ios - Issue with UIControlEventTouchDragOutside implementation -

i have 2-d button array in main view , want able move them dragging inside view. buttons pretty narrow, around 23x23 pixels. have added targets control events touchdragexit , touchdragoutside fired many pixels after moved finger outside button. hence subclassed uibutton , overrode continuetrackingwithtouch code found in so. notice don't call superclass implementation.

-(bool)continuetrackingwithtouch:(uitouch *)touch withevent:(uievent *)event {     cgfloat boundsextension = 5.0f;     cgrect outerbounds = cgrectinset(self.bounds, -1 * boundsextension, -1 * boundsextension);      bool touchoutside = !cgrectcontainspoint(outerbounds, [touch locationinview:self]);     if(touchoutside)     {         bool previoustouchinside = cgrectcontainspoint(outerbounds, [touch previouslocationinview:self]);         if(previoustouchinside)         {             [self sendactionsforcontrolevents:uicontroleventtouchdragexit];         }         else         {             [self sendactionsforcontrolevents:uicontroleventtouchdragoutside];         }     }     return self.tracking; } 

both events fired correctly uicontroleventtouchdragoutside action receives wrong touch info when action called. here first part of implementation:

-(void) dragoutside:(uibutton *) sender withevents:(uievent *) event {     uitouch *touch = [[event alltouches] anyobject];     cgpoint relativeloctoinitialcell = [touch locationinview:sender];      nslog(@"translation %f %f numtouch %d",relativeloctoinitialcell.x, relativeloctoinitialcell.y, [[event alltouches] count]);     ...    } 

[[event alltouches] count] still returns 0 until move finger away button. of course relativeloctoinitialcell fields x , y both 0, values use later computations. idea might problem?

edit: deleted answer suggested using uipangesturerecognizer instead of touchdrag events, couldn't use because firing rapidly before handling 1 event got one.

i ended having handle uicontroleventtouchdraginside event. though looks workaround, thinking on fundamentals of these touch drag events makes reasonable solution. drag events sourced touchesbegan, touchesmoved , touchesended . apple added threshold before uicontroleventtouchdragoutside sent, until threshold uicontroleventtouchdraginside event sent.

my solution remove overridden continuetrackingwithtouch method , go on default implementation. handled both inside , outside events, , moved initialization code exit event inside event, , added control statements in inside event. abstracted code looks below:

-(void) draginside:(uibutton *) sender withevents:(uievent *) event {     if(stillinsideoriginalcontrol) return;      uitouch *touch = [[event alltouches] anyobject];     cgpoint relativeloctoinitialcell = [touch locationinview:sender];      [self processtouch]; }  -(void) dragoutside:(uibutton *) sender withevents:(uievent *) event {     uitouch *touch = [[event alltouches] anyobject];     cgpoint relativeloctoinitialcell = [touch locationinview:sender];      [self processtouch]; }