db/Configured: store database file in cache directory

Add class Context which wraps the Android/Java Context class and add a
JNI wrapper for method Context.getCacheDir().

src/android/Context.cxx

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Context.hxx"
+#include "java/Class.hxx"
+#include "java/File.hxx"
+#include "fs/AllocatedPath.hxx"
+
+AllocatedPath
+Context::GetCacheDir(JNIEnv *env) const
+{
+	assert(env != nullptr);
+
+	Java::Class cls(env, env->GetObjectClass(Get()));
+	jmethodID method = env->GetMethodID(cls, "getCacheDir",
+					    "()Ljava/io/File;");
+	assert(method);
+
+	jobject file = env->CallObjectMethod(Get(), method);
+	if (file == nullptr) {
+		env->ExceptionClear();
+		return AllocatedPath::Null();
+	}
+
+	return Java::File::ToAbsolutePath(env, file);
+}

src/android/Context.hxx

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_ANDROID_CONTEXT_HXX
+#define MPD_ANDROID_CONTEXT_HXX
+
+#include "java/Object.hxx"
+
+class AllocatedPath;
+
+class Context : public Java::Object {
+public:
+	Context(JNIEnv *env, jobject obj):Java::Object(env, obj) {}
+
+	gcc_pure
+	AllocatedPath GetCacheDir(JNIEnv *env) const;
+};
+
+#endif