Add clock plugin interface

More flexible to test any clock plugin in the future

Bug: 111971817
Test: manual test
Change-Id: I45fa2d1ca99446abdb315cc28b58956d8e409283

packages/SystemUI/docs/plugin_hooks.md

@@ -51,6 +51,10 @@ Expected interface: [NotificationSwipeActionHelper](/packages/SystemUI/plugin/sr
 
 Use: Control over swipes/input for notification views, can be used to control what happens when you swipe/long-press
 
+### Action: com.android.systemui.action.PLUGIN_CLOCK
+Expected interface: [ClockPlugin](/packages/SystemUI/plugin/src/com/android/systemui/plugins/ClockPlugin.java)
+
+Use: Allows replacement of the keyguard main clock.
 
 # Global plugin dependencies
 These classes can be accessed by any plugin using PluginDependency as long as they @Requires them.

packages/SystemUI/plugin/src/com/android/systemui/plugins/ClockPlugin.java

@@ -0,0 +1,47 @@
+/*
+ * 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.systemui.plugins;
+
+import com.android.systemui.plugins.annotations.ProvidesInterface;
+
+import android.graphics.Paint.Style;
+import android.view.View;
+
+/**
+ * This plugin is used to replace main clock in keyguard.
+ */
+@ProvidesInterface(action = ClockPlugin.ACTION, version = ClockPlugin.VERSION)
+public interface ClockPlugin extends Plugin {
+
+    String ACTION = "com.android.systemui.action.PLUGIN_CLOCK";
+    int VERSION = 1;
+
+    /**
+     * Get clock view.
+     * @return clock view from plugin.
+     */
+    View getView();
+
+    /**
+     * Set clock paint style.
+     * @param style The new style to set in the paint.
+     */
+    void setStyle(Style style);
+
+    /**
+     * Set clock text color.
+     * @param color A color value.
+     */
+    void setTextColor(int color);
+}