思路：在字体改变时，重新计算行数，和宽高

Paste_Image.png

  private void refitText(String text, int textWidth, int textHeight) {
        if (textWidth > 0 && textHeight > 0) {
            /**
             * 当前的宽高
             */
            int currentWidth = textWidth - this.getPaddingLeft() - this.getPaddingRight();
            int currentHeight = textHeight - this.getPaddingBottom() - this.getPaddingTop();
            //by the line calculate allow displayWidth
            int autoWidth = currentWidth;
            float mult = 1f;
            float add = 0;
            if (Build.VERSION.SDK_INT > 16) {
                mult = getLineSpacingMultiplier();
                add = getLineSpacingExtra();
            } else {
                //the mult default is 1.0f,if you need change ,you can reflect invoke this field;
            }
            float trySize = maxTextSize;
            mTextPaint.setTextSize(trySize);
            int oldline = 1, newline = 1;
            //计算最大宽高
            while ((trySize > minTextSize)) {
                //拿到一行字体所占的宽
                int displayW = (int) mTextPaint.measureText(text);
                //拿到一行字体所占高
                int displaH = round(mTextPaint.getFontMetricsInt(null) * mult + add);
                if (displayW < autoWidth) {
                    break;
                }
                //计算最大行数
                newline = currentHeight / displaH;
                //如果行数改变了，重新计算宽度
                if (newline > oldline) {
                    oldline = newline;
                    autoWidth = currentWidth * newline;
                    continue;
                }
                //try more small TextSize
                trySize -= 1;
                if (trySize <= minTextSize) {
                    trySize = minTextSize;
                    break;
                }

                mTextPaint.setTextSize(trySize);
            }
            //setMultiLine
            if (newline >= 2) {
                this.setSingleLine(false);
                this.setMaxLines(newline);
            }
            this.setTextSize(TypedValue.COMPLEX_UNIT_PX, trySize);
        }
    }