Java 扫描程序问题 (JFrame)答案

【问题标题】：Java Scanner issues (JFrame)Java 扫描程序问题 (JFrame)
【发布时间】：2012-05-20 19:33:14
【问题描述】：

我正在尝试使用扫描仪来编辑我的塔防游戏的关卡。但是，它不会将级别（平铺图像）更新为自定义文件的级别（0 是草 1 是石头 -1 什么都不是，等等）。我找到了错误，但我该如何解决它，我需要添加/更改什么来摆脱它？

java.lang.NullPointerException
    at Levels.loadLevels(Levels.java:11)
    at Window.define(Window.java:28)
    at Window.paintComponent(Window.java:44)

第 11 行：for(int y=0;y<Window.room.block.length;y++) { 第 28 行：levels.loadLevels(new File("levels/level1.level")); 第 44 行：define();

这是扫描仪文件：

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) {              
        }
    }
}

这是窗口文件：

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) {
            }               
        }           
    }       
}

这是房间文件：

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);
            }
        }
    }    
}

这是块文件：

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);
        }           
    }       
}

最后这是扫描仪应该读取的自定义文件：

1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  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

抱歉这个愚蠢的问题，我是初学者。

【问题讨论】：

“最让我沮丧的是没有错误” } catch(Exception e) { } 将其（以及所有类似的声明）更改为catch(Exception e) { e.printStackTrace(); }（..或交替保留在黑暗）。
吞下异常后怎么知道没有错误：catch (Exception e) {}。显然，如果您忽略任何可能引发的异常，您会得到没有错误的印象。但这种印象很有可能不是现实。
“抱歉，帖子太长了”如需尽快获得更好的帮助，请发帖SSCCE。
new ImageIcon("resources/tileset_ground.png") 这让我想起了。在所有那些假定String 代表File 路径的方法/构造函数中，它可能需要URL。这些类型的“嵌入式资源”在运行时将无法作为File 对象访问。
int y=0;不能抛出 NPE，也不能抛出 y++。所以 Window.room.block 或 Window.room 或 Window 为空。

标签： java image file jframe java.util.scanner

【解决方案1】：

一个快速而肮脏的解决方案是，测试 Window.room 不为空，以及 .block：

        Scanner loadLevelsScanner = new Scanner (loadPath);
        if ((Window.room != null) && 
            (Window.room.block != null)) {
            // ... block until catch block 
        }

到目前为止，我编写的一个简单的 Testapp 作品，如果这样做的话。

但是您需要了解什么是“静态”，以及为什么以及如何使用它。一个常见的初学者错误是，插入“静态”关键字只是为了让编译器保持沉默。

调查，以何种顺序初始化您的类及其属性。

在 Block 中，要访问 Window，您必须有一个引用。引用可以传递给Block的ctor：

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);
        }
    }
}

谁创建块？它是 Room，所以 Room 本身需要了解 Window（只要您不从根本上改变设计）。

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);
        }
    }
}

一个块数组被创建、初始化，并且块被传递给窗口参数。

在绘图中，您不会一遍又一遍地重新创建数组，也不会重新创建块，而只是重新绘制它们：

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);
        }
    }
}

在 Window 中，您创建 Room，并将 window-reference 传递给它：

public void define () {
    room = new Room (this);
    levels = new Levels ();

【讨论】：

好的，我知道只有 Window.room.block 为空，但我该如何解决？
我想我需要更改 Room.java 中的某些内容，但是什么？
或许你可以把block = 的初始化放到Room的ctor里面？我想知道为什么每次调用“draw”时都需要创建一个新的 Block 数组。但我不确定您的代码的语义。您不仅要重新创建块数组，还要重新创建里面的块。