Below is the code to read a text file from SD card.

First, we have to define path of the text file to a File.

Second step is to use BufferedReader class to read line by line.

File sdcard = Environment.getExternalStorageDirectory();


File readFile = new File(sdcard,"reading.txt");

//Read text from file
StringBuilder stringBuilder = new StringBuilder();

try {
    BufferedReader bufferedReader = new BufferedReader(new FileReader(readFile));
    String str;

    while ((str = bufferedReader.readLine()) != null) {
        stringBuilder.append(line);
        stringBuilder.append('\n');
    }
    bufferedReader.close();
}
catch (IOException e) {
    System.out.println("Error : "+e.getMessage());
}

TextView messageFile = (TextView)findViewById(R.id.message_text);

messageFile.setText(text.toString());