来自JNI中资源Uri的文件

Question

Hi I'm trying to get a File object from the Uri of a drawable resource. I'm using this code:

jclass clazz;
jmethodID methodID;
jstring string1, string2, string3;
jobject object1, object2;

clazz = env->FindClass("android/net/Uri");
methodID = env->GetStaticMethodID(clazz, "parse", "(Ljava/lang/String;)Landroid/net/Uri;");
string1 = env->NewStringUTF("android.resource://com.appsite.android/drawable/grass");
object1 = env->CallStaticObjectMethod(clazz, methodID, string1);
methodID = env->GetMethodID(clazz, "toString", "()Ljava/lang/String;");
string1 = (jstring)env->CallObjectMethod(object1, methodID);

clazz = env->FindClass("java/net/URLEncoder");
methodID = env->GetStaticMethodID(clazz, "encode", "(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;");
string2 = (jstring)env->NewStringUTF("UTF-8");
string3 = (jstring)env->CallStaticObjectMethod(clazz, methodID, string1, string2);


clazz = env->FindClass("java/net/URI");
methodID = env->GetMethodID(clazz, "<init>", "(Ljava/lang/String;)V");
object1 = env->NewObject(clazz, methodID, string3);

clazz = env->FindClass("java/io/File");
methodID = env->GetMethodID(clazz, "<init>", "(Ljava/net/URI;)V");
object2 = env->NewObject(clazz, methodID, object1);

The application crashes at the last call to NewObject . What are the possible reasons for that?

EDIT :

It seems like a problem with passing a jobject as parameter to NewObject like that. What is the proper way to pass a jobject to NewObject ?

Answer 1

This is not related to JNI.

The problem is that there no java.io.File for the drawable resource. The grass drawable is embedded in the APK in PNG or other image format, and the resource manager extracts the bitmap for Resources.getDrawable(int) by looking into the APK directly.

If you need to access your bitmap with file i/o methods, the closest you can get is thorough Resources.openRawResourceFd() method (limited to uncompressed resources). You can also put the bitmap in assets instead of res .