add dex class loader

jnius/jnius_export_class.pxi

@@ -208,6 +208,10 @@ class MetaJavaClass(MetaJavaBase):
             class_name = str_for_c(__javaclass__)
             jcs.j_cls = j_env[0].FindClass(j_env,
                     <char *>class_name)
+            try:
+                check_exception(j_env)
+            except JavaException as e:
+                jcs.j_cls = load_class_from_dex_jni(class_name)
             if jcs.j_cls == NULL:
                 raise JavaException('Unable to find the class'
                         ' {0}'.format(__javaclass__))

jnius/jnius_export_func.pxi

@@ -1,3 +1,5 @@
+from libc.stdlib cimport getenv
+
 def cast(destclass, obj):
     cdef JavaClass jc
     cdef JavaClass jobj = obj
@@ -19,10 +21,86 @@ def find_javaclass(namestr):
     cdef JNIEnv *j_env = get_jnienv()
 
     jc = j_env[0].FindClass(j_env, name)
-    check_exception(j_env)
+    try:
+        check_exception(j_env)
+    except JavaException as e:
+        jc = load_class_from_dex_jni(name)
+        if jc == NULL:
+            raise
 
     cls = Class(noinstance=True)
     cls.instanciate_from(create_local_ref(j_env, jc))
     j_env[0].DeleteLocalRef(j_env, jc)
     return cls
 
+cdef jclass load_class_from_dex_jni(const char* class_name):
+    cdef JNIEnv *j_env = get_jnienv()
+    cdef jclass dex_class_loader_class
+    cdef jmethodID load_class_id
+    cdef jobject dex_class_loader
+    cdef jstring j_class_name
+    cdef jclass loaded_class
+
+    dex_class_loader = get_dex_class_loader()
+    if dex_class_loader == NULL:
+        return NULL
+
+    load_class_id = j_env[0].GetMethodID(j_env, j_env[0].GetObjectClass(j_env, dex_class_loader), b"loadClass", b"(Ljava/lang/String;)Ljava/lang/Class;")
+    check_exception(j_env)
+
+    j_class_name = j_env[0].NewStringUTF(j_env, class_name)
+    loaded_class = <jclass>j_env[0].CallObjectMethod(j_env, dex_class_loader, load_class_id, j_class_name)
+    try:
+        check_exception(j_env)
+    finally:
+        j_env[0].DeleteLocalRef(j_env, j_class_name)
+
+    return loaded_class
+
+cdef get_dex_class_loader_python():
+    cdef jobject loader = get_dex_class_loader()
+    cdef JNIEnv *j_env = get_jnienv()
+    obj = convert_jobject_to_python(j_env, <bytes> 'Ldalvik/system/DexClassLoader;', loader)
+    return obj
+
+cdef jobject get_dex_class_loader():
+    cdef JNIEnv *j_env = get_jnienv()
+    cdef jclass dex_class_loader_class
+    cdef jmethodID constructor_id
+    cdef jobject dex_class_loader
+    cdef jstring j_dex_path
+    cdef const char* dex_path
+    global dex_class_loader_instance
+
+    if dex_class_loader_instance != NULL:
+        return dex_class_loader_instance
+
+    cdef const char* varname = "PYJNIUS_DEX_PATH"
+    dex_path = getenv(varname)
+    if dex_path == NULL:
+        return NULL
+
+    import os
+
+    dex_paths = dex_path.decode('utf-8').split(':')
+    for path in dex_paths:
+        if not os.access(path, os.R_OK):
+            raise JavaException(f"DEX file not accessible: {path}")
+
+    dex_class_loader_class = j_env[0].FindClass(j_env, b"dalvik/system/DexClassLoader")
+    check_exception(j_env)
+
+    constructor_id = j_env[0].GetMethodID(j_env, dex_class_loader_class, b"<init>", b"(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/ClassLoader;)V")
+    check_exception(j_env)
+
+    j_dex_path = j_env[0].NewStringUTF(j_env, dex_path)
+    dex_class_loader = j_env[0].NewObject(j_env, dex_class_loader_class, constructor_id, j_dex_path, NULL, NULL, NULL)
+    try:
+        check_exception(j_env)
+    finally:
+        j_env[0].DeleteLocalRef(j_env, j_dex_path)
+
+    dex_class_loader_instance = dex_class_loader
+    return dex_class_loader_instance
+
+cdef jobject dex_class_loader_instance = NULL

jnius/jnius_proxy.pxi

@@ -186,6 +186,11 @@ cdef create_proxy_instance(JNIEnv *j_env, py_obj, j_interfaces, javacontext):
         j_obj = Proxy.newProxyInstance(
                 classLoader, j_interfaces, nih)
 
+    elif javacontext == 'dex':
+        classLoader = get_dex_class_loader_python()
+        j_obj = Proxy.newProxyInstance(
+                classLoader, j_interfaces, nih)
+
     else:
         raise Exception(
                 'Invalid __javacontext__ {}, must be app or system.'.format(