Android: How to detect a directory in the assets folder?

Question

I\'m retrieving files like this

String[] files = assetFiles.list(\"EngagiaDroid\"); 

How can we know whether it is a file or is a director

Answer 1

You can check if a File represents a directory using http://developer.android.com/reference/java/io/File.html#isDirectory(). Is that what you mean?

Answer 2

You may use list method of AssetManager. Any directory in asset should have one file at least, empty directory will be ignored when building your application. So, to determine if some path is directory, use like this:

AssetManager manager = activity.getAssets();
try {
    String[] files = manager.list(path);
    if (files.length > 0) {
        //directory
    } else {
        //file
    }
} catch (Exception e) {
    //not exists.
}

Answer 3

In your particular case, since you retrieved the files through list, you already know that these names exist. This simplifies the problem a lot. You can simply use this:

public static boolean isAssetAFolder(AssetManager assetManager, String assetPath) throws IOException {

    // Attempt opening as a file,
    try {
        InputStream inputStream = assetManager.open(assetPath); inputStream.close();
        return false; // A file indeed.
    } catch (FileNotFoundException e) {
        // We already know this name exists. This is a folder.
        return true;
    }
}

On the other hand, if you need a generic solution to detect if a certain path both exists and is a folder, you can use this:

public static boolean isAssetAFolder(AssetManager assetManager, String assetPath) throws IOException {

    // Attempt opening as a file,
    try {
        InputStream inputStream = assetManager.open(assetPath); inputStream.close();
        return false; // A file indeed.
    } catch (FileNotFoundException e) {
        // This could be a folder, or this path doesn't exist at all. Further checking needed,
        return assetPathExists(assetManager, assetPath);
    }
}

// If you are checking a file name "icon.png" inside your assets folder, the assetPath should be "icon.png".
public static boolean assetPathExists(AssetManager assetManager, String assetPath) throws IOException {

    // Assume that "" exists by default,
    if (assetPath.isEmpty()) return true;

    // Reject paths that point outside the assets folder,
    if (assetPath.startsWith("..") || assetPath.startsWith("/")) return false;

    // For other file/folder paths, we'll search the parent folder,
    File fileOrFolder = new File(assetPath);
    String parent = ((parent=fileOrFolder.getParent()) != null) ? parent : ""; // Handle null parents.
    if (!Arrays.asList(assetManager.list(parent)).contains(fileOrFolder.getName())) return false;

    // Getting this far means that the specified assetPath indeed exists. However, we didn't handle files
    // with trailing "/". For instance, "icon.png/" shouldn't be considered existing although "icon.png"
    // does.

    // If the path doesn't end with a "/", we are safe,
    if (!assetPath.endsWith("/")) return true;

    // Remove the trailing slash,
    assetPath = assetPath.substring(0, assetPath.length()-1);

    // Attempt opening as a file,
    try {
        InputStream inputStream = assetManager.open(assetPath); inputStream.close();
        return false; // It's indeed a file (like "icon.png"). "icon.png/" shouldn't exist.
    } catch (FileNotFoundException e) {
        return true; // This is a folder that exists.
    }
}

I wrote these for a web server, so I couldn't make assumptions about the shape of the input path. But it can be simplified a bit if you have some rules set. This code returns immediately once it becomes certain of the type of the asset, to avoid the extra processing overhead.