UITextView与底锚iOS的问题

我已经为一个聊天应用程序创建了一个输入容器。容器由以下材料制成: UIView UIImageView , UITextView 和 UIButton 都是程序化的。但我的问题是我不能动 UITextView视图 bottomAnchor 不动了 UITextView视图 但是 topAnchor

我试过很多方法,但都不能成功。这是密码 和 constraints :

lazy var inputTextField: UITextView = {
    let textField = UITextView()
    textField.text = "Enter message..."
    textField.translatesAutoresizingMaskIntoConstraints = false
    textField.font = UIFont(name: (textField.font?.fontName)!, size: 18)
    textField.layer.borderWidth = 1
    textField.layer.borderColor = UIColor.gray.cgColor
    textField.layer.cornerRadius = 25
    textField.textContainerInset = UIEdgeInsets(top: 15.0, left: 8.0, bottom: 0, right: 8.0)
    textField.delegate = self
    return textField
}()

和约束条件:

        addSubview(self.inputTextField)
    //x,y,w,h
    self.inputTextField.leftAnchor.constraint(equalTo: uploadImageView.rightAnchor, constant: 8).isActive = true
    self.inputTextField.rightAnchor.constraint(equalTo: sendButton.leftAnchor).isActive = true
    self.inputTextField.heightAnchor.constraint(equalTo: heightAnchor).isActive = true
    self.inputTextField.topAnchor.constraint(equalTo: separatorLineView.topAnchor, constant: 5.0).isActive = true

//bottom anchor doesn't work
    self.inputTextField.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: 5.0)
        .isActive = true