How to get FileInputStream to File in assets folder

Question

I know how to use the AssetManager to read a File from the res/raw directory with an InputStream , but for my special use case I need a FileInputStream . The reason I need a FileInputStream specifically is because I need to get the FileChannel object from it by calling getChannel() .

This is the code I have so far, it reads the data (in my case a list of primitives) from a File :

public static int[] loadByMappedBuffer(Context context, String filename) throws IOException{
    FileInputStream fis = context.openFileInput(filename);
    FileChannel ch = fis.getChannel();

    MappedByteBuffer mbuff = ch.map(MapMode.READ_ONLY, 0, ch.size());
    IntBuffer ibuff = mbuff.asIntBuffer();

    int[] array = new int[ibuff.limit()];
    ibuff.get(array);

    fis.close();
    ch.close();

    return array;
} 

I had tried to create File from an Uri , but that just results in a FileNotFoundException :

Uri uri = Uri.parse("android.resource://com.example.empty/raw/file");
File file = new File(uri.getPath());
FileInputStream fis = new FileInputStream(file);

Is there a way I can get a FileInputStream to a File in the res/raw directory?

Answer 1

You can get a FileInputStream to a resource in your assets like this:

AssetFileDescriptor fileDescriptor = assetManager.openFd(fileName);
FileInputStream stream = fileDescriptor.createInputStream();

The fileName you supply to openFd() should be the relative path to the asset, the same fileName you would supply to open() .

Alternatively you can also create the FileInputStream like this:

AssetFileDescriptor assetFileDescriptor = assetManager.openFd(fileName);  
FileDescriptor fileDescriptor = assetFileDescriptor.getFileDescriptor();  
FileInputStream stream = new FileInputStream(fileDescriptor);