Develop Reference

How to check obfuscation results of flutter app?

In native android development I could check whether my minifyEnabled had taken effect.
I used this script (in linux) which allows me to extract the apk and view the java files to see if my code is readable, or has been obfuscated :
#! /bin/bash
d2j=/work/installs/dex2jar-2.0
jdgui=/work/installs/jd-gui-1.4.0.jar
apk_loc=/work/projects/my_app/build/app/outputs/app-release.apk
mkdir -p /work/tmp/dex
rm -rf /work/tmp/dex/*
cd /work/tmp
cp $apk_loc ./app-release.zip
unzip app-release.zip -d dex
cd dex
chmod +x $d2j/*.sh
$d2j/d2j-dex2jar.sh classes.dex
java -jar $jdgui classes-dex2jar.jar
If I use this script on a flutter apk, I don't see any files containing anything related to my original code.

Flutter's dart code is compiled to native and embedded to flutter.so runtime, so decompiling flutter is not as easy as byte code of java/kotlin
However decompiling .so file is possible. You can use the toolchains inside the android ndk to perform the type of disassembling you want to
./android-ndk-r15b/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin/arm-linux-androideabi-objdump -T "flutter.so | less
but this is just give you an objdump.

FlatBuffer unable to generate .bin file

I am using FlatBuffer 1.8 release (windows flatc)
Here are few commands which i have tried in cmd windows.
C:\>C:\Flat\flatc.exe flatbuffer -b -j "C:\Akash\FlatBuffer\app\src\main\res\raw\sample_schema.fbs" "C:\Akash\FlatBuffer\app\src\main\res\raw\sample_json.json"
one more using flatbuffer jar file
C:\>C:\Akash\FlatBuffer\app\libs>flatbuffers-java-1.3.0-SNAPSHOT.jar flatc C:\Akash\FlatBuffer\app\src\main\res\raw\job_schema.fbs C:\Akash\FlatBuffer\app\src\main\res\raw\job.json
which gives me following error
sample_schema.fbs & sample_json.json is available on this link
What am I missing here?

Your command includes the word flatbuffer, which does not fit the specification of the command:
flatc.exe [OPTION]... FILE... [-- FILE...]
To fix the command, remove that word:
C:>C:\Flat\flatc.exe -b -j "C:\Akash\FlatBuffer\app\src\main\res\raw\sample_schema.fbs" "C:\Akash\FlatBuffer\app\src\main\res\raw\sample_json.json"
With this example, three files should be created: Friend.java, People.java, PeopleList.java, and sample_json.bin.

Running apktool in a bash script

I am trying to write a bash script that decompiles several .apk files using apktool. Each apk file is located in a subdirectory of the sample folder.
#!bin/bash
for item in $(ls samples);
do
for apk in $(ls "samples/$item");
do
echo ./apktool/apktool d "./samples/$item$apk"
$(./apktool/apktool d "./samples/$item$apk")
done
done
When I run the script I get the following output:
./apktool/apktool d ./samples/ADRD/53dc.apk*
Input file (./samples/ADRD/53dc.apk*) was not found or was not readable.
The input file error message is the standard for when apktool cannot find a file. However, if I run the following command in the terminal the apktool will work correctly.
./apktool/apktool d ./samples/ADRD/53dc.apk*
I have changed the permissions of all the files located in the samples folder to rw for all users. I also have tried using sudo with the shell script, but this causes the script to hang. However, when I use sudo with the apktool in the command line it also hangs. Therefore, I am not sure if using sudo with apktool is doable.
Any help is appreciated, thanks.

So it looks like this ls gives you an output with an asterisk * appended at the end of the apk filename, because the file is executable.
for apk in $(ls "samples/$item");
This is not the default behaviour of ls, you are getting this probably because you have aliased ls to ls -F or similar. To bypass the alias, rewrite the line this way:
for apk in $(\ls "samples/$item");
Notice the \ I added there.
BTW, is it normal that an apk file is executable? Perhaps you can remove the executable bit:
find samples -name '*.apk' -exec chmod -x {} \;
Also, possibly your script can be replaced with this one liner:
find samples -name '*.apk' -exec ./apktool/apktool d {} \;
Mind you, this is not exactly the same thing, because it may go deeper than two directories. If you need to limit the depth, that's possible too, see man find

how to generate apk file using a command line?

please tell me how to build apk files of a project without the use of ECLIPSE ide. i found some infos about using a batch file but i don't know how to remake it.
echo on
SET PREV_PATH=%CD%
cd /d %0\..
REM Clear bin folder
rmdir "bin" /S /Q
rmdir "gen" /S /Q
mkdir "bin" || goto EXIT
mkdir "gen" || goto EXIT
REM Set your application name
SET APP_NAME=SecureSms
REM Define minimal Android revision
SET ANDROID_REV=android-8
REM Define aapt add command
SET ANDROID_AAPT_ADD="%ANDROID-SDK%\platforms\%ANDROID_REV%\tools\aapt.exe" add
REM Define aapt pack and generate resources command
SET ANDROID_AAPT_PACK="%ANDROID-SDK%\platforms\%ANDROID_REV%\tools\aapt.exe" package -v -f -I "%ANDROID-SDK%\platforms\%ANDROID_REV%\android.jar"
REM Define class file generator command
SET ANDROID_DX="%ANDROID-SDK%\platform-tools\dx.bat" --dex
REM Define Java compiler command
SET JAVAC="%JAVABIN%\javac.exe" -classpath "%ANDROID-SDK%\platforms\%ANDROID_REV%\android.jar"
SET JAVAC_BUILD=%JAVAC% -sourcepath "src;gen" -d "bin"
REM Generate R class and pack resources and assets into resources.ap_ file
call %ANDROID_AAPT_PACK% -M "AndroidManifest.xml" -A "assets" -S "res" -m -J "gen" -F "bin\resources.ap_" || goto EXIT
REM Compile sources. All *.class files will be put into the bin folder
call %JAVAC_BUILD% src\org\secure\sms\*.java || goto EXIT
REM Generate dex files with compiled Java classes
call %ANDROID_DX% --output="%CD%\bin\classes.dex" %CD%\bin || goto EXIT
REM Recources file need to be copied. This is needed for signing.
copy "%CD%\bin\resources.ap_" "%CD%\bin\%APP_NAME%.ap_" || goto EXIT
REM Add generated classes.dex file into application package
call %ANDROID_AAPT_ADD% "%CD%\bin\%APP_NAME%.ap_" "%CD%\bin\classes.dex" || goto EXIT
REM Create signed Android application from *.ap_ file. Output and Input files must be different.
call "%JAVABIN%\jarsigner" -keystore "%CD%\keystore\my-release-key.keystore" -storepass "password" -keypass "password" -signedjar "%CD%\bin\%APP_NAME%.apk" "%CD%\bin\%APP_NAME%.ap_" "alias_name" || goto EXIT
REM Delete temp file
del "bin\%APP_NAME%.ap_"
:EXIT
cd "%PREV_PATH%"
ENDLOCAL
exit /b %ERRORLEVEL%
i got this codes from a site. (http://www.apriorit.com/our-company/dev-blog/233-how-to-build-apk-file-from-command-line)
i downloaded the source code sample and opened the batch file in there but it didn't generate it's apk file. usually the apk file is located at its bin\ right? but when i opened the folder, the file is not in there. please help me how to use this one. i'd appreciate you help.

You’ll have to have Apache ant for this one:
ant debug
This will build and sign the necessary .apk files.
For more info, please see this: http://codeseekah.com/2012/02/09/command-line-android-development-basics/
EDIT:
ant is not a part of standard Android SDK setup. You'll have to install it.
Download the latest ant zip file from The Apache Ant Project.
Extract the zip file to a folder, say c:\ant\
Add c:\ant to your path environment variable
Once these are done, you'll be able to run ant from the command line

The apk by default is located under bin and this is correct, but when you distribute source code it's better to not add any apk because a "fresh" compiled apk is always a better solution.
if you have a file called build.xml in the root of your project just do
ant debug
otherwise you need to update your project with the minimum informations required for the building phase with
android update project -t android-10 -p .
in this case android-10 is a target for your apk/app/api and you can customize this option for your targeted device.
After this you get your build.xml and everything is in place for generating an apk.

ant debug install
is actually viable if you create project with (note that you should specify the virtual device with "adb -s" command while installing if you're running multiple devices)
android create project -n <project_name>
-t <target_version> -p <path> -k <package> -a <activity>
and use this command to run on the avd (if you've started one)
adb -e shell "am start -a android.intent.action.MAIN -n com.your.package/.YourActivity"
(change -e option to -d if you're running on devices)
reference
better use "AVD Manager.exe" to start a virtual device if you don't know those command or parameters, as there're quite a lot.

One of the best example I found on Internet for creating Android APK is https://geosoft.no/development/android.html.Also you can use assembleDebug command in root directory (make sure setting gradle as environment variable), if you are using Gradle.

compile ffmpeg with android ndk r5b

compile ffmpeg with android ndk r5b.
ffmpeg 0.6.1
android ndk r5b
cygwin 1.7
build reference url : http://www.cnblogs.com/scottwong/archive/2010/12/17/1909455.html
but, ffmpeg ./configure result error! (below config.err file)
check_cc
BEGIN /tmp/ffconf.GlDiY1P8.c
1 int main(void){ return 0; }
END /tmp/ffconf.GlDiY1P8.c
/android-ndk-r5b/toolchains/arm-eabi-4.4.0/prebuilt/windows/bin/arm-eabi-gcc -fPIC -DANDROID -c -o /tmp/ffconf.1kQLpGaU.o /tmp/ffconf.GlDiY1P8.c
arm-eabi-gcc.exe: /tmp/ffconf.GlDiY1P8.c: No such file or directory
arm-eabi-gcc.exe: no input files
C compiler test failed.
so, i just try test code.
// test.c code
int main(){
return 0;
}
/android-ndk-r5b/toolchains/arm-eabi-4.4.0/prebuilt/windows/bin/arm-eabi-gcc -fPIC -DANDROID -c -o ./test.o ./test.c
ok!!!! no problem.
but,
cp ./test.c /tmp (copy to /tmp)
/android-ndk-r5b/toolchains/arm-eabi-4.4.0/prebuilt/windows/bin/arm-eabi-gcc -fPIC -DANDROID -c -o ./test.o /tmp/test.c
arm-eabi-gcc.exe: /tmp/test.c: No such file or directory
arm-eabi-gcc.exe: no input files
fail!!!
difference is only file path. /tmp directory exist, and permission is right. /home/test.c is same result.
what's wrong?

I have had a hard time to get it working in Windows, but finally I've managed to do it!
The previous posts were correct - there's a problem with Cygwin paths and Windows paths.
I have tried the solution described in the post above as the very first thing, but it was not working. Finally I've understand the reason: even if you put into your build_android.sh file the Windows path, the config for FFmpeg still contains the wrong path.
So in my case I have changed partially the config file in FFmpeg root directory from:
#set temporary file name
: ${TMPDIR:=$TEMPDIR}
: ${TMPDIR:=$TMP}
: ${TMPDIR:=/tmp}
to this:
# set temporary file name
#: ${TMPDIR:=$TEMPDIR}
#: ${TMPDIR:=$TMP}
: ${TMPDIR:=D:/InstallTools/Android/Cygwin_Root/tmp}
After this, I got it compiling.

You don't set the tmp directory. You can set it in /etc/profile or just in the terminal with export TMPDIR=/your/tmp/directory.
Notice:
1. If you compile with cygwin, the directory must be like D:/tmp. You can't use /cygdrive/d/tmp.
2. You must have the permission of the folder.

I could not get this to work either, I had the exact same problem. However I was able to compile using "android-ndk-r4". I am not sure at the moment what is causing the problem but if I ever get around to figuring it out I'll post that too.
So for now workaround is to use ndk r4.

I managed to build it, using NDK R6, cygwin. Indeed, it does not support /cydrive/ paths, simply use paths like windows; example below:
NDK=e:/AndroidSDK/NDK6
PLATFORM=$NDK/platforms/android-9/arch-arm/
PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows

If you have not solved this problem, check the last part of config.log in the ffmpeg directory; it is most likely a path or CC parameter problem.

I have been having the exact same problem with r6. I have tried Lambage's suggestion with r4 but still could not get this to work.
I have been looking into the problem quite a lot and I think I've discovered the reason.
1)configure is calling the android cross compiler which is a windows .exe file.
2)It is calling it through cygwin which uses unix file naming conventions. E.G /cygdrive/c/directory instead of C:\directory
3)It says in the android NDK toolchain documentation that the cross compilers do NOT accept cygwin style filepaths (source: NDK/docs/STANDALONE_TOOLCHAIN.html):
5.1/ Windows support:
The Windows binaries do not depend on Cygwin. The good news is that they
are thus faster, the bad news is that they do not understand the Cygwin
path specification like /cygdrive/c/foo/bar (instead of C:/foo/bar).
I'm still trying to find a way to do this. If i solve it then I'll come back and edit this post...tbc