Develop Reference

How to replace FileObserver in Android 10?

android.os.FileObserver requires a java.io.File to function.
But with Android 10 Google restricted access to everything but your app's private directory due to the famous "Storage Access Framework". Thus, accessing anything via java.io.File breaks and renders FileObserver useless unless you intend to use it in your app's private directory. However, I want to be notified when something is changed in a certain directory on external storage. I would also like to avoid periodically checking for changes.
I tried using ContentResolver.registerContentObserver(uri,notifyForDescendants,observer) and ran into some problems with that method:
Every Uri I have plugged in so far was accepted
It neither fails nor notifies if the Uri doesn't work
I cannot find any documentation telling me which Uris actually work
The only thing I got working to some extent is the following approach:
// works, but returns all changes to the external storage
contentResolver.registerContentObserver(MediaStore.Files.getContentUri("external"), true, contentObserver)
Unfortunately this includes all of the external storage and only returns Media Uris when changes happen - for example content://media/external/file/67226.
Is there a way to find out whether or not that Uri points to my directory?
Or is there a way to make registerContentObserver() work with a Uri in such a way that I get a notification whenever something in the folder has changed?
I also had no success trying various Uris related to DocumentsFile and external storage Uris.

I kept getting errors when even trying to use the base constructor such as the following -
No direct method <init>(Ljava/util/List;I)V in class Landroid/os/FileObserver; or its super classes (declaration of 'android.os.FileObserver' appears in /system/framework/framework.jar!classes2.dex)
From a comment on Detect file change using FileObserver on Android:
I saw that message (or something like that) when i was trying to use constructor FileObserver(File). Use of deprecated FileObserver(String) solved my problem.... Original FileObserver has bugs.
Full disclosure, I was using the Xamarin.Android API; however, the gist and the commenter I quoted were both working with Java. At any rate, indeed - tried again using the counterpart String constructor and I was finally able to make and use the observer. Grinds my gears to use a deprecated API, but apparently they're hanging onto it at least up to and including Android 12.0.0_r3... still, would much prefer the supported constructors actually work. Maybe there's some warrant here for filing an issue.

I found a way to implement FileObserver on Android 10 with ContentObserver, but it might only work with media files since it works with media content uris.
The uri for ContentResolver.registerContentObserver() should be the file's corresponding media uri (e.g. content://media/external/file/49) which is queried by file path.
fun getMediaUri(context: Context, file: File): Uri? {
val externalUri = MediaStore.Files.getContentUri("external")
context.contentResolver.query(
externalUri,
null,
"${MediaStore.Files.FileColumns.DATA} = ?",
arrayOf(file.path),
null
)?.use { cursor ->
if (cursor.moveToFirst()) {
val idIndex = cursor.getColumnIndex("_id")
val id = cursor.getLong(idIndex)
return Uri.withAppendedPath(externalUri, "$id")
}
}
return null
}
Then ContentObserver.onChange() will be triggered for every file change with uri: content://media/external/file/{id}; uri in ContentObserver.onChange(boolean selfChange, Uri uri) will always be content://media/external/file; only registered file will be with id (e.g. content://media/external/file/49?deletedata=false).
Does what FileObserver used to do when input uri's path matches registered uri.

I have a temporary solution for this issue, so let's see if this can help.
I start an infinite while loop watching for file created and file deleted (if you want file modified or file renamed you have to implement more) using DocumentFile. Below is my sample:
private static int currentFileIndirectory = 0;
private static final int FILE_CREATED = 0;
private static final int FILE_DELETED = 1;
private static DocumentFile[] onDirectoryChanged(DocumentFile[] documentFiles, int event) {
Log.d("FileUtil", "onDirectoryChanged: " + event);
if (event == FILE_CREATED) {
} else {
}
return documentFiles;
}
private static boolean didStartWatching = false;
private static void startWatchingDirectory(final DocumentFile directory) {
if (!didStartWatching) {
didStartWatching = true;
DocumentFile[] documentFiles = directory.listFiles();
if (null != documentFiles && documentFiles.length > 0) {
currentFileIndirectory = documentFiles.length;
}
new Thread(new Runnable() {
public void run() {
while (true) {
DocumentFile[] documentFiles = directory.listFiles();
if (null != documentFiles && documentFiles.length > 0) {
if (documentFiles.length != currentFileIndirectory) {
if (documentFiles.length > currentFileIndirectory) {//file created
DocumentFile[] newFiles = new DocumentFile[documentFiles.length - currentFileIndirectory];
onDirectoryChanged(newFiles, FILE_CREATED);
} else {//file Deleted
onDirectoryChanged(null, FILE_DELETED);
}
currentFileIndirectory = documentFiles.length;
}
}
}
}
}).start();
}
}

Copy image to resources Xamarin

I have a Xamarin Forms project in which I need the user to be able to "load" an image. I can already press a button and search for a file using FilePicker like this:
async void OnUpload(object sender, EventArgs e)
{
try
{
FileData filedata = await CrossFilePicker.Current.PickFile();
// the dataarray of the file will be found in filedata.DataArray
// file name will be found in filedata.FileName;
//etc etc.
}
catch (Exception ex)
{
}
}
What I would need now is to copy that "filedata" (the image) to the resource folder of the project in order to access to the file easily. I have tried:
await CrossFilePicker.Current.SaveFile(filedata.FileName);
but it doesn't save any file into the project folder.
Moreover, I only need it to work on UWP and Android.

The SaveFile method saves it in a very specific folder.
If you want to save it somewhere of your choosing you have to implement it with the DependencyService. IO operations are very specific to the OS, so are the filepaths. I will give you a simple example for you to build on.
Start with defining an interface in your shared code, like so:
public interface IFileManager
{
void SaveFile(Stream stream);
}
Of course, it can have other methods as well, or extra parameters if you would like to specify things like filename, that is up to you. You would also probably like some kind of return value to know what happened.
Now, per platform implement this interface. For example for Android, it could look like this:
[assembly: Xamarin.Forms.Dependency (typeof (FileManager_Android))]
public class FileManager_Android : IFileManager
{
public void SaveFile(Stream stream)
{
var dir = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDcim);
        string filename = System.DateTime.Now.ToString("yyyyMMddHHmmssfff") + ".jpg";
string filePath = System.IO.Path.Combine(dir, name);
try
        {
         System.IO.File.WriteAllBytes(filePath, imageData);
}
catch (Exception ex)
{
System.Console.WriteLine(e.ToString());
}
}
}
(Saving code inspired by this link)
This will take the stream and save it to a path of your choosing.
For UWP you will need to implement it as well, which is quite similar, except for the implementation of SaveFile. As far as I know there is no plugin yet which makes this easier for you. There is PCLStorage, but this plugin only seems to work with text files. You could still look into it for inspiration though.

In Unity, how can I populate this allRoundData array from a json file in a way that works on Android?

I am new to Unity and Android development, but please do not mark this as a duplicate - I've looked all over the stacks for an answer to this, but similar topics and questions haven't yielded any working solutions, or are wanting on details, or outdated, or seem not to fit my specific need.
Ok, I have a quiz app built from following part 1 & 2 of this tutorial. That link contains all the source files anyone might need for reference, and everything works fine on ios and in the unity editor, fyi.
The trouble is with the loadGameData function from the DataController script in Android. Again, everything works fine in iOS and the unity editor, but when I make an Android sdk, the quiz is blank and the console says the data couldn't be loaded.
Here is how the function is currently written (full file in tutorial link):
private void LoadGameData ()
{
string filePath = Path.Combine (Application.streamingAssetsPath, gameDataFileName);
if (File.Exists (result))
{
string dataAsJson = File.ReadAllText (result);
GameData loadedData = JsonUtility.FromJson<GameData> (dataAsJson);
allRoundData = loadedData.allRoundData;
} // #if(File.Exists...
else
{
Debug.LogError ("Cannot load game data!");
} // #else
} // #LoadGameData
If you check the same tutorial on youtube, you'll see lots of people have noted the same problem with the Android build and have been left unanswered. Same goes with unity forums - that's one reason why I don't think this question is a duplicate and could be helpful to others in a similar situation.
I've found that Android has always been sorta tricky with this and that there used to different ways of accessing a file based on platform, but these days "Application.streamingAssetsPath" should find the streaming assets directory on any platform, even Android.
What I've also learned is that in android, even if the path is correct, the file is compressed and will only return a url. So the url needs to be converted using unity's WWW class. I get that, but as of yet, I haven't been able to re-write my loadGameData function to work properly and load the allRoundData array.
Here's an example of some things I've tried:
IEnumerator androidData()
{
string filePath = Path.Combine (Application.streamingAssetsPath, gameDataFileName);
if (filePath.Contains("://"))
{
WWW www = new WWW(filePath);
yield return www;
result = www.text;
} // #if(filePath.Contains
} // #androidData
private void LoadGameData ()
{
androidData();
if (File.Exists (result))
{
string dataAsJson = File.ReadAllText (result);
GameData loadedData = JsonUtility.FromJson<GameData> (dataAsJson);
allRoundData = loadedData.allRoundData;
} // #if(File.Exists...
else
{
Debug.LogError ("Cannot load game data!");
} // #else
} // #LoadGameData
I know I'm close, and this is probably simple -- but I just can't seem to get to the finish line on this. Can some one help me figure out how to write the loadGameData function so it will load this allRoundData array on android?
An example code would be awesome and much appreciated, not just by me, but I'm sure many others would appreciate it also - Thank you!
UPDATE:
Based on the first answer, I've tested some code that works on the unity editor, but crashes in Android. In the Unity editor, I get the "file already exists" message. Here is the code I've tested:
Already had: private string gameDataFileName = "data.json";
I added the copyFile call above loadGameDate in Start() and wrote the copy file and loadGameData functions like so ..
int copyFileToPersistentDataPath(string gameDataFileName)
{
string persistentPath = Application.persistentDataPath + "/" + gameDataFileName;
try
{
//Copy only if gameDataFileName does not exist
if (!System.IO.File.Exists(persistentPath))
{
string path = System.IO.Path.Combine(Application.streamingAssetsPath, gameDataFileName);
WWW www = new WWW(path);
while (!www.isDone) { }
System.IO.File.WriteAllBytes(persistentPath, www.bytes);
Debug.Log(gameDataFileName + " Successfully Copied File to " + persistentPath);
return 1;
}
else
{
Debug.Log(gameDataFileName + " File already exist here. There is no need to copy it again");
return 0;
}
}
catch (Exception e)
{
Debug.Log(gameDataFileName + " Failed To Copy File. Reason: " + e.Message);
return -1;
}
}
private void LoadGameData ()
{
string tempPath = Path.Combine(Application.persistentDataPath, gameDataFileName);
string dataAsJson = File.ReadAllText(tempPath);
GameData loadedData = JsonUtility.FromJson<GameData>(dataAsJson);
allRoundData = loadedData.allRoundData;
} // #LoadGameData
This works with or without the call to copy the file in the editor, but crashes either way in Android.

I ended up putting the files in a Resources folder and going the resources.load a json file into a text asset and throw that into a string to parse route. I now have two different load functions, one that works in ios etc. and one that works in android. Here is the android function (the resourcesGameDataFile does not have the .json extension):
public void LoadDataForAndroid()
{
TextAsset dataFile = Resources.Load(resourcesGameDataFile) as TextAsset;
string dataAsJson = dataFile.ToString();
GameData loadedData = JsonUtility.FromJson<GameData>(dataAsJson);
allRoundData = loadedData.allRoundData;
Debug.Log ("Android data loaded with" + resourcesGameDataFile);
} // #LoadDataForAndroid
And this works in the unity editor and in Bluestacks (android simulator).

As for loading and saving games, this is a duplicate. I marked and remove this as a duplicate because the answer in the duplicated questions did not explain how to read from the StreamingAssets folder. It only talked about saving and loading data.
Make sure that Write Permission is set to External (SDCard).
The first thing to do is to copy the file from StreamingAssets to the persistentDataPath location.
I've found reading data from Application.streamingAssetsPath problematic but I use two methods to solve this.
int copyFileToPersistentDataPath(string fileNameWithExtensionName)
{
string persistentPath = Application.persistentDataPath + "/" + fileNameWithExtensionName;
try
{
//Copy only if fileNameWithExtensionName does not exist
if (!System.IO.File.Exists(persistentPath))
{
string path = System.IO.Path.Combine(Application.streamingAssetsPath, fileNameWithExtensionName);
WWW www = new WWW(path);
while (!www.isDone) { }
System.IO.File.WriteAllBytes(persistentPath, www.bytes);
Debug.Log(fileNameWithExtensionName + " Successfully Copied File to " + persistentPath);
return 1;
}
else
{
Debug.Log(fileNameWithExtensionName + " File already exist here. There is no need to copy it again");
return 0;
}
}
catch (Exception e)
{
Debug.Log(fileNameWithExtensionName + " Failed To Copy File. Reason: " + e.Message);
return -1;
}
}
If that does not work for you, use the method with WebClient below:
void copyFileToPersistentDataPath(string fileNameWithExtensionName)
{
string path = System.IO.Path.Combine(Application.streamingAssetsPath, fileNameWithExtensionName);
string persistentPath = Application.persistentDataPath + "/" + fileNameWithExtensionName;
Debug.Log("Dir: " + persistentPath);
WebClient webClient = new WebClient();
webClient.Proxy = null;
webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(OnDownloadComplete);
webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(OnUpdateDownloadProgress);
Uri uri = new Uri(path);
webClient.DownloadFileAsync(uri, persistentPath);
}
void OnDownloadComplete(object sender, AsyncCompletedEventArgs e)
{
Debug.Log("Finished Downloading: " + e.Error.Message);
}
void OnUpdateDownloadProgress(object sender, DownloadProgressChangedEventArgs e)
{
Debug.Log("Uploading Progreess: " + e.ProgressPercentage);
}
File Copy Usage:
copyFileToPersistentDataPath("yourFileName.txt");
After copying the file, you can then read and convert it to Json like this:
string fileNameWithExtensionName = "questionfile.txt";
string tempPath = Path.Combine(Application.persistentDataPath, fileNameWithExtensionName);
string dataAsJson = File.ReadAllText(fileNameWithExtensionName);
GameData loadedData = JsonUtility.FromJson<GameData>(dataAsJson);

WWW.LoadFromCacheOrDownload is not working in augmented reality app on android phone using unity

I am trying to build an augmented reality app and in that app i want some prefabs to load dynamically. So that with some 3d model prefabs on unity store i created myasset.unity3d . I am using WWW.LoadFromCacheOrDownload to download that unity3d file and using it.
When i am debugging in my laptop the file is downloading and i am using it as i want but when i add build in and try it on android phone download is not happening.
The code i am using to download is
IEnumerator DownloadAndCache() {
while (!Caching.ready)
yield return null;
string bundleURL = "http://s3-ap-southeast-1.amazonaws.com/cf-export/sofa.unity3d";
www = WWW.LoadFromCacheOrDownload (bundleURL, 1);
yield return www;
Debug.Log (www.assetBundle);
AssetBundle bundle = www.assetBundle;
}
So please help me .
i also tried other way of doing it but still i did not succeed
IEnumerator Start () {
WWW www = WWW.LoadFromCacheOrDownload (BundleURL, 1);
yield return www;
AssetBundle bundle = www.assetBundle;
AssetBundleRequest request = bundle.LoadAssetAsync (AssetName, typeof(GameObject));
yield return request;
GameObject obj = request.asset as GameObject;
Instantiate (obj);
bundle.Unload(false);
www.Dispose();
}
The above two methods are working in when testing in unity IDE but if i build using android and install it in android device its not working. I gave internet access to app while building
I printed the error using a text in mobile and please check the screen shot attached below
the first error text is www (variable for downloading) and second is www.error ( actual error). i did not get what that error meant. So please help me

the issue is asset bundle version is not sync with app version. So while making asset bundle i added small code which made my code working. To make Asset bundle my code is
using UnityEditor;
public class CreateAssetBundles
{
[MenuItem ("Assets/Build AssetBundles")]
static void BuildAllAssetBundles ()
{
BuildPipeline.BuildAssetBundles ("Assets/AssetBundles", BuildAssetBundleOptions.None, BuildTarget.Android);
}
}

To use AssetBuundle for Mobile platform:
While creating AssetBundle it must be platform specific. For Android use following Script to create AssetBundle. put it inside "Editor"
using UnityEngine;
using System.Collections;
using UnityEditor;
public class ExportAssetBundles : Editor {
[MenuItem("Assets/Build AssetBundle")]
static void ExportResource()
{
string path = "Assets/AssetBundle/myAssetBundle.unity3d";
Object[] selection = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);
BuildPipeline.BuildAssetBundle(Selection.activeObject, selection, path,
BuildAssetBundleOptions.CollectDependencies
| BuildAssetBundleOptions.CompleteAssets,BuildTarget.Android);
}
}
Then Create folder "AssetBundle" inside Asset
When you create Assetbundle the AssetBundle.unity3d file will store inside this folder
Now you need to use Created Assetbundle at runtime. For this,
Write a script AssetBundleAugmenter
public class AssetBundleAugmenter : MonoBehaviour {
public string AssetName;
public int Version;
private GameObject mBundleInstance = null;
private bool mAttached = false;
void Start() {
StartCoroutine(DownloadAndCache());
}
// Update is called once per frame
IEnumerator DownloadAndCache() {
while(!Caching.ready)
yield return null;
//you can use remote URL like: www.arprabhu.com/assetBundle OR Local URL
// example URL of file on PC filesystem (Windows)
// string bundleURL = "file:///D:/Unity/AssetBundles/MyAssetBundle.unity3d";
// example URL of file on Android device SD-card
string bundleURL = System.IO.File.ReadAllText("/mnt/sdcard/filepath.txt");
Debug.Log ("Asset Loaded");
using (WWW www = WWW .LoadFromCacheOrDownload(bundleURL, Version)) {
yield return www;
if (www .error != null)
throw new UnityException("WWW Download had an error: " + www .error);
AssetBundle bundle = www .assetBundle;
if (AssetName == "")
Instantiate(bundle.mainAsset);
else
Instantiate(bundle.LoadAsset(AssetName));
// Unload the AssetBundles compressed contents to conserve memory
bundle.Unload(false);
}
}}
Attach this Script to Empty GameObject in your Scene
Congrats!, you are ready to go.

Try checking your androidManifest.xml for the permission to connect to external servers.
Then, if everything seems alright and still doesn't work, my advice is to download the Device Console plugin for the Unity Editor, which is a really nice way to access the internal Android Debugger.
https://www.assetstore.unity3d.com/en/#!/content/44935
Or if you're truly brave: use logcat within the terminal...

How to get screenshot saved path by Cocos2d-x on android

I use saveToFile method to save screenshot, and I check CCLOG, it shows /data/data/com.xxx.xxx/files/xxx.png
However, when I use Java to get this file, it says "No such file or directory"....
What can I do?

I had the same problem. Apparently, cocos2dx never creates the writable path directory so the screenshot doesn't get saved.
My solution was to, instead of calling CCRenderTexture::saveToFile, copy its implementation and manually save the file to a different path:
std::string MyClass::takeScreenshot(CCScene* scene) {
cocos2d::CCSize screenSize = cocos2d::CCDirector::sharedDirector()->getWinSize();
cocos2d::CCRenderTexture* tex = cocos2d::CCRenderTexture::create(screenSize.width, screenSize.height);
tex->setPosition(ccp(screenSize.width/2, screenSize.height/2));
//use a different dir than cocos default writable path
std::string filename = "/sdcard/Android/data/screenshot.png";
tex->begin();
scene->getParent()->visit();
cocos2d::CCImage* img = tex->newCCImage(true);
img->saveToFile(filename.c_str(), true);
CC_SAFE_DELETE(img);
tex->end();
return filename;
}

I also had the same problem. When I try renderTexture->saveToFile method, I can't submit path to java. No matter, I used getWritablePath() or set the path directly "/sdcard/Android/data/com.xxx.xxx/snapshot.jpg".
I try also to solve this problem on the advice of Facundo Olano. But CCImage compose only solid black image.
Finally I combine this two methods. First, I make an image by renderTexture->saveToFile:
void MyScene::pressFaceBook()
{
...
RenderTexture* renderTexture = RenderTexture::create(sharedImage->getBoundingBox().size.width, sharedImage->getBoundingBox().size.height, Texture2D::PixelFormat::RGBA8888);
renderTexture->begin();
sharedImage->visit();
renderTexture->end();
renderTexture->saveToFile("snapshot.jpg", Image::Format::JPG);
const std::string fullpath = FileUtils::getInstance()->getWritablePath() + "snapshot.jpg";
sharedImage->setVisible(false);
this->runAction(Sequence::create(DelayTime::create(2.0f),
CallFunc::create(std::bind(&MyScene::shareFaceBook, this, fullpath)),
NULL));
}
And then I use initWithImageFile with the transferred file name:
void MyScene::shareFaceBook(const std::string& outputFile)
{
const std::string joutputFile = "/sdcard/Android/data/com.xxx.xxx/snapshot.jpg";
cocos2d::Image* img = new Image;
img->initWithImageFile(fullpath);
img->saveToFile(joutputFile);
CC_SAFE_DELETE(img);
singleton->shareFaceBook(joutputFile);
}
A delay of 2 seconds is needed to capture the screenshot.
Of course, instead com.xxx.xxx you must substitute your app name.