// Blue playing border
g.setPaint( Color.blue ); // Paint Colour
g.draw( new Rectangle2D.Float( B, M, W-B*2, H-M-B ) );
// Display the ball
display( g, ball );
// Display the bricks that make up the game
// *[3]**********************************************************
// * Fill in code to display bricks (A brick may not exist) *
// **************************************************************
for(int i = 0; i <= BRICKS -1; i++)
{
if (bricks[i].getX() != 0 || bricks[i].getY() != 0)
{
display( g, bricks[i]);
}
}
for(int i = 0; i < ModelActivePart.getItemCount() ; i++)
{
display( g, item[i]);
}
// Display the bat
display( g, bat );
// Display state of game
g.setPaint( Color.black );
FontMetrics fm = getFontMetrics( font );
String fmt = "BreakOut: Score = [%6d] fps=%5.1f";
String text = String.format(fmt, score,
frames/(Timer.readTimeTaken()/1000.0 )
);
if ( frames > 100 ) { frames = 0; Timer.startTimer(); }
g.drawString( text, W/2-fm.stringWidth(text)/2, (int)M*2 );
}
private void display( Graphics2D g, GameObject go )
{
switch( go.getColour() )
{
case GRAY: g.setColor( Color.gray );
break;
case BLUE: g.setColor( Color.blue );
break;
case RED: g.setColor( Color.red );
break;
case WHITE: g.setColor( Color.white );
}
g.fill( new Rectangle2D.Float( go.getX(), go.getY(),
go.getWidth(), go.getHeight() ) );
}
/**
* Called from the model when its state has changed
*/
@Override
public void update( Observable aModel, Object arg )
{
ModelBreakout model = (ModelBreakout) aModel;
// Get from the model the ball, bat, bricks & score
ball = model.getBall(); // Ball
bricks = model.getBricks(); // Bricks
bat = model.getBat(); // Bat
score = model.getScore(); // Score
item = model.getItem(); // Item
Debug.trace("Update");
repaint(); // Re draw game
}
@Override
public void update( Graphics g ) // Called by repaint
{
drawPicture( (Graphics2D) g ); // Draw Picture
}
@Override
public void paint( Graphics g ) // When 'Window' is first
{ // shown or damaged
drawPicture( (Graphics2D) g ); // Draw Picture
}
private BufferedImage theAI; // Alternate Image
private Graphics2D theAG; // Alternate Graphics
public void drawPicture( Graphics2D g ) // Double buffer
{ // to avoid flicker
if ( theAG == null )
{
Dimension d = getSize(); // Size of curr. image
theAI = (BufferedImage) createImage( d.width, d.height );
theAG = theAI.createGraphics();
}
drawActualPicture( theAG ); // Draw Actual Picture
g.drawImage( theAI, 0, 0, this ); // Display on screen
}
/**
* Need to be told where the controller is
*/
public void setController(ControllerBreakout aPongController)
{
controller = aPongController;
}
/**
* Methods Called on a key press
* calls the controller to process
*/
class Transaction implements KeyListener // When character typed
{
@Override
public void keyPressed(KeyEvent e) // Obey this method
{
// Make -ve so not confused with normal characters
controller.userKeyInteraction( -e.getKeyCode() );
}
@Override
public void keyReleased(KeyEvent e)
{
// Called on key release including specials
}
@Override
public void keyTyped(KeyEvent e)
{
// Send internal code for key
controller.userKeyInteraction( e.getKeyChar() );
}
}
}