java Applet 中线程 "AWT-EventQueue-1" java.lang.NullPointerException 中的异常

Question

我正在 java 中创建一个程序，它从 applet 读取文本文件并将颜色放入由文件定义的 applet window 像素中。问题是，当我运行这个程序发生异常时，我已尽我所能解决它，但没有成功。

我的小程序代码是

GUIIO.java

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class GUIIO extends Applet {
Color color = new Color(2);
InputStream inputStream;
BufferedReader bufferedReader;

@Override
public void init() {
    try {
        inputStream = new FileInputStream("Sample In.txt");
    } catch (Exception e) {
        e.printStackTrace();
    }
}

@Override
public void paint(Graphics g) {
    Point point = new Point();
    try {
        bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        point = this.getImageResolution(bufferedReader);
        char c, ch[] = {'a', 'b', 'c', 'd', 'e', 'f' };
        int i = 0, x = 0, y = 0;
        putPixel(1, 100, String.valueOf(ch), g);
        while((c = (char)bufferedReader.read()) != 'z') {
            if(c == 'y') {  
                y++;
                x = 0;
            }
            else if(i < 6) {
                ch[i] = c;
                i++;
            }
            if (i == 6) {
                putPixel(x, y, String.valueOf(ch), g);
                x++;
                i = 0;
                ch[i] = c;
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    g.drawString(point.x+" "+point.y, 30, 10);
    repaint();
}

private Point getImageResolution(BufferedReader bufferedReader) throws IOException {
    boolean xFlag = false;
    StringBuilder x = new StringBuilder(), y = new StringBuilder();
    String check = null;
    char chars[] = bufferedReader.readLine().toCharArray();
    for(int i=0;i<chars.length;i++) {
        check = String.valueOf(chars[i]);
        if(check.equals("x"))   xFlag = true;
        else if(xFlag == true)  y.append(check);
        else    x.append(check);
    }
    Point point = new Point();
    point.x = Integer.parseInt(x.toString());
    point.y = Integer.parseInt(y.toString());
    return point;
}

private void putPixel(int x, int y, String color, Graphics g) {
    g.setColor(Color.decode("0x"+color));
    g.drawLine(x, y, x, y);
}
}

输入文本文件。

样本In.txt

8x8
000000ff000000ff000000ff000000ff000000ff000000ffy000000ff000000ff000000ff000000ff000000ff000000ffy000000ff000000ff000000ff000000ff000000ff000000ffy000000ff000000ff000000ff000000ff000000ff000000ffy000000ff000000ff000000ff000000ff000000ff000000ffy000000ff000000ff000000ff000000ff000000ff000000ffy000000ff000000ff000000ff000000ff000000ff000000ffy000000ff000000ff000000ff000000ff000000ff000000ffyz

我在eclipse中遇到的异常或错误

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at GUIIO.getImageResolution(GUIIO.java:61)
at GUIIO.paint(GUIIO.java:30)
at sun.awt.RepaintArea.paintComponent(Unknown Source)
at sun.awt.RepaintArea.paint(Unknown Source)
at sun.awt.windows.WComponentPeer.handleEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access0(Unknown Source)
at java.awt.EventQueue.run(Unknown Source)
at java.awt.EventQueue.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.run(Unknown Source)
at java.awt.EventQueue.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

更新：我已经在 cmd 中尝试了这段代码，它运行非常完美，但是当我调整 window 的大小时，我给出了同样的错误。

请帮忙。

Answer 1

您的代码中存在多个问题。首先，您无法从 bufferedReader 读取、读取和读取，因为有时它会是空的，并且您不检查从 bufferedReader 读取的行是否为空。

还有一个问题，有时候你的color String是???????? .

为什么每次重绘apllet都要读文件？您可以在 init() 方法中读取一次文件，仅此而已！

java Applet 中线程 "AWT-EventQueue-1" java.lang.NullPointerException 中的异常

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException in java Applet

java

nullpointerexception

applet