I have updated AlphaArray which is used to create path that mimics shadow

Sample/src/main/res/layout/activity_badge.xml

@@ -40,6 +40,7 @@
                 android:layout_alignParentBottom="true"
                 android:layout_gravity="bottom"
                 app:centre_part_linear="false"
+                app:space_background_color="@color/space_white"
                 app:layout_behavior="com.luseen.spacenavigation.SpaceNavigationViewBehavior" />
         </RelativeLayout>
     </LinearLayout>

build.gradle

@@ -2,16 +2,18 @@
 buildscript {
     repositories {
         jcenter()
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.1'
+        classpath 'com.android.tools.build:gradle:3.3.0'
         classpath 'com.novoda:bintray-release:0.8.0'
     }
 }
 
 allprojects {
     repositories {
         jcenter()
+        google()
     }
 }
 

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Wed Mar 14 18:44:51 IST 2018
+#Wed Feb 20 14:48:23 KST 2019
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.1-all.zip

spacelib/src/main/java/com/luseen/spacenavigation/NavigationViewShadow.java

@@ -0,0 +1,124 @@
+package com.luseen.spacenavigation;
+
+import android.annotation.SuppressLint;
+import android.content.Context;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.graphics.Path;
+import android.support.v4.content.ContextCompat;
+import android.widget.RelativeLayout;
+
+@SuppressLint("ViewConstructor")
+public class NavigationViewShadow extends RelativeLayout {
+    private final int spaceNavigationShadowHeight = (int) Math.ceil(getResources().getDimension(R.dimen.space_navigation_shadow_width));
+
+    private Paint paint;
+
+    private int bezierWidth, bezierHeight, navigationWidth;
+
+    private Context context;
+
+    private boolean isLinear=false;
+
+    int [] alphaArray = new int[]{11, 9, 7, 6, 5, 4, 3, 2, 1, 0};
+
+    NavigationViewShadow(Context context) {
+        super(context);
+        this.context = context;
+        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
+        paint.setStrokeWidth(2);
+        paint.setAntiAlias(true);
+        paint.setStyle(Paint.Style.STROKE);
+    }
+
+    @Override
+    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
+        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
+        setBackgroundColor(ContextCompat.getColor(context, R.color.space_transparent));
+    }
+
+    @Override
+    protected void onDraw(Canvas canvas) {
+        // translate canvas by shadow width. Otherwise canvas clips top part bezier curve
+        canvas.translate(0, spaceNavigationShadowHeight);
+
+        // Should draw paths "spaceNavigationShadowHeight" times
+        for (int i = 0; i<spaceNavigationShadowHeight; i++){
+            /**
+             * Draw shadow
+             */
+            // If path count exceeds alpha array size then assign alpha level of zero to the rest of paths
+            if (i >= alphaArray.length){
+                canvas.drawPath(drawPathWithOffset(0, i), paint);
+            }else {
+                canvas.drawPath(drawPathWithOffset(alphaArray[i], i), paint);
+            }
+
+        }
+    }
+
+    private Path drawPathWithOffset(int alpha, int offset){
+
+        int offsettedBeizerHeight = bezierHeight - offset;
+
+        Path path = new Path();
+        /**
+         * Reset path before drawing
+         */
+        path.reset();
+
+        /**
+         * Set paint color to draw the path with
+         */
+        paint.setColor(Color.BLACK);
+
+
+        /**
+         * Set alpha to change opacity of path
+         */
+        paint.setAlpha(alpha);
+
+        /**
+         * Start point for drawing
+         */
+        path.moveTo(0, offsettedBeizerHeight);
+
+        /**
+         * Draw line over left main-content
+         */
+        path.lineTo((navigationWidth-bezierWidth)/2, offsettedBeizerHeight);
+
+        if(!isLinear){
+            /**
+             * Seth half path of bezier view
+             */
+            path.cubicTo(bezierWidth / 4+(navigationWidth-bezierWidth)/2, offsettedBeizerHeight, bezierWidth / 4+(navigationWidth-bezierWidth)/2, -offset, bezierWidth / 2+(navigationWidth-bezierWidth)/2, -offset);
+            /**
+             * Seth second part of bezier view
+             */
+            path.cubicTo((bezierWidth / 4) * 3 +(navigationWidth-bezierWidth)/2, -offset, (bezierWidth / 4) * 3 +(navigationWidth-bezierWidth)/2, offsettedBeizerHeight, bezierWidth+(navigationWidth-bezierWidth)/2, offsettedBeizerHeight);
+        }
+
+        /**
+         * Draw line over right main-content
+         */
+        path.lineTo(navigationWidth, offsettedBeizerHeight);
+
+        return path;
+    }
+
+    /**
+     * Build bezier view with given width and height
+     *
+     * @param bezierWidth  Given width
+     * @param bezierHeight Given height
+     * @param isLinear True, if curves are not needed
+     */
+    void build(int navigationWidth, int bezierWidth, int bezierHeight,boolean isLinear) {
+        this.navigationWidth = navigationWidth;
+        this.bezierWidth = bezierWidth;
+        this.bezierHeight = bezierHeight;
+        this.isLinear=isLinear;
+    }
+}

spacelib/src/main/java/com/luseen/spacenavigation/SpaceNavigationView.java

@@ -69,10 +69,12 @@ public class SpaceNavigationView extends RelativeLayout {
 
     private static final int MIN_SPACE_ITEM_SIZE = 2;
     private final int spaceNavigationHeight = (int) getResources().getDimension(com.luseen.spacenavigation.R.dimen.space_navigation_height);
+    private final int spaceNavigationShadowHeight = (int) Math.ceil(getResources().getDimension(R.dimen.space_navigation_shadow_width));
     private final int mainContentHeight = (int) getResources().getDimension(com.luseen.spacenavigation.R.dimen.main_content_height);
     private final int centreContentWight = (int) getResources().getDimension(com.luseen.spacenavigation.R.dimen.centre_content_width);
     private final int itemContentWight = (int) getResources().getDimension(com.luseen.spacenavigation.R.dimen.item_content_width);
     private final int centreButtonSize = (int) getResources().getDimension(com.luseen.spacenavigation.R.dimen.space_centre_button_default_size);
+    private int spaceNavigationWidth;
     private List<SpaceItem> spaceItems = new ArrayList<>();
     private List<View> spaceItemList = new ArrayList<>();
     private List<RelativeLayout> badgeList = new ArrayList<>();
@@ -85,6 +87,7 @@ public class SpaceNavigationView extends RelativeLayout {
     private RelativeLayout centreBackgroundView;
     private LinearLayout leftContent, rightContent;
     private BezierView centreContent;
+    private NavigationViewShadow navigationViewBorderLine;
     private Typeface customFont;
     private Context context;
     private int spaceItemIconSize = NOT_DEFINED;
@@ -221,7 +224,8 @@ protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
          */
         ViewGroup.LayoutParams params = getLayoutParams();
         params.width = ViewGroup.LayoutParams.MATCH_PARENT;
-        params.height = spaceNavigationHeight;
+        // width increase by shadow width to allow shadow be visible, otherwise shadow will be clipped
+        params.height = spaceNavigationHeight+spaceNavigationShadowHeight;
         setBackgroundColor(ContextCompat.getColor(context, R.color.space_transparent));
         setLayoutParams(params);
     }
@@ -230,6 +234,8 @@ protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     protected void onSizeChanged(int width, int height, int oldWidth, int oldHeight) {
         super.onSizeChanged(width, height, oldWidth, oldHeight);
 
+        spaceNavigationWidth = width;
+
         /**
          * Restore current item index from savedInstance
          */
@@ -289,6 +295,7 @@ private void initAndAddViewsToMainView() {
         rightContent = new LinearLayout(context);
 
         centreContent = buildBezierView();
+        navigationViewBorderLine = buildBezierBorderline();
 
         centreButton = new CentreButton(context);
 
@@ -343,6 +350,13 @@ public boolean onLongClick(View v) {
         centreContentParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
         centreContentParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
 
+        /**
+         * Borderline params
+         */
+        LayoutParams borderLineParams = new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, spaceNavigationHeight);
+        borderLineParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
+        borderLineParams.addRule(RelativeLayout.ALIGN_PARENT_TOP);
+
         /**
          * Centre Background View content size and position
          */
@@ -371,6 +385,11 @@ public boolean onLongClick(View v) {
          */
         setBackgroundColors();
 
+        /**
+         * Adding shadow first, so it appears under all views
+         */
+        addView(navigationViewBorderLine, borderLineParams);
+
         /**
          * Adding view to centreContent
          */
@@ -438,7 +457,7 @@ private void addSpaceItems(LinearLayout leftContent, LinearLayout rightContent)
                 targetWidth = contentWidth;
             }
 
-            RelativeLayout.LayoutParams textAndIconContainerParams = new RelativeLayout.LayoutParams(
+            LayoutParams textAndIconContainerParams = new LayoutParams(
                     targetWidth, mainContentHeight);
             RelativeLayout textAndIconContainer = (RelativeLayout) inflater.inflate(R.layout.space_item_view, this, false);
             textAndIconContainer.setLayoutParams(textAndIconContainerParams);
@@ -716,6 +735,17 @@ private BezierView buildBezierView() {
         return bezierView;
     }
 
+    /**
+     * Creating borderline with params
+     *
+     * @return created borderline view
+     */
+    private NavigationViewShadow buildBezierBorderline() {
+        NavigationViewShadow borderline = new NavigationViewShadow(context);
+        borderline.build(spaceNavigationWidth, centreContentWight, spaceNavigationHeight - mainContentHeight,isCentrePartLinear);
+        return borderline;
+    }
+
     /**
      * Throw Array Index Out Of Bounds Exception
      *

spacelib/src/main/res/values/dimens.xml

@@ -10,4 +10,5 @@
     <dimen name="space_item_text_default_size">14sp</dimen>
     <dimen name="badge_left_margin">5dp</dimen>
     <dimen name="view_bottom_margin">50dp</dimen>
+    <dimen name="space_navigation_shadow_width">4dp</dimen>
 </resources>