Cleaning up build rules to simplify customizing derivative projects

> Using {packageName} instead of hardcoding com.android.launcher3 in AndroidManifest.xml
  for strings which are dependent on packageName
> Adding proguard rule to prevent obfuscating any overridable class
> Making it easier to extend SettingsActivity by overriding the fragment class

Change-Id: I5668c3f33b4cf20ad01d7f54b3d79cc0d268d391

2 files changed, 56 insertions, 3 deletions

diff --git a/src/com/android/launcher3/util/InstantAppResolver.java b/src/com/android/launcher3/util/InstantAppResolver.java
index 4485427f5..5dc7af855 100644
--- a/src/com/android/launcher3/util/InstantAppResolver.java
+++ b/src/com/android/launcher3/util/InstantAppResolver.java
@@ -23,7 +23,6 @@ import android.util.Log;
 
 import com.android.launcher3.AppInfo;
 import com.android.launcher3.R;
-import com.android.launcher3.Utilities;
 
 import java.util.Collections;
 import java.util.List;
@@ -31,10 +30,10 @@ import java.util.List;
 /**
  * A wrapper class to access instant app related APIs.
  */
-public class InstantAppResolver {
+public class InstantAppResolver implements ResourceBasedOverride {
 
     public static InstantAppResolver newInstance(Context context) {
-        return Utilities.getOverrideObject(
+        return Overrides.getObject(
                 InstantAppResolver.class, context, R.string.instant_app_resolver_class);
     }
 
diff --git a/src/com/android/launcher3/util/ResourceBasedOverride.java b/src/com/android/launcher3/util/ResourceBasedOverride.java
new file mode 100644
index 000000000..e2c4992a4
--- /dev/null
+++ b/src/com/android/launcher3/util/ResourceBasedOverride.java
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.launcher3.util;
+
+import android.content.Context;
+import android.text.TextUtils;
+import android.util.Log;
+
+import java.lang.reflect.InvocationTargetException;
+
+/**
+ * An interface to indicate that a class is dynamically loaded using resource overlay, hence its
+ * class name and constructor should be preserved by proguard
+ */
+public interface ResourceBasedOverride {
+
+    class Overrides {
+
+        private static final String TAG = "Overrides";
+
+        public static <T extends ResourceBasedOverride> T getObject(
+                Class<T> clazz, Context context, int resId) {
+            String className = context.getString(resId);
+            if (!TextUtils.isEmpty(className)) {
+                try {
+                    Class<?> cls = Class.forName(className);
+                    return (T) cls.getDeclaredConstructor(Context.class).newInstance(context);
+                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException
+                        | ClassCastException | NoSuchMethodException | InvocationTargetException e) {
+                    Log.e(TAG, "Bad overriden class", e);
+                }
+            }
+
+            try {
+                return clazz.newInstance();
+            } catch (InstantiationException|IllegalAccessException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+}