add a cpp callback demo

Author: REBOOTERS

build.gradle

@@ -1,8 +1,8 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 plugins {
-    id 'com.android.application' version '8.13.0' apply false
-    id 'com.android.library' version '8.13.0' apply false
+    id 'com.android.application' version '8.13.1' apply false
+    id 'com.android.library' version '8.13.1' apply false
     id 'org.jetbrains.kotlin.android' version '2.2.10' apply false
     id 'com.google.devtools.ksp' version '2.2.10-2.0.2' apply false
     id 'org.jetbrains.kotlin.plugin.compose' version '2.2.10' apply false

buildSrc/build.gradle

@@ -9,7 +9,7 @@ dependencies {
 //    implementation localGroovy()
     implementation 'org.jetbrains.kotlin:kotlin-stdlib:2.2.0'
     // 添加了这个，就可以看 Android Gradle 插件的源码了
-    implementation 'com.android.tools.build:gradle-api:8.13.0'
+    implementation 'com.android.tools.build:gradle-api:8.13.1'
 //    implementation "org.jetbrains.kotlin:kotlin-script-runtime:1.3.40"
     implementation 'com.google.code.gson:gson:2.13.1'
     implementation 'com.android.tools:common:31.11.1'

subs/cpp_native/src/main/cpp/cpp_native.cpp

@@ -2,6 +2,7 @@
 #include <string>
 #include "androidlog.h"
 #include "bspatch.h"
+#include <thread>
 
 using namespace std;
 
@@ -36,4 +37,55 @@ Java_com_example_cpp_1native_internal_PatchUtil_patchAPK(JNIEnv *env, jclass cla
     env->ReleaseStringUTFChars(old_apk_file, argv[1]);
     env->ReleaseStringUTFChars(new_apk_file, argv[2]);
     env->ReleaseStringUTFChars(patch_file, argv[3]);
-}
+}
+
+static JavaVM* gVm = nullptr;   // 全局保存，供子线程 attach
+
+// so 被加载时会把 JavaVM 存下来
+JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void*) {
+    gVm = vm;
+    return JNI_VERSION_1_6;
+}
+
+// 子线程里真正干活的函数
+void worker(JNIEnv* env, jobject gCallback) {
+    // 1. 模拟耗时 2 秒
+    std::this_thread::sleep_for(std::chrono::seconds(2));
+
+    // 2. 找到接口类
+    jclass clazz = env->GetObjectClass(gCallback);
+    jmethodID onResult = env->GetMethodID(clazz,
+                                          "onResult",
+                                          "(Ljava/lang/String;)V");
+
+    // 3. 拼结果
+    jstring msg = env->NewStringUTF("C++ 线程执行完毕");
+
+    // 4. 回调 Java
+    env->CallVoidMethod(gCallback, onResult, msg);
+
+    // 5. 清理局部引用
+    env->DeleteLocalRef(msg);
+    env->DeleteLocalRef(clazz);
+}
+
+extern "C"
+JNIEXPORT void JNICALL
+Java_com_example_cpp_1native_internal_NativeHouse_doHeavyWorkAsync(JNIEnv *env, jobject thiz,
+                                                                   jobject callback) {
+    // 1. callback 是局部变量，跨线程必须提升为全局引用
+    jobject gCallback = env->NewGlobalRef(callback);
+    if (gCallback == nullptr) return;
+    // 2. 起 C++ 线程
+    std::thread([gCallback]() {
+        JNIEnv* env = nullptr;
+        // 3. 子线程 attach
+        if (gVm->AttachCurrentThread(&env, nullptr) != 0) return;
+        worker(env, gCallback);   // 真正干活
+        // 4. 别忘了 detach，否则线程退出会崩
+        gVm->DetachCurrentThread();
+        // 5. 全局引用用完要释放
+        env->DeleteGlobalRef(gCallback);
+    }).detach();
+}
+

subs/cpp_native/src/main/java/com/example/cpp_native/app/NativeRoot.kt

@@ -14,6 +14,10 @@ object NativeRoot {
 
     fun test() {
         lg(nativeHouse.nativeMessage)
+
+        nativeHouse.doHeavyWorkAsync {
+            lg("result is $it")
+        }
     }
 
     private fun lg(msg: String) {

subs/cpp_native/src/main/java/com/example/cpp_native/internal/NativeHouse.java

@@ -7,4 +7,12 @@ public class NativeHouse {
     }
 
     public native String getNativeMessage();
+
+    // 3. 声明 native：把耗时任务丢给 C++，并传一个 callback 实例
+    public native void doHeavyWorkAsync(ResultCallback cb);
+
+
+    public interface ResultCallback {
+        void onResult(String msg);   // 也可以带 int、byte[] 等多参数
+    }
 }