android copy file from assets to sd card

Question

this is MyNewMain.java

        CopyAssets();


    private void CopyAssets() {
        AssetManager assetManager = getAssets();
        String[] files = null;
        try {
            files = assetManager.list("Files");
        } catch (IOException e) {
            Log.e("tag", e.getMessage());
        }

        for(String filename : files) {
            System.out.println("File name => "+filename);
            InputStream in = null;
            OutputStream out = null;
            try {
                in = assetManager.open("Files/"+filename);
                out = new FileOutputStream(Environment.getExternalStorageDirectory().toString() +"/" + filename);
                copyFile(in, out);
                in.close();
                in = null;
                out.flush();
                out.close();
                out = null;
            } catch(Exception e) {
                Log.e("tag", e.getMessage());
            }
        }
    }
    private void copyFile(InputStream in, OutputStream out) throws IOException {
        byte[] buffer = new byte[1024];
        int read;
        while((read = in.read(buffer)) != -1){
            out.write(buffer, 0, read);
        }
    }

in my assets folder i have folder called Files. there is .txt file onCreate methed i am calling CopyAssets();

lower are the methods i used.

the problem is that this does nothing. i have absoluteli no idea why my file is not being copied. in my manifest i have added

and app.iml contains

Answer 1

I know this has been answered but I have a slightly more elegant way to copy from asset directory to a file on the sdcard. It requires no "for" loop but instead uses File Streams and Channels to do the work.

(Note) If using any type of compressed file, APK, PDF, ... you may want to rename the file extension before inserting into asset and then rename once you copy it to SDcard)

AssetManager am = context.getAssets();
AssetFileDescriptor afd = null;
try {
    afd = am.openFd( "MyFile.dat");

    // Create new file to copy into.
    File file = new File(Environment.getExternalStorageDirectory() + java.io.File.separator + "NewFile.dat");
    file.createNewFile();

    copyFdToFile(afd.getFileDescriptor(), file);

} catch (IOException e) {
    e.printStackTrace();
}

A way to copy a file without having to loop through it.

public static void copyFdToFile(FileDescriptor src, File dst) throws IOException {
    FileChannel inChannel = new FileInputStream(src).getChannel();
    FileChannel outChannel = new FileOutputStream(dst).getChannel();
    try {
        inChannel.transferTo(0, inChannel.size(), outChannel);
    } finally {
        if (inChannel != null)
            inChannel.close();
        if (outChannel != null)
            outChannel.close();
    }
}

Thanks to JPM's Answer

Answer 2

on android api 22, call getFileDescriptor() on a AssetFileDescriptor object will return the FileDescriptor of whole apk file. so @Salmaan's answer is wrong on android api 22.

I don not see the source code in other api. So i don't know the behaviour of getFileDescriptor() in other api.

I find the answer under this question .