2019/08/01 16:26

33

Macro

Regarding predefined macros, there is the famous predef.sf.net.

Looking for Android brings up the devices page. There:

Android

The following macros have to be included from the header file.

Type    | Macro           | Format  | Description
Version | __ANDROID_API__ | V       | V = API Version


Example

Android Version | __ANDROID_API__
1.0             | 1
1.1             | 2
1.5             | 3
1.6             | 4
2.0             | 5
2.0.1           | 6
2.1             | 7
2.2             | 8
2.3             | 9
2.3.3           | 10
3.0             | 11


Examples

#ifdef __ANDROID__
# include <android/api-level.h>
#endif

#ifdef __ANDROID_API__
this will be contained on android
#endif

#ifndef __ANDROID_API__
this will NOT be contained for android builds
#endif

#if defined(WIN32) || defined(__ANDROID_API__)
this will be contained on android and win32
#endif


If you want to include a code block for versions for a high enough version, you must first check for existence, and then you can do arithmetic comparisons:

#ifdef __ANDROID_API__
# if __ANDROID_API__ > 6
at least android 2.0.1
# else
less than 2.0.1
# endif
#endif


Multiple conditions

You can't do #ifdef FOO || BAR. The standard only defines the syntax

# ifdef identifier new-line


but you can use the unary operator defined:

#if defined(FOO) && defined(BAR)


you can also negate the result using !:

#if !defined(FOO) && defined(BAR)
this is included only if there is no FOO, but a BAR.


and of course there's a logical-or:

#if defined(FOO) || defined(BAR)
this is included if there is FOO or BAR (or both)

0
0 收藏

0 评论
0 收藏
0