添加图片信息按钮与信息窗口

gallery/src/main/res/drawable/ic_info.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M12,2C6.48,2 2,6.48 2,12s4.48,10 10,10 10,-4.48 10,-10S17.52,2 12,2zM13,17h-2v-6h2v6zM13,9h-2L11,7h2v2z"/>
+</vector>

gallery/src/main/res/layout/activity_image_viewer.xml

@@ -44,6 +44,14 @@
             android:src="@drawable/ic_share"
             android:contentDescription="Share"/>
 
+        <ImageButton
+            android:id="@+id/btn_info"
+            android:layout_width="48dp"
+            android:layout_height="48dp"
+            android:background="?attr/selectableItemBackgroundBorderless"
+            android:src="@drawable/ic_info"
+            android:contentDescription="Info"/>
+
         <ImageButton
             android:id="@+id/btn_delete"
             android:layout_width="48dp"