Invoke FileDescriptor#sync after copying each file.

import android.os.RemoteException;

import android.provider.DocumentsContract;

import android.provider.DocumentsContract.Document;

import android.system.ErrnoException;

import android.system.Os;

import android.system.OsConstants;

import android.text.format.DateUtils;

import android.util.Log;

import android.webkit.MimeTypeMap;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.io.SyncFailedException;

import java.text.NumberFormat;

import java.util.ArrayList;

import java.util.List;

                    makeCopyProgress(len);

                }

                // Need to invoke Os#fsync to ensure the file is written to the storage device.

                try {

                    Os.fsync(dstFile.getFileDescriptor());

                } catch (ErrnoException error) {

                    // fsync will fail with fd of pipes and return EROFS or EINVAL.

                    if (error.errno != OsConstants.EROFS && error.errno != OsConstants.EINVAL) {

                        throw new SyncFailedException(

                                "Failed to sync bytes after copying a file.");

                    }

                }

                // Need to invoke IoUtils.close explicitly to avoid from ignoring errors at flush.

                IoUtils.close(dstFile.getFileDescriptor());

                srcFile.checkError();