UITextField 明文/密文切换导致光标位置偏移

点击button切换明文/密文

- (void)buttonClick {    
    self.passwordTextField.enabled = NO; 
    // 切换明文/密文
    self.passwordTextField.secureTextEntry = !self.passwordTextField.secureTextEntry;
    self.passwordTextField.enabled = YES;  
    [self.passwordTextField becomeFirstResponder]; 
}