TextView可滑动，并保持显示最后一行

1 设置可以滑动：
布局中： android:scrollbars=“vertical”
代码中：tv_text_hint.movementMethod = ScrollingMovementMethod.getInstance()
2 显示最后一行文字：

 val offset = getTextHintViewHeight(tv_text_hint)
                    if (offset > tv_text_hint.height) {
                        tv_text_hint.scrollTo(0, offset - tv_text_hint.height)
                    }
 
    private fun getTextHintViewHeight(view: TextView): Int {
        val layout = view.layout
        val desired = layout.getLineTop(view.lineCount)
        val padding = view.compoundPaddingTop + view.compoundPaddingBottom
        return desired + padding
    }