VS2012中QT资源文件qrc加载失败(Q_INIT_RESOURCE报错)
在QT中如果需要使用资源时，会用到一个qrc文件.qrc文件本质上是一个XML文件，里面描述了相应资源的位置。一般将需要引用的资源放到与main.cpp同级的目录。我用VS2012开发QT，如果按正常的情况来建立QT，会带有一个qrc文件和对就的qrc*.cpp的文件，如下图（qrcexample.qrc和qrc_qrcexample.cpp）。
其中qrc_qrcexample.cpp是自动生成的，是在qrc名字的前面加了一个qrc_的前缀。如果这样正常添加资源文件是没有问题的，但是我却误删了qrc_qrcexample.cpp文件。等到想用qrc来加载图片时，按着正常的操作，在qrcexample.qrc中加了相应的图片，可是编译之后，怎么引用路径都无法得到图片。这到底是怎么了？找了很多资料，说是可以用Q_INT_RESOURCE在main函数中强制加载qrc文件，可是却报错了。（附：Q_INT_RESOURCE的调用方式是，Q_INT_RESOURCE(qrc文件名)，注意一定要是qrc文件名。）
一般来说，无法解析外部符号，是因为函数有定义却没有去实现。那这里的qInitResources_qrcexample(void)根本就没有定义过，又怎么可能去实现呢？那只有一种解释，该函数是由系统自动生成并实现了。现在系统生成了该函数的定义，却没有相应的实现。那怎么办？
于是网上查找资料，后面找到了一篇文章，说是系统会生成一个与qrc资源文件相对应的CPP（也就是前面误删的qrc_qrcexample.cpp）。既然误删了，那是不是可以再建一个相同的？结果证明，这种想法太天真了。因为只是建一个这样的文件，里面什么内容都没有，那不是形同虚设吗？
想着，这个文件既然是系统生成的，那必然会在系统中有所配置，可是在找遍了配置项后，都没有找到一个对应的。后面就想着，VS的工程文件中有对引用和编译信息的配置，会不是存在那里呢？如果存在了那里，那我又要如何才能分辨出哪个是呢？最后的办法就是找一个正常的来对比。立即新建一个项目test，自动生成了test.qrc和qrc_test.cpp，用UE打开test.vcxproj，是一个XML格式的文件，搜索qrc_test.cpp，果然有相应的配置信息。
<ClCompile Include="GeneratedFiles\qrc_test.cpp">
<PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
</PrecompiledHeader>
<PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
</PrecompiledHeader>
</ClCompile>依样画葫芦，用UE打开QrcExample.vcxproj，然后找到相应的位置，添加上相应的节点内容，下图的红框部分就是添加的。
然后重新加载项目，这时系统自动生成了qrc_qrcexample.cpp，其内容如下。
/****************************************************************************
** Resource object code
**
** Created by: The Resource Compiler for Qt version 5.1.1
**
** WARNING! All changes made in this file will be lost!
*****************************************************************************/
#include <QtCore/qglobal.h>
QT_BEGIN_NAMESPACE
QT_END_NAMESPACE
int QT_MANGLE_NAMESPACE(qInitResources_qrcexample)()
{
return 1;
}
Q_CONSTRUCTOR_FUNCTION(QT_MANGLE_NAMESPACE(qInitResources_qrcexample))
int QT_MANGLE_NAMESPACE(qCleanupResources_qrcexample)()
{
return 1;
}
Q_DESTRUCTOR_FUNCTION(QT_MANGLE_NAMESPACE(qCleanupResources_qrcexample))
这时再编译，已经OK了。再回过头来看一下，会看到前面报错的qInitResources_qrcexample，这个文件中已经有相应的实现了。不过，仔细的朋友会发现，这个文件已经不是在GeneratedFiles的文件夹下，而是在SourceFiles文件夹了。那会不会有影响呢？我们可以添加一些资源进去，编译后资源会被写到qrc_qrcexapmle.cpp中，那一串串的十六进制就是图片的数据。测试结果证明是OK的。
/****************************************************************************
** Resource object code
**
** Created by: The Resource Compiler for Qt version 5.1.1
**
** WARNING! All changes made in this file will be lost!
*****************************************************************************/
#include <QtCore/qglobal.h>
static const unsigned char qt_resource_data[] = {
// G:/Code/QT/QrcExample/QrcExample/images/about.png
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};
static const unsigned char qt_resource_name[] = {
// images
0x0,0x6,
0x7,0x3,0x7d,0xc3,
0x0,0x69,
0x0,0x6d,0x0,0x61,0x0,0x67,0x0,0x65,0x0,0x73,
// about.png
0x0,0x9,
0x6,0xc7,0x98,0x67,
0x0,0x61,
0x0,0x62,0x0,0x6f,0x0,0x75,0x0,0x74,0x0,0x2e,0x0,0x70,0x0,0x6e,0x0,0x67,
};
static const unsigned char qt_resource_struct[] = {
// :
0x0,0x0,0x0,0x0,0x0,0x2,0x0,0x0,0x0,0x1,0x0,0x0,0x0,0x1,
// :/images
0x0,0x0,0x0,0x0,0x0,0x2,0x0,0x0,0x0,0x1,0x0,0x0,0x0,0x2,
// :/images/about.png
0x0,0x0,0x0,0x12,0x0,0x0,0x0,0x0,0x0,0x1,0x0,0x0,0x0,0x0,
};
QT_BEGIN_NAMESPACE
extern Q_CORE_EXPORT bool qRegisterResourceData
(int, const unsigned char *, const unsigned char *, const unsigned char *);
extern Q_CORE_EXPORT bool qUnregisterResourceData
(int, const unsigned char *, const unsigned char *, const unsigned char *);
QT_END_NAMESPACE
int QT_MANGLE_NAMESPACE(qInitResources_qrcexample)()
{
QT_PREPEND_NAMESPACE(qRegisterResourceData)
(0x01, qt_resource_struct, qt_resource_name, qt_resource_data);
return 1;
}
Q_CONSTRUCTOR_FUNCTION(QT_MANGLE_NAMESPACE(qInitResources_qrcexample))
int QT_MANGLE_NAMESPACE(qCleanupResources_qrcexample)()
{
QT_PREPEND_NAMESPACE(qUnregisterResourceData)
(0x01, qt_resource_struct, qt_resource_name, qt_resource_data);
return 1;
}
Q_DESTRUCTOR_FUNCTION(QT_MANGLE_NAMESPACE(qCleanupResources_qrcexample))
除了这个方法外，还有两种方法也可以达到目的（这两种方法生成的qrc_*.cpp会在GeneratedFiles文件夹下）。
1.直接将qrc也删除，然后再建一个qrc，系统会自动生成相应的qrc_*.cpp文件。如果是一个解决方案中含有多个项目时，可能会失败，我就遇到这个问题。
2.如果是一个解决方案中的多个项目，建议将该项目独立打开，然后将qrc删除，然后再添加qrc。我是这样解决的。
另外，在引用qrc资源时要注意，是:/prefix/images/xxx.png.其中冒号是必须的，表明是引用的路径。/prefix是qrc资源文件中设置的前缀。images/xxx.png，是该图片对应qrc的相对路径。当然也可以将/prefix直接换成/，这样引用会方便一点(:/images/xxx.png)。下面是qrc的代码。
<RCC>
<qresource prefix="/prefix">
<file>images/about.png</file>
</qresource>
</RCC>
转载请注明出处http://blog.csdn.net/xxdddail/article/details/17410371。
