Unity3D C#中GUI.TextField的传递

学习了一周的Unity3D，在学习控件的时候，GUI.TextField在几乎找不到错误的情况下不断报以下错误：
NullReferenceException: Object reference not set to an instance of an object

UnityEngine.TextEditor.ClampTextIndex (System.Int32& index) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/TextEditor.cs:1379)

UnityEngine.TextEditor.set_text (System.String value) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/TextEditor.cs:40)

UnityEngine.GUI.DoTextField (Rect position, Int32 id, UnityEngine.GUIContent content, Boolean multiline, Int32 maxLength, UnityEngine.GUIStyle style, System.String secureText, Char maskChar) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUI.cs:634)

我知道是传递参数找不到为空，但是我的程序极其简单，几乎没有逻辑，最后才发现是定义String的是时候，习惯性定为了private,就因为这个找不到，望天~修改为public即可.

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