Starting from an empty Qt for Android project, created with Qt Creator, how do I execute native Java code?
For example, if I have this java method:
class HelloJava {
public static String sayHello(int a, int b) {
return "Hello from Java, a+b=" + (a+b);
}
}
And I have this Qt method which should call the HelloJava.sayHello() method:
QString call_HelloJava_sayHello(int a, int b) {
// What goes in here?
}
Where do I put the Java code in my project, and what goes inside the call_HelloJava_sayHello() method?
The Qt doc is pretty verbose on the subject:
// Java class
package org.qtproject.qt5;
class TestClass
{
static String fromNumber(int x) { ... }
static String[] stringArray(String s1, String s2) { ... }
}
// C++ code
// The signature for the first function is "(I)Ljava/lang/String;"
QAndroidJniObject stringNumber = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/TestClass",
"fromNumber"
"(I)Ljava/lang/String;",
10);
// the signature for the second function is "(Ljava/lang/String;Ljava/lang/String;)[Ljava/lang/String;"
QAndroidJniObject string1 = QAndroidJniObject::fromString("String1");
QAndroidJniObject string2 = QAndroidJniObject::fromString("String2");
QAndroidJniObject stringArray = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/TestClass",
"stringArray"
"(Ljava/lang/String;Ljava/lang/String;)[Ljava/lang/String;"
string1.object<jstring>(),
string2.object<jstring>());
So the sig of your function should be "(I;I;)Ljava/lang/String;"
And also this:
ANDROID_PACKAGE_SOURCE_DIR: This variable can be used to specify a
directory where additions and modifications can be made to the default
Android package template. The androiddeployqt tool will copy the
application template from Qt into the build directory, and then it
will copy the contents of the ANDROID_PACKAGE_SOURCE_DIR on top of
this, overwriting any existing files. The update step where parts of
the source files are modified automatically to reflect your other
settings is then run on the resulting merged package. If you, for
instance, want to make a custom AndroidManifest.xml for your
application, then place this directly into the folder specified in
this variable. You can also add custom Java files in
ANDROID_PACKAGE_SOURCE_DIR/src.
Note: When adding custom versions of the build files (like
strings.xml, libs.xml, AndroidManifest.xml, etc.) to your project,
make sure you copy them from the package template, which is located in
$QT/src/android/java. You should never copy any files from the build
directory, as these files have been altered to match the current build
settings.
So it seems you need to specify that and the java files are automatically deployed.
Just add this to your .pro file (assuming your java sources are placed at /path/to/project/myjava/src:
android {
ANDROID_PACKAGE_SOURCE_DIR=$$_PRO_FILE_PWD_/android
QT += androidextras
}
_PRO_FILE_PWD_ is a qmake variable that will resolve to the project directory.
Related
I have a simple C++ function compiled into a dylib file that I'm trying to run on an Android phone. The function is super simple, it just adds to numbers and returns the result. However, I keep getting this error:
Another exception was thrown: Invalid argument(s): Failed to load dynamic library 'libadd.dylib': dlopen failed: library "libadd.dylib" not found .
I'm really not sure what I'm doing wrong. I've done the following steps:
My Dart implementation:
import 'dart:ffi' as ffi;
import 'dart:io' show Platform, Directory;
import 'package:path/path.dart' as path;
typedef C_ADD = ffi.Int Function(
ffi.Int a, ffi.Int b); // FFI signature of C function
typedef ADD = int Function(int a, int b);
void linkAndCallFunction() {
var libraryPath = path.join(Directory.current.path, "libadd.dylib");
final dylib = ffi.DynamicLibrary.open(libraryPath);
final ADD add = dylib.lookup<ffi.NativeFunction<C_ADD>>("add").asFunction();
final result = add(40, 2);
print(result);
}
I've added these to the build.gradle files:
build.gradle:
buildscript{
ext{
ndkVersion = "25.1.8937393"
}
...
and app/build.gradle:
android {
ndkVersion rootProject.ext.ndkVersion
externalNativeBuild {
cmake {
path "../../lib/CMakeLists.txt"
}
}
This is my CMakeLists.txt file:
cmake_minimum_required(VERSION 3.10.2)
project(add LANGUAGES CXX C)
set(CMAKE_INSTALL_RPATH "$ORIGIN/lib")
add_library(add SHARED ./add.cpp)
and my file structure of the project looks like this:
lib/
- add.cpp
- add.o
- CMakeLists.txt
- libadd.dylib
- main.dart
it also may be worth mentioning that in order to compile add.cpp into a dylib I ran the following commands:
g++ -c add.cpp
ar rvs libadd.dylib add.o
and if you're wondering, add.cpp looks like this:
#define EXPORT extern "C" __attribute__((visibility("default")))
__attribute__((used))
EXPORT
int add(int a, int b){
return a + b;
}
Where is this error coming from? am I compiling to a dylib incorrectly?
The answer to this problem was relatively simple, it just stemmed from my lack of knowledge on how Android actually compiles to a static library. Hopefully it helps someone else who is trying to understand how to setup external C++ code in a flutter program.
The static library is generated automatically and is set up in CMakeLists.txt.
Firstly, I moved all the C++ files into the android folder. Then, I set up CMakeLists.txt like this:
cmake_minimum_required(VERSION 3.10.2)
add_library( add // library name, will create libadd.so
SHARED
add.cpp
)
The problem before was that I was trying to manually compile the file myself, when I should have been letting CMakeLists do it instead. According to the android documentation:
"The convention CMake uses to name the file of your library is as follows:
liblibrary-name.so
For example, if you specify "native-lib" as the name of your shared library in the build script, CMake creates a file named libnative-lib.so. "
https://developer.android.com/studio/projects/configure-cmake
So when I run the program, the static library is created automatically and placed in the correct place. Then, the Dart FFI can find it with the DynamicLibrary.open() function. In this case, CMakeLists will generate a file called libadd.so, and I can callDynamicLibrary.open('libadd.so') and the program works.
I am attempting to use Gstreamer library on multiple platforms with my Qt project (for audio only). I already have it working on macOS with the binary files available online by just adding the framework to my .pro file:
LIBS += -F$$PWD/macOS/libs/ -framework GStreamer
INCLUDEPATH += $$PWD/macOS/libs/GStreamer.framework/Versions/1.0/Headers
DEPENDPATH += $$PWD/macOS/libs/GStreamer.framework/Versions/1.0/include
But now I want to use the binaries available at the same page for android. But because it is not "bundled" in a framework like on OS X I can't add it as easily. Furthermore the official explanations are made for a gradle build (which I don't know anything and don't use in Qt creator) and for use in Java. But, because I want to directly use the C API in Qt C++ I don't need JNI, and would like to directly use the library in my app like on OSX.
Thus, I tried to add the library like I would do it on any other linux, but recursively, since there is a multitude of library and header folders:
contains(ANDROID_TARGET_ARCH,arm64-v8a) {
ANDROID_PACKAGE_SOURCE_DIR = $$PWD/android
GSTREAMER_INCLUDE_FILES = $$files($$PWD/android/libs/gstreamer/arm64/include/*, true)
for(FILE, GSTREAMER_INCLUDE_FILES) {
BASEDIR = $$dirname(FILE)
if(!contains(INCLUDEPATH, $$BASEDIR)){
INCLUDEPATH += $$BASEDIR
}
}
GSTREAMER_DEPEND_FILES = $$files($$PWD/android/libs/gstreamer/arm64/include/*, true)
for(FILE, GSTREAMER_INCLUDE_FILES) {
BASEDIR_DEP = $$dirname(FILE)
if(!contains(DEPENDPATH, $$BASEDIR_DEP)){
DEPENDPATH += $$BASEDIR_DEP
}
}
GSTREAMER_LIB_FILES = $$files($$PWD/android/libs/gstreamer/arm64/lib/*.a, true)
for(FILE, GSTREAMER_LIB_FILES) {
BASENAME = $$basename(FILE)
LIBS += -l$$replace(BASENAME,\.a,)
}
}
But when I try the include
#include <gst/gst.h>
, it doesn't work and output 37 errors on unknown members of the global namespace related to time management like :
/Users/user/Library/Android/sdk/ndk/19.2.5345600/sources/cxx-stl/llvm-libc++/include/ctime:70:9: error: no member named 'asctime' in the global namespace
using ::asctime;
~~^
I really don't know how to use gstreamer and bundle it for android from the available official binaries and don't want to use any wrapper like qt-gstreamer (which isn't maintained by the way) or JNI.
Thanks for any help or input !
The following was done with Android Studio 3.4, Android Gradle Plugin 3.3.2 and Gradle 4.10.3.
In the build.gradle file, I have configured some unit test options like this:
android {
testOptions {
unitTests.all {
systemProperty "debug","true"
}
}
}
I do have a test function that tries to read this property:
package com.demo;
public class SysPropTestDemo {
#Test
public static void dumpSysProps() {
System.out.println("sysprop(debug)=" + System.getProperty("debug"));
}
}
When run via command line gradlew test --test com.demo.SysPropTestDemo I will get the property debug set correctly to true. If I run the same test via Android Studio without setting any options, the value shown will be null.
In order to get the same result from Android Studio, I explicitly have to enter some values in the "Run/Debug Configurations" panel, i.e something like -Ddebug=true in the VM options.
Now this is a trivial example, but what I really want to do, is to add some path to the java.library.path property in order to be able to load a JNI library compiled within the project. (I do need to write some tests that make use a modified SQLite lib, so not using JNI is not an option here)
It does work when setting additional options, but I think this is very inconvenient, since I can't enter a variable based value in the configuration options (or at least, I don't know how to). To sum it up: when setting or changing values, I do have to go through a bunch of config screens where I would really prefer to have one place in a config file.
Shouldn't Android Studio somehow make use of the values specified in the build.gradle file? If not, the docs don't make it clear that the testOptions.unitTests.all settings can only be used via gradlew invocation.
Skybow,
I feel you have two questions
1. How to load jni lib for androidTest(not for 'test[non instrumented unit tests])
- copy your jni library in corresponding folder [JNI libraries: [app/src/androidTestFLAVORNAMEDebug/jniLibs]
- load your jni library
static {
try {
System.loadLibrary("xyzjni");
} catch (Exception e) {
Logger.error("Exception on loading the jni library : " + e.getMessage());
}
}
2. How to make android studio use your config variables defined for unitTests.
- It would have great if some text file is there which has all configs.
- Or it is part of build.gradle
- I don't have any detail on this.
It's the first time I try to create a library c++ for Android/iOS.
I'm using Visual Studio 2015 - Xamarin.
First I created a project : Visual C++ -> Cross Platform -> Shared Library. In the hared library, I created 2 files.
SayHello.h :
#pragma once
#include <string.h>
class SayHello {
public:
SayHello();
~SayHello();
static char* Hello();
};
SayHello.cpp :
#include "SayHello.h"
extern "C"
{
SayHello::SayHello(){}
SayHello::~SayHello(){}
char * SayHello::Hello()
{
return "Hello !";
}
}
Then I generated a file libSayHello.so and created a project Android with xamarin to try to call the function hello.
There is my MainActivity.cs :
[DllImport("libSayHello.so")]
static extern String Hello();
protected override void OnCreate(Bundle bundle)
{
// I paste only my added code :
String hello = Hello();
Toast.MakeText(this.ApplicationContext, hello, ToastLength.Long);
}
I did all steps in this tutorial, but I have an exception :
System.DllNotFoundException: libSayHello.so
I searched for this, but I must be so noob cause I did not find anything. How should I use my libSayHello.so ?
EDIT:
There is my libSayHello.so seen with 7zip:
And my project :
I think this will be the best sample for you.
This all works according to the following scheme:
Android supports 7 CPU architectures.
But Xamarin supports 5 of them. So in the settings of your Xamarin.Android project check which architectures you will support:
[Xamarin.Droid.project]->[Properties]->[Android Options]->[Advanced]->[Supported architectures]
Check which archs are necessary for your project. According to this your shared library should be compiled for these archs. And you should put your shared libraries in Xamarin.Droid.project's folder lib:
To see them in Solution Explorer you should mention them in your Xamarin.Android project's .CSPROJ.
Add there next item groups:
<ItemGroup>
<AndroidNativeLibrary Include="lib\{ARCH}\libCLib.so">
<Abi>{ARCH}</Abi>
<CopyToOutputDirectory>Always</CopyToOutputDirectory>
</AndroidNativeLibrary>
</ItemGroup>
{ARCH} could be next: armeabi, armeabi-v7a, arm64-v8a, x86, x86_64.
Now you can put DllImport in your code:
[DllImport("libCLib", EntryPoint = "clib_add")]
public static extern int Add(int left, int right);
I think you have to tell about entry point, because i had runtime errors without this statement System.EntryPointNotFoundException.
And don't forget to add next in your code:
using System.Runtime.InteropServices;
Confirm the library is put in "/lib/{arch}/" folder.
Try [DllImport("SayHello")]. the engine may add "lib" and ".so" automatically.
I have a MonoDroid application project (let's call it mainApp). This references app.Screen project, which is a MFA library project. Initially, my activities were in the mainApp project. Everything was working fine. I needed to put some Activities (and resource, drawables, etc) in the app.Screen project.
I have moved all the resources I need to the app.Screen project. It builds fine and in my activities (which are sitting in app.screens) I can access Resource.Layout.filename and even Layout.Id.name.
However, when I run the application, in SetContentView(Resource.Layout.filename) I get the wrong layout file . This causes FindById<Button>() to return null obviously because it does not have these buttons in this layout file.
I found that same Layout file has different Id in my MFA library project than what is in the mainApp project like this:
// In the mainApp project
public partial class Layout
{
// aapt resource value: 0x7f030001
public const int DeliveryScreenLayout = 2130903041;
// aapt resource value: 0x7f03000a
public const int splash_screen_layout = 2130903050;
private Layout()
{
}
}
// in app.screen library project
public partial class Layout
{
// aapt resource value: 0x7f030000
public static int has_hello_layout = 2130903040;
// aapt resource value: 0x7f030001
public static int splash_screen_layout = 2130903041;
private Layout()
{
}
}
I am using VS 2010 with MFA 4.0 and my projects are targeting Android 4.0. I have tried Clean & Build, Removing /Bin and /Obj folder, with no luck.
Any help would be much appreciated.
This appeared to be a bug in MonoDroid, here is the link to the bug in Xamarin bugzilla
This is caused by the Resource.Designer.cs in the MFA library project has a different ID (int) values than what the main project has in its Resource.Designer.cs file.
I have worked out a workaround for it. In my mainApp I manually call mainApp.Resources.UpdateIdValues(); and that would update the Resources id values in the other MFA library projects
Xamarin said that this bug was resolved in 4.6.4. I have not tested this fix though