Any simple way to log in Android NDK code?

You can use the Android logging facilities:

#include <android/log.h>#define APPNAME "MyApp"__android_log_print(ANDROID_LOG_VERBOSE, APPNAME, "The value of 1 + 1 is %d", 1+1);

Make sure you also link against the logging library, in your Android.mk file:

  LOCAL_LDLIBS := -llog

No one has posted info about different log levels so far. The answer is an attempt to make the logging "picture" full.

#include <android/log.h>#define TAG "MY_TAG"#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,    TAG, __VA_ARGS__)#define LOGW(...) __android_log_print(ANDROID_LOG_WARN,     TAG, __VA_ARGS__)#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,     TAG, __VA_ARGS__)#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,    TAG, __VA_ARGS__)

Usage:

char err[] = "wrong";LOGE("Something went %s", err);

Link Android log library as below.

Android.mk:

LOCAL_LDLIBS := -llog

CMakeLists.txt:

find_library( log-lib log )target_link_libraries( ${log-lib} )

Further reading: Logging

The easiest way is probably to redirect printf() statements to the system log (based on the "Viewing stdout and stderr" section of the official ADB reference manual.

Type these 3 commands on a command line:

adb shell stopadb shell setprop log.redirect-stdio trueadb shell start

Then you can view the output of your "printf()" statements by looking at the "LogCat" window of Eclipse Debugger, or by typing this on a command line:

adb logcat

Just be aware that since the data is buffered before transferring from the emulator or device, you should definitely flush the stdout buffer, eg:

printf("Hello, I am %d years old!\n", 30);fflush(stdout);

You should then see a log message starting with "I/stdout:"