FindClass crashes in Android NDK

Issue

I have a purely native Android app, where the entry point is:

 void android_main(struct android_app* state) 
 {
 }

I need to access device information such as, android.os.Build.MODEL and in my android_main, have the following:

JNIEnv *env = state->activity->env;
    jclass build_class = env->FindClass("android/os/Build");
    jfieldID brand_id = env->GetStaticFieldID(build_class, "MODEL", "Ljava/lang/String;");
    jstring brand_obj = (jstring)env->GetStaticObjectField(build_class, brand_id);
const char *nativeString = env->GetStringUTFChars(brand_obj, 0);

Unfortunately it crashes at the second line - "FindClass". I know that env is not null because I checked for this, but otherwise I am unable to debug this and find out why it is crashing :(

Solution

Turns out I had to:

 state->activity->vm->AttachCurrentThread(&env, NULL);

instead of

 JNIEnv *env = state->activity->env;

This post was helpful: http://blog.tewdew.com/post/6852907694/using-jni-from-a-native-activity

Answered By - lost_bits1110