feat(UI): Adding button to scroll to top quickly in torrent list view (fixes #587)

app/src/main/java/org/transdroid/core/gui/TorrentsFragment.java

@@ -21,7 +21,9 @@
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
+import android.widget.AbsListView;
 import android.widget.AbsListView.MultiChoiceModeListener;
+import android.widget.ImageButton;
 import android.widget.ListView;
 import android.widget.ProgressBar;
 import android.widget.TextView;
@@ -109,9 +111,10 @@ public class TorrentsFragment extends Fragment implements OnLabelPickedListener
     @ViewById
     protected TextView nosettingsText;
     @ViewById
-    protected TextView errorText;
-    @ViewById
+    protected TextView errorText;    @ViewById
     protected ProgressBar loadingProgress;
+    @ViewById
+    protected ImageButton scrollToTopButton;
     private MultiChoiceModeListener onTorrentsSelected = new MultiChoiceModeListener() {
 
         private SelectionManagerMode selectionManagerMode;
@@ -233,9 +236,7 @@ public void onDestroyActionMode(ActionMode mode) {
             addmenuButton.setVisibility(View.VISIBLE);
         }
 
-    };
-
-    @AfterViews
+    };    @AfterViews
     protected void init() {
 
         // Load the requested sort order from the user settings
@@ -258,6 +259,59 @@ protected void init() {
         }
         nosettingsText.setText(getString(R.string.navigation_nosettings, getString(R.string.app_name)));
 
+        // Set up the scroll to top button
+        scrollToTopButton.setOnClickListener(v -> scrollToTop());
+        // Add scroll listener to show/hide scroll to top button
+        torrentsList.setOnScrollListener(new AbsListView.OnScrollListener() {
+
+            @Override
+            public void onScrollStateChanged(AbsListView view, int scrollState) {
+                // No implementation needed
+            }
+
+            @Override
+            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
+                // Show button when scrolling down, hide when at top
+                if (totalItemCount > 0) {
+                    if (firstVisibleItem > 1) {
+                        // User has scrolled down, show the button with animation
+                        if (scrollToTopButton.getVisibility() != View.VISIBLE) {
+                            scrollToTopButton.setVisibility(View.VISIBLE);
+                            scrollToTopButton.startAnimation(android.view.animation.AnimationUtils.loadAnimation(
+                                    getActivity(), R.anim.fade_in));
+                        }
+                    } else {
+                        // User is at the top, hide the button with animation
+                        if (scrollToTopButton.getVisibility() == View.VISIBLE) {
+                            android.view.animation.Animation fadeOut = android.view.animation.AnimationUtils.loadAnimation(
+                                    getActivity(), R.anim.fade_out);
+                            fadeOut.setAnimationListener(new android.view.animation.Animation.AnimationListener() {
+                                @Override
+                                public void onAnimationStart(android.view.animation.Animation animation) {}
+
+                                @Override
+                                public void onAnimationEnd(android.view.animation.Animation animation) {
+                                    scrollToTopButton.setVisibility(View.GONE);
+                                }
+
+                                @Override
+                                public void onAnimationRepeat(android.view.animation.Animation animation) {}
+                            });
+                            scrollToTopButton.startAnimation(fadeOut);
+                        }
+                    }
+                }
+            }
+        });
+    }
+
+    /**
+     * Scrolls the torrents list to the top position
+     */
+    private void scrollToTop() {
+        if (torrentsList != null) {
+            torrentsList.smoothScrollToPosition(0);
+        }
     }
 
     /**
@@ -472,9 +526,7 @@ public void updateError(String connectionErrorMessage) {
         } else {
             updateViewVisibility();
         }
-    }
-
-    private void updateViewVisibility() {
+    }    private void updateViewVisibility() {
         if (!hasAConnection) {
             return;
         }
@@ -486,6 +538,11 @@ private void updateViewVisibility() {
         loadingProgress.setVisibility(!hasError && isLoading ? View.VISIBLE : View.GONE);
         emptyText.setVisibility(!hasError && !isLoading && isEmpty ? View.VISIBLE : View.GONE);
         swipeRefreshLayout.setEnabled(true);
+
+        // If list is not visible, ensure scroll to top button is also hidden
+        if (torrentsList.getVisibility() != View.VISIBLE) {
+            scrollToTopButton.setVisibility(View.GONE);
+        }
     }
 
     /**

app/src/main/res/anim/fade_in.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<alpha xmlns:android="http://schemas.android.com/apk/res/android"
+    android:duration="250"
+    android:fromAlpha="0.0"
+    android:toAlpha="1.0" />

app/src/main/res/anim/fade_out.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<alpha xmlns:android="http://schemas.android.com/apk/res/android"
+    android:duration="250"
+    android:fromAlpha="1.0"
+    android:toAlpha="0.0" />

app/src/main/res/drawable/ic_arrow_up.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24.0"
+    android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M7.41,15.41L12,10.83l4.59,4.58L18,14l-6,-6 -6,6z"/>
+</vector>

app/src/main/res/drawable/scroll_to_top_background.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="oval">
+    <solid android:color="?attr/colorAccent" />
+</shape>

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

@@ -37,6 +37,20 @@
 
     </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
 
+    <ImageButton
+        android:id="@+id/scroll_to_top_button"
+        android:layout_width="48dp"
+        android:layout_height="48dp"
+        android:layout_gravity="bottom|end"
+        android:layout_margin="16dp"
+        android:background="@drawable/scroll_to_top_background"
+        android:contentDescription="@string/action_scroll_to_top"
+        android:elevation="6dp"
+        android:src="@drawable/ic_arrow_up"
+        android:translationY="-16dp"
+        android:visibility="gone"
+        tools:visibility="visible" />
+
     <ProgressBar
         android:id="@+id/loading_progress"
         android:layout_width="128dp"

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

@@ -74,6 +74,7 @@
     <string name="action_removesettings">Remove settings</string>
     <string name="action_visitwebsite">Visit transdroid.org</string>
     <string name="action_close">Close</string>
+    <string name="action_scroll_to_top">Scroll to top</string>
 
     <string name="navigation_opendrawer">Select server and filter</string>
     <string name="navigation_closedrawer">Close filters list</string>