Add infra for adding Snackbar to Layouts.

android/app/src/main/java/com/reactnativenavigation/bridge/NavigationReactModule.java

 import com.facebook.react.bridge.ReadableArray;
 import com.facebook.react.bridge.ReadableMap;
 import com.reactnativenavigation.controllers.NavigationCommandsHandler;
+import com.reactnativenavigation.params.SnackbarParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
 import com.reactnativenavigation.params.TitleBarLeftButtonParams;
+import com.reactnativenavigation.params.parsers.SnackbarParamsParser;
 import com.reactnativenavigation.params.parsers.TitleBarButtonParamsParser;
 import com.reactnativenavigation.params.parsers.TitleBarLeftButtonParamsParser;
 
     public void dismissTopModal() {
         NavigationCommandsHandler.dismissTopModal();
     }
+
+    @ReactMethod
+    public void showSnackbar(final ReadableMap params) {
+        SnackbarParams snackbarParams = new SnackbarParamsParser().parse(BundleConverter.toBundle(params));
+        NavigationCommandsHandler.showSnackbar(snackbarParams);
+    }
 }

android/app/src/main/java/com/reactnativenavigation/controllers/NavigationActivity.java

 import com.reactnativenavigation.layouts.LayoutFactory;
 import com.reactnativenavigation.params.ActivityParams;
 import com.reactnativenavigation.params.ScreenParams;
+import com.reactnativenavigation.params.SnackbarParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
 import com.reactnativenavigation.params.TitleBarLeftButtonParams;
 import com.reactnativenavigation.react.JsDevReloadHandler;
             ((BottomTabsLayout) layout).setBottomTabBadgeByNavigatorId(navigatorId, badge);
         }
     }
+
+    public void showSnackbar(SnackbarParams params) {
+        layout.showSnackbar(params);
+    }
 }

android/app/src/main/java/com/reactnativenavigation/controllers/NavigationCommandsHandler.java

 import com.reactnativenavigation.NavigationApplication;
 import com.reactnativenavigation.params.ActivityParams;
 import com.reactnativenavigation.params.ScreenParams;
+import com.reactnativenavigation.params.SnackbarParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
 import com.reactnativenavigation.params.TitleBarLeftButtonParams;
 import com.reactnativenavigation.params.parsers.ActivityParamsParser;
             }
         });
     }
+
+    public static void showSnackbar(final SnackbarParams params) {
+        final NavigationActivity currentActivity = NavigationActivity.currentActivity;
+        if (currentActivity == null) {
+            return;
+        }
+
+        NavigationApplication.instance.runOnMainThread(new Runnable() {
+            @Override
+            public void run() {
+                currentActivity.showSnackbar(params);
+            }
+        });
+    }
 }

android/app/src/main/java/com/reactnativenavigation/layouts/BottomTabsLayout.java

 import com.reactnativenavigation.params.ActivityParams;
 import com.reactnativenavigation.params.ScreenParams;
 import com.reactnativenavigation.params.SideMenuParams;
+import com.reactnativenavigation.params.SnackbarParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
 import com.reactnativenavigation.params.TitleBarLeftButtonParams;
 import com.reactnativenavigation.screens.ScreenStack;
 import com.reactnativenavigation.views.BottomTabs;
 import com.reactnativenavigation.views.SideMenu;
+import com.reactnativenavigation.views.SnackbarContainer;
 
 import java.util.List;
 
 
     private final AppCompatActivity activity;
     private ActivityParams params;
+    private SnackbarContainer snackbarContainer;
     private BottomTabs bottomTabs;
     private ScreenStack[] screenStacks;
     private final SideMenuParams sideMenuParams;
         createBottomTabs();
         addBottomTabs();
         addScreenStacks();
+        createSnackbarContainer();
         showInitialScreenStack();
     }
 
         getScreenStackParent().addView(bottomTabs, lp);
     }
 
+    private void createSnackbarContainer() {
+        snackbarContainer = new SnackbarContainer(getContext());
+        RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(MATCH_PARENT, WRAP_CONTENT);
+        lp.addRule(ABOVE, bottomTabs.getId());
+        snackbarContainer.setLayoutParams(lp);
+    }
+
     private void showInitialScreenStack() {
         showStackAndUpdateStyle(screenStacks[0]);
     }
         }
     }
 
+    @Override
+    public void showSnackbar(SnackbarParams params) {
+        // TODO: implement me
+    }
+
     public void selectBottomTabByTabIndex(Integer index) {
         bottomTabs.setCurrentItem(index);
     }

android/app/src/main/java/com/reactnativenavigation/layouts/Layout.java

 
 import android.view.View;
 
+import com.reactnativenavigation.params.SnackbarParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
 import com.reactnativenavigation.params.TitleBarLeftButtonParams;
 
     void toggleSideMenuVisible(boolean animated);
 
     void setSideMenuVisible(boolean animated, boolean visible);
+
+    void showSnackbar(SnackbarParams params);
 }

android/app/src/main/java/com/reactnativenavigation/layouts/SingleScreenLayout.java

 
 import com.reactnativenavigation.params.ScreenParams;
 import com.reactnativenavigation.params.SideMenuParams;
+import com.reactnativenavigation.params.SnackbarParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
 import com.reactnativenavigation.params.TitleBarLeftButtonParams;
 import com.reactnativenavigation.screens.ScreenStack;
         }
     }
 
+    @Override
+    public void showSnackbar(SnackbarParams params) {
+        // TODO: implement me
+    }
+
     @Override
     public boolean onTitleBarBackButtonClick() {
         if (leftButtonOnClickListener != null) {

android/app/src/main/java/com/reactnativenavigation/params/SnackbarParams.java

+package com.reactnativenavigation.params;
+
+public class SnackbarParams {
+    public String text;
+    public StyleParams.Color textColor;
+    public String buttonText;
+    public StyleParams.Color buttonColor;
+}

android/app/src/main/java/com/reactnativenavigation/params/StyleParams.java

 
     public boolean drawScreenAboveBottomTabs;
 
+    public Color snackbarTextColor;
+    public Color snackbarButtonColor;
+
     public boolean bottomTabsHidden;
     public boolean bottomTabsHiddenOnScroll;
     public Color bottomTabsColor;

android/app/src/main/java/com/reactnativenavigation/params/parsers/Parser.java

 
 import android.os.Bundle;
 
+import com.reactnativenavigation.params.StyleParams;
+
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
         return bundle.keySet().contains(key);
     }
 
-
     protected static void assertKeyExists(Bundle bundle, String key) {
         if (!hasKey(bundle, key)) {
             throw new KeyDoesNotExistsException(key);
         }
         return result;
     }
+
+    protected StyleParams.Color getColor(Bundle bundle, String key, StyleParams.Color defaultColor) {
+        StyleParams.Color color = StyleParams.Color.parse(bundle.getString(key));
+        return color.hasColor() || defaultColor == null ? color : defaultColor;
+    }
 }

android/app/src/main/java/com/reactnativenavigation/params/parsers/SnackbarParamsParser.java

+package com.reactnativenavigation.params.parsers;
+
+import android.os.Bundle;
+
+import com.reactnativenavigation.params.AppStyle;
+import com.reactnativenavigation.params.SnackbarParams;
+import com.reactnativenavigation.params.StyleParams;
+
+public class SnackbarParamsParser extends Parser {
+    public SnackbarParams parse(Bundle params) {
+        SnackbarParams result = new SnackbarParams();
+        result.text = params.getString("text");
+        result.textColor = getColor(params, "textColor", AppStyle.appStyle.snackbarTextColor);
+        result.buttonText = params.getString("buttonText");
+        result.buttonColor = getColor(params, "buttonColor", AppStyle.appStyle.snackbarButtonColor);
+        return result;
+    }
+}

android/app/src/main/java/com/reactnativenavigation/params/parsers/TitleBarButtonParamsParser.java

 import android.os.Bundle;
 
 import com.reactnativenavigation.params.AppStyle;
-import com.reactnativenavigation.params.StyleParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
 import com.reactnativenavigation.react.ImageLoader;
 
         return result;
     }
 
-    private StyleParams.Color getColor(Bundle bundle, String key, StyleParams.Color defaultColor) {
-        StyleParams.Color color = StyleParams.Color.parse(bundle.getString(key));
-        return color.hasColor() || defaultColor == null ? color : defaultColor;
-    }
-
     private static TitleBarButtonParams.ShowAsAction parseShowAsAction(String showAsAction) {
         if (showAsAction == null) {
             return TitleBarButtonParams.ShowAsAction.IfRoom;

android/app/src/main/java/com/reactnativenavigation/views/SnackbarContainer.java

+package com.reactnativenavigation.views;
+
+import android.content.Context;
+import android.widget.LinearLayout;
+
+public class SnackbarContainer extends LinearLayout {
+
+    public SnackbarContainer(Context context) {
+        super(context);
+        setOrientation(LinearLayout.VERTICAL);
+    }
+}

src/Screen.js

     return platformSpecific.navigatorSwitchToTab(this, params);
   }
 
+  showSnackbar(params = {}) {
+    return platformSpecific.showSnackbar(this, params);
+  }
+
   setOnNavigatorEvent(callback) {
     this.navigatorEventHandler = callback;
     if (!this.navigatorEventSubscription) {

src/deprecated/platformSpecificDeprecated.android.js

   screen.navigatorStyle = Object.assign({}, screen.navigatorStyle, Screen.navigatorStyle);
 }
 
+function showSnackbar(navigator, params) {
+  return newPlatformSpecific.showSnackbar(params.text);
+}
+
 export default {
   startTabBasedApp,
   startSingleScreenApp,
   navigatorSwitchToTab,
   navigatorToggleDrawer,
   navigatorToggleTabs,
-  navigatorToggleNavBar
+  navigatorToggleNavBar,
+  showSnackbar
 };

src/platformSpecific.android.js

   NativeReactModule.setBottomTabBadgeByNavigatorId(navigatorId, badge);
 }
 
+function showSnackbar(text) {
+  NativeReactModule.showSnackbar(text);
+}
+
 module.exports = {
   startApp,
   push,
   selectBottomTabByNavigatorId,
   selectBottomTabByTabIndex,
   setBottomTabBadgeByNavigatorId,
-  setBottomTabBadgeByIndex
+  setBottomTabBadgeByIndex,
+  showSnackbar
 };