Android Studio 3.1.2调用C++子程序报错：No implementation found

Let's break down the possible issues causing this error and fix them step by step:

1. You're not loading the native library in your Java code #

This is the most common culprit. Your Tab1 class doesn't include code to load the native-lib library you built with CMake. Without loading it, the JVM has no way to locate the native implementation.

Add this static block inside your Tab1.java class:

static {
    System.loadLibrary("native-lib");
}

Note: Use the exact library name you set in CMake (native-lib) — no file extensions like .so or .dll are needed here.

2. Double-check your JNI function signature (name and parameters) #

While your signature looks correct at first glance, let's verify every detail to rule out typos:

• Package name: com.labyrinthsys.crltext matches perfectly between Java and C++
• Class name: Tab1 is correctly capitalized in both files
• Method name: crlTCheckkey has the exact same casing and spelling
• Parameters: Your C++ function accepts JNIEnv*, jobject, jstring — which aligns with the non-static native method in Java (non-static methods receive the class instance as the second parameter)

Also, confirm the entire JNIEXPORT function declaration is wrapped in extern "C" to avoid C++ name mangling. Your code shows this, but make sure there are no syntax errors here. A complete, valid implementation example would look like:

#include <jni.h>
#include <string>
using namespace std;

extern "C" JNIEXPORT jstring JNICALL
Java_com_labyrinthsys_crltext_Tab1_crlTCheckkey(
        JNIEnv *env,
        jobject /* this */,
        jstring keyFilePath) {
    // Extract the string from Java to native
    const char* nativeKeyPath = env->GetStringUTFChars(keyFilePath, nullptr);
    string result = "Processed path: " + string(nativeKeyPath);
    
    // Clean up resources
    env->ReleaseStringUTFChars(keyFilePath, nativeKeyPath);
    
    // Return result to Java
    return env->NewStringUTF(result.c_str());
}

3. Verify your CMake configuration builds the library correctly #

• Ensure the path to your cpp file (src/main/cpp/crlTCheckkey.cpp) is accurate relative to your CMakeLists.txt. If the CMake file is in your module root, this path should work — double-check that the file exists at that location.
• Check your build output to confirm native-lib compiles successfully (look for logs referencing crlTCheckkey.cpp being compiled).

4. Clean and rebuild your project #

Stale build artifacts can sometimes cause mismatched libraries. Do a full clean to ensure you're using the latest compiled code:

• In Android Studio: Go to Build > Clean Project, then Build > Rebuild Project

After trying these steps, your JNI call should locate the native implementation without errors.

内容的提问来源于stack exchange，提问作者John F Donigan