QFontDatabase: Cannot find font directory

现象：

今天在银河麒麟操作系统上编译Qt 写的程序，报如下 错误：

QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.
QFontDatabase: Cannot find font directory /home/tgm/qt/qt_sdk/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from http://dejavu-fonts.org for example) or switch to fontconfig.

分析原因：这是因为Qt安装目录下没有字体文件导致的，我的Qt安装目录为：

/usr/local/Qt 5.9.2

字体目录一般在Qt安装目录下的lib/fonts下即：

/usr/local/Qt 5.9.2/lib/fonts

解决方法：

找一个安装了windows操作系统的机器，将其字体库（一般在C:\Windows\Fonts目录下，有的还很大，几百兆吧）拷贝到/usr/local/Qt 5.9.2/lib/fonts目录或者系统字体目录，如：我的银河麒麟操作系统字体存放目录为：

/usr/share/fonts

然后执行：

sudo vim /etc/profile

在其后加入如下代码：

export QT_QPA_FONTDIR=/usr/share/fonts

或

/usr/local/Qt 5.9.2/lib/fonts

重启系统即可。

注意：windows下的字体库很大，我的444MB，对于嵌入式的、磁盘空间有限的情况，请根据你要的字体进行删减，以节约空间。