Unity 3d Importing .png via script

Question

I have a problem. When I try to import texture via script to my assets, I get this error:

Assertion failed: Assertion failed on expression: '!(o->TestHideFlag(Object::kDontSaveInEditor) && (options & kAllowDontSaveObjectsToBePersistent) == 0)' UnityEditor.AssetDatabase:CreateAsset(Object, String) Editor.TextureImportWindow:OnGUI() (at Assets/Scripts/Editor/TextureImportWindow.cs:40) UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

and this:

Could not create texture from Assets/Textures/importedTexture13.png: File could not be read UnityEditor.AssetDatabase:CreateAsset(Object, String) Editor.TextureImportWindow:OnGUI() (at Assets/Scripts/Editor/TextureImportWindow.cs:40) UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

My code:

 public class TextureImportWindow : EditorWindow
 {
     [MenuItem("Window/Pixel Terrain/Import Texture")]
     public static void ShowWindow()
     {
         GetWindow<TextureImportWindow>("Import Texture");
     }

     private Texture2D _texture;
     private string _path;

     private void OnGUI()
     {
         if (GUILayout.Button("Select File"))
         {
             _path = EditorUtility.OpenFilePanel("Choose texture", "", "png");
             if (_path.Length != 0)
             {
                 var www = new WWW("file:///" + _path);
                 _texture = Texture2D.blackTexture;
                 www.LoadImageIntoTexture(_texture);
             }
         }

         if (_texture != null)
         {
             if (GUILayout.Button("Import"))
             {
                 if (!AssetDatabase.IsValidFolder("Assets/Textures"))
                 {
                     AssetDatabase.CreateFolder("Assets", "Textures");
                 }
                 AssetDatabase.CreateAsset(_texture, "Assets/Textures/importedTexture12.png");
                 AssetDatabase.SaveAssets();
                 AssetDatabase.Refresh();
             }
         }
     }
 }

Answer 1

First of all, AssetDatabase.CreateAsset supports few extensions and png is not one of them. According to the doc, these are the supported formats:

• .mat for materials
• .cubemap for cubemaps
• .GUISkin for skins
• .anim for animations
• .asset for arbitrary other assets.)

PNG is not mentioned anywhere so you get error when you try to import it with that function. AssetDatabase.ImportAsset is more appropriate for this but since it requires a relative path, it won't work because you are using an absolute path provided from EditorUtility.OpenFilePanel.

To import png file into your project from EditorUtility.OpenFilePanel, just copy it to the destination with File.Copy or FileUtil.CopyFileOrDirectory(Recommended) then call AssetDatabase.Refresh().

Replace:

AssetDatabase.CreateAsset(_texture, "Assets/Textures/importedTexture12.png");
AssetDatabase.SaveAssets();
AssetDatabase.Refresh();

with:

FileUtil.CopyFileOrDirectory(_path, "Assets/Textures/importedTexture12.png");
AssetDatabase.Refresh();