String fullPath = myEditText.getText().toString().trim();
String folderPath = fullPath.substring ( 0, fullPath.indexOf ( "/" ) );
String fileName = fullPath.substring ( fullPath.indexOf ( "/" ) + 1 );

// First Create folder by coding,

File folder = new File(Environment.getExternalStorageDirectory().toString() + folderPath );
if (!folder.exists())
{
      folder.mkdirs();
}

// Note: your path must not have recursive folders like myPath1/myPath2/myFile.txt, otherwise you need to create folder in 2 steps.

// Now creating file
File file = new File(Environment.getExternalStorageDirectory().toString() + folderPath + fileName );

if ( !file.exists() )
{
    success = file.createFile();
}

// Now your file is created, you can do writing code now onwards.