How to Write Files to External Public Storage in Android So That They Are Visible from Windows

How to write files to external public storage in Android so that they are visible from Windows?

What is wrong with my implementation?

MediaStore has not discovered your newly-created files yet. What you see in Windows — and in many on-device "gallery" apps — is based on what MediaStore has indexed.

Use MediaScannerConnection and its scanFile() method to tell MediaStore about your file, once you have written out your data to disk:

public void scanFile(Context ctxt, File f, String mimeType) {
    MediaScannerConnection
        .scanFile(ctxt, new String[] {f.getAbsolutePath()},
                  new String[] {mimeType}, null);
}

or, in Kotlin:

fun scanFile(ctxt: Context, f: File, mimeType: String) {
  MediaScannerConnection.scanFile(ctxt, arrayOf(f.getAbsolutePath()), arrayOf(mimeType), null)
}

How to make visible the images in the gallery after insertion in the internal storage?

Give this a try:

File photosFolder = null;
if(Build.VERSION_CODES.R>Build.VERSION.SDK_INT) {
    photosFolder = new File(Environment.getExternalStorageDirectory(), "myPictures");//this will create a seperate directory in your external storage if you are using android 10 device
}
else
{
    photosFolder=new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath(),"myPictures");//though depreciated it still works.In android 11 you can create your directory inside public directories using this method.
}
if (!file.exists()) {
    file.mkdir();
}

String[] pictures = null;

try {
    pictures = assetManager.list("photos");
} catch (IOException e) {
    Log.e("tag", "Failed to get asset file list.", e);
}
for(String filename : pictures) {
    InputStream in = null;
    OutputStream out = null;
    try {
        in = assetManager.open("photos/"+filename);
        File outFile = new File(photosFolder, filename);
        out = new FileOutputStream(outFile);
        copyFile(in, out);
        in.close();
        in = null;
        out.flush();
        out.close();
        out = null;
        MediaScannerConnection.scanFile(this,
                new String[] { outFile.toString() }, null,
                new MediaScannerConnection.OnScanCompletedListener() {
                    public void onScanCompleted(String path, Uri uri) {
                        Log.i("ExternalStorage", "Scanned " + path + ":");
                        Log.i("ExternalStorage", "-> uri=" + uri);
                    } catch(IOException e) {
                        Log.e("tag", "Failed to copy asset file: " + filename, e);
                    }
                }
    }

You can check the documentation here.

How to write files to external public storage in Android so that they are visible from Windows?

What is wrong with my implementation?

MediaStore has not discovered your newly-created files yet. What you see in Windows — and in many on-device "gallery" apps — is based on what MediaStore has indexed.

Use MediaScannerConnection and its scanFile() method to tell MediaStore about your file, once you have written out your data to disk:

public void scanFile(Context ctxt, File f, String mimeType) {
    MediaScannerConnection
        .scanFile(ctxt, new String[] {f.getAbsolutePath()},
                  new String[] {mimeType}, null);
}

or, in Kotlin:

fun scanFile(ctxt: Context, f: File, mimeType: String) {
  MediaScannerConnection.scanFile(ctxt, arrayOf(f.getAbsolutePath()), arrayOf(mimeType), null)
}

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