java - 无法解析 JNIfunction : Android ndk

Question

我想通过从 C++ 代码调用 Android 方法来获取 Android 中已安装应用程序的列表。找到第一个方法 ( getPackageManager() )，但是 getInstalledApplications() 方法每次都是 nil。这里有什么问题？

JNIEXPORT jobject JNICALL Java_com_example_davidt_ndkexample_TestNdk_getListOfInstalledApps
    (JNIEnv* env, jobject obj, jobject activity){
     jclass contextWrapperClass = env->FindClass("android/content/ContextWrapper");
     jmethodID getPackageManagerId = env->GetMethodID(contextWrapperClass,"getPackageManager","()Landroid/content/pm/PackageManager;");
     if (getPackageManagerId == 0) {
         fprintf(stderr, "packageManager() not found");
     }

     jobject pm = env->CallObjectMethod(activity, getPackageManagerId);

     jclass PackageManagerClass = env->GetObjectClass(pm);
     jmethodID getInstalledApplicationsId = env->GetMethodID(PackageManagerClass,"getInstalledApplications","(I)[Landroid/content/pm/ApplicationInfo;");
     if (getInstalledApplicationsId == 0) {
        fprintf(stderr, "getInstalledApplications() not found");
     }

     return env->CallObjectMethod(pm, getInstalledApplicationsId);
 }

Answer 1

看起来您的签名描述符是错误的。我用javap工具查过了

javap -s -bootclasspath <Your SDK Installation Path>/platforms/android-25/android.jar android.content.pm.PackageManager

对于 getInstalledApplications 它返回

public abstract java.util.List<android.content.pm.ApplicationInfo> getInstalledApplications(int);
    descriptor: (I)Ljava/util/List;

所以，在你的情况下，它必须是

jmethodID getInstalledApplicationsId = env->GetMethodID(PackageManagerClass,"getInstalledApplications","(I)Ljava/util/List");