Prevent toggling when messages are less.

Don't toggle toolbar and floating button
if messages doesn't occupy full screen.

Author: jainkuniya

app/src/main/java/com/zulip/android/activities/MessageListFragment.java

@@ -164,6 +164,7 @@ public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                 }
             }
         });
+        mListener.setLayoutBehaviour(linearLayoutManager,adapter);
         return view;
     }
 
@@ -701,6 +702,8 @@ public interface Listener {
         void recyclerViewScrolled();
 
         void clearChatBox();
+
+        void setLayoutBehaviour(LinearLayoutManager linearLayoutManager , RecyclerMessageAdapter adapter);
     }
 
     public void showLatestMessages() {

app/src/main/java/com/zulip/android/activities/ZulipActivity.java

@@ -45,6 +45,7 @@
 import android.support.v4.widget.DrawerLayout;
 import android.support.v4.widget.SimpleCursorAdapter;
 import android.support.v7.app.AppCompatDelegate;
+import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.Toolbar;
 import android.text.Editable;
 import android.text.TextUtils;
@@ -102,6 +103,7 @@
 import com.zulip.android.util.AnimationHelper;
 import com.zulip.android.util.FilePathHelper;
 import com.zulip.android.util.MutedTopics;
+import com.zulip.android.util.RemoveViewsOnScroll;
 import com.zulip.android.util.SwipeRemoveLinearLayout;
 import com.zulip.android.util.UrlHelper;
 import com.zulip.android.util.ZLog;
@@ -254,6 +256,10 @@ public void removeChatBox(boolean animToRight) {
             hideSoftKeyBoard();
         }
         AnimationHelper.hideViewX(chatBox, animToRight);
+        //show fab button
+        CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) fab.getLayoutParams();
+        RemoveViewsOnScroll removeViewsOnScroll = (RemoveViewsOnScroll) layoutParams.getBehavior();
+        removeViewsOnScroll.showView(fab);
     }
 
     public HashMap<String, Bitmap> getGravatars() {
@@ -1648,6 +1654,17 @@ public void clearChatBox() {
         }
     }
 
+    @Override
+    public void setLayoutBehaviour(LinearLayoutManager linearLayoutManager, RecyclerMessageAdapter adapter) {
+        CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
+        layoutParams.setBehavior(new RemoveViewsOnScroll(linearLayoutManager, adapter));
+        appBarLayout.requestLayout();
+
+        layoutParams = (CoordinatorLayout.LayoutParams) fab.getLayoutParams();
+        layoutParams.setBehavior(new RemoveViewsOnScroll(linearLayoutManager, adapter));
+        fab.setLayoutParams(layoutParams);
+    }
+
     @Override
     public void onBackPressed() {
         //check for drawer

app/src/main/java/com/zulip/android/util/RemoveViewsOnScroll.java

@@ -8,13 +8,15 @@
 import android.support.design.widget.FloatingActionButton;
 import android.support.v4.view.ViewCompat;
 import android.support.v4.view.animation.FastOutSlowInInterpolator;
+import android.support.v7.widget.LinearLayoutManager;
 import android.util.AttributeSet;
 import android.util.TypedValue;
 import android.view.View;
 import android.view.ViewPropertyAnimator;
 import android.view.animation.Interpolator;
 
 import com.zulip.android.R;
+import com.zulip.android.activities.RecyclerMessageAdapter;
 
 /**
  * This hides the {@link AppBarLayout} and {@link android.support.design.widget.FloatingActionButton} when the
@@ -27,6 +29,8 @@ public class RemoveViewsOnScroll extends CoordinatorLayout.Behavior<View> {
     private boolean mIsShowing;
     private boolean isViewHidden;
     private View chatBox;
+    private LinearLayoutManager linearLayoutManager;
+    private RecyclerMessageAdapter adapter;
 
     public RemoveViewsOnScroll(Context context, AttributeSet attrs) {
         super(context, attrs);
@@ -35,33 +39,42 @@ public RemoveViewsOnScroll(Context context, AttributeSet attrs) {
             toolbarHeight = TypedValue.complexToDimensionPixelSize(tv.data, context.getResources().getDisplayMetrics());
     }
 
+    public RemoveViewsOnScroll(LinearLayoutManager linearLayoutManager, RecyclerMessageAdapter adapter) {
+        this.linearLayoutManager = linearLayoutManager;
+        this.adapter = adapter;
+    }
+
     @Override
     public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, View child, View directTargetChild, View target, int nestedScrollAxes) {
         return (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
     }
 
     @SuppressLint("NewApi")
     @Override
-    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dx, int dy, int[] consumed) {
-        if (dy > 0 && changeInYDir < 0 || dy < 0 && changeInYDir > 0) {
-            child.animate().cancel();
-            changeInYDir = 0;
-        }
+    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dx, int dy, int[] consumed) throws NullPointerException {
+        //count index starts from 1 where as position starts from 0, thus difference 1
+        //we have 2 loading layouts one at top and another at bottom of the messages which should be ignored
+        //resulting in a overall difference of 3
+        if (linearLayoutManager.findLastCompletelyVisibleItemPosition() < adapter.getItemCount() - 3) {
+            if (dy > 0 && changeInYDir < 0 || dy < 0 && changeInYDir > 0) {
+                child.animate().cancel();
+                changeInYDir = 0;
+            }
 
-        changeInYDir += dy;
-        if (changeInYDir > toolbarHeight && child.getVisibility() == View.VISIBLE && !isViewHidden)
-            hideView(child);
-        else if (changeInYDir < 0 && child.getVisibility() == View.GONE && !mIsShowing) {
-            if (child instanceof FloatingActionButton) {
-                if (chatBox == null)
-                    chatBox = coordinatorLayout.findViewById(R.id.messageBoxContainer);
-                if (chatBox.getVisibility() == View.VISIBLE) {
-                    return;
+            changeInYDir += dy;
+            if (changeInYDir > toolbarHeight && child.getVisibility() == View.VISIBLE && !isViewHidden)
+                hideView(child);
+            else if (changeInYDir < 0 && child.getVisibility() == View.GONE && !mIsShowing) {
+                if (child instanceof FloatingActionButton) {
+                    if (chatBox == null)
+                        chatBox = coordinatorLayout.findViewById(R.id.messageBoxContainer);
+                    if (chatBox.getVisibility() == View.VISIBLE) {
+                        return;
+                    }
                 }
+                showView(child);
             }
-            showView(child);
         }
-
     }
 
     @SuppressLint("NewApi")
@@ -98,7 +111,7 @@ public void onAnimationRepeat(Animator animator) {
     }
 
     @SuppressLint("NewApi")
-    private void showView(final View view) {
+    public void showView(final View view) {
         mIsShowing = true;
         ViewPropertyAnimator animator = view.animate()
                 .translationY(0)