Question

我有一个工作列表由一个类填充（或者我假设）并且我试图在表单上的一组文本框中显示唯一的记录。

public partial class frm_people : Form
{

    public frm_people()
    {
        // Loads the Form
        InitializeComponent();

        LoadData();

        ShowData();

    }

    // Global Variables

    private People peopleClass;
    private ArrayList peopleArrayList;

    private int numberOfPeople;
    private int currentPeopleShown;

    private void ShowData()
    {
        // Add to Text Box based on current Record
        txt_peopleName.Text = ((People)peopleArrayList[currentPeopleshown]).name;**
    }

    private void LoadData()
    {

        List<People> peopleList = new List<People>();

        People data = new People("James Bond", false, "Cardiff");

        peopleList.Add(data);

        numberOfPeople = 1;
        currentPeopleShown = 0;
    }
}

我收到错误（以**表示）：

＆＃34;对象引用未设置为对象的实例。＆＃34;

我知道通过引用来处理类，如何尝试这种显示记录的方式？最终目标是能够使用currentPeopleShown变量自由地在多个记录之间滚动。

Answer 1

试试这个：

    private void ShowData()
    {
        // Add to Text Box based on current Record
      if(peopleArrayList[currentPeopleshown]!=null)
        txt_peopleName.Text = ((People)peopleArrayList[currentPeopleshown]).name;
    }

Answer 2

您的peopleList超出范围。

List<People> peopleList = new List<People>();

private void LoadData()
{
  //...
}

数组未被使用，因此请使用peopleList：

txt_peopleName.Text = peopleList[currentPeopleshown].name;

您不需要numberOfPeople变量，只需使用peopleList.Count

即可

Answer 3

你在哪里设置peopleArrayList？

在这些方面尝试一些事情：

private void LoadData()
{
    peopleArrayList = new ArrayList();
    People data = new People("James Bond", false, "Cardiff");

    peopleArrayList.Add(data);

    numberOfPeople = 1;
    currentPeopleShown = 0;
}

Answer 4

或者您可以一起消除ArrayList，只需执行此操作

public partial class frm_people : Form
{
   List<People> peopleList;
    public frm_people()
    {
        // Loads the Form
        InitializeComponent();

        peopleList = new List<People>();
        LoadData();

        ShowData();

    }

    // Global Variables

    private People peopleClass;

    private int numberOfPeople;
    private int currentPeopleShown;

    private void ShowData()
    {
        // Add to Text Box based on current Record
        txt_peopleName.Text = (peopleList[0]).name;**
    }

    private void LoadData()
    {

        People data = new People("James Bond", false, "Cardiff");

        peopleList.Add(data);

        numberOfPeople = 1;
        currentPeopleShown = 0;
    }
}

在表单上显示类内容

4 个答案: