unity的模型为什么在放到streamingassets文件夹下以后就不能拖到场景中了

将模型放到StreamingAssets文件夹下后，它变成了一个文件，而不再是一个Unity场景中的对象。因此，您不能再像将场景中的对象一样将它拖到场景中。如果您需要在场景中使用该模型，可以使用代码将其加载到场景中。以下是一个加载模型的示例代码：

using UnityEngine;
using System.Collections;

public class LoadModel : MonoBehaviour {

    public string modelName;
    public string modelPath;

    IEnumerator Start () {
        string path = Application.streamingAssetsPath + "/" + modelPath + "/" + modelName;

        // Load model asynchronously
        AssetBundleCreateRequest bundleCreateRequest = AssetBundle.LoadFromFileAsync(path);
        yield return bundleCreateRequest;

        AssetBundle assetBundle = bundleCreateRequest.assetBundle;
        if (assetBundle == null)
        {
            Debug.LogError("Failed to load AssetBundle!");
            yield break;
        }

        // Load model
        AssetBundleRequest assetRequest = assetBundle.LoadAssetAsync<GameObject>(modelName);
        yield return assetRequest;

        GameObject model = Instantiate(assetRequest.asset) as GameObject;
        model.transform.position = transform.position;
        model.transform.rotation = transform.rotation;

        assetBundle.Unload(false);
    }
}

在上面的示例代码中，我们使用AssetBundle加载模型，并将其实例化到场景中。您需要将modelName和modelPath设置为您模型的名称和路径。