如何使用NativeActivity写入内部存储文件系统？

#include <jni.h>
#include <android/native_activity.h>
#include <android/native_window_jni.h>
#include <android/log.h>
#include <stdio.h>

extern "C" {
    JNIEXPORT void JNICALL Java_com_example_nativeactivity_MainActivity_nativeWriteFile(JNIEnv* env, jobject thiz, jstring filePath, jstring content) {
        const char* file_path = env->GetStringUTFChars(filePath, NULL);
        const char* file_content = env->GetStringUTFChars(content, NULL);

        FILE* file = fopen(file_path, "w");
        if (file != NULL) {
            fputs(file_content, file);
            fclose(file);
        }

        env->ReleaseStringUTFChars(filePath, file_path);
        env->ReleaseStringUTFChars(content, file_content);
    }
}

#include <jni.h>

extern "C" {
    JNIEXPORT void JNICALL Java_com_example_nativeactivity_MainActivity_nativeWriteFile(JNIEnv* env, jobject thiz, jstring filePath, jstring content);
}

public class MainActivity extends NativeActivity {
    static {
        System.loadLibrary("native-lib");
    }

    public native void nativeWriteFile(String filePath, String content);

    // 调用nativeWriteFile函数写入文件
    public void writeFile(String filePath, String content) {
        nativeWriteFile(filePath, content);
    }
}

MainActivity activity = new MainActivity();
activity.writeFile("file.txt", "Hello, World!");