Builder: store context.getApplicationContext to prevent leaks.

Author: greenrobot-team

objectbox-java/src/main/java/io/objectbox/BoxStoreBuilder.java

@@ -178,7 +178,7 @@ public BoxStoreBuilder androidContext(Object context) {
         if (context == null) {
             throw new NullPointerException("Context may not be null");
         }
-        this.context = context;
+        this.context = getApplicationContext(context);
 
         File baseDir = getAndroidBaseDir(context);
         if (!baseDir.exists()) {
@@ -195,6 +195,14 @@ public BoxStoreBuilder androidContext(Object context) {
         return this;
     }
 
+    private Object getApplicationContext(Object context) {
+        try {
+            return context.getClass().getMethod("getApplicationContext").invoke(context);
+        } catch (ReflectiveOperationException e) {
+            throw new RuntimeException("context must be a valid Android Context", e);
+        }
+    }
+
     /**
      * Pass a custom ReLinkerInstance, for example {@code ReLinker.log(logger)} to use for loading the native library
      * on Android devices. Note that setting {@link #androidContext(Object)} is required for ReLinker to work.