Android NDK重新導向std::cout輸出到log

標籤：android ndk

第一步，繼承std::streambuf

#include <iostream>#include <streambuf>class MyStreamBuf : public std::streambuf{enum{BUFFER_SIZE = 255,};public:MyStreamBuf(){buffer_[BUFFER_SIZE] = '\0';setp(buffer_, buffer_ + BUFFER_SIZE - 1);}~MyStreamBuf(){sync();}protected:virtual int_type overflow(int_type c){if (c != EOF){*pptr() = c;pbump(1);}flush_buffer();return c;}virtual int sync(){flush_buffer();return 0;}private:int flush_buffer(){int len = int(pptr() - pbase());if (len <= 0)return 0;if (len <= BUFFER_SIZE)buffer_[len] = '\0';#ifdef ANDROID  android_LogPriority t = ANDROID_LOG_INFO;__android_log_write(t, "mylog", buffer_);#else  printf("%s", buffer_);#endif  pbump(-len);return len;}private:char buffer_[BUFFER_SIZE + 1];};

第二步，建立MyStreamBuf對象，並指定給std::cout

MyStreamBuf g_MyStreamBuf;std::cout.rdbuf(&g_MyStreamBuf);//NOTE: std::endl會立即調用sync方法將緩衝區字元寫入log，並不只是換行用std::cout << "hello " << 123 << std::endl;std::cout << "pi = " << 3.14 << std::endl;

這樣，就可以是Eclipse的LogCat查看std::cout輸出了。

Android NDK重新導向std::cout輸出到log