在 lejos 中将 Lines 添加到 LineMap 时出现空指针异常，找不到

Posted 2023-02-19

【中文标题】在 lejos 中将 Lines 添加到 LineMap 时出现空指针异常，找不到

【英文标题】：Null pointer exception from adding Lines to a LineMap in lejos, cant find

【发布时间】：2018-03-09 20:27:28

【问题描述】：

我在一些 lejos 代码中找不到空指针异常，这是针对 EV3 乐高机器人的。 下面是类状态和构造函数：

public class Mapper 

private LineMap CurrentMap;
private Line[] lines;
private boolean[] userDrawn;
private Rectangle boundary = new Rectangle(0, 0, 594, 891);
private int counter;

/**
 * Initializes an empty map with just a boundary
 * 
 * @author Ben
 */
public Mapper()

    counter = 0;
    lines = new Line[counter];
    userDrawn = new boolean[counter];
    CurrentMap = new LineMap(lines,boundary);

还有让我伤心的功能

public void addLine(float x1, float y1, float x2, float y2, boolean isUserDrawn)
    counter++;
    Line[] oldLines = lines;
    boolean[] oldUserDrawn = userDrawn;
    lines = new Line[counter];
    userDrawn = new boolean[counter];

    for(int i = 0; i < counter - 1; i++)
        lines[i] = oldLines[i];
        userDrawn[i] = oldUserDrawn[i];
    

    lines[counter-1] = new Line(x1,y1,x2,y2);
    if(isUserDrawn == true)
        userDrawn[counter - 1] = true;
    
    else
        userDrawn[counter - 1] = false;
    
    CurrentMap = new LineMap(lines,boundary);

关于什么可能是空指针异常的来源的任何想法：

【参考方案1】：

别担心，这段代码没有问题。并且已经解决了。