嵌入式学习之QT学习---14 QT跨平台运行之把QT程序交叉编译到ARM开发板
想要把qt工程放到开发板上运行，就需要用到交叉编译。由于qt是跨平台的，所以只需要换个编译器编译一下就可以。
以qt学习–计时器的例子为例，在移植之前还需要进行一个准备工作，在windows下运行的时候，电脑屏幕很大，但是运行的窗口只有一点点大，开发板也有外接屏幕，如何让运行窗口自动适配开发板的外接屏幕呢？令其占满屏幕显示，而不是一小块。
一、编译生成在开发板上的可执行文件
第一步：需要设置一下，先给ui布局，如果不布局，控件就不会随着屏幕的大小的变化而变化。利用代码来获取屏幕的大小，给widget.cpp文件下添加如下代码
#include
#include
#include
QDesktopWidget *deskTopWidget = QApplication::desktop();
QRect deskRect = deskTopWidget->availableGeometry();
int appH = deskRect.height();
int appW = deskRect.width();
this->setFixedSize(appW, appH);
setGeometry(0, 0, appW, appH);
添加完后，编译运行一下，会看到现在运行结果显示框与电脑屏幕一样大。将layoutstrength处的（0,0，0）改成了（5,2，3），可以使得界面更美观。
第二步：用ssh软件把time文件夹传到ubuntu下
root@ubuntu:~# cd /home/qt/
root@ubuntu:/home/qt# ls
qt_source qt_system
root@ubuntu:/home/qt# mkdir qt_demo
root@ubuntu:/home/qt# ls
qt_demo qt_source qt_system
root@ubuntu:/home/qt# cd qt_demo/
root@ubuntu:/home/qt/qt_demo# ls
time
第三步：删掉.pro.user文件，以免影响后面
root@ubuntu:/home/qt/qt_demo# cd time/
root@ubuntu:/home/qt/qt_demo/time# ls
main.cpp time.pro time.pro.user widget.cpp widget.h widget.ui
root@ubuntu:/home/qt/qt_demo/time# rm time.pro.user
root@ubuntu:/home/qt/qt_demo/time#
root@ubuntu:/home/qt/qt_demo/time# ls
main.cpp time.pro widget.cpp widget.h widget.ui
第四步：执行make
root@ubuntu:/home/qt/qt_demo/time# make
make: *** 没有指明目标并且找不到 makefile。 停止。
显示找不到makefile，需要在命令行写上之前执行脚本文件并执行make以及make install的时候生成的文件的路径，我的在“/usr/local/Qt-5.7.0/bin/qmake ”路径下。
root@ubuntu:/home/qt/qt_demo/time# /usr/local/Qt-5.7.0/bin/qmake
Info: creating stash file /home/qt/qt_demo/time/.qmake.stash
按道理执行完这条路径指令之后应该没有任何提示的，删除生成的makefile重新执行一下
root@ubuntu:/home/qt/qt_demo/time# ls
main.cpp Makefile time.pro widget.cpp widget.h widget.ui
root@ubuntu:/home/qt/qt_demo/time# rm Makefile
root@ubuntu:/home/qt/qt_demo/time# /usr/local/Qt-5.7.0/bin/qmake
root@ubuntu:/home/qt/qt_demo/time#
root@ubuntu:/home/qt/qt_demo/time# ls
main.cpp Makefile time.pro widget.cpp widget.h widget.ui
root@ubuntu:/home/qt/qt_demo/time# make
root@ubuntu:/home/qt/qt_demo/time# ls
main.cpp Makefile moc_widget.o time.pro widget.cpp widget.o
main.o moc_widget.cpp time ui_widget.h widget.h widget.ui
生成time之后，在ubuntu界面再执行一条指令查看一下time的属性，看是否能够在开发板上运行。如果是属于ARM平台的二进制文件，则可以在开发板上执行；如果是x86-64，那就是x86上位机平台文件，不可以在开发板执行。
说明：
鉴于之前在开发板上烧写qt5.7未能成功，就选择使用早之前在开发板上可以运行的qt4.7版本了。
- 针对qt4.7版本，其
qmake文件所在路径为：/opt/qt-4.7.1/bin/qmake - 写完路径之后，执行make，如果报错
root@ubuntu:/home/qt/qt_demo/time# make
arm-linux-g++ -Wl,-O1 -Wl,-rpath,/opt/qt-4.7.1/lib -o time main.o widget.o moc_widget.o -L/opt/qt-4.7.1/lib -lQtGui -L/usr/local/tslib/lib -L/opt/qt-4.7.1/lib -lQtNetwork -lQtCore -lpthread
main.o: file not recognized: File format not recognized
collect2: ld returned 1 exit status
make: *** [time] 错误 1
root@ubuntu:/home/qt/qt_demo/time# ls
main.cpp Makefile moc_widget.o ui_widget.h widget.h widget.ui
main.o moc_widget.cpp time.pro widget.cpp widget.o
root@ubuntu:/home/qt/qt_demo/time# rm Makefile
root@ubuntu:/home/qt/qt_demo/time# /opt/qt-4.7.1/bin/qmake
root@ubuntu:/home/qt/qt_demo/time# ls
main.cpp Makefile moc_widget.o ui_widget.h widget.h widget.ui
main.o moc_widget.cpp time.pro widget.cpp widget.o
root@ubuntu:/home/qt/qt_demo/time# make
arm-linux-g++ -Wl,-O1 -Wl,-rpath,/opt/qt-4.7.1/lib -o time main.o widget.o moc_widget.o -L/opt/qt-4.7.1/lib -lQtGui -L/usr/local/tslib/lib -L/opt/qt-4.7.1/lib -lQtNetwork -lQtCore -lpthread
main.o: file not recognized: File format not recognized
collect2: ld returned 1 exit status
make: *** [time] 错误 1
解决办法：执行make clean命令，然后再执行make命令
root@ubuntu:/home/qt/qt_demo/time# make clean
rm -f moc_widget.cpp
rm -f ui_widget.h
rm -f main.o widget.o moc_widget.o
rm -f *~ core *.core
root@ubuntu:/home/qt/qt_demo/time# make
root@ubuntu:/home/qt/qt_demo/time# ls
main.cpp Makefile moc_widget.o time.pro widget.cpp widget.o
main.o moc_widget.cpp time ui_widget.h widget.h widget.ui
root@ubuntu:/home/qt/qt_demo/time# file time
time: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.3, for GNU/Linux 2.6.14, not stripped
二、开发板上电启动qt系统，执行可执行文件
我选择的是用U盘拷贝可执行文件，然后在超级终端上挂载U盘，执行该可执行文件。
~ # ls /mnt/
disk usb1
~ # mount /dev/udisk /mnt/usb1/
~ # cd /mnt/usb1/
/mnt/usb1 # ls
1.wav
myPhonon1
myPhonon11
python
scope_0.png
scope_1.png
scope_2.png
scope_3.png
t1110_success.slx
time
/mnt/usb1 # time -qws
time: invalid option -- 'q'
BusyBox v1.21.1 (2013-11-02 04:41:24 AMST) multi-call binary.
Usage: time [-v] PROG ARGS
Run PROG, display resource usage when it exits
-v Verbose
/mnt/usb1 # ./time
[ 240.998293] hub 1-0:1.0: port 3 disabled by hub (EMI?), re-enabling...
[ 241.003575] usb 1-3: USB disconnect, device number 2
[ 241.008424] usb 1-3.2: USB disconnect, device number 3
[ 241.019297] dm9620 1-3.2:1.0: eth0: unregister 'dm9620' usb-s5p-ehci-3.2, Davicom DM9620 USB Ethernet
[ 241.027855] mmc_sd_detect(mmc1): Unable to re-detect card (-123)
[ 241.033468] mmc1: card 0001 removed
[ 241.115188] dm9620_unbind():
[ 241.116630] flg_txdbg 0
[ 241.119149] rx_length_errors 0
[ 241.125103] rx_over_errors 0
[ 241.126708] rx_crc_errors 0
[ 241.129745] rx_frame_errors 0
[ 241.230112] rx_fifo_errors 0
[ 241.231719] rx_missed_errors 0
[ 241.310260] usb 1-3.3: USB disconnect, device number 4
[ 241.830040] usb 1-3: new high speed USB device number 5 using s5p-ehci
[ 241.901373] s5p-ehci s5p-ehci: port 3 reset error -110
[ 242.576434] s5p-ehci s5p-ehci: port 3 reset error -110
[ 242.850140] *******mmc1: inserted!!!!!******
[ 242.939305] mmc1: new high speed SDHC card at address 0001
[ 242.955253] mmcblk1: mmc1:0001 SD16G 14.5 GiB
[ 242.961626] mmcblk1: p1 p2 p3 p4
[ 243.196451] s5p-ehci s5p-ehci: port 3 reset error -110
[ 243.816889] s5p-ehci s5p-ehci: port 3 reset error -110
[ 244.436869] s5p-ehci s5p-ehci: port 3 reset error -110
[ 244.850336] hub 1-0:1.0: Cannot enable port 3. Maybe the USB cable is bad?
[ 244.911890] s5p-ehci s5p-ehci: port 3 reset error -110
[ 245.586859] s5p-ehci s5p-ehci: port 3 reset error -110
[ 246.206867] s5p-ehci s5p-ehci: port 3 reset error -110
[ 246.826865] s5p-ehci s5p-ehci: port 3 reset error -110
[ 247.446869] s5p-ehci s5p-ehci: port 3 reset error -110
[ 247.860332] hub 1-0:1.0: Cannot enable port 3. Maybe the USB cable is bad?
[ 247.921888] s5p-ehci s5p-ehci: port 3 reset error -110
[ 248.596869] s5p-ehci s5p-ehci: port 3 reset error -110
[ 249.216888] s5p-ehci s5p-ehci: port 3 reset error -110
[ 249.836890] s5p-ehci s5p-ehci: port 3 reset error -110
[ 250.456890] s5p-ehci s5p-ehci: port 3 reset error -110
[ 250.870335] hub 1-0:1.0: Cannot enable port 3. Maybe the USB cable is bad?
[ 250.931868] s5p-ehci s5p-ehci: port 3 reset error -110
[ 251.606868] s5p-ehci s5p-ehci: port 3 reset error -110
[ 252.226889] s5p-ehci s5p-ehci: port 3 reset error -110
[ 252.846890] s5p-ehci s5p-ehci: port 3 reset error -110
[ 253.466892] s5p-ehci s5p-ehci: port 3 reset error -110
[ 253.880497] hub 1-0:1.0: Cannot enable port 3. Maybe the USB cable is bad?
[ 253.886133] hub 1-0:1.0: unable to enumerate USB device on port 3
终于可以在开发板上跑程序啦，哭辽，经历了两天左右的时间呢。给大家浅看一下在开发板上运行的图片。