xamarin.ios - Detect backspace in UITextField in iOS8 -

for detecting backspace, i've overridden deletebackward method (should work ios5+)

var input = new backspacetextfield(rectanglef.empty); etc input.becomefirstresponder(); 

here's code

public sealed class backspacetextfield : uitextfield {     public backspacetextfield(rectanglef frame) : base(frame)     {     }      public override void deletebackward ()     {         console.writeline ("deletebackward");     } } 

when press "backspace" button nothing happens. expect "deletebackward" message should appear

environment: ios8, xamarin

edit: 0

similar question on objective-c: detect backspace in uitextfield

i've done additional check. deletebackwardis method uikeyinput protocol, i've check inserttext method, method works perfactly.

public override void inserttext (string text) {    base.inserttext(text); } 

i've checked deletebackward on objective-c , works too.

do have ideas how detect backspace in uitextfield in ios8?

could please clarify why deletebackward method not called?

edit: 1

i've submitted same question xamarin's forum. looks bug in ios8 + xamarin, because in ios 7.1 works perfactly.

it's bug. here's details

a lot of people have been saying bug, being problem still exists in gm i'm starting think might change in logic. said, wrote bit of code app , have tested on ios 7-8.

this code before red line of private api's, should have no problem using it. app code in app store.

add following method uitextfield subclass.

- (bool)keyboardinputshoulddelete:(uitextfield *)textfield {     bool shoulddelete = yes;      if ([uitextfield instancesrespondtoselector:_cmd]) {         bool (*keyboardinputshoulddelete)(id, sel, uitextfield *) = (bool (*)(id, sel, uitextfield *))[uitextfield instancemethodforselector:_cmd];          if (keyboardinputshoulddelete) {             shoulddelete = keyboardinputshoulddelete(self, _cmd, textfield);         }     }      bool isios8 = ([[[uidevice currentdevice] systemversion] intvalue] == 8);     bool islessthanios8_3 = ([[[uidevice currentdevice] systemversion] floatvalue] < 8.3f);      if (![textfield.text length] && isios8 && islessthanios8_3) {         [self deletebackward];     }      return shoulddelete; } 

to explain little, calling super's implementation of method avoid losing inherited code. after going call -deletebackward if there no text , ios version between 8-8.2.

edit: 1/28/15

it might helpful subclass -deletebackward method of subclassed uitextfield. fixes few conditional bugs. 1 being if use custom keyboard. heres example of method.

- (void)deletebackward {     bool shoulddismiss = [self.text length] == 0;      [super deletebackward];      if (shoulddismiss) {         if ([self.delegate respondstoselector:@selector(textfield:shouldchangecharactersinrange:replacementstring:)]) {             [self.delegate textfield:self shouldchangecharactersinrange:nsmakerange(0, 0) replacementstring:@""];         }     } } 

edit: answer translated xamarin, original question asked xamarin.

    [preserve]     [export("keyboardinputshoulddelete:")]     private bool keyboardinputshoulddelete(uitextfield textfield)     {         var shoulddelete = true;          if(respondstoselector(new selector("_cmd")))         {             //call base class             shoulddelete = messaging.bool_objc_msgsend_intptr(handle, selector.gethandle("_cmd"), textfield.handle);         }          //ios8 "bug": call deletebackward if field empty         if(utils.isios8)         {             deletebackward();             return false;         }          return shoulddelete;     } 

verified on ios 7.1 , 8.1

edit: 4/14/15

as of ios 8.3 issue has been fixed. objective-c code has been updated reflect changes.

edit: 7/24/15

as @nischalhada commented, state exists text fields -textfield:shouldchangecharactersinrange:replacementstring: called twice. problem exists on ios >= 8.3 while using custom keyboard. solution not ideal job , i'm not sure if there's other way. since both calls method performed on same run loop we'll use bool keep track of when execute code , dispatch async reset bool.

- (bool)textfield:(uitextfield *)textfield shouldchangecharactersinrange:(nsrange)range replacementstring:(nsstring *)string {     bool toreturn = no;      if (!self.shouldtextfieldpreventchange) {         self.shouldtextfieldpreventchange = yes;          dispatch_async(dispatch_get_main_queue(), ^{             // ios8.3 custom keyboards might call method along internal ios             // code. allowing changes on next run loop helps avoid issue.             self.shouldtextfieldpreventchange = no;         });          // work...     }      return toreturn; }