问题描述
我正在尝试将一些使用SDL的代码转换为Java.我正在使用sdljava绑定.
I'm trying to convert to Java some code that uses SDL. I'm using the sdljava bindings.
sdljava使用SWIG作为C数据类型和Java之间的桥梁.为了获得等同于SDL_GetKeyState()的值，sdljava提供了方法SWIG_SDLEvent.SDL_GetKeyState()，该方法返回称为SWIGTYPE_p_unsigned_char的内容.
sdljava uses SWIG as the bridge between the C datatypes and Java. To get the equivalent of SDL_GetKeyState(), sdljava provides the method SWIG_SDLEvent.SDL_GetKeyState(), which returns something called a SWIGTYPE_p_unsigned_char.
当然，Java没有unsigned char类型，我不知道编译器认为该SWIG类型实际上代表Java什么.在C/C ++中正常使用SDL_GetKeyState()类似于:
Of course, Java has no unsigned char type, and I don't know what the compiler thinks this SWIG type actually represents to Java. Normal use of SDL_GetKeyState() in C/C++ would be something like:
Uint8 *ks = SDL_GetKeyState(NULL);
if ( ks[SDLK_UP] ) { /* handle Up key */ }
...，其中SDL键状态值(如SDLK_UP)索引到数组中.
... where the SDL keystate values like SDLK_UP index into an array.
但是，以下Java代码:
However, the following Java code:
SWIGTYPE_p_unsigned_char ks = SWIG_SDLEvent.SDL_GetKeyState(null);
if ( ks[SDLKeyValues.SDLK_UP] != 0) { /* handle Up key */ }
导致编译器错误，表达式的类型必须是数组类型，但已解析为SWIGTYPE_p_unsigned_char."
results in the compiler error, "The type of the expression must be an array type, but it resolved to SWIGTYPE_p_unsigned_char."
我想知道的是，在调用SWIG_SDLEvent.SDL_GetKeyState()之后，如何使用它返回的内容来检查各个键的状态?
What I want to know is, after calling SWIG_SDLEvent.SDL_GetKeyState(), how do you use what it returns to inspect the state of the individual keys?
推荐答案
我与负责SWIG Java支持的William Fulton进行了交谈，他回答:
I spoke with William Fulton, who is responsible for SWIG Java support, and he responded:
SWIGTYPE_p_unsigned_char的存在表明包装器还没有被很好地考虑过，因为该类型包装器"类对于从Java中访问不是很有用.
The existence of SWIGTYPE_p_unsigned_char indicates the wrappers have not been thought through very well as this "type wrapper" class is not very useful for access from Java.
请阅读Java章节中有关数组的解决方案- http://www.swig .org/Doc1.3/Java.html 或仅添加一个可以从Java调用的助手方法:
Please read the Java chapter for solutions for arrays - http://www.swig.org/Doc1.3/Java.html or just add in a helper method which you can then call from Java:
%inline %{
Uint8 getValueFromArray(Uint8* array, size_t i) {
return array[i];
}
%}
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