编辑：我已经解决了这个问题，因为我没有在异步任务中实现解析，所以它给出了一个错误。无论如何，谢谢你的回复！
我一直在尝试解析一个网站。当我作为一个Java项目，它正常工作并返回一个干净的结果，但是当我尝试在Android中做同样的事情时，它给了我java.lang.NullPointerException。我正在使用.jar文件并认为问题可能发生在jar类中，反编译它但没有改变。这是课程。任何帮助将不胜感激。
PS：奇怪的是，当它是一个jar文件时，没有与类相关的错误，但是当我反编译它时，它在Keyboard类的第96行给了我错误，所以我对它进行了评论。再次感谢你们这些人。
StdIO Class
package com.example.parsetester;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.PrintStream;
public class StdIO
{
public static final String version = "StdIO:v1.0:15/12/2003";
static final String stdOutStreamName = "Screen";
static final String stdInStreamName = "Keyboard";
private static PrintStream origOut = System.out;
private static PrintStream stdout = null;
private static String outStreamName = "Screen";
private static InputStream origIn = System.in;
private static InputStream stdin = null;
private static String inStreamName = "Keyboard";
public static boolean exists(String paramString)
{
File localFile = new File(paramString);
return localFile.exists();
}
public static String getInStreamName()
{
return inStreamName;
}
public static void from(String paramString)
{
if (stdin != null) {
resetIn();
}
try
{
stdin = new FileInputStream(paramString);
System.setIn(stdin);
inStreamName = paramString;
Keyboard.reset();
}
catch (Exception localException)
{
System.err.println("Error: Unable to open input file [" + paramString + "]");
System.exit(1);
}
}
public static void resetIn()
{
try
{
if (stdin != null)
{
stdin.close();
stdin = null;
}
System.setIn(origIn);
inStreamName = "Keyboard";
Keyboard.reset();
}
catch (Exception localException)
{
System.err.println("Error: Unable to close [" + inStreamName + "]");
System.exit(1);
}
}
public static String getOutStreamName()
{
return outStreamName;
}
public static void addTo(String paramString)
{
to(paramString, true);
}
public static void to(String paramString)
{
to(paramString, false);
}
public static void to(String paramString, boolean paramBoolean)
{
if (stdout != null) {
resetOut();
}
try
{
stdout = new PrintStream(new FileOutputStream(paramString, paramBoolean));
System.setOut(stdout);
outStreamName = paramString;
}
catch (Exception localException)
{
System.err.println("Error: Unable to open output file [" + paramString + "]");
System.exit(1);
}
}
public static void resetOut()
{
try
{
if (stdout != null)
{
stdout.close();
stdout = null;
}
System.setOut(origOut);
outStreamName = "Screen";
}
catch (Exception localException)
{
System.err.println("Error: Unable to close [" + outStreamName + "]");
System.exit(1);
}
}
}
SimpleURLReader类
package com.example.parsetester;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.URL;
public class SimpleURLReader
{
public static final String version = "SimpleURLReader:v1.0:03/03/2002";
String pageContents;
int lineCount;
public SimpleURLReader(String paramString)
{
try
{
URL localURL = new URL(paramString);
BufferedReader localBufferedReader = new BufferedReader(new InputStreamReader(localURL.openStream()));
this.lineCount = 0;
String str = localBufferedReader.readLine();
while (str != null)
{
this.pageContents = (this.pageContents + str + "\n");
this.lineCount += 1;
str = localBufferedReader.readLine();
}
}
catch (Exception localException)
{
System.out.println(localException);
}
}
public String getPageContents()
{
return pageContents;
}
public int getLineCount()
{
return this.lineCount;
}
}
MySimpleURLReader类
package com.example.parsetester;
public class MySimpleURLReader extends SimpleURLReader {
String url;
String name;
// constructor, extends the one in SimpleURLReader class.
public MySimpleURLReader(String url)
{
super (url);
this.url = url;
}
// getter method for URL.
public String getURL ()
{
return this.url;
}
// getter method for file name, looks at the end of the link, then substrings the page extension.
public String getName()
{
name = url.substring(url.lastIndexOf('/')+1, url.length());
return name;
}
// overrides cs1.getPageContents() method, deletes "null" word, which is a mistake in super method.
public String getPageContents()
{
return super.getPageContents().substring(4);
}
}
键盘类
package com.example.parsetester;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.util.StringTokenizer;
public class Keyboard
{
public static final String version = "Keyboard:v1.0:15/12/2003";
private static boolean printErrors = true;
private static int errorCount = 0;
public static int getErrorCount()
{
return errorCount;
}
public static void resetErrorCount(int paramInt)
{
errorCount = 0;
}
public static boolean getPrintErrors()
{
return printErrors;
}
public static void setPrintErrors(boolean paramBoolean)
{
printErrors = paramBoolean;
}
private static void error(String paramString)
{
errorCount += 1;
if (printErrors) {
System.out.println(paramString);
}
}
private static String current_token = null;
private static StringTokenizer reader;
private static BufferedReader in = new BufferedReader(new InputStreamReader(System.in), 1);
public static void reset()
{
resetErrorCount(0);
current_token = null;
reader = null;
in = new BufferedReader(new InputStreamReader(System.in), 1);
}
public static void Wait()
{
try
{
current_token = null;
reader = null;
in.readLine();
}
catch (Exception localException)
{
error("OOPS.. ");
}
}
private static String getNextToken()
{
return getNextToken(true);
}
private static String getNextToken(boolean paramBoolean)
{
String str;
if (current_token == null)
{
str = getNextInputToken(paramBoolean);
}
else
{
str = current_token;
current_token = null;
}
return str;
}
private static String getNextInputToken(boolean paramBoolean)
{
String str = null;
try
{
if (reader == null)
{
reader = new StringTokenizer(in.readLine(), " \t\n\r\f", true);
//break label68;
}
label68:
do
{
do
{
while (!reader.hasMoreTokens()) {
reader = new StringTokenizer(in.readLine(), " \t\n\r\f", true);
}
str = reader.nextToken();
} while (str == null);
if (" \t\n\r\f".indexOf(str) < 0) {
break;
}
} while (paramBoolean);
}
catch (Exception localException)
{
str = null;
}
return str;
}
public static boolean endOfLine()
{
return !reader.hasMoreTokens();
}
public static String readString()
{
String str;
try
{
str = getNextToken(false);
while (!endOfLine()) {
str = str + getNextToken(false);
}
}
catch (Exception localException)
{
error("Error reading String data, null value returned.");
str = null;
}
return str;
}
public static String readWord()
{
String str;
try
{
str = getNextToken();
}
catch (Exception localException)
{
error("Error reading String data, null value returned.");
str = null;
}
return str;
}
public static boolean readBoolean()
{
String str = getNextToken();
boolean bool;
try
{
if (str.toLowerCase().equals("true"))
{
bool = true;
}
else if (str.toLowerCase().equals("false"))
{
bool = false;
}
else
{
error("Error reading boolean data, false value returned.");
bool = false;
}
}
catch (Exception localException)
{
error("Error reading boolean data, false value returned.");
bool = false;
}
return bool;
}
public static char readChar()
{
String str = getNextToken(false);
char c;
try
{
if (str.length() > 1) {
current_token = str.substring(1, str.length());
} else {
current_token = null;
}
c = str.charAt(0);
}
catch (Exception localException)
{
error("Error reading char data, MIN_VALUE value returned.");
c = '\000';
}
return c;
}
public static int readInt()
{
String str = getNextToken();
int i;
try
{
i = Integer.parseInt(str);
}
catch (Exception localException)
{
error("Error reading int data, MIN_VALUE value returned.");
i = -2147483648;
}
return i;
}
public static long readLong()
{
String str = getNextToken();
long l;
try
{
l = Long.parseLong(str);
}
catch (Exception localException)
{
error("Error reading long data, MIN_VALUE value returned.");
l = -9223372036854775808L;
}
return l;
}
public static float readFloat()
{
String str = getNextToken();
float f;
try
{
f = new Float(str).floatValue();
}
catch (Exception localException)
{
error("Error reading float data, NaN value returned.");
f = (0.0F / 0.0F);
}
return f;
}
public static double readDouble()
{
String str = getNextToken();
double d;
try
{
d = new Double(str).doubleValue();
}
catch (Exception localException)
{
error("Error reading double data, NaN value returned.");
d = (0.0D / 0.0D);
}
return d;
}
}
HTMLFilteredReader类
package com.example.parsetester;
public class HTMLFilteredReader extends MySimpleURLReader {
String url;
//constructor, extends MySimpleURLReader.
public HTMLFilteredReader(String url)
{
super(url);
this.url = url;
}
// filtered method, returns user page's content without HTML codes.
public String getPageContents ()
{
String partFirst = "asd";
String partSecond = "asd";
int temp = 0;
String newContent=super.getPageContents();
// first for loop, counts how many '<' characters there are in the page.
for (int i = 0; i<newContent.length(); i++)
{
if (newContent.charAt(i) == '<')
temp++;
}
// second for loop, deletes the HTML code by starting at the end of the page.
for (int i=0; i<temp; i++)
{
partFirst = newContent.substring (0, newContent.lastIndexOf("<")); // and this one will substring the parts after the last HTML code, as the second for loop deletes from the end of the page.
partSecond = newContent.substring (newContent.indexOf(">", newContent.lastIndexOf ("<"))+1);// and this one will substring the parts after the last HTML code, as the second for loop deletes from the end of the page.
newContent = partFirst + partSecond; // concatenates this two parts to get the complete page.
}
return newContent;
}
// getUnfilteredPageContents method, returns the unfiltered page by getting it from its parent class.
public String getUnfilteredPageContents ()
{
return super.getPageContents();
}
}
最后我的MainActivity：
package com.example.parsetester;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
HTMLFilteredReader reader = new HTMLFilteredReader("http://kafemud.bilkent.edu.tr/monu_eng.html");
reader.getPageContents();
}
}
这是LogCat：
03-18 21:11:45.623: E/AndroidRuntime(8310): FATAL EXCEPTION: main
03-18 21:11:45.623: E/AndroidRuntime(8310): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.parsetester/com.example.parsetester.MainActivity}: java.lang.NullPointerException
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2304)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.app.ActivityThread.access$700(ActivityThread.java:165)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1326)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.os.Handler.dispatchMessage(Handler.java:99)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.os.Looper.loop(Looper.java:137)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.app.ActivityThread.main(ActivityThread.java:5450)
03-18 21:11:45.623: E/AndroidRuntime(8310): at java.lang.reflect.Method.invokeNative(Native Method)
03-18 21:11:45.623: E/AndroidRuntime(8310): at java.lang.reflect.Method.invoke(Method.java:525)
03-18 21:11:45.623: E/AndroidRuntime(8310): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
03-18 21:11:45.623: E/AndroidRuntime(8310): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
03-18 21:11:45.623: E/AndroidRuntime(8310): at dalvik.system.NativeStart.main(Native Method)
03-18 21:11:45.623: E/AndroidRuntime(8310): Caused by: java.lang.NullPointerException
03-18 21:11:45.623: E/AndroidRuntime(8310): at com.example.parsetester.MySimpleURLReader.getPageContents(MySimpleURLReader.java:31)
03-18 21:11:45.623: E/AndroidRuntime(8310): at com.example.parsetester.HTMLFilteredReader.getPageContents(HTMLFilteredReader.java:28)
03-18 21:11:45.623: E/AndroidRuntime(8310): at com.example.parsetester.MainActivity.onCreate(MainActivity.java:14)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.app.Activity.performCreate(Activity.java:5369)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
03-18 21:11:45.623: E/AndroidRuntime(8310): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
答案 0 :(得分：1)
pageContents中的 SimpleURLReader在使用前未初始化。我能看到它的唯一地方就是：
String str = localBufferedReader.readLine();
while (str != null)
{
this.pageContents = (this.pageContents + str + "\n");
this.lineCount += 1;
str = localBufferedReader.readLine();
}
如果while循环永远不会被执行，pageContents将保持null。这可能就是发生了什么。如果执行while循环 ，则在此声明中
this.pageContents = (this.pageContents + str + "\n");
当你连接字符串时，结果中会出现四个字符"null" - 你注意到了吗？
无论如何，请在某处初始化为""。某处之前 try，虽然我质疑为什么你的SimpleURLReader捕获异常，但是即使发生异常也允许构造对象。这是意图吗？如果是，则pageContents仍然需要设置为某种内容。