defining default_realm_file_directory using application context

react-native/android/app/src/main/java/com/reacttests/RealmReactAndroid.java

@@ -11,19 +11,26 @@ import java.util.HashMap;
 import android.widget.Toast;
 import com.facebook.react.bridge.Callback;
 import android.util.Log;
+import java.io.IOException;
 
 public class RealmReactAndroid extends ReactContextBaseJavaModule {
 	private static final String DURATION_SHORT_KEY = "SHORT";
     private static final String DURATION_LONG_KEY = "LONG";
+    private String filesDirPath;
 
 	public RealmReactAndroid(ReactApplicationContext reactContext) {
 		super(reactContext);
+        try {
+            filesDirPath = getReactApplicationContext().getFilesDir().getCanonicalPath();
+        } catch (IOException e) {
+            throw new IllegalStateException(e);
+        }
 		ReLinker.loadLibrary(reactContext, "realmreact");
     }
 
     @Override
     public void initialize() {
-        Log.w("RealmReactAndroid", injectRealmJsContext());
+        Log.w("RealmReactAndroid", injectRealmJsContext(filesDirPath));
     }
 
     @Override
@@ -37,7 +44,7 @@ public class RealmReactAndroid extends ReactContextBaseJavaModule {
         constants.put(DURATION_SHORT_KEY, Toast.LENGTH_SHORT);
         constants.put(DURATION_LONG_KEY, Toast.LENGTH_LONG);
 
-        Log.w("RealmReactAndroid", injectRealmJsContext());
+        Log.w("RealmReactAndroid", injectRealmJsContext(filesDirPath));
 
         return constants;
     }
@@ -45,7 +52,7 @@ public class RealmReactAndroid extends ReactContextBaseJavaModule {
     @ReactMethod
     public void resultOfJsContextInjection(Callback successCallback) {
         // Inject our JS Context
-        successCallback.invoke(injectRealmJsContext());
+        successCallback.invoke(injectRealmJsContext(filesDirPath));
     }
 
     @ReactMethod
@@ -53,5 +60,6 @@ public class RealmReactAndroid extends ReactContextBaseJavaModule {
         Toast.makeText(getReactApplicationContext(), message, duration).show();
     }
 
-	private native String injectRealmJsContext();
+    // fileDir: path of the internal storage of the application
+	private native String injectRealmJsContext(String fileDir);
 }

src/android/com_reacttests_RealmReactAndroid.cpp

@@ -16,13 +16,18 @@
  * Signature: ()Ljava/lang/String;
  */
 JNIEXPORT jstring JNICALL Java_com_reacttests_RealmReactAndroid_injectRealmJsContext
-  (JNIEnv *env, jclass) 
+  (JNIEnv *env, jclass, jstring fileDir) 
   {
   	
   	void* handle = dlopen ("libreactnativejni.so", RTLD_LAZY);
   	if (!handle) {
         return env->NewStringUTF("Cannot open library");
     }
+    
+    // Getting the internal storage path for the application
+    const char* strFileDir = env->GetStringUTFChars(fileDir , NULL);
+    std::string absoluteAppPath(strFileDir); 
+    env->ReleaseStringUTFChars(fileDir , strFileDir); 
 
     // load the symbol
 	typedef std::unordered_map<JSContextRef, facebook::react::JSCExecutor*> (*get_jsc_context_t)();
@@ -35,7 +40,7 @@ JNIEXPORT jstring JNICALL Java_com_reacttests_RealmReactAndroid_injectRealmJsCon
 	  	msg << "Got the globalContext map, size=" << s_globalContextRefToJSCExecutor.size();
 
           for (auto pair : s_globalContextRefToJSCExecutor) {
-			  RJSInitializeInContext(pair.first);
+			  RJSInitializeInContextUsingPath(pair.first, absoluteAppPath);
 		  }
 
 	  	return env->NewStringUTF(msg.str().c_str());

src/android/com_reacttests_RealmReactAndroid.h

@@ -13,7 +13,7 @@ extern "C" {
  * Signature: ()Ljava/lang/String;
  */
 JNIEXPORT jstring JNICALL Java_com_reacttests_RealmReactAndroid_injectRealmJsContext
-  (JNIEnv *, jclass);
+  (JNIEnv *, jclass, jstring);
 
 #ifdef __cplusplus
 }

src/android/platform.cpp

@@ -3,13 +3,15 @@
  */
 
 #include "../platform.hpp"
+ #include "../js_init.h"
 #include <string>
 
 namespace realm {
 
 std::string default_realm_file_directory()
 {
-    return std::string("/data/data/com.demo/files/");
+	// appFilesDir is defined in js_init.cpp
+	return appFilesDir;
 }
 
 void ensure_directory_exists_for_file(const std::string &fileName)

src/js_init.cpp

@@ -78,6 +78,16 @@ void RJSInitializeInContext(JSContextRef ctx) {
     assert(!exception);
 }
 
+// The default (internal) storage for each application is unique
+// the only way to get this path is using the android.content.Context via the JNI
+// we set this path when we initialise the Realm by calling RJSConstructorCreate, as it's the
+// only contact between the JNI layer and the Realm JS API.
+std::string appFilesDir; 
+void RJSInitializeInContextUsingPath(JSContextRef ctx, std::string path) {
+    RJSInitializeInContext(ctx);
+    appFilesDir = path;
+}
+
 void RJSClearTestState() {
     realm::Realm::s_global_cache.clear();
     realm::remove_realm_files_from_directory(realm::default_realm_file_directory());

src/js_init.h

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <JavaScriptCore/JSBase.h>
+#include <string>
 
 #ifdef __cplusplus
 extern "C" {
@@ -12,8 +13,11 @@ extern "C" {
 
 JSObjectRef RJSConstructorCreate(JSContextRef ctx);
 void RJSInitializeInContext(JSContextRef ctx);
+void RJSInitializeInContextUsingPath(JSContextRef ctx, std::string path);
 void RJSClearTestState(void);
 
+extern std::string appFilesDir;
+
 #ifdef __cplusplus
 }
 #endif