Develop Reference

Android Studio link prebuilt library .so error

I'm developing an Android app using FFmpeg. I have built FFmpeg into *.so files and put them into jniLibs as follows:
src
--main
----jniLibs
------armeabi
--------libavcodec-57.so
--------libavformat-57.so
--------xx.so
While in grade script, abifilter of ndk is armeabi.
In java files, I have succeeded load these .so files and the built apk also contains them. However, when I use any API (e.g. av_register_all()) of them in a .c file under src/jni folder, build error comes:
Error:(14) undefined reference to 'av_register_all'
Error:Execution failed for task ':app:compileDebugNdk'.
com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/Users/zhouyf/Library/Android/sdk/ndk-bundle/ndk-build'' finished with non-zero exit value 2
It seems that problem exists in linker. But I found answer that just putting .so files to jniLibs/armeabi will be OK.
Do I need modify build.gradle file to link those .so files or else?
P.S.
If I don't call the API, the app will run successfully, only with warning: W/linker: libavformat-57.so: unused DT entry: type 0x6ffffffe arg 0x60e0
W/linker: libavformat-57.so: unused DT entry: type 0x6fffffff arg 0x2
Environment:
Android Studio 2.1.1
Mac OS X 10.11.5

You should add libraries as dependencies when you build by using ndk-build.
Disable default ndk-build, in your build.gradle
sourceSets.main {
jniLibs.srcDir 'src/main/libs'
jni.srcDirs = []
}
Add your own ndk-build task, in your build.gradle
def ndkDir = properties.getProperty("ndk.dir")
task ndkBuild(type: Exec) {
if (Os.isFamily(Os.FAMILY_WINDOWS)) {
commandLine ndkDir + File.separator + 'ndk-build.cmd', '-C', file('src/main/jni').absolutePath
} else {
commandLine ndkDir + File.separator + 'ndk-build', '-C', file('src/main/jni').absolutePath
}
}
tasks.withType(JavaCompile) {
compileTask -> compileTask.dependsOn ndkBuild
}
Finally, in your Android.mk, add the libraries like this.
LOCAL_MODULE := # ...
# ...
LOCAL_LDFLAGS += -L/path/of/the/libraries -lavcodec-57 -lavformat-57 ...

Running ./gradlew buildNative passes, but gradle build does not

I'm currently working on a nbk project for android. I have the current commands in my build.gradle, so that I can build from my gradle wrapper:
def ndkDir = "/Development/android-sdk-macosx/ndk-bundle"
task buildNative(type: Exec, description: 'Compile JNI source via NDK') {
commandLine "$ndkDir/ndk-build",
'-C', file('src/main/jni').absolutePath,
'-j', Runtime.runtime.availableProcessors(),
'all',
'NDK_DEBUG=1'
}
task cleanNative(type: Exec, description: 'Clean JNI object files') {
commandLine "$ndkDir/ndk-build",
'-C', file('src/main/jni').absolutePath,
'clean'
}
I am able to build using ./gradlew buildNative, but when I try gradle assembleDebug I get errors:
compiling TextRenderer.cpp failed.
/Users/user/android-ndk/san-angeles/app/src/main/jni/src/Renderers/TextRenderer.cpp:5:10: fatal error: 'ft2build.h' file not found
#include <ft2build.h>
^
1 error generated.
compiling BoxRenderer.cpp successful.
compiling triangle.cpp successful.
Finished compileSanangelesArmeabi-v7aDebugSharedLibrarySanangelesMainCpp, see full log file:///Users/user/android-ndk/san-angeles/app/build/tmp/compileSanangelesArmeabi-v7aDebugSharedLibrarySanangelesMainCpp/output.txt.
I am using a freetype library that I cross compiled with issues, but I got it passed that point (I think):
Was able to cross compile Freetype2, now what?
Edit:
I have changed my gradle build to this:
apply plugin: 'com.android.model.application'
model {
android {
...
sourceSets.main {
jniLibs.srcDir 'src/main/jni/freetype/lib'
jni.srcDirs = []
}
...
}
}
task buildNative (...){
...
}
task cleanNative (...){
...
}
But now I get this error:
Gradle sync failed: Cause: com.android.build.gradle.managed.AndroidConfig$Impl

If you don't want to struggle with the ever-changing C++ support of the experimental gradle plugin, you can simply use build.gradle generated by Android Studio. To disable automatic compilation of C++ files in the jni folder, you can override jni.srcDirs:
jni.srcDirs = []
jniLibs.srcDir 'src/main/jni/freetype/lib'
Here I override jniLibs.srcDir so that the library compiled with ndk-build will be included in the APK file.
Actually, I prefer to keep jni.srcDirs pointing at my C++ files (this way, I don't need another IDE running to work with them), and I disable the gradle tasks (somewhere in build.gradle file):
tasks.all {
task -> if (task.name.contains('compileDebugNdk') ||
task.name.contains('compileReleaseNdk'))
task.enabled = false
}
I can also teach the system to run buildNative and cleanNative when necessary:
tasks.withType(JavaCompile) {
compileTask -> compileTask.dependsOn buildNative
}
clean.dependsOn cleanNative
Note that the next version of Android Studio, 2.2 (now in public beta), makes ndk-build a first class citizen.

Android Studio: exclude gradle task from build

I wrote a small task, which updates an Android library from the web. This should only be done on request. I know, that there is a '-x' option, but this seems to apply only on gradle itself. The task gets executed whenever I try to build my project with Android Studio. Is there a way to exclude specific task from being executed?
My gradle task look like:
task downloadSDK {
print 'Downloading SDK...'
Properties properties = new Properties()
properties.load(project.rootProject.file('local.properties').newDataInputStream())
ant.get(
src: 'http://example.com/SDK.zip',
username:properties.getProperty('USERNAME', null),
password:properties.getProperty('PASSWORD', null),
dest:"${buildDir}/sdk.zip",
verbose:true)
println 'done'
}
task updateSDK(type: Copy) {
print 'Copying SDK...'
delete "src/main/java/"
def zipFile = file("${buildDir}/sdk.zip")
def outputDir = file("src/main/java")
from zipTree(zipFile)
into outputDir
println 'done'
}
updateSDK.dependsOn downloadSDK
I thought that I just have to add << to my updateSDK, but it doesn't seem to work with the Copy task.

Reading the gradle spec more deeply, I found out, that Copy is actually not a task but rather a function. So, my gradle task has to look like:
task updateSDK << {
print 'Copying SDK...'
delete "src/main/java/"
def zipFile = file("${buildDir}/sdk.zip")
def outputDir = file("src/main/java")
copy {
from zipTree(zipFile)
into outputDir
}
println 'done'
}
The difference is that I call the copy function inside a task so that doLast will work correctly.

Gradle: How to execute task after create lib.aar file?

I have gradle task which unbacks lib-debug.aar
need execute this task after crate this lib-debug.aar file
task unzip<<{
copy {
def aarFile = file("${buildDir}/outputs/aar/lib-debug.aar")
def outputDir = file("${buildDir}/outputs/eclipse")
from zipTree(aarFile)
into outputDir
}

You can just do:
unzip.dependsOn assemble
That will make it so that whenever you run the unzip task, the assemble task has to have run before.

Gradle file copy not working in Android Studio

I have the following script in build.gradle of an app project. All the println lines work fine meaning the task is run. However no files are copied. I am new to Gradle. I am probably missing something very simple. Any tip will be greatly appreciated.
assembleRelease.doLast {
android.applicationVariants.all { variant ->
if (variant.buildType.name == 'release') {
def releaseBuildTask = tasks.create(name: 'copy', type: Copy) {
println("Step A")
from 'build/outputs/apk/'
println("Step B")
into 'build/outputs/debug/'
println("Finished")
}
releaseBuildTask.mustRunAfter variant.assemble
}
}
println "copying task finished"
}
Update (2015-01-02)
I have noticed that I can do other file tasks such as deleting, renaming without any problem, but not copying.