jna 使用笔记

12 Jul 2012 in java on jna - Hits()

最近用到jna想实现获得当前用户选中文本的功能，结果发现这是个不好做的功能，后来想通过发送WM_COPY来通过粘贴板获得也是不行。只好放弃。

jna我没仔细看，只是初略了解了下。

扩展：

user32这样的类，没有完全暴露user32的接口，因此，如果有你想用的api但是jna又没封装的话，只要自己定义接口就行了,例如

public interface MyUser32 extends User32
{
	MyUser32 INSTANCE = (MyUser32) Native.loadLibrary("user32", MyUser32.class);

	WinDef.HWND GetForegroundWindow();

	long GetLastError();

	long SendMessageW(HWND hWnd, int msg, int num1, int num2);

	boolean IsClipboardFormatAvailable(int cfText);

	boolean OpenClipboard(HWND hWnd);

	void CloseClipboard();

	Pointer GetClipboardData(int format);

	boolean AttachThreadInput(int idAttach, int idAttachTo, boolean fAttach);

	int GetCurrentThreadId();

	boolean BringWindowToTop(HWND hwnd);

	int WM_KEYUP = 0x0101;

	int VK_CONTROL = 0x11;
	
	int VK_C = 0x43;

	int WM_COPY = 0x0301;
	int CF_TEXT = 1;
}

这各类中我暴露了GetForegroundWindow这样的多个user32 api。主要注意类型匹配，这个是个关键，怎样匹配可从官网文档上看:http://jna.java.net/javadoc/overview-summary.html

C Type	Native Representation	Java Type
char	8-bit integer	byte
wchar_t	platform-dependent	char
short	16-bit integer	short
int	32-bit integer	int
int	boolean flag	boolean
enum	enumeration type	int (usually)
long long, __int64	64-bit integer	long
float	32-bit floating point	float
double	64-bit floating point	double
pointer (e.g. void*)	platform-dependent (32- or 64-bit pointer to memory)	`Buffer` `Pointer`
pointer (e.g. void*), array	32- or 64-bit pointer to memory (argument/return) contiguous memory (struct member)	<P>[] (array of primitive type)
In addition to the above types, which are supported at the native layer, the JNA Java library automatically handles the following types. All but `NativeMapped` and `NativeLong` are converted to `Pointer` before being passed to the native layer.
long	platform-dependent (32- or 64-bit integer)	`NativeLong`
const char*	NUL-terminated array (native encoding or `jna.encoding`)	`String`
const wchar_t*	NUL-terminated array (unicode)	`WString`
char**	NULL-terminated array of C strings	`String[]`
wchar_t**	NULL-terminated array of wide C strings	`WString[]`
void**	NULL-terminated array of pointers	`Pointer[]`
struct* struct	pointer to struct (argument or return) (`or explicitly`) struct by value (member of struct) (`or explicitly`)	`Structure`
union	same as `Structure`	`Union`
struct[]	array of structs, contiguous in memory	`Structure[]`
void (*FP)()	function pointer (Java or native)	`Callback`
pointer (<T> *)	same as `Pointer`	`PointerType`
other	integer type	`IntegerType`
other	custom mapping, depends on definition	`NativeMapped`

具体情况那还得自己钻研，我还不是很熟。

例如一个hwnd型既可以用jna的HWND也可以用pointer,到底用哪个取决于你的需要，同时申明两个函数对应同一个api也是可行的。

像

boolean OpenClipboard(HWND hWnd);

boolean OpenClipboard(Pointer hWnd);

都是对应OpenClipboard，只是参数类型不一样,最终会转到windows api认同的类型。

继承

Myuser32 extends User32 这样的写法不能继承User32 声明的接口，如果要用User32 的接口，还是应该使用user32.instance来调用。

所以Myuser32 extends StdCallLibrary才比较合适。

java的char是unicode所以对于字符串缓存，如果java 的byte[]对应api的char,java的char[]对应api的wchar

而且应该使用Native.toString来转换到java的String。

int的指针对应IntByReference,其他类推。