以编程方式在视图中央设置自动布局 iOS

问：

我是iOS的新手，使用整个屏幕的模糊效果视图，并希望以编程方式为视图中心的Textfield设置自动布局，我的代码是：

UIBlurEffect *blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark];
blurEffectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect];
[blurEffectView setFrame:self.view.bounds];
[self.view addSubview:blurEffectView];

// Vibrancy effect
UIVibrancyEffect *vibrancyEffect = [UIVibrancyEffect effectForBlurEffect:blurEffect];
UIVisualEffectView *vibrancyEffectView = [[UIVisualEffectView alloc] initWithEffect:vibrancyEffect];
[vibrancyEffectView setFrame:self.view.bounds];

UITextField *EmailTextField = [[UITextField alloc] init;
vibrancyEffectView.translatesAutoresizingMaskIntoConstraints = NO;
NSArray *heightConstraint = [NSLayoutConstraint      constraintsWithVisualFormat:@"V:[EmailTextField(30)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(EmailTextField)];
NSArray *widthConstraint = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[EmailTextField(240)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(EmailTextField)];
NSArray *xConstraint = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-42-[EmailTextField(240)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(EmailTextField)];
NSArray *yConstraint = [NSLayoutConstraint constraintsWithVisualFormat:@"V:-150-[EmailTextField(30)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(EmailTextField)];
EmailTextField.textColor = [UIColor redColor];
EmailTextField.font = [UIFont fontWithName:@"Helvetica" size:16];
EmailTextField.backgroundColor=[UIColor clearColor];
EmailTextField.borderStyle = UITextBorderStyleRoundedRect;
[EmailTextField.layer setCornerRadius:10.0f];
EmailTextField.layer.borderWidth = 1.0;
EmailTextField.layer.borderColor = [UIColor whiteColor].CGColor;
EmailTextField.placeholder=@"Email ID";
EmailTextField.textAlignment= NSTextAlignmentCenter;
[[vibrancyEffectView contentView] addSubview:EmailTextField];
[[blurEffectView contentView] addSubview:vibrancyEffectView];
[vibrancyEffectView addConstraints:widthConstraint];
[vibrancyEffectView addConstraints:heightConstraint];
[vibrancyEffectView addConstraints:xConstraint];
[vibrancyEffectView addConstraints:yConstraint];

但给出错误：

由于未捕获的异常“NSInvalidArgumentException”而终止应用，原因：“无法分析约束格式： 无法解释“|”字符，因为相关视图没有超级视图 H：|-42-[EmailTextField（240）]

我想要两个解决方案- 1.请更正文本字段相同x=42，y=150位置的代码 2.Texfield位于视野的中心。

如果有人可以帮助我使用正确的代码，请提前致谢