java - trouble using printwriter from another class -

-

my main problem nullpointerexception when use chatpanel.pw.println(chatpanel.name + " has disconnected chat.") while printwriter in chatpanel class , i'm trying use printwriter send message through socket. if me understand , maybe give me solution problem. did remove lot of code but, should compile.

import java.io.*; import java.awt.*; import java.net.*; import javax.swing.*; import java.awt.event.*; import javax.swing.jcomponent; public class chatframe1 extends jframe{      public chatframe1(){       setlayout(new gridbaglayout());       setsize(1000,600);         settitle("chat");       setresizable(true);         addwindowlistener(new windowadapter(){          public void windowclosing(windowevent we){              //the problem here.             chatpanel.pw.println(chatpanel.name + " has disconnected chat.");             system.out.println(chatpanel.name);             system.exit(0);         }       });       chatpanel sp = new chatpanel();       setvisible(true);    }    public static void main(string[] args){         new chatframe1();      } } class chatpanel extends jpanel implements actionlistener, runnable{     thread t;     jtextfield tf;     jtextarea ta;     jbutton b;     socket s;     bufferedreader br;     public static printwriter pw;     string temp;     boolean connected;     public static string name;      public chatpanel(){          gridbagconstraints gbc = new gridbagconstraints();         name = (string)joptionpane.showinputdialog(null,"enter username "+                 "(please use letters , numbers) :",                  "username login",                 joptionpane.plain_message, null, null, "user-name");         setlayout(new gridbaglayout());         tf = new jtextfield();         tf.addactionlistener(this);         ta = new jtextarea();         b = new jbutton("press connect");         b.addactionlistener(this);      }     public void actionperformed(actionevent ae){         if((tf != null) && (!connected)){          b.setlabel("press connect");         }         if((ae.getsource() == b) && (!connected)){             try{                 s = new socket("127.0.0.1", 2020);                 pw = new printwriter(s.getoutputstream(), true);                 tf.settext("");              }catch(unknownhostexception uhe){                 system.out.println(uhe.getmessage());               }catch(ioexception ioe){                  system.out.println(ioe.getmessage());              }                connected = true;             t = new thread(this);             b.setlabel("disconnect");             t.start();          }else if((ae.getsource() == b) && (connected)){               connected = false;             try{                 pw.println(name +" has disconnected chat.");                 ta.settext("");                 s.close(); //no buffering so, ok             }catch(ioexception ioe){                 system.out.println(ioe.getmessage());             }             b.setlabel("press reconnect");         }else{         temp = tf.gettext();             tf.settext("");         }     }     public void run(){          try{             bufferedreader br = new bufferedreader(new inputstreamreader(s.getinputstream()));             while(((temp = br.readline()) != null) && connected){             ta.append(temp + "\n");             }         }catch(ioexception ioe){             system.out.println(ioe.getmessage());         }     } }

i think giving nullpointerexception

chatpanel.pw.println(chatpanel.name + " has disconnected chat.");

because chatpanel.pw has never been initialized in code, , therefore null

you should ensure chatpanel.pw has been initialized somewhere (maybe within constructor) inside chatpanel class before calling chatpanel.pw.println()


Comments

Post a Comment

Popular posts from this blog

python - mat is not a numerical tuple : openCV error -

-
i have write down code showing error ma not getting it: please help: showing mat not numerical tuple: import cv import cv2 capture = cv2.videocapture("j.3gp") while(1): _, frame1 = capture.read() grayimage1 = cv2.cvtcolor(frame1, cv2.color_bgr2gray) _, frame2 = capture.read() grayimage2 = cv2.cvtcolor(frame2, cv2.color_bgr2gray) differenceimage = cv2.absdiff(grayimage1,grayimage2) thresholdimage = cv2.threshold(differenceimage,25,255,cv2.thresh_binary) cv2.imshow("difference image", differenceimage) cv2.imshow("threshold image", thresholdimage) cv2.imshow("image", frame1) k = cv2.waitkey(30) & 0xff error arising : ----------------------------------------------------------------------------------------- traceback (most recent call last): file "desk.py", line 15, in <module> cv2.imshow("threshold image", thresholdimage) typeerror: mat not numerical tuple ...
Read more

c# - MSAA finds controls UI Automation doesn't -

-
i'm working on automating windows application. i'm using teststack white framework. i've hit problem. program has 'window' object cannot see inside of. white shows no controls inside of it. inspect.exe shows no controls inside of either when running in ui automation mode. if switch inspect msaa see controls inside fine. there anyway me use msaa c# handle on these controls? if can identify msaa functions need, can use p/invoke call them c#. here's example article doing msaa: http://www.codeproject.com/articles/38906/ui-automation-using-microsoft-active-accessibility also, pinvoke.net can used identify iaccessible (msaa) functions: http://www.pinvoke.net/search.aspx?search=iaccessible&namespace=[all] here's answer along lines: msaa com-based? finally, alternative p/invoke, might able use tlbimp.exe create wrapper assembly oleacc.dll, , access msaa functions through it. i'm not sure if works msaa, it's worth try. as e...
Read more

wordpress - .htaccess: RewriteRule: bad flag delimiters -

-
pulling hair out on one. have following .htaccess file custom redirects in addition wordpress's default settings. when tested on local wamp server worked fine after moving production i'm not getting rewriterule: bad flag delimiters error in server log , after while site goes down internal server error any appreciated. in advance! <ifmodule mod_rewrite.c> rewriteengine on rewritebase / rewriterule ^rockford_weddings___welcome\.html$ /wedding/ [r=301,l] rewriterule ^blog/?$ /journal/ [r=301,l] rewriterule ^blog/(.*)$ /$1 [r=301,l] rewriterule ^portraitinvestment/?$ /portraitinvestment\.pdf [r=301,l] rewriterule ^weddinginvestment/?$ /weddinginvestment\.pdf [r=301,l] rewriterule ^holidaycards2014/?$ /holidaycards2014\.pdf [r=301,l] </ifmodule> # begin wordpress <ifmodule mod_rewrite.c> rewriteengine on rewritebase / rewriterule ^index\.php$ - [l] rewritecond %{request_filename} !-f rewritecond %{request_filename} !-d rewriterule . /index.php [l] </...
Read more