问题
I am trying to use a scanner to edit the level of my tower defense game. However it will not update the level (the tile images) to that of the custom file (0 is grass 1 is stone -1 is nothing, etc.). I have found the error but how do i fix it, what do i need to add/change to get rid of this?
java.lang.NullPointerException
at Levels.loadLevels(Levels.java:11)
at Window.define(Window.java:28)
at Window.paintComponent(Window.java:44)
line 11: for(int y=0;y<Window.room.block.length;y++) {
line 28: levels.loadLevels(new File("levels/level1.level"));
line 44: define();
This is the scanner file:
import java.io.*;
import java.util.*;
public class Levels {
public void loadLevels(File loadPath) {
try {
Scanner loadLevelsScanner = new Scanner(loadPath);
while(loadLevelsScanner.hasNext()) {
for(int y=0;y<Window.room.block.length;y++) {
for(int x=0;x<Window.room.block[0].length;x++) {
Window.room.block[y][x].groundID = loadLevelsScanner.nextInt();
}
}
for(int y=0;y<Window.room.block.length;y++) {
for(int x=0;x<Window.room.block[0].length;x++) {
Window.room.block[y][x].airID = loadLevelsScanner.nextInt();
}
}
}
loadLevelsScanner.close();
} catch(Exception e) {
}
}
}
this is the window file:
import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
import java.io.*;
public class Window extends JPanel implements Runnable {
public Thread thread = new Thread(this);
public static Image[] tileset_ground = new Image[100];
public static Image[] tileset_air = new Image[100];
public static int myWidth, myHeight;
public static boolean isFirst = true;
public static Room room;
public static Levels levels;
public Window() {
thread.start();
}
public void define() {
room = new Room();
levels = new Levels();
levels.loadLevels(new File("levels/level1.level"));
for(int i=0;i<tileset_ground.length; i++) {
tileset_ground[i] = new ImageIcon("resources/tileset_ground.png").getImage();
tileset_ground[i] = createImage(new FilteredImageSource(tileset_ground[i].getSource(), new CropImageFilter(0, 32 * i, 32, 32)));
}
for(int i=0;i<tileset_air.length; i++) {
tileset_air[i] = new ImageIcon("resources/tileset_air.png").getImage();
tileset_air[i] = createImage(new FilteredImageSource(tileset_air[i].getSource(), new CropImageFilter(0, 32 * i, 32, 32)));
}
}
public void paintComponent(Graphics g) {
if(isFirst) {
define();
isFirst = false;
}
g.clearRect(0, 0, getWidth(), getHeight());
room.draw(g);
}
public void run() {
while(true) {
if(!isFirst) {
room.physic();
}
repaint();
try {
Thread.sleep(1);
} catch(Exception e) {
}
}
}
}
This is the room file:
import java.awt.*;
public class Room {
public int worldWidth = 40;
public int worldHeight = 20;
public int blockSize = 32;
public Block[][] block;
public Room () { }
public void define () { }
public void physic () { }
public void draw(Graphics g) {
block = new Block[worldHeight][worldWidth];
for(int y=0;y<block.length;y++) {
for(int x=0;x<block[0].length;x++) {
block[y][x] = new Block(x * blockSize, y * blockSize, blockSize, blockSize, Value.groundGrass, Value.airAir);
block[y][x].draw(g);
}
}
}
}
this is the block file:
import java.awt.*;
public class Block extends Rectangle {
public int groundID;
public int airID;
public Block(int x, int y, int width, int height, int groundID, int airID) {
setBounds(x, y, width, height);
this.groundID = groundID;
this.airID = airID;
}
public void draw(Graphics g) {
g.drawImage(Window.tileset_ground[groundID], x, y, width, height, null);
if(airID != Value.airAir) {
g.drawImage(Window.tileset_air[airID], x, y, width, height, null);
}
}
}
And lastly this is the custom file the scanner is supposed to read:
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
sorry for the stupid question, i'm a beginner.
回答1:
A quick-and-dirty solution is, to test for Window.room not to be null, as well as .block:
Scanner loadLevelsScanner = new Scanner (loadPath);
if ((Window.room != null) &&
(Window.room.block != null)) {
// ... block until catch block
}
A simple Testapp I've written works so far, if done so.
But you need to understand what "static" is, and why and how to use it. A common beginner mistake is, to instert "static" keywords just to make the compiler silent.
Investigate, in which order to initialize your classes and their attributes.
In Block, to access the Window, you have to have a reference. The reference can be passed to the ctor of Block:
class Block extends Rectangle {
public int groundID;
public int airID;
Window window;
public Block (int x, int y, int width, int height, int groundID, int airID, Window window) {
setBounds (x, y, width, height);
this.groundID = groundID;
this.airID = airID;
this.window = window;
}
public void draw (Graphics g) {
g.drawImage (window.tileset_ground [groundID], x, y, width, height, null);
if (airID != Value.airAir) {
g.drawImage (window.tileset_air [airID], x, y, width, height, null);
}
}
}
Who creates Blocks? It is Room, so Room itself needs to know about the Window (as long as you don't change your design fundamentally).
public Room (Window w) {
block = new Block [worldHeight] [worldWidth];
for (int y=0; y <block.length; y++) {
for (int x=0; x <block [0].length; x++) {
block [y] [x] = new Block (x * blockSize, y * blockSize, blockSize, blockSize, Value.groundGrass, Value.airAir, w);
}
}
}
A block array is created, initialized, and the Blocks are passed the Window-parameter.
In draw, you don't recreate the array over and over again, nor do you recreate the Blocks, but just redraw them:
public void draw (Graphics g) {
for (int y=0; y <block.length; y++) {
for (int x=0; x <block [0].length; x++) {
block [y] [x].draw (g);
}
}
}
In Window, you create the Room, and pass it the window-reference:
public void define () {
room = new Room (this);
levels = new Levels ();
来源：https://stackoverflow.com/questions/10564311/java-scanner-issues-jframe