Forty-four practical Android skills: Hello, Native!

Forty-four practical Android skills: Hello, Native!

Running C Programs on Android is a little unfamiliar with top-layer apps, because the development of Android apps is still far from Java.
However, for underlying driver developers, this is common because Android is a Linux Branch and the underlying is a world of C/C ++.

Sometimes, to test some functions, we also write C Programs that run directly on the Android terminal. The premise is that you have the root permission for the Android cross compiler and Android system.

Cross-compilation tool

Ndk has done a lot of work for us to develop native programs. Next we will separate the Android cross-compilation tool from ndk.
My system is 64-bit Ubuntu 14.04, So I downloaded the 64-bit ndk (android-ndk-r10e-linux-x86_64.bin ).

ndk$ chmod a+x android-ndk-r10e-linux-x86_64.binndk$ ./android-ndk-r10e-linux-x86_64.bin

Now, ndk can work. Let's change the cross-compilation tool.

$ ./build/tools/make-standalone-toolchain.sh --platform=android-19 --toolchain=arm-linux-androideabi-4.9Copying prebuilt binaries...Copying sysroot headers and libraries...Copying c++ runtime headers and libraries...Creating package file: /tmp/ndk-linc/arm-linux-androideabi-4.9.tar.bz2Cleaning up...Done.

Find the appropriate path and decompress it:

build-tools$ tar jxvf arm-linux-androideabi-4.9.tar.bz2arm-linux-androideabi-4.9/...

Hello, native

Compile the main_test.c file.

#include 
  
   int main() {    printf(just a test,linc!hello, native!);    return 0;}
  

Compile it:

$ ~/bin/build-tools/arm-linux-androideabi-4.9/bin/arm-linux-androideabi-gcc -o main_test main_test.c

Run:
Copy main_test to Android and run:

$ adb push main_test /data/app137 KB/s (6192 bytes in 0.043s)$ adb shellroot@hammerhead:/ # cd data/app                                               root@hammerhead:/data/app # lsmain_testroot@hammerhead:/data/app # ./main_test                                       just a test,linc!hello, native!

As we wish, the program runs smoothly, just like in Linux. Next we will compile the program for two files.
Shooter. c

#include shooter.h#include 
  
   void bubble_sort(int *array,int n) {    int i,j,tmp;    for(i=0;i
   
    i;j--) {            if(array[j-1]>array[j]) {                tmp = array[j-1];                array[j-1]=array[j];                array[j]=tmp;            }        }    }}int A(int a) {    int n = 10;    int i;    int array[] = {54,12,346,5,23,67,234,324,45,98};        for(i=0;i
    
   
  

shooter_tester.c

#include  #include shooter.hint main() { int result = A(0); printf(A result: %d,result); return 0;} 

Compile and run it:

$ ~/bin/build-tools/arm-linux-androideabi-4.9/bin/arm-linux-androideabi-gcc -o test shooter_tester.c shooter.c $ adb push test /data/app/143 KB/s (6344 bytes in 0.043s)$ adb shellroot@hammerhead:/ # cd data/app root@hammerhead:/data/app # ./test 54, 12, 346, 5, 23, 67, 234, 324, 45, 98, A result: 5

Use random number

Next, try to test the code in "do a dynamic link library" in Android and try to port this so to the Android platform.
Shooter. c only generates random numbers using rand and srand.

#include shooter.h#include  #include  void bubble_sort(int *array,int n) { int i,j,tmp; for(i=0;i  i;j--) { if(array[j-1]>array[j]) { tmp = array[j-1]; array[j-1]=array[j]; array[j]=tmp; } } }}int A(int a) { int n = 10; int i; int array[n]; srand(time(NULL)); for(i=0;i    

The problem only occurs during compilation:

 error: undefined reference to 'srand' error: undefined reference to 'rand'

The header file of the random number method is changed to stdlib.
45 of Android issues: undefined reference to 'srand'
The compilation and running results are as follows:

$ ~/bin/build-tools/arm-linux-androideabi-4.9/bin/arm-linux-androideabi-gcc -o test shooter_tester.c shooter.c $ adb shellroot@hammerhead:/ # cd data/app root@hammerhead:/data/app # ./test 18, 95, 91, 55, 13, 37, 74, 85, 83, 66, A result: 13root@hammerhead:/data/app # ./test 59, 100, 84, 32, 26, 46, 11, 50, 44, 83, A result: 11

Conclusion

Now, you can use Android as a Linux player. Have a good time!