第 3 方库

Using a third-party library with Qt is a simple process. Suppose you know of a cross-platform library that accepts audio samples of a cat's meows and translates them into English words. This library is named CatWhisperer , and has several files that it provides as part of its library. Your project, MyQtApp , stores these files in a folder named 3rdparty :

MyQtApp/
- MyQtApp.pro
- src/
  - main.cpp
- 3rdparty/
  - CatWhisperer
    - include/
      - CatWhisperer.h
    - lib/
      - libCatWhisperer.so
      - CatWhisperer.lib
    - bin/
      - CatWhisperer.dll

要使用 CatWhisperer library in MyQtApp , qmake requires the location and names of the CatWhisperer libraries. Optionally, you can also:

Provide the location of the CatWhisperer source code so that you don't have to type out the full path to each file when you include them in your own code.
Choose the destination in which the MyQtApp executable will be created.

The information above is provided in the .pro file, so that qmake can parse it and produce makefiles. Makefiles contain all the information needed by your compiler and linker to produce output, whether it is an executable, another library file, etc. The next sections explain the syntax with which qmake expects you to provide this information.

源代码

To be able to write

#include <CatWhisperer.h>

而不是

#include <3rdparty/CatWhisperer/include/CatWhisperer.h>

you can provide the path to the CatWhisperer 包括 directory, using the INCLUDEPATH 变量：

INCLUDEPATH += 3rdparty/CatWhisperer/include

Library Files

To let qmake know where to find the CatWhisperer library files, use the LIBS 变量：

LIBS += -L"3rdparty/CatWhisperer/lib" -lCatWhisperer

The first part of the expression lets the linker know in which directory it should look for the library files. The double quotes are only necessary when the path contains spaces, so we could have omitted them in this example.

The second part tells the linker which libraries to link against. We have two different library files for UNIX platforms and Windows, respectively: libCatWhisperer.so and CatWhisperer.lib . It is not necessary to specify the .lib extension, nor the lib prefix (on UNIX platforms).

Destination Directory

默认情况下， qmake creates the executable in the same directory as the .pro file. We can choose our own directory using the DESTDIR 变量：

DESTDIR = bin

That's it! You can now use the CatWhisperer library in your project. The final .pro file looks like this:

TARGET = MyQtApp
TEMPLATE = app
INCLUDEPATH += 3rdparty/CatWhisperer/include
SOURCES += src/main.cpp
LIBS += -L"3rdparty/CatWhisperer/lib" -lCatWhisperer

另请参阅 qmake 手册 and Qt Creator: Adding Libraries to Projects .