增加了低版本水波纹背景的替代图

app/src/main/res/drawable/ripple_blue_bg.xml

@@ -1,6 +1,32 @@
 <?xml version="1.0" encoding="utf-8"?>
-<shape android:shape="rectangle"
-    xmlns:android="http://schemas.android.com/apk/res/android"
-    >
-
-</shape>
+<!-- 低版本显示不了水波纹，这里用了一个形状来代替 -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <item>
+        <shape
+            android:innerRadius="15px"
+            android:shape="ring"
+            android:thickness="4px"
+            android:useLevel="false"
+            >
+
+            <solid android:color="@color/colorAccent" />
+        </shape>
+    </item>
+
+    <item
+        android:bottom="20px"
+        android:left="20px"
+        android:right="20px"
+        android:top="20px"
+        >
+        <shape android:shape="oval">
+            <size
+                android:width="20px"
+                android:height="20px"
+                />
+
+            <solid android:color="@color/colorPrimary" />
+        </shape>
+    </item>
+</layer-list>

app/src/main/res/layout/ripple_layout.xml

@@ -11,6 +11,7 @@
         android:layout_width="80dp"
         android:layout_height="80dp"
         android:background="@drawable/ripple_blue_bg"
+        android:contentDescription="原生方式，低版本不显示水波纹"
         />
 
     <kale.ui.view.SelectorTextView

lib/src/main/java/kale/injection/SelectorInjection.java

@@ -194,6 +194,7 @@ private void setSelectorDrawableToView() {
         }
 
         if (showRipple && Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            // https://blog.csdn.net/AwayEagle/article/details/52583913
             RippleDrawable ripple = (RippleDrawable) view.getResources().getDrawable(R.drawable.si_ripple);
             assert ripple != null;