How to use the ChromiumJniGenerator
1 Dependencies
1.1 C ++ dependencies
Copy two directories: chromium-jni-generator-native-essential and chromium-jni-generator-native-gen-script to your project 
The chromium-jni-generator-neutral-essential directory contains the chromium_jni_generator_native_essential .h and chromium_jni_generator_native_essential.cc 
The chromium-jni-generator-native-gen-script directory contains python scripts that generate native code 
chromium_native_code_gen.sh is an example of using python scripts to generate native code
#!/bin/bash
#create code generation directories
rm -rf ./gen
mkdir -p gen/cpp
mkdir -p gen/java
#generate native code
./jni_generator.py --input_file XXXXA.java --input_file XXXXB.java --output_file gen/cpp/XXXXA.h --output_file gen/cpp/XXXXB.h
1.2 Java dependencies
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}
dependencies {
compileOnly 'com.github.allenxuan.ChromiumJniGenerator:chromium-jni-generator-jvm-annotations:v1.0.0'
kapt 'com.github.allenxuan.ChromiumJniGenerator:chromium-jni-generator-jvm-compiler:v1.0.0'
}
2 Java Layer Access C/C ++ Layer ( JNI )
Define native functions in the Java layer
`ChromiumJniTestA.java`
@JNINamespace("test::your::name::space")
public class ChromiumJniTestA {
//Work
public static native boolean nativeFunctionAA(boolean param1, float param2);
//Not work. "static" should be put in front of "native".
public native static boolean nativeFunctionAB(boolean param1, float param2);
//Work
public native long nativeFunctionAC(String param1);
//Not work. The function name should starts with "native".
public native long functionAD(String param1);
}
Or define native methods with @NativeMethods annotations
`ChromiumJniTestB.java`
@JNINamespace("test::your::name::space")
public class ChromiumJniTestB {
@NativeMethods
interface Natives {
boolean nativeFunctionBA(boolean param1, float param2);
float functionBB(String param1);
}
}
Java Annotation Processor generates auxiliary classes ChromiumJniTestBJni.java and GEN_JNI.java from @NativeMethods
`ChromiumJniTestBJni.java`
class ChromiumJniTestBJni implements ChromiumJniTestB.Natives {
@Override
public boolean nativeFunctionBA(boolean param1, float param2) {
return (boolean)GEN_JNI.org_chromium_chromiumjnigenerator_ChromiumJniTestB_nativeFunctionBA(param1, param2);
}
@Override
public float functionBB(String param1) {
return (float)GEN_JNI.org_chromium_chromiumjnigenerator_ChromiumJniTestB_functionBB(param1);
}
public static ChromiumJniTestB.Natives get() {
return new ChromiumJniTestBJni();
}
}
`GEN_JNI.java`
public final class GEN_JNI {
/**
* org.chromium.chromiumjnigenerator.ChromiumJniTestB.functionBB
* @param param1 (java.lang.String)
* @return (float)
*/
public static final native float org_chromium_chromiumjnigenerator_ChromiumJniTestB_functionBB(
String param1);
/**
* org.chromium.chromiumjnigenerator.ChromiumJniTestB.nativeFunctionBA
* @param param1 (boolean)
* @param param2 (float)
* @return (boolean)
*/
public static final native boolean org_chromium_chromiumjnigenerator_ChromiumJniTestB_nativeFunctionBA(
boolean param1, float param2);
}
Generate JNI functions through jni_generator.py
./jni_generator.py --input_file ../java/org/chromium/chromiumjnigenerator/ChromiumJniTestA.java --output_file ../cpp/gen/ChromiumJniTestA.h --input_file ../java/org/chromium/chromiumjnigenerator/ChromiumJniTestB.java --output_file ../cpp/gen/ChromiumJniTestB.h
`ChromiumJniTestA.h`
static jboolean JNI_ChromiumJniTestA_FunctionAA(JNIEnv* env, jboolean param1,
jfloat param2);
JNI_GENERATOR_EXPORT jboolean
Java_org_chromium_chromiumjnigenerator_ChromiumJniTestA_nativeFunctionAA(
JNIEnv* env,
jclass jcaller,
jboolean param1,
jfloat param2) {
return JNI_ChromiumJniTestA_FunctionAA(env, param1, param2);
}
static jlong JNI_ChromiumJniTestA_FunctionAC(JNIEnv* env, const
chromium::android::JavaParamRef
& jcaller,
const chromium::android::JavaParamRef
& param1);
JNI_GENERATOR_EXPORT jlong
Java_org_chromium_chromiumjnigenerator_ChromiumJniTestA_nativeFunctionAC(
JNIEnv* env,
jobject jcaller,
jstring param1) {
return
JNI_ChromiumJniTestA_FunctionAC(env, chromium::android::JavaParamRef
(env,
jcaller), chromium::android::JavaParamRef
(env, param1));
}
`ChromiumJniTestB.h`
static jboolean JNI_ChromiumJniTestB_NativeFunctionBA(JNIEnv* env, jboolean param1,
jfloat param2);
JNI_GENERATOR_EXPORT jboolean
Java_org_chromium_base_natives_GEN_1JNI_org_1chromium_1chromiumjnigenerator_1ChromiumJniTestB_1nativeFunctionBA(
JNIEnv* env,
jclass jcaller,
jboolean param1,
jfloat param2) {
return JNI_ChromiumJniTestB_NativeFunctionBA(env, param1, param2);
}
static jfloat JNI_ChromiumJniTestB_FunctionBB(JNIEnv* env, const
chromium::android::JavaParamRef
& param1);
JNI_GENERATOR_EXPORT jfloat
Java_org_chromium_base_natives_GEN_1JNI_org_1chromium_1chromiumjnigenerator_1ChromiumJniTestB_1functionBB(
JNIEnv* env,
jclass jcaller,
jstring param1) {
return
JNI_ChromiumJniTestB_FunctionBB(env, chromium::android::JavaParamRef
(env,
param1));
}
Create ChromiumJniTestA.cc and ChromiumJniTestB.cc to implement ChromiumJniTestA.h and ChromiumJniTestB.h
`ChromiumJniTestA.cc`
#include <ChromiumJniTestA.h>
jboolean JNI_ChromiumJniTestA_FunctionAA(JNIEnv *env, jboolean param1,
jfloat param2) {
return true;
}
jlong JNI_ChromiumJniTestA_FunctionAC(JNIEnv *env, const
chromium::android::JavaParamRef
&jcaller,
const chromium::android::JavaParamRef
¶m1) {
return
1000.
f;
}
`ChromiumJniTestB.cc`
#include <ChromiumJniTestB.h>
jboolean JNI_ChromiumJniTestB_NativeFunctionBA(JNIEnv* env, jboolean param1,
jfloat param2){
return true;
}
jfloat JNI_ChromiumJniTestB_FunctionBB(JNIEnv* env, const
chromium::android::JavaParamRef
& param1){
return
3888.
2f;
}
Remember to add the chromium-jni-generator-native-essential directory to the compilation process.
add_library(chromium_jni_generator_test_jni SHARED
jni_main.cc
ChromiumJniTestA.cc
ChromiumJniTestB.cc)
target_include_directories(chromium_jni_generator_test_jni
PRIVATE ./
PRIVATE ./gen)
add_subdirectory(../chromium-jni-generator-native-essential chromium_jni_generator_native_essential)
target_link_libraries(chromium_jni_generator_test_jni
PRIVATE chromium_jni_generator_native_essential)
3 C/C ++ Layer Access to Java Layer
Add @CalledByNative annotations to Java methods
`ChromiumJniTestA.java`
@JNINamespace("test::your::name::space")
public class ChromiumJniTestA {
...
...
@CalledByNative
public static float functionAE(String param1, boolean param2){
return 9.7f;
}
}
Generate C/C ++ code through jni_generator.py
g_org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz(nullptr); #ifndef org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz_defined #define org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz_defined inline jclass org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz(JNIEnv* env) { return chromium::android::LazyGetClass(env, kClassPath_org_chromium_chromiumjnigenerator_ChromiumJniTestA, &g_org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz); } #endif static std::atomic
g_org_chromium_chromiumjnigenerator_ChromiumJniTestA_functionAE(nullptr); static jfloat Java_ChromiumJniTestA_functionAE(JNIEnv* env, const chromium::android::JavaRef
& param1, jboolean param2) { jclass clazz = org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz(env); CHECK_CLAZZ(env, clazz, org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz(env), 0); chromium::android::JniJavaCallContextChecked call_context; call_context.Init< chromium::android::MethodID::TYPE_STATIC>( env, clazz, "functionAE", "(Ljava/lang/String;Z)F", &g_org_chromium_chromiumjnigenerator_ChromiumJniTestA_functionAE); jfloat ret = env->CallStaticFloatMethod(clazz, call_context.base.method_id, param1.obj(), param2); return ret; }">
`ChromiumJniTestA.h` JNI_REGISTRATION_EXPORT extern const char kClassPath_org_chromium_chromiumjnigenerator_ChromiumJniTestA[]; const char kClassPath_org_chromium_chromiumjnigenerator_ChromiumJniTestA[] = "org/chromium/chromiumjnigenerator/ChromiumJniTestA"; // Leaking this jclass as we cannot use LazyInstance from some threads. JNI_REGISTRATION_EXPORT std::atomicg_org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz( nullptr); # ifndef org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz_defined # define org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz_defined inline jclass org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz(JNIEnv* env) { return chromium::android::LazyGetClass(env, kClassPath_org_chromium_chromiumjnigenerator_ChromiumJniTestA, &g_org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz); } # endif static std::atomic g_org_chromium_chromiumjnigenerator_ChromiumJniTestA_functionAE( nullptr); static jfloat Java_ChromiumJniTestA_functionAE(JNIEnv* env, const chromium::android::JavaRef & param1, jboolean param2) { jclass clazz = org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz(env); CHECK_CLAZZ(env, clazz, org_chromium_chromiumjnigenerator_ChromiumJniTestA_clazz(env), 0); chromium::android::JniJavaCallContextChecked call_context; call_context. Init< chromium::android::MethodID::TYPE_STATIC>( env, clazz, "functionAE", "(Ljava/lang/String;Z)F", &g_org_chromium_chromiumjnigenerator_ChromiumJniTestA_functionAE); jfloat ret = env-> CallStaticFloatMethod(clazz, call_context. base. method_id, param1. obj(), param2); return ret; }
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