Java：实例化时未设置作为其他类实例的类数据成员

Question

我正在开发一个 Android 应用程序，我有一个基本的 Customer 类，它有一个国籍数据成员，而该成员又是另一个公共类。当我实例化一个新客户时，国籍和出生日期成员（非原始数据类型）都没有设置（调用他们的 getter 会导致空引用异常）。

顺便说一句，我使用的是 Android Studio，并且我正在通过一个 JSON 包装器创建一个新的 Customer 实例，该包装器接收来自 RESTFUL Web 服务调用的数据。

public class Customer
{
    // Private fields
    private int Id;
    private String FirstName;
    private String LastName;
    private String OfficeNumber;
    private String MobileNumber;
    private String EmailAddress;
    private boolean Gender;
    private Date BirthDate;
    private Nationality Nationality;

    /* Setters & Getters */
    public int getId() {
        return Id;
    }
    public void setId(int id) {
        Id = id;
    }

    public String getFirstName() {
        return FirstName;
    }
    public void setFirstName(String firstName) {
        FirstName = firstName;
    }

    public String getLastName() {
        return LastName;
    }
    public void setLastName(String lastName) {
        LastName = lastName;
    }

    public String getOfficeNumber() {
        return OfficeNumber;
    }
    public void setOfficeNumber(String officeNumber) {
        OfficeNumber = officeNumber;
    }

    public String getMobileNumber() {
        return MobileNumber;
    }
    public void setMobileNumber(String mobileNumber) {
        MobileNumber = mobileNumber;
    }

    public String getEmailAddress() {
        return EmailAddress;
    }
    public void setEmailAddress(String emailAddress) {
        EmailAddress = emailAddress;
    }

    public boolean getGender() {
        return Gender;
    }
    public void setGender(boolean gender) {
        Gender = gender;
    }

    public Date getBirthDate() {
        return BirthDate;
    }
    public void setBirthDate(Date birthDate) {
        BirthDate = birthDate;
    }

    public Nationality getNationality() {
        return Nationality;
    }
    public void setNationality(Nationality nationality) {Nationality = nationality; }
}

国籍等级

public class Nationality
{
    // Private Fields
    private int Id;
    private String NationalityEn;
    private String NationalityAr;

    public Nationality(int id, String nationalityEn, String nationalityAr)
    {
        setId(id);
        setNationalityEn(nationalityEn);
        setNationalityAr(nationalityAr);
    }

    public Nationality(){}

    // Setters & Getters
    public int getId() {
        return Id;
    }

    public void setId(int id) {
        Id = id;
    }

    public String getNationalityEn() {
        return NationalityEn;
    }

    public void setNationalityEn(String nationalityEn) {
        NationalityEn = nationalityEn;
    }

    public String getNationalityAr() {
        return NationalityAr;
    }

    public void setNationalityAr(String nationalityAr) {
        NationalityAr = nationalityAr;
    }
}

包装器：

public class JSONToObjectWarpper
{
    public Customer getCustomerObject(JSONObject jsonObject)
    {
        Customer customer = new Customer();

        try
        {
            JSONObject js = jsonObject.getJSONObject("Customer");
            Nationality nationality = new Nationality(
                    js.getJSONObject("Nationality").getInt("Id"),
                    js.getJSONObject("Nationality").getString("NationalityEn"),
                    js.getJSONObject("Nationality").getString("NationalityAr")
            );
            Date date = ConvertFromWCFDate(js.getString("BirthDate"));

            customer.setId(js.getInt("Id"));
            customer.setFirstName(js.getString("FirstName"));
            customer.setLastName(js.getString("LastName"));
            customer.setOfficeNumber(js.getString("OfficeNumber"));
            customer.setMobileNumber(js.getString("MobileNumber"));
            customer.setEmailAddress(js.getString("EmailAddress"));
            customer.setGender(js.getBoolean("Gender"));
            customer.setBirthDate(date);
            customer.setNationality(nationality);

        }
        catch (JSONException e)
        {
            // Handle the Exception Here
        }
        return customer;
    }
}

我在这里错过了什么？！提前感谢您的帮助。

Answer 1

在 catch 块中处理异常并打印异常堆栈以查看到底发生了什么以及异常究竟来自哪里。此外，打印您的 JSON 对象以确保实际接收到数据并且您获得了正确的属性。