swift 监听UITextDield内容变化，改变按钮的颜色，图片等

注意：给文本框添加一个解决方法，for：设置成.editingChanged

代码如下：

        phoneTF.tfV.addTarget(self, action: #selector(clearpasswordTextFeildBtnColor), for: .editingChanged)

        passTF.tfV.addTarget(self, action: #selector(clearpasswordTextFeildBtnColor), for: .editingChanged)

        inviteCodeTF.tfV.addTarget(self, action: #selector(clearpasswordTextFeildBtnColor), for: .editingChanged)

        registerPassTF.tfV.addTarget(self, action: #selector(clearpasswordTextFeildBtnColor), for: .editingChanged)

        inviteCodeTF.tfV.addTarget(self, action: #selector(clearpasswordTextFeildBtnColor), for: .editingChanged)

    }

    //改变按钮颜色设置

    @objc func clearpasswordTextFeildBtnColor(){

        if phoneTF.tfV.text != "" && passTF.tfV.text != "" && inviteCodeTF.tfV.text != "" && registerPassTF.tfV.text != "" && inviteCodeTF.tfV.text != "" {

            loginBtn.backgroundColor = titleYellowColor

        }else{

            loginBtn.backgroundColor = titleShelvesColor

        }

    }