android - How to interpret Debugging information? -


this 2 questions. first relates program, , second more general question regarding debugging.

in code, have 2 button listeners. when first clicked, onclicklistener creates locationlistener, locationmanager requests updates locationlistener. (see below...) 

locationmanager locationmanager = (locationmanager)  getsystemservice(context.location_service); locationmanager.requestlocationupdates(locationmanager.gps_provider, 0, 0, locationlistener);

on click of second button, try unregister listener follows...

locationmanager.removeupdates(locationlistener);

however, end force close , following info in debugger...

error/androidruntime(310): fatal exception: main error/androidruntime(310): java.lang.nullpointerexception error/androidruntime(310):     @ com.ryan.gcal.gruncal$2.onclick(gruncal.java:94) error/androidruntime(310):     @ android.view.view.performclick(view.java:2408) error/androidruntime(310):     @ android.view.view$performclick.run(view.java:8816) error/androidruntime(310):     @ android.os.handler.handlecallback(handler.java:587) error/androidruntime(310):     @ android.os.handler.dispatchmessage(handler.java:92) error/androidruntime(310):     @ android.os.looper.loop(looper.java:123) error/androidruntime(310):     @ android.app.activitythread.main(activitythread.java:4627) error/androidruntime(310):     @ java.lang.reflect.method.invokenative(native method) error/androidruntime(310):     @ java.lang.reflect.method.invoke(method.java:521) error/androidruntime(310):     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:868) error/androidruntime(310):     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:626) error/androidruntime(310):     @ dalvik.system.nativestart.main(native method)

line 94 of code, error originates, tried remove location listener. assume not removing location listener properly, not sure wrong. locationmanager declared @ start of code...

locationmanager locationmanager;

my first question is, doing wrong in removing listener? , secondly, can provide tips/advice on learning interpret debug errors meaningfully? thanks.

you need either:

a) define locationmanager instance class variable, or retrieve again in onclick.

locationmanager locationmanager;  public void onclick1() {     locationmanager = (locationmanager)  getsystemservice(context.location_service);             locationmanager.requestlocationupdates(locationmanager.gps_provider, 0, 0, locationlistener);  }  public void onclick2() {     locationmanager.removeupdates(locationlistener); }

you need make sure in onclick1() instead of 

locationmanager locationmanager = (locationmanager)  getsystemservice(context.location_service);

you put 

locationmanager = (locationmanager)  getsystemservice(context.location_service);

specifying locationmanager locationmanager makes scope of declaration enclosed method assign in, rather in scope of class. means in 2nd click locationmanager infact null.


Comments

Post a Comment

Popular posts from this blog

asp.net - repeatedly call AddImageUrl(url) to assemble pdf document -

i'm using abcpdf , i'm curious if can recursively call addimageurl() function assemble pdf document compile multiple urls? something like: int pagecount = 0; int theid = thedoc.addimageurl("http://stackoverflow.com/search?q=abcpdf+footer+page+x+out+of+", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetochain(theid); } pagecount = thedoc.pagecount; console.writeline("1 document page count:" + pagecount); //flatten document (int = 1; <= pagecount; i++) { thedoc.pagenumber = i; thedoc.flatten(); } //now try again theid = thedoc.addimageurl("http://stackoverflow.com/questions/1980890/pdf-report-generation", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetoc...
Read more

java - Android recognize cell phone with keyboard or not? -

in android app, want detect user's device if device has keyboard(like motorola milestone) , show corresponding user interface. guys know how that? ! regards justicepenny http://developer.android.com/reference/android/content/res/configuration.html public int keyboard the kind of keyboard attached device. 1 of: keyboard_nokeys, keyboard_qwerty, keyboard_12key. that's it!
Read more

iphone - How would you achieve a LED Scrolling effect? -

how achieve led scrolling effect example below? led sign - led ticker emulator iphone , ipad http://img.skitch.com/20101201-rsfh4p1bajb1wp94k466pdpiuj.preview.jpg sometimes remunerates comment in other posts :) have put code you, should implement font '8pin matrix' realistic feeling. uilabel *label; - (void)viewdidload { [super viewdidload]; label = [[uilabel alloc]initwithframe:cgrectmake(10, 50, 300, 20)]; label.font = [uifont fontwithname:@"courier-bold" size:16.0]; label.backgroundcolor = [uicolor blackcolor]; label.textcolor = [uicolor greencolor]; label.linebreakmode = uilinebreakmodecharacterwrap; // otherwise "…" label.text = @"this led text scrolled "; // blanks space between [self.view addsubview:label]; [nstimer scheduledtimerwithtimeinterval:0.12f target:self selector:@selector(scrolllabel) use...
Read more