smooth scroll works!

android/app/src/main/java/com/reactnativenavigation/screens/FragmentScreen.java

@@ -38,7 +38,7 @@ public class FragmentScreen extends Screen {
     }
 
     private void addContent() {
-        ContentView contentView = new ContentView(getContext(), screenParams.screenId, screenParams.passProps, screenParams.navigationParams, null);
+        ContentView contentView = new ContentView(getContext(), screenParams.screenId, screenParams.passProps, screenParams.navigationParams, topBar);
         addView(contentView, 0, 0);
         LayoutParams params = new LayoutParams(MATCH_PARENT, MATCH_PARENT);
         if (screenParams.styleParams.drawScreenBelowTopBar) {

android/app/src/main/java/com/reactnativenavigation/screens/Screen.java

@@ -9,7 +9,6 @@ import android.util.Log;
 import android.view.Window;
 import android.widget.RelativeLayout;
 
-import com.reactnativenavigation.animation.VisibilityAnimator;
 import com.reactnativenavigation.params.ScreenParams;
 import com.reactnativenavigation.params.StyleParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
@@ -25,13 +24,12 @@ import java.util.List;
 import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
 import static android.view.ViewGroup.LayoutParams.WRAP_CONTENT;
 
-public abstract class Screen extends RelativeLayout implements ScrollDirectionListener.OnScrollChanged {
+public abstract class Screen extends RelativeLayout {
 
     protected final AppCompatActivity activity;
     protected final ScreenParams screenParams;
     protected TopBar topBar;
     private final TitleBarBackButtonListener titleBarBackButtonListener;
-    private VisibilityAnimator topBarVisibilityAnimator;
 
     public Screen(AppCompatActivity activity, ScreenParams screenParams, TitleBarBackButtonListener titleBarBackButtonListener) {
         super(activity);
@@ -59,22 +57,10 @@ public abstract class Screen extends RelativeLayout implements ScrollDirectionLi
 
     private void createTopBar() {
         topBar = new TopBar(getContext());
-        createTopBarVisibilityAnimator();
         addView(topBar, new LayoutParams(MATCH_PARENT, WRAP_CONTENT));
     }
 
-    private void createTopBarVisibilityAnimator() {
-        ViewUtils.runOnPreDraw(topBar, new Runnable() {
-            @Override
-            public void run() {
-                if (topBarVisibilityAnimator == null) {
-                    topBarVisibilityAnimator = new VisibilityAnimator(topBar, VisibilityAnimator.HideDirection.Up, topBar.getHeight());
-                }
-            }
-        });
-    }
-
-    private void setStyle(StyleParams styleParams) {
+    private void setStyle(ScreenStyleParams styleParams) {
         setStatusBarColor(styleParams.statusBarColor);
         setNavigationBarColor(styleParams.navigationBarColor);
         topBar.setStyle(styleParams);
@@ -122,11 +108,6 @@ public abstract class Screen extends RelativeLayout implements ScrollDirectionLi
         Log.d("LOG", "Screen.onDetachedFromWindow " + this);
     }
 
-    @Override
-    public void onScrollChanged(ScrollDirectionListener.Direction direction) {
-        topBarVisibilityAnimator.onScrollChanged(direction);
-    }
-
     public abstract void ensureUnmountOnDetachedFromWindow();
 
     public abstract void preventUnmountOnDetachedFromWindow();
@@ -138,7 +119,7 @@ public abstract class Screen extends RelativeLayout implements ScrollDirectionLi
     }
 
     public void setTopBarVisible(boolean visible, boolean animate) {
-        topBarVisibilityAnimator.setVisible(visible, animate);
+//        topBarVisibilityAnimator.setVisible(visible, animate); TODO
     }
 
     public void setTitleBarTitle(String title) {

android/app/src/main/java/com/reactnativenavigation/screens/SingleScreen.java

@@ -19,7 +19,7 @@ public class SingleScreen extends Screen {
 
     @Override
     protected void createContent() {
-        contentView = new ContentView(getContext(), screenParams.screenId, screenParams.passProps, screenParams.navigationParams, this);
+        contentView = new ContentView(getContext(), screenParams.screenId, screenParams.passProps, screenParams.navigationParams, topBar);
         LayoutParams params = new LayoutParams(MATCH_PARENT, MATCH_PARENT);
         if (screenParams.styleParams.drawScreenBelowTopBar) {
             params.addRule(BELOW, topBar.getId());

android/app/src/main/java/com/reactnativenavigation/screens/ViewPagerScreen.java

@@ -39,8 +39,7 @@ public class ViewPagerScreen extends Screen {
             ContentView contentView = new ContentView(getContext(),
                     topTabParam.screenId,
                     screenParams.passProps,
-                    screenParams.navigationParams,
-                    this);
+                    screenParams.navigationParams, topBar);
             addContent(contentView);
             contentViews.add(contentView);
         }

android/app/src/main/java/com/reactnativenavigation/utils/SdkSupports.java

@@ -7,4 +7,8 @@ public class SdkSupports {
     public static boolean lollipop() {
         return Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP;
     }
+
+    public static boolean marshmallow() {
+        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.M;
+    }
 }

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

@@ -3,6 +3,7 @@ package com.reactnativenavigation.views;
 import android.content.Context;
 import android.os.Bundle;
 import android.view.View;
+import android.widget.ScrollView;
 
 import com.facebook.react.ReactInstanceManager;
 import com.facebook.react.ReactRootView;
@@ -14,17 +15,57 @@ public class ContentView extends ReactRootView {
     private final String screenId;
     private final Bundle passProps;
     private Bundle navigationParams;
-    private ScrollViewAttacher scrollViewAttacher;
+    private ScrollViewDelegate scrollViewDelegate = new ScrollViewDelegate();
 
-    public ContentView(Context context, String screenId, Bundle passProps, Bundle navigationParams, ScrollDirectionListener.OnScrollChanged scrollListener) {
+    public ContentView(Context context, final String screenId, Bundle passProps, Bundle navigationParams, final TopBar topBar) {
         super(context);
         this.screenId = screenId;
         this.passProps = passProps;
         this.navigationParams = navigationParams;
-        if (scrollListener != null) {
-            scrollViewAttacher = new ScrollViewAttacher(scrollListener);
-        }
         attachToJS();
+
+        scrollViewDelegate.setListener(new ScrollViewDelegate.OnScrollListener() {
+
+            private ScrollDirection scrollDirectionComputer;
+
+
+            @Override
+            public void onScroll(ScrollView scrollView) {
+                /**
+                 * do our magic
+                 */
+                if (scrollDirectionComputer == null) {
+                    scrollDirectionComputer = new ScrollDirection(scrollView);
+                }
+
+                int currentTopBarTranslation = (int) topBar.getTranslationY();
+                int delta = scrollDirectionComputer.getScrollDelta();
+
+                int minTranslation = -topBar.getTitleBar().getHeight();
+                int maxTranslation = 0;
+
+                ScrollDirection.Direction direction = scrollDirectionComputer.getScrollDirection();
+
+                boolean reachedMinimum = direction == ScrollDirection.Direction.Up && currentTopBarTranslation <= minTranslation;
+                boolean reachedMaximum = direction == ScrollDirection.Direction.Down && currentTopBarTranslation >= maxTranslation;
+
+                if (direction == ScrollDirection.Direction.None || reachedMinimum || reachedMaximum) {
+                    if (reachedMinimum) {
+                        topBar.animate().translationY(minTranslation);
+                    }
+                    if (reachedMaximum) {
+                        topBar.animate().translationY(maxTranslation);
+                    }
+                } else {
+
+                    int target = currentTopBarTranslation - delta;
+                    int bound = Math.min(Math.max(minTranslation, target), maxTranslation);
+
+                    topBar.setTranslationY(bound);
+                }
+
+            }
+        });
     }
 
     private void attachToJS() {
@@ -35,9 +76,7 @@ public class ContentView extends ReactRootView {
     @Override
     public void onViewAdded(View child) {
         super.onViewAdded(child);
-        if (scrollViewAttacher != null) {
-            scrollViewAttacher.onViewAdded(child);
-        }
+        scrollViewDelegate.onViewAdded(child);
     }
 
     private Bundle mergePropsAndNavigationParams() {

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

@@ -0,0 +1,50 @@
+package com.reactnativenavigation.views;
+
+import android.widget.ScrollView;
+
+public class ScrollDirection {
+
+    public enum Direction {
+        Up, Down, None
+    }
+
+    private final ScrollView scrollView;
+    private int lastScrollY = 0;
+
+    public ScrollDirection(ScrollView scrollView) {
+        this.scrollView = scrollView;
+    }
+
+    public Direction getScrollDirection() {
+        Direction direction = Direction.None;
+
+        final int scrollY = scrollView.getScrollY();
+        if (isScrollPositionChanged(scrollY) && !isTopOverscroll(scrollY) && !isBottomOverscroll(scrollY)) {
+            direction = getScrollDirection(scrollY);
+            lastScrollY = scrollY;
+        }
+        return direction;
+    }
+
+    public int getScrollDelta() {
+        return scrollView.getScrollY() - lastScrollY;
+    }
+
+
+    private Direction getScrollDirection(int scrollY) {
+        return scrollY > lastScrollY ? Direction.Up : Direction.Down;
+    }
+
+    private boolean isBottomOverscroll(int scrollY) {
+        return scrollY >= (scrollView.getChildAt(0).getHeight() - scrollView.getHeight());
+    }
+
+    private boolean isTopOverscroll(int scrollY) {
+        return scrollY <= 0;
+    }
+
+    private boolean isScrollPositionChanged(int scrollY) {
+        return scrollY != lastScrollY;
+    }
+
+}

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

@@ -1,32 +0,0 @@
-package com.reactnativenavigation.views;
-
-import android.view.View;
-import android.widget.ScrollView;
-
-public class ScrollViewAttacher {
-
-    private final ScrollDirectionListener.OnScrollChanged onChanged;
-    private ScrollView scrollView;
-    private ScrollDirectionListener scrollDirectionListener;
-
-    public ScrollViewAttacher(ScrollDirectionListener.OnScrollChanged onChanged) {
-        this.onChanged = onChanged;
-    }
-
-    public void onViewAdded(View child) {
-        if (child instanceof ScrollView) {
-            detach();
-            scrollView = (ScrollView) child;
-            scrollDirectionListener = new ScrollDirectionListener(scrollView, onChanged);
-            scrollView.getViewTreeObserver().addOnScrollChangedListener(scrollDirectionListener);
-        }
-    }
-
-    private void detach() {
-        if (scrollView != null) {
-            scrollView.getViewTreeObserver().removeOnScrollChangedListener(scrollDirectionListener);
-            scrollDirectionListener = null;
-            scrollView = null;
-        }
-    }
-}

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

@@ -0,0 +1,59 @@
+package com.reactnativenavigation.views;
+
+import android.view.View;
+import android.view.ViewTreeObserver;
+import android.widget.ScrollView;
+
+import com.reactnativenavigation.utils.SdkSupports;
+
+public class ScrollViewDelegate implements ViewTreeObserver.OnScrollChangedListener {
+
+    public interface OnScrollListener {
+        void onScroll(ScrollView scrollView);
+    }
+
+    private ScrollView scrollView;
+    private OnScrollListener listener;
+
+    public ScrollViewDelegate() {
+    }
+
+    public void onViewAdded(View child) {
+        if (child instanceof ScrollView) {
+            detach();
+            scrollView = (ScrollView) child;
+            if (SdkSupports.marshmallow()) {
+                scrollView.setOnScrollChangeListener(new View.OnScrollChangeListener() {
+                    @Override
+                    public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
+                        ScrollViewDelegate.this.onScrollChanged();
+                    }
+                });
+            } else {
+                scrollView.getViewTreeObserver().addOnScrollChangedListener(this);
+            }
+        }
+    }
+
+    private void detach() {
+        if (scrollView != null) {
+            if (SdkSupports.marshmallow()) {
+                scrollView.setOnScrollChangeListener(null);
+            } else {
+                scrollView.getViewTreeObserver().removeOnScrollChangedListener(this);
+            }
+            scrollView = null;
+        }
+    }
+
+    public void setListener(OnScrollListener listener) {
+        this.listener = listener;
+    }
+
+    @Override
+    public void onScrollChanged() {
+        if (this.listener != null) {
+            this.listener.onScroll(scrollView);
+        }
+    }
+}

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

@@ -58,4 +58,8 @@ public class TopBar extends AppBarLayout {
                                        TitleBarLeftButtonParams titleBarLeftButtonParams) {
         titleBar.setLeftButton(titleBarLeftButtonParams, titleBarBackButtonListener, navigatorEventId);
     }
+
+    public TitleBar getTitleBar() {
+        return titleBar;
+    }
 }