C#中对象的实例

Question

我在尝试制作的游戏中遇到错误。我收到以下错误。

NullReferenceException: Object reference not set to an instance of an object

同样的代码在我的其他脚本之一中工作正常，但在这个脚本中它继续通过这个错误。我以为我将它设置为对象的一个实例，但我猜不是。

UnityEngine.Component book001GUIOld = GameObject.FindWithTag("Book001Canvas").GetComponent("Canvas");
UnityEngine.Behaviour book001GUI = (UnityEngine.Behaviour)book001GUIOld;

有什么建议吗？如果您需要更多代码，请告诉我。我也试过了。

UnityEngine.Behaviour book001GUI = GameObject.FindWithTag("Book001Canvas").GetComponent("Canvas") as behaviour;

Answer 1

一定是因为GameObject.FindWithTag("Book001Canvas")返回了null，然后 .GetComponent("Canvas"); 抛出异常。

Answer 2

来自 GameObject.FindWithTag 文档：

Description

Returns one active GameObject tagged tag. Returns null if no GameObject was found.

所以您可能想尝试捕获错误：

var book001Canvas = GameObject.FindWithTag("Book001Canvas");

if (book001Canvass != null)
{
    UnityEngine.Component book001GUIOld = book001Canvas.GetComponent("Canvas");
}
else
{
    // Recover from not finding an object with the Book001Canvas tag
}

C#中对象的实例

Instance of an object in C#

c#

unity3d