@Override protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    final int height = getHeight();
    final int bottom = height;
    final int left = mCurrText.getLeft() - mTabPadding;
    final int right = mCurrText.getRight() + mTabPadding;
    final int top = bottom - mIndicatorHeight;

    mTabPaint.setColor(mTabAlpha << 24 | (mIndicatorColor & 0xFFFFFF));
    canvas.drawRect(left, top, right, bottom, mTabPaint);

    if (mDrawFullUnderline) {
      mTabPaint.setColor(0xFF << 24 | (mIndicatorColor & 0xFFFFFF));
      canvas.drawRect(getPaddingLeft(), height - mFullUnderlineHeight,
          getWidth() - getPaddingRight(), height, mTabPaint);
    }
  }
Return whether or not this tab strip will draw a full-width underline.
This defaults to true if no background is set.

@return true if this tab strip will draw a full-width underline in the
current tab indicator color.
sample/src/main/java/android/support/v4/view/PagerTabStripV22.java