different color on each line in textview

Question

I'm having issues trying to set a different color on each line depending on the first character. This is what I currently have. Nothing ever populates in the textview.

TextView output=(TextView) findViewById(R.id.textView1);
    File file = new File("/sdcard/file.txt");
    StringBuilder text = new StringBuilder();
    try {
        BufferedReader br = new BufferedReader(new FileReader(file));
        String line;
        while ((line = br.readLine()) != null) {
            if (line.substring(0,1).equals("r")) {
                appendColoredText(output, line, Color.RED);
            } else if (line.substring(0,1).equals("y")) {
                appendColoredText(output, line, Color.YELLOW);
            } else if (line.substring(0,1).equals("c")) {
                appendColoredText(output, line, Color.CYAN);
            } else {
                appendColoredText(output, line, Color.BLACK);
            }
            //text.append('\n');
        }
        output.setText(text);
    }
    catch (IOException e) {
        Toast.makeText(getApplicationContext(),"Error reading file!",Toast.LENGTH_LONG).show();
        e.printStackTrace();
    }

public static void appendColoredText(TextView tv, String text, int color) {
    int start = tv.getText().length();
    tv.append(text);
    int end = tv.getText().length();

    Spannable spannableText = (Spannable) tv.getText();
    spannableText.setSpan(new ForegroundColorSpan(color), start, end, 0);
}

Answer 1

public void displayOutput()
{
    TextView output=(TextView) findViewById(R.id.textView1);
    output.setMaxLines(20000);
    //File sdcard = Environment.getExternalStorageDirectory();
    File file = new File("/sdcard/file.txt");
    try {
        BufferedReader br = new BufferedReader(new FileReader(file));
        String line;
        while ((line = br.readLine()) != null) {
            if (line.substring(0,1).equals("R")) {
                appendColoredText(output, line, Color.RED);
            } else if (line.substring(0,1).equals("Y")) {
                appendColoredText(output, line, Color.YELLOW);
            } else if (line.substring(0,1).equals("C")) {
                appendColoredText(output, line, Color.CYAN);
            } else {
                appendColoredText(output, line, Color.WHITE);
            }   
        }
    }
    catch (IOException e) {
        Toast.makeText(getApplicationContext(),"Error reading file!",Toast.LENGTH_LONG).show();
        e.printStackTrace();
    }
}

public static void appendColoredText(TextView tv, String text, int color) {
    int start = tv.getText().length();
    tv.append(text);
    int end = tv.getText().length();
    Spannable spannableText = (Spannable) tv.getText();
    spannableText.setSpan(new ForegroundColorSpan(color), start, end, 0);
    tv.append("\n");
}

This is the code that ended up working for me

My goal was to read a text file line by line and depending on the first character of the line assign that line in a textview a color. My problem with the original code was that nothing ever showed up in the textview in any color.