i absolute beginner android. started learning android 8 days ago. getting error using sqlite database in fragment. please wrong code?
my database helper class
public class databasehelper extends sqliteopenhelper { private static final int database_version = 1; private static final string database_name = "todo.db"; private static final string table_name = "task"; private static final string column_id = "id"; private static final string column_description = "description"; private static final string column_date ="date"; private static final string column_done = "done"; private static final string create_table = "create table "+table_name+" ("+column_id+" integer primary key autoincrement,"+column_description+" text,"+ column_date+" date,"+column_done+" boolean)"; sqlitedatabase db; public databasehelper(context context) { super(context,database_name,null,database_version); } @override public void oncreate(sqlitedatabase db) { this.db = db; db.execsql(create_table); } @override public void onupgrade(sqlitedatabase db, int oldversion, int newversion) { string query = "drop table if exists "+table_name; db.execsql(query); this.oncreate(db); } public void inserttask(task task) { db = getwritabledatabase(); contentvalues values = new contentvalues(); values.put(column_description,task.getdescription()); values.put(column_date,task.getdate().tostring()); values.put(column_done,boolean.false.tostring()); db.insert(table_name, null, values); db.close(); } } this fragment class
public class createtaskfragment extends fragment{ private databasehelper dbhelper = new databasehelper(getactivity()); private button savebtn; private edittext tfdescription,tfdate; private int yy,mm,dd; @nullable @override public view oncreateview(layoutinflater inflater, viewgroup container, bundle savedinstancestate) { view view = inflater.inflate(r.layout.create_task,container,false); tfdescription = (edittext)view.findviewbyid(r.id.tf_task_description); tfdate = (edittext)view.findviewbyid(r.id.tf_task_date); tfdate.setonclicklistener(new view.onclicklistener() { @override public void onclick(view v) { setpickerdate(v); } }); savebtn = (button)view.findviewbyid(r.id.btn_save_task); savebtn.setonclicklistener(new view.onclicklistener() { @override public void onclick(view v) { savetask(); } }); return view; } public void setpickerdate(view v) { final calendar calendar = calendar.getinstance(); int yy = calendar.get(calendar.year); int mm = calendar.get(calendar.month); int dd = calendar.get(calendar.day_of_month); datepickerdialog datepicker = new datepickerdialog(getactivity(), new datepickerdialog.ondatesetlistener() { @override public void ondateset(datepicker view, int year, int monthofyear, int dayofmonth) { string date = string.valueof(monthofyear+1)+"/"+string.valueof(dayofmonth)+"/"+string.valueof(year); tfdate.settext(date); } }, yy, mm, dd); datepicker.show(); } public void savetask() { string description = tfdescription.gettext().tostring(); string date = tfdate.gettext().tostring(); if(description.isempty()) { toast.maketext(getactivity().getbasecontext(),"description required",toast.length_short).show(); } else if(date.isempty()) { toast.maketext(getactivity().getbasecontext(),"date required",toast.length_short).show(); } else if(description.length()<getresources().getinteger(r.integer.min_description_length)) { string minchar = string.valueof(getresources().getinteger(r.integer.min_description_length)); toast.maketext(getactivity().getbasecontext(),"description should minium "+minchar+" characters",toast.length_short).show(); } else{ //check date simpledateformat format = new simpledateformat("mm/dd/yyyy"); boolean parseok = false; date taskdate = new date(); try{ taskdate = format.parse(date); task task = new task(); task.setdescription(description); task.setdate(taskdate); dbhelper.inserttask(task); parseok = true; } catch(parseexception e) { parseok = false; } if(parseok) { //insert task database toast.maketext(getactivity().getbasecontext(),"task saved",toast.length_short).show(); } else{ toast.maketext(getactivity().getbasecontext(),"invalid date format",toast.length_short).show(); } } } } when click save button. throwing error.
this logcat after click save button
01-24 15:49:30.007 575-575/? v/inputmethodservice: onevaluateinputviewshown: config.hardkeyboardhidden = 1 01-24 15:49:30.011 575-597/? e/binarydictionarygetter: not find dictionary pack 01-24 15:49:30.011 575-597/? e/activitythread: failed find provider info com.android.inputmethod.latin.dictionarypack 01-24 15:49:31.167 1765-1765/? d/androidruntime: shutting down vm 01-24 15:49:31.167 1765-1765/? w/dalvikvm: threadid=1: thread exiting uncaught exception (group=0xa6206908) 01-24 15:49:31.167 1765-1765/? e/androidruntime: fatal exception: main 01-24 15:49:31.167 1765-1765/? e/androidruntime: java.lang.nullpointerexception 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ android.database.sqlite.sqliteopenhelper.getdatabaselocked(sqliteopenhelper.java:224) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ android.database.sqlite.sqliteopenhelper.getwritabledatabase(sqliteopenhelper.java:164) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ com.waiyanhein.todo.todo.databasehelper.inserttask(databasehelper.java:46) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ com.waiyanhein.todo.todo.createtaskfragment.savetask(createtaskfragment.java:100) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ com.waiyanhein.todo.todo.createtaskfragment$2.onclick(createtaskfragment.java:49) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ android.view.view.performclick(view.java:4204) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ android.view.view$performclick.run(view.java:17355) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ android.os.handler.handlecallback(handler.java:725) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ android.os.handler.dispatchmessage(handler.java:92) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ android.os.looper.loop(looper.java:137) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ android.app.activitythread.main(activitythread.java:5041) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ java.lang.reflect.method.invokenative(native method) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ java.lang.reflect.method.invoke(method.java:511) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:793) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ com.android.internal.os.zygoteinit.main(zygoteinit.java:560) 01-24 15:49:31.167 1765-1765/? e/androidruntime: @ dalvik.system.nativestart.main(native method) 01-24 15:49:31.167 415-426/? w/activitymanager: force finishing activity com.waiyanhein.todo.todo/.mainactivity 01-24 15:49:31.231 415-426/? d/dalvikvm: gc_for_alloc freed 1480k, 53% free 6135k/12844k, paused 5ms, total 6ms 01-24 15:49:31.239 415-418/? d/dalvikvm: gc_concurrent freed 46k, 47% free 6925k/12844k, paused 2ms+1ms, total 10ms 01-24 15:49:31.251 415-431/? d/dalvikvm: gc_for_alloc freed 107k, 45% free 7160k/12844k, paused 7ms, total 7ms 01-24 15:49:31.263 415-418/? d/dalvikvm: gc_concurrent freed 1k, 36% free 8260k/12844k, paused 1ms+0ms, total 10ms 01-24 15:49:31.263 415-431/? d/dalvikvm: wait_for_concurrent_gc blocked 3ms 01-24 15:49:31.267 415-431/? i/dalvikvm-heap: grow heap (frag case) 10.614mb 2536932-byte allocation 01-24 15:49:31.279 415-423/? d/dalvikvm: gc_for_alloc freed <1k, 30% free 10737k/15324k, paused 13ms, total 13ms 01-24 15:49:31.743 415-428/? w/activitymanager: activity pause timeout activityrecord{5325c494 u0 com.waiyanhein.todo.todo/.mainactivity} 01-24 15:49:31.747 415-470/? i/qtaguid: failed write_ctrl(s 1 10023) res=-1 errno=1 01-24 15:49:31.747 415-470/? w/networkmanagementsockettagger: setkernelcountset(10023, 1) failed errno -1 01-24 15:49:31.791 598-598/? w/egl_genymotion: eglsurfaceattrib not implemented 01-24 15:49:32.359 415-470/? i/qtaguid: failed write_ctrl(s 0 10062) res=-1 errno=1 01-24 15:49:32.359 415-470/? w/networkmanagementsockettagger: setkernelcountset(10062, 0) failed errno -1 01-24 15:49:42.307 415-428/? w/activitymanager: activity destroy timeout activityrecord{5325c494 u0 com.waiyanhein.todo.todo/.mainactivity}
the error null pointer exception on line 101 of fragment. it's hard tell post line 101 represents, i'm assuming line has:
dbhelper.inserttask(task); you declare dbhelper member variable @ top of class, never instantiate it. instead, call:
new databasehelper(getactivity()); without ever attaching dbhelper. change line to:
dbhelper = new databasehelper(getactivity()); it fix error.
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