scroll - auto-scrolling TextView in android to bring text into view

Question

I have a TextView that I'm dynamically adding text to.

in my main.xml file I have the properties set to make my max lines 19 and scrollbars vertical.

in the .java file I am using textview.setMovementMethod(new ScrollingMovementMethod()); to allow for scrolling.

The scrolling works great. As soon as 19 lines are taken up, and more lines are added it starts scrolling just as it should. The problem is, I want the new text to scroll into view.

I am writing out the value for textview.getScrollY() and it stays at 0 no matter what (even if I manually scroll it down and add a new line of text).

consequently textview.scrollTo(0, textview.getScrollY()); does nothing for me.

Is there another method I should be using to obtain the vertical scroll amount for the textview? Everything I've read says that for all intents and purposes, what I'm doing should be working :/

Answer 1

Took some digging through the TextView source but here's what I came up with. It doesn't require you to wrap the TextView in a ScrollView and, as far as I can tell, works perfectly.

// function to append a string to a TextView as a new line
// and scroll to the bottom if needed
private void addMessage(String msg) {
    // append the new string
    mTextView.append(msg + "
");
    // find the amount we need to scroll.  This works by
    // asking the TextView's internal layout for the position
    // of the final line and then subtracting the TextView's height
    final int scrollAmount = mTextView.getLayout().getLineTop(mTextView.getLineCount()) - mTextView.getHeight();
    // if there is no need to scroll, scrollAmount will be <=0
    if (scrollAmount > 0)
        mTextView.scrollTo(0, scrollAmount);
    else
        mTextView.scrollTo(0, 0);
}

Please let me know if you find a case where this fails. I'd appreciate being able to fix any bugs in my app ;)

Edit: I should mention that I also use

mTextView.setMovementMethod(new ScrollingMovementMethod());

after instantiating my TextView.