Data Storage - How to read/write files

Hi everybody, greetings from Colombia!.

We are porting an iPad application to Android tablet, that use a lot write and read data from the disk(memory). On the iPad and Editor we get the cache path in this way:

Code (csharp):

1.  
2. public string GetCachePath ()
3. {
4.        
5.             string cachePath="Noset";
6.            
7.         if (Application.isEditor) {
8.             return "cache/";
9.         }
10.        
11.         if(Application.platform == RuntimePlatform.IPhonePlayer)
12.         {
13.             //for iPhone
14.             //path should be <Application_Home>/Library/Caches
15.             //app data Path is /<Application_Home>/AppName.app/Data    
16.             string dataPath = Application.dataPath;
17.             cachePath = dataPath.Replace ("/Data", "");
18.             //find index of "/" in /AppName.app
19.             int index = cachePath.LastIndexOf ("/");
20.             cachePath = cachePath.Substring (0, cachePath.Length - (cachePath.Length - index));
21.             cachePath = cachePath + "/Library/Caches/";
22.         }
23. ...
24.  

So, first thanks for the RC2 that fix Application.dataPath on Android just in time but it´s seems that is not enough to write files, we are trying this:

Code (csharp):

1.     if(Application.platform == RuntimePlatform.Android)
2.         {
3.         //  Application.dataPath returns: /data/app/net.xorgames.mapp.apk/
4.        
5.                  // maybe the cache path should be this:
6.         // -> /data/<package_name>/files/     OR
7.         // /Android/data/<package_name>/cache/
8.            
9.             string dataPath = Application.dataPath;
10.            
11.             cachePath = dataPath.Replace(".apk", "/files/");
12.             cachePath = cachePath.Replace("app/", "");
13.            
14.         }
15. ...

But doesn´t work according with Android SDK Documentation: http://developer.android.com/guide/topics/data/data-storage.html , there are different locations to write a file, and each one is calling by a method that returns the FileStreaming ready to use and not a path.

We pretend to use internal or external(SD memory) storage.

Any info to solve this is welcome

thanks!

 

thank you Enrique!, i´m going to try this way and tell how it works :wink:

 

Is all this still necessary just to get a path to a writable folder? Seems like it would have been added to Unity by now.

 

+3

Wouldn't it make sense for 'Application.dataPath' to return a writable directory on all platforms - iOS, Android, Mac, PC, etc?

I started an idea on the wish-list, click below to vote it up:

http://feedback.unity3d.com/forums/...apath-return-writable-directory-on-?ref=title

 

Hello, I'm testing the android output, thus i'm interest for the exemple. But when I try to access it, I have the page 403...
Can you help me, please?
Thanks

 

Is this still the only way to get a path to a folder we can write to? I agree with the earlier suggestion that Application.datapath should return a useable folder on all platforms. Couldn't we at least have a few prebuilt plugins for things like this which are currently missing/broken? Surely it couldn't take long if you know what you're doing, but it's reinventing the wheel for us all to do it independently.



EDIT: Well here's some C++ code which apparently works. Now all I have to do is figure out the NDK, the JDK, how plugins work and I'm there.

Code (csharp):

1.    1. JNIEXPORT void JNICALL Java_com_jongwook_test_TestActivity_test(JNIEnv * env, jobject obj)  
2.    2. {  
3.    3.  jclass cls = env->GetObjectClass(obj);  
4.    4.  jmethodID getFilesDir = env->GetMethodID(cls, "getFilesDir", "()Ljava/io/File;");  
5.    5.  jobject dirobj = env->CallObjectMethod(obj,getFilesDir);  
6.    6.  jclass dir = env->GetObjectClass(dirobj);  
7.    7.  jmethodID getStoragePath =  
8.    8.                        env->GetMethodID(dir, "getAbsolutePath", "()Ljava/lang/String;");  
9.    9.  jstring path=(jstring)env->CallObjectMethod(dirobj, getStoragePath);  
10.   10.  const char *pathstr=env->GetStringUTFChars(path, 0);  
11.   11.  chdir(pathstr);  
12.   12.  env->ReleaseStringUTFChars(path, pathstr);  
13.   13. }  

 

Would anyone be so kind as to modify the GetCacheDir example above to use GetFilesDir instead? I've tried. My inane ramblings on this forum alone demonstrate that I've tried. I can't do it though. I can't even understand what is there. It grabs a method called getActivityCacheDir but googling that function name turns up precisely zero, so where am I suppose to get this method name from?

EDIT: Oh never mind. I thought this circumvented all the SDK stuff, but I see now that it doesn't. So disregard.

 

well, there's an Application.persistentDataPath and Application.temporaryCachePath for that reason in Unity 3.2. No need to use any Java code.

Anyway, here's a small project that saves and deletes the file using no native code. Enjoy.

 

Excellent. Thanks very much.

 

Is it still working correct or I need some changes?

I get error:
Assets/FileIO.cs(39,52): error CS0117: `System.IO.File' does not contain a definition for `CreateText'

 

Well, I can't seem to get this to work with XML using C#. I've gotten it to work on the Mac, but when
I do it on the android I don't know what goes wrong. Took a look at that zip and I seem to be doing the saving
and loading the same way and still it doesn't work.

 

Thanks Wozik!!

 

How about getting Environment.SpecialFolder on Android?
I want to load some photo from SD Card, but it keep crashing when I call this line in c#:
string path = Environment.GetFolderPath(Environment.SpecialFolder.Personal)

edit:
When I use absolute path /sdcard/ to do other file operation and use www to load local texture on sd is ok,
Just Environment.GetFolderPath(Environment.SpecialFolder.Personal) keep crashing the player on android.
Is it made not to work on android by design?

 

Environment is a part of the .NET/Mono Framework and it usually reads out the Windows special folder structure. I don't think there is such a structure for android, especially since Android basically have a per-app folder structure.

Every android app has a data folder in /data/data/com.yourcompany.yourgame.packagename/, where you have subfolders (files, databases, cache, pictures) etc. Then you also have a similar structure on the SD-card, just that the path is /sdcard/Android/com.yourcompany.yourgame.packagename/).

But the only secure way to get the right folder is by using the getExternalFilesDir, if you want to save content on the SD Card or getFilesDir for internal storage via JNI.

If you take a look at the Android Documentation, with getExternalFilesDir you get folder path to androids "specialfolders"
http://developer.android.com/refere...per.html#getExternalFilesDir(java.lang.String)

 

So accessing photo folder on android need to use JNI and call getExternalStoragePublicDirectory, and no generic way to do it?

 

what if you want to include (and access) an asset file (e.g. a sqlite database) within the apk itself?

 

Some additional info about reading/writing files in Unity can be found here: http://www.previewlabs.com/file-io-in-unity3d/

 

This may be a newcomer's question, but why not just write the data using PlayerPrefs?

 

there is hard limit of how much data you can store using prefs..

 

"there is hard limit of how much data you can store using prefs.."

I had a hard time!! to make a storing of 209 products with setInt and getInt, i needed to make 12 functions, to win to make this working.
On starts i had only 1 function. and the app have closed. and after divided it in 4 functions, and after 12.
To finaly got the android be ok.

 

Yes its better to do it the right way, don'rt know about any generic way to do this.

 

Anyone know some encryption methods in C# that work on Android?
Seems the System.Cryptography namespace is not welcome.

 

If you're using a DB you might get away with md5 hash like in the server side high scores on the wiki?

There's even a MD5 class: http://wiki.unity3d.com/index.php?title=MD5

 

This was simply for encrypting PlayerPrefs. But it seems Android doesn't like anything to do with System.Security.Cryptopgraphy

 

You can get your Android apps internal path directly from Unity without a plugin. Similar code can be used to get any other path. I spent 2 days on this . First I made my own Java plugin, but as I do not like to extend my current Activity or Application I ran into problems. Finally I pieced together how to do it directly from Unity with the following code:

Code (CSharp):

1. string path = "";
2. #if UNITY_ANDROID &&  !UNITY_EDITOR
3. try {
4.          IntPtr obj_context = AndroidJNI.FindClass("android/content/ContextWrapper");
5.          IntPtr method_getFilesDir = AndroidJNIHelper.GetMethodID(obj_context, "getFilesDir", "()Ljava/io/File;");
6.  
7.          using (AndroidJavaClass cls_UnityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer")) {
8.             using (AndroidJavaObject obj_Activity = cls_UnityPlayer.GetStatic<AndroidJavaObject>("currentActivity")) {
9.                IntPtr file = AndroidJNI.CallObjectMethod(obj_Activity.GetRawObject(), method_getFilesDir, new jvalue[0]);
10.                IntPtr obj_file = AndroidJNI.FindClass("java/io/File");
11.                IntPtr method_getAbsolutePath = AndroidJNIHelper.GetMethodID(obj_file, "getAbsolutePath", "()Ljava/lang/String;");  
12.                                
13.                path = AndroidJNI.CallStringMethod(file, method_getAbsolutePath, new jvalue[0]);                    
14.  
15.                if(path != null) {
16.                   Debug.Log("Got internal path: " + path);
17.                }
18.                else {
19.                   Debug.Log("Using fallback path");
20.                   path = "/data/data/*** YOUR PACKAGE NAME ***/files";
21.                }
22.             }
23.          }
24.       }
25.       catch(Exception e) {
26.          Debug.Log(e.ToString());
27.       }
28. #else
29.       path = Application.persistentDataPath;
30. #endif

I hope it will help some devs without Java knowledge (like myself ) to save some time and headache.