密码输入

  passcodeField.textAlignment = UITextAlignmentCenter;
  passcodeField.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin;
  passcodeField.secureTextEntry = YES;
  passcodeField.font = [UIFont systemFontOfSize:42];
  passcodeField.keyboardType = UIKeyboardTypeNumberPad;
  passcodeField.delegate = self;
  passcodeField.borderStyle = UITextBorderStyleBezel;