iOS keyboard Click the ENTER key to what happened

#import   "ViewController.h" @interface  ViewController  ()  <uitextfielddelegate>@ property  (weak, nonatomic)  IBOutlet UITextField *usernameTextfield; @property   ( weak, nonatomic)  IBOutlet UITextField *passwordTextfield; @property   (weak,  nonatomic)  IBOutlet UIButton *loginBtn; @end @implementation viewcontroller-  (void) Viewdidload {    [super viewdidload];    // do any  additional setup after loading the view, typically from a  nib.        //setting Usernametextfield and Passwordtextfield related properties          //setting  usernameTextfield  keyboard type     /*      typedef ns_enum (Nsinteger, uikeyboardtype)  {      uikeyboardtypedefault,                 // default type  for the current input method.      Uikeyboardtypeasciicapable,           // displays  a keyboard which can enter ascii characters, non-ascii keyboards  remain active     UIKeyboardTypeNumbersAndPunctuation,  //  numbers and assorted punctuation.     uikeyboardtypeurl,                     //  A type optimized for URL entry  (shows . / .com  prominently) .     uikeyboardtypenumberpad,               //&nBsp a number pad  (0-9) . suitable for pin entry.      uikeyboardtypephonepad,                // A phone pad  (1-9, *, 0, #, with letters under  The numbers) .     uikeyboardtypenamephonepad,            // A type optimized for entering a  Person ' s name or phone number.     uikeyboardtypeemailaddress,            // a type optimized for  multiple email address entry  (shows space @ . prominently).      uikeyboardtypedecimalpad ns_enum_available_ios (4_1),    //  a number pad&nbsP;with a decimal point.     uikeyboardtypetwitter ns_enum_ Available_ios (5_0),      // a type optimized for  twitter text entry  (easy access to @ #)       Uikeyboardtypewebsearch ns_enum_available_ios (7_0),    // a default  keyboard type with url-oriented addition  (shows space . prominently).           UIKeyboardTypeAlphabet =  uikeyboardtypeasciicapable, // deprecated           };     */        // self.usernametextfield.keyboardtype = uikeyboardtypenumberpad;         //Setting the  returnkey    s of Usernametextfieldelf.usernametextfield.returnkeytype = uireturnkeynext;         //You must allow this class to support the protocol before setting up the agent, and set the proxy to itself     self.usernameTextfield.delegate = self;             //Settings  usernameTextfield     self.passwordTextfield.keyboardType = UIKeyboardTypeEmailAddress;     self.passwordTextfield.returnKeyType = UIReturnKeyDone;     self.passwordtextfield.delegate =self;        //makes the password you enter into a small origin. and general applications are doing so     self.passwordTextfield.secureTextEntry = YES;     }-  (void) didreceivememorywarning {    [super didreceivememorywarning] ;    // dispose of any resources that can be  Recreated.} -  (ibaction) clickloginbtn: (Uibutton *) Sender {    nslog (@ "Login successful");} #pragma  mark - UITextFieldDelegate-  (BOOL) Textfieldshouldreturn: (uitextfield *) textfield{    if  (Textfield == self.usernametextfield)  {         //self.usernametextfield abandons the first responder, while Self.passwordtextfield becomes the first responder          [self.usernameTextfield resignFirstResponder];         [self.passwordtextfield becomefirstresponder];    }  else if (Textfield == self.passwordtextfield)  {         //self.passwordtextfield discards the first responder and calls the login function         [ self.passwordtextfield resignfirstresponder];        [ Self.loginbtn sendactionsforcontrolevents:uicontroleventtouchupinside];        //[self clickloginbtn:self.loginbtn];    }     return yes;} @end

What happens when you click the ENTER key on the iOS keyboard