Android EditText: How to create an empty bullet paragraph by BulletSpan?

I use the same title with this question, because I think my question is very similar to that one, I read and tested the accepted answer very carefully, however the accepted answer doesn't work for me. Let me describe my question:

My code looks like:

 EditText myEdit = (EditText) this.findViewById(R.id.myedit);
 myEdit.setText("a\nb\n");
 Spannable s = myEdit.getText();
 s.setSpan(new BulletSpan(30), 0, 1, Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
 s.setSpan(new BulletSpan(30), 2, 3,  Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
 s.setSpan(new BulletSpan(30), 4, 4,  Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
 myEdit.setText(s);

What I want to see is:

• a
• b
• [I want to see the 3rd bullet here, but it doesn't show up]

I tried Spannable.SPAN_INCLUSIVE_INCLUSIVE, Spannable.SPAN_INCLUSIVE_EXCLUSIVE, Spannable.SPAN_EXCLUSIVE_INCLUSIVE,Spannable.SPAN_EXCLUSIVE_EXCLUSIVE, but none of these flags works for me.

And if I use these codes:

EditText myEdit = (EditText) this.findViewById(R.id.myedit);
myEdit.setText("a\nb\nc");
Spannable s = myEdit.getText();
s.setSpan(new BulletSpan(30), 0, 1, Spannable.SPAN_EXCLUSIVE_INCLUSIVE);
s.setSpan(new BulletSpan(30), 2, 3,  Spannable.SPAN_EXCLUSIVE_INCLUSIVE);
s.setSpan(new BulletSpan(30), 4, 5,  Spannable.SPAN_EXCLUSIVE_INCLUSIVE);
myEdit.setText(s);

Then I get the expected result:

• a
• b
• c

I am working on a rich text editor, when user clicks bullet icon, I need to show an empty bullet, but now I am not sure what the problem might be, as I want to make a new empty BulletSpan (with only a dot, but no chars after it), but if there are no chars in the span's start and end, the dot doesn't show up.

It is an ugly solution, but I have not found any better - try adding an empty character in the end (something like zero-width space). This is producing the result you'd like (at least visually):

public void setBulletText(EditText myEdit, String text) {
        String[] lines = TextUtils.split(text, "\n");
        SpannableStringBuilder spannableStringBuilder = new SpannableStringBuilder();
        String line = null;
        for (int index = 0; index < lines.length; ++index) {
            line = lines[index];
            int length = spannableStringBuilder.length();
            spannableStringBuilder.append(line);
            if (index != lines.length - 1) {
                spannableStringBuilder.append("\n");
            } else if (TextUtils.isEmpty(line)) {
                spannableStringBuilder.append("\u200B");
            }
            spannableStringBuilder.setSpan(new BulletSpan(30), length, length + 1,
                Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
        }
        myEdit.setText(spannableStringBuilder);
    }

The result is:

Ideally I'd make a custom EditText class which appends this character internally, but removes it when the text is being sent to any other object.