Draw Lines for different measurements around a TextView in Android

LinesView.java

// Using https://medium.com/@orhanobut/android-and-typography-101-5f06722dd611 for reference
// Update with https://github.com/suragch/AndroidFontMetrics/blob/master/app/src/main/java/net/studymongolian/fontmetrics/FontMetricsView.java
// Need to take into account multiple lines

public class LinesView extends FrameLayout {
    private static final Paint
            RED_PAINT = new Paint(Color.RED),
            BLUE_PAINT = new Paint(Color.BLUE),
            GREEN_PAINT = new Paint(Color.GREEN),
            PURPLE_PAINT = new Paint(Color.MAGENTA);
    private final List<Line> lines = new ArrayList<>();

    public LinesView(@NonNull Context context) {
        this(context, null);
    }

    public LinesView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        setWillNotDraw(false);
        updateLines();
    }

    private void updateLines() {
        getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                TextView tv = (TextView) getChildAt(0);
                createLines(tv);
                getViewTreeObserver().removeOnGlobalLayoutListener(this);
            }
        });
    }

    private void createLines(TextView tv) {
        lines.clear();

        final int[] location = new int[2];
        tv.getLocationOnScreen(location);
        final Paint tvPaint = tv.getPaint();
        final int baseLine = tv.getBaseline();
        final Paint.FontMetrics tvFontMetrics = tvPaint.getFontMetrics();
        final float startX = location[0];
        final float stopX = tv.getMeasuredWidth() + startX;

        // Top
        final float topY = baseLine - tvFontMetrics.top;
        final Line topLine = new Line("top", startX, topY, stopX, topY, RED_PAINT);
        lines.add(topLine);

        // Ascent
        final float ascentY = baseLine - tvFontMetrics.ascent;
        final Line ascentLine = new Line("ascent", startX, ascentY, stopX, ascentY, BLUE_PAINT);
        lines.add(ascentLine);

        // Mean Line
//        final float meanLineY = tvFontMetrics.??;
//        Line meanLine = new Line("mean", startX, meanLineY, stopX, meanLineY, GREEN_PAINT);
//        lines.add(meanLine);

        // Baseline
        final Line baseLineY = new Line("base", startX, baseLine, stopX, baseLine, PURPLE_PAINT);
        lines.add(baseLineY);

        // Descent
        final float descentLineY = baseLine + tvFontMetrics.descent;
        final Line descentLine = new Line("decent", startX, descentLineY, stopX, descentLineY, BLUE_PAINT);
        lines.add(descentLine);

        // Bottom
        final float bottomLineY = baseLine + tvFontMetrics.bottom;
        final Line bottomLine = new Line("bottom", startX, bottomLineY, stopX, bottomLineY, RED_PAINT);
        lines.add(bottomLine);

        requestLayout();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        for (Line line : lines) {
            line.draw(canvas);
        }
    }

    private static class Line {
        private final String tag;
        private final float startX, startY, stopX, stopY;
        private final Paint paint;

        public Line(float startX, float startY, float stopX, float stopY, Paint paint) {
            this("line", startX, startY, stopX, stopY, paint);
        }

        public Line(String tag, float startX, float startY, float stopX, float stopY, Paint paint) {
            this.tag = tag;
            this.startX = startX;
            this.startY = startY;
            this.stopX = stopX;
            this.stopY = stopY;
            this.paint = paint;
        }

        public void draw(Canvas canvas) {
            Timber.d(toString());
            canvas.drawLine(startX, startY, stopX, stopY, paint);
        }

        @Override
        public String toString() {
            return String.format(Locale.US, "Drawing line (%1$s) at x1: %2$f, y1: %3$f, x2: %4$f, y2: %5$f",
                    tag, startX, startY, stopX, stopY);
        }
    }
}