public void check4PDF(File dir) {
    String pdfPattern = ".pdf";
    File listFile[] = dir.listFiles();
    if (listFile != null) {
        for (int i = 0; i < listFile.length; i++) {
            if (listFile[i].isDirectory()) {
                check4PDF(listFile[i]);
            } else {
                if (listFile[i].getName().endsWith(pdfPattern)) {
                    FileDetails mFileDetails = new FileDetails();
                    mFileDetails.setmFilename(listFile[i].getName());
                    mFileDetails.setmPath(listFile[i].getAbsolutePath());
                    pdfDetails.add(mFileDetails);
                }
            }
        }
    }
}
this code does not give any result in nexus.
if (!Environment.MEDIA_MOUNTED.equals(storageState)
            && !Environment.MEDIA_MOUNTED_READ_ONLY.equals(storageState)) {
        Toast.makeText(getActivity(), "SD Card not found.",
                Toast.LENGTH_SHORT).show();
    } else {
        Toast.makeText(getActivity(),
                Environment.getExternalStorageDirectory() + "",
                Toast.LENGTH_SHORT).show();
        ScanSDCardTask temp = new ScanSDCardTask(
                Environment.getExternalStorageDirectory(), getActivity());
        temp.execute(".pdf");
    }
I think it is the problem with the path please help.
 
                        
Search in this way..it is fast and efficient than your searching file..