Lazy Mode: Automatically scroll down the recyclerview in PostFragment to view posts without using hands.

app/src/main/java/ml/docilealligator/infinityforreddit/FragmentCommunicator.java

@@ -2,4 +2,6 @@ package ml.docilealligator.infinityforreddit;
 
 interface FragmentCommunicator {
     void refresh();
+    default void startLazyMode() {};
+    default void stopLazyMode() {};
 }

app/src/main/java/ml/docilealligator/infinityforreddit/MainActivity.java

@@ -12,10 +12,23 @@ import android.widget.ImageView;
 import android.widget.LinearLayout;
 import android.widget.TextView;
 
+import androidx.annotation.NonNull;
+import androidx.appcompat.app.ActionBarDrawerToggle;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.appcompat.widget.Toolbar;
+import androidx.core.view.GravityCompat;
+import androidx.drawerlayout.widget.DrawerLayout;
+import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProviders;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
 import com.bumptech.glide.Glide;
 import com.bumptech.glide.RequestManager;
 import com.bumptech.glide.request.RequestOptions;
 import com.ferfalk.simplesearchview.SimpleSearchView;
+import com.google.android.material.appbar.AppBarLayout;
+import com.google.android.material.appbar.CollapsingToolbarLayout;
 
 import java.util.ArrayList;
 
@@ -30,15 +43,6 @@ import SubscribedSubredditDatabase.SubscribedSubredditViewModel;
 import SubscribedUserDatabase.SubscribedUserData;
 import SubscribedUserDatabase.SubscribedUserRoomDatabase;
 import SubscribedUserDatabase.SubscribedUserViewModel;
-import androidx.appcompat.app.ActionBarDrawerToggle;
-import androidx.appcompat.app.AppCompatActivity;
-import androidx.appcompat.widget.Toolbar;
-import androidx.core.view.GravityCompat;
-import androidx.drawerlayout.widget.DrawerLayout;
-import androidx.fragment.app.Fragment;
-import androidx.lifecycle.ViewModelProviders;
-import androidx.recyclerview.widget.LinearLayoutManager;
-import androidx.recyclerview.widget.RecyclerView;
 import butterknife.BindView;
 import butterknife.ButterKnife;
 import jp.wasabeef.glide.transformations.RoundedCornersTransformation;
@@ -50,10 +54,12 @@ public class MainActivity extends AppCompatActivity {
     private static final String FRAGMENT_OUT_STATE = "FOS";
     private static final String FETCH_USER_INFO_STATE = "FUIS";
     private static final String INSERT_SUBSCRIBED_SUBREDDIT_STATE = "ISSS";
+    private static final String IS_IN_LAZY_MODE_STATE = "IILMS";
 
     private static final int LOGIN_ACTIVITY_REQUEST_CODE = 0;
 
     @BindView(R.id.drawer_layout) DrawerLayout drawer;
+    @BindView(R.id.collapsing_toolbar_layout_main_activity) CollapsingToolbarLayout collapsingToolbarLayout;
     @BindView(R.id.search_view_main_activity) SimpleSearchView simpleSearchView;
     @BindView(R.id.transparent_overlay_main_activity) View transparentOverlay;
     @BindView(R.id.subscribed_subreddit_recycler_view_main_activity) RecyclerView subscribedSubredditRecyclerView;
@@ -69,6 +75,7 @@ public class MainActivity extends AppCompatActivity {
 
     private Fragment mFragment;
     private RequestManager glide;
+    private AppBarLayout.LayoutParams params;
 
     private String mName;
     private String mProfileImageUrl;
@@ -77,9 +84,13 @@ public class MainActivity extends AppCompatActivity {
     private boolean mFetchUserInfoSuccess = false;
     private boolean mInsertSuccess = false;
 
+    private Menu mMenu;
+
     private SubscribedSubredditViewModel mSubscribedSubredditViewModel;
     private SubscribedUserViewModel mSubscribedUserViewModel;
 
+    private boolean isInLazyMode = false;
+
     @Inject
     @Named("user_info")
     SharedPreferences mUserInfoSharedPreferences;
@@ -109,6 +120,8 @@ public class MainActivity extends AppCompatActivity {
         drawer.addDrawerListener(toggle);
         toggle.syncState();
 
+        params = (AppBarLayout.LayoutParams) collapsingToolbarLayout.getLayoutParams();
+
         transparentOverlay.setOnClickListener(view -> simpleSearchView.onBackPressed());
 
         simpleSearchView.setOnQueryTextListener(new SimpleSearchView.OnQueryTextListener() {
@@ -170,6 +183,7 @@ public class MainActivity extends AppCompatActivity {
 
                 mFetchUserInfoSuccess = savedInstanceState.getBoolean(FETCH_USER_INFO_STATE);
                 mInsertSuccess = savedInstanceState.getBoolean(INSERT_SUBSCRIBED_SUBREDDIT_STATE);
+                isInLazyMode = savedInstanceState.getBoolean(IS_IN_LAZY_MODE_STATE);
             }
 
             glide = Glide.with(this);
@@ -347,24 +361,50 @@ public class MainActivity extends AppCompatActivity {
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.main_activity, menu);
-
+        mMenu = menu;
-        simpleSearchView.setMenuItem(menu.findItem(R.id.action_search_main_activity));
+        simpleSearchView.setMenuItem(mMenu.findItem(R.id.action_search_main_activity));
+        MenuItem lazyModeItem = mMenu.findItem(R.id.action_lazy_mode_main_activity);
+        if(isInLazyMode) {
+            lazyModeItem.setTitle(R.string.action_stop_lazy_mode);
+            params.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_NO_SCROLL);
+            collapsingToolbarLayout.setLayoutParams(params);
+        } else {
+            lazyModeItem.setTitle(R.string.action_start_lazy_mode);
+            params.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL | AppBarLayout.LayoutParams.SCROLL_FLAG_ENTER_ALWAYS);
+            collapsingToolbarLayout.setLayoutParams(params);
+        }
 
         return true;
     }
 
     @Override
     public boolean onOptionsItemSelected(MenuItem item) {
+        if (mFragment instanceof FragmentCommunicator) {
             switch (item.getItemId()) {
                 case R.id.action_refresh_main_activity:
-                if (mFragment instanceof FragmentCommunicator) {
                     ((FragmentCommunicator) mFragment).refresh();
                     mFetchUserInfoSuccess = false;
                     mInsertSuccess = false;
                     loadUserData();
+                    return true;
+                case R.id.action_lazy_mode_main_activity:
+                    MenuItem lazyModeItem = mMenu.findItem(R.id.action_lazy_mode_main_activity);
+                    if(isInLazyMode) {
+                        isInLazyMode = false;
+                        ((FragmentCommunicator) mFragment).stopLazyMode();
+                        lazyModeItem.setTitle(R.string.action_start_lazy_mode);
+                        params.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL | AppBarLayout.LayoutParams.SCROLL_FLAG_ENTER_ALWAYS);
+                        collapsingToolbarLayout.setLayoutParams(params);
+                    } else {
+                        isInLazyMode = true;
+                        ((FragmentCommunicator) mFragment).startLazyMode();
+                        lazyModeItem.setTitle(R.string.action_stop_lazy_mode);
+                        params.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_NO_SCROLL);
+                        collapsingToolbarLayout.setLayoutParams(params);
                     }
                     return true;
             }
+        }
         return false;
     }
 
@@ -383,7 +423,7 @@ public class MainActivity extends AppCompatActivity {
     }
 
     @Override
-    protected void onSaveInstanceState(Bundle outState) {
+    protected void onSaveInstanceState(@NonNull Bundle outState) {
         super.onSaveInstanceState(outState);
         if (mFragment != null) {
             getSupportFragmentManager().putFragment(outState, FRAGMENT_OUT_STATE, mFragment);
@@ -391,5 +431,6 @@ public class MainActivity extends AppCompatActivity {
 
         outState.putBoolean(FETCH_USER_INFO_STATE, mFetchUserInfoSuccess);
         outState.putBoolean(INSERT_SUBSCRIBED_SUBREDDIT_STATE, mInsertSuccess);
+        outState.putBoolean(IS_IN_LAZY_MODE_STATE, isInLazyMode);
     }
 }

app/src/main/java/ml/docilealligator/infinityforreddit/PostFragment.java

@@ -4,18 +4,23 @@ package ml.docilealligator.infinityforreddit;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.os.Bundle;
+import android.os.Handler;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.Window;
+import android.view.WindowManager;
 import android.widget.ImageView;
 import android.widget.LinearLayout;
 import android.widget.TextView;
+import android.widget.Toast;
 
 import androidx.annotation.NonNull;
 import androidx.coordinatorlayout.widget.CoordinatorLayout;
 import androidx.fragment.app.Fragment;
 import androidx.lifecycle.ViewModelProviders;
 import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.LinearSmoothScroller;
 import androidx.recyclerview.widget.RecyclerView;
 
 import com.bumptech.glide.Glide;
@@ -39,6 +44,7 @@ public class PostFragment extends Fragment implements FragmentCommunicator {
 
     static final String NAME_KEY = "NK";
     static final String POST_TYPE_KEY = "PTK";
+    private static final String IS_IN_LAZY_MODE_STATE = "IILMS";
 
     @BindView(R.id.coordinator_layout_post_fragment) CoordinatorLayout mCoordinatorLayout;
     @BindView(R.id.recycler_view_post_fragment) RecyclerView mPostRecyclerView;
@@ -51,11 +57,17 @@ public class PostFragment extends Fragment implements FragmentCommunicator {
 
     private String mName;
     private int mPostType;
+    private boolean isInLazyMode = false;
 
     private PostRecyclerViewAdapter mAdapter;
+    private RecyclerView.SmoothScroller smoothScroller;
 
     PostViewModel mPostViewModel;
 
+    private Window window;
+    private Handler lazyModeHandler;
+    private Runnable lazyModeRunnable;
+
     @Inject @Named("no_oauth")
     Retrofit mRetrofit;
 
@@ -89,6 +101,24 @@ public class PostFragment extends Fragment implements FragmentCommunicator {
 
         EventBus.getDefault().register(this);
 
+        lazyModeHandler = new Handler();
+
+        smoothScroller = new LinearSmoothScroller(getActivity()) {
+            @Override
+            protected int getVerticalSnapPreference() {
+                return LinearSmoothScroller.SNAP_TO_START;
+            }
+        };
+
+        window = getActivity().getWindow();
+
+        if(savedInstanceState != null) {
+            isInLazyMode = savedInstanceState.getBoolean(IS_IN_LAZY_MODE_STATE);
+            if(isInLazyMode) {
+                startLazyMode();
+            }
+        }
+
         mLinearLayoutManager = new LinearLayoutManager(getActivity());
         mPostRecyclerView.setLayoutManager(mLinearLayoutManager);
 
@@ -165,6 +195,12 @@ public class PostFragment extends Fragment implements FragmentCommunicator {
         return rootView;
     }
 
+    @Override
+    public void onSaveInstanceState(@NonNull Bundle outState) {
+        super.onSaveInstanceState(outState);
+        outState.putBoolean(IS_IN_LAZY_MODE_STATE, isInLazyMode);
+    }
+
     @Override
     public void refresh() {
         mPostViewModel.refresh();
@@ -179,6 +215,36 @@ public class PostFragment extends Fragment implements FragmentCommunicator {
         }
     }
 
+    @Override
+    public void startLazyMode() {
+        Toast.makeText(getActivity(), getString(R.string.lazy_mode_start, 2.5), Toast.LENGTH_SHORT).show();
+        window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
+        isInLazyMode = true;
+        lazyModeRunnable = new Runnable() {
+            @Override
+            public void run() {
+                int nPosts = mAdapter.getItemCount();
+                int firstVisiblePosition = mLinearLayoutManager.findFirstVisibleItemPosition();
+                if(firstVisiblePosition != RecyclerView.NO_POSITION && nPosts > firstVisiblePosition) {
+                    smoothScroller.setTargetPosition(firstVisiblePosition + 1);
+                    mLinearLayoutManager.startSmoothScroll(smoothScroller);
+                }
+                if(isInLazyMode) {
+                    lazyModeHandler.postDelayed(this, 2500);
+                }
+            }
+        };
+        lazyModeHandler.postDelayed(lazyModeRunnable, 2500);
+    }
+
+    @Override
+    public void stopLazyMode() {
+        lazyModeHandler.removeCallbacks(lazyModeRunnable);
+        window.clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
+        isInLazyMode = false;
+        Toast.makeText(getActivity(), getString(R.string.lazy_mode_stop), Toast.LENGTH_SHORT).show();
+    }
+
     @Subscribe
     public void onPostUpdateEvent(PostUpdateEventToPostList event) {
         Post post = mAdapter.getCurrentList().get(event.positionInList);
@@ -190,6 +256,23 @@ public class PostFragment extends Fragment implements FragmentCommunicator {
         }
     }
 
+    @Override
+    public void onStart() {
+        super.onStart();
+        if(isInLazyMode) {
+            startLazyMode();
+        }
+    }
+
+    @Override
+    public void onStop() {
+        super.onStop();
+        if(isInLazyMode) {
+            stopLazyMode();
+        }
+        isInLazyMode = true;
+    }
+
     @Override
     public void onDestroy() {
         EventBus.getDefault().unregister(this);

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

@@ -12,6 +12,7 @@
         android:theme="@style/AppTheme.AppBarOverlay">
 
         <com.google.android.material.appbar.CollapsingToolbarLayout
+            android:id="@+id/collapsing_toolbar_layout_main_activity"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             app:titleEnabled="false"

app/src/main/res/menu/main_activity.xml

@@ -3,17 +3,22 @@
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     tools:context="ml.docilealligator.infinityforreddit.MainActivity">
-    <item
-        android:id="@+id/action_refresh_main_activity"
-        android:orderInCategory="2"
-        android:title="@string/action_refresh"
-        android:icon="@drawable/ic_refresh_white_24dp"
-        app:showAsAction="never" />
-
     <item
         android:id="@+id/action_search_main_activity"
         android:orderInCategory="1"
         android:title="@string/action_search"
         android:icon="@drawable/ic_search_white_24dp"
         app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/action_refresh_main_activity"
+        android:orderInCategory="2"
+        android:title="@string/action_refresh"
+        app:showAsAction="never" />
+
+    <item
+        android:id="@+id/action_lazy_mode_main_activity"
+        android:orderInCategory="3"
+        android:title="@string/action_start_lazy_mode"
+        app:showAsAction="never" />
 </menu>

app/src/main/res/values/strings.xml

@@ -10,6 +10,8 @@
     <string name="action_download">Download</string>
     <string name="action_refresh">Refresh</string>
     <string name="action_search">Search</string>
+    <string name="action_start_lazy_mode">Start Lazy Mode</string>
+    <string name="action_stop_lazy_mode">Stop Lazy Mode</string>
 
     <string name="tap_to_retry">Error loading image. Tap to retry.</string>
     <string name="load_posts_error">Error loading posts.\nTap to retry.</string>
@@ -63,4 +65,7 @@
     <string name="app_label">Infinity</string>
     <string name="search_hint">Search anything</string>
 
+    <string name="lazy_mode_start">Lazy Mode starts in %1$fs</string>
+    <string name="lazy_mode_stop">Lazy Mode stopped</string>
+
 </resources>