When undoing a removal, always return to the page it came from

We were already returning to the current page, but this wasn't
always right, e.g. when removing the last item on the last page.
So now we mark the page the item was removed from, and bind that
page first when undo is clicked.

This also addresses an issue where we incorrectly returned to the
first page if currentPage = INVALID_RESTORE_PAGE, which happens if
there are no items on the first page.

Bug: 118846684
Change-Id: I4ec1f64b24ba1cc308ce08bfb3111b5981fae99b

src/com/android/launcher3/DeleteDropTarget.java

@@ -113,10 +113,11 @@ public class DeleteDropTarget extends ButtonDropTarget {
     public void completeDrop(DragObject d) {
         ItemInfo item = d.dragInfo;
         if (canRemove(item)) {
+            int itemPage = mLauncher.getWorkspace().getCurrentPage();
             onAccessibilityDrop(null, item);
             ModelWriter modelWriter = mLauncher.getModelWriter();
             Snackbar.show(mLauncher, R.string.item_removed, R.string.undo,
-                    modelWriter::commitDelete, modelWriter::abortDelete);
+                    modelWriter::commitDelete, () -> modelWriter.abortDelete(itemPage));
         }
     }
 

src/com/android/launcher3/Launcher.java

@@ -2112,7 +2112,7 @@ public class Launcher extends BaseDraggingActivity implements LauncherExterns,
      *
      * Implementation of the method from LauncherModel.Callbacks.
      */
-    public void finishBindingItems(int currentScreen) {
+    public void finishBindingItems(int pageBoundFirst) {
         TraceHelper.beginSection("finishBindingItems");
         mWorkspace.restoreInstanceStateForRemainingPages();
 
@@ -2127,7 +2127,8 @@ public class Launcher extends BaseDraggingActivity implements LauncherExterns,
         InstallShortcutReceiver.disableAndFlushInstallQueue(
                 InstallShortcutReceiver.FLAG_LOADER_RUNNING, this);
 
-        mWorkspace.setCurrentPage(currentScreen);
+        // When undoing the removal of the last item on a page, return to that page.
+        mWorkspace.setCurrentPage(pageBoundFirst);
 
         TraceHelper.endSection("finishBindingItems");
     }

src/com/android/launcher3/LauncherModel.java

@@ -142,7 +142,7 @@ public class LauncherModel extends BroadcastReceiver
         public void bindItems(List<ItemInfo> shortcuts, boolean forceAnimateIcons);
         public void bindScreens(IntArray orderedScreenIds);
         public void finishFirstPageBind(ViewOnDrawExecutor executor);
-        public void finishBindingItems(int currentScreen);
+        public void finishBindingItems(int pageBoundFirst);
         public void bindAllApplications(ArrayList<AppInfo> apps);
         public void bindAppsAddedOrUpdated(ArrayList<AppInfo> apps);
         public void preAddApps();
@@ -372,11 +372,16 @@ public class LauncherModel extends BroadcastReceiver
         }
     }
 
+    public void forceReload() {
+        forceReload(-1);
+    }
+
     /**
      * Reloads the workspace items from the DB and re-binds the workspace. This should generally
      * not be called as DB updates are automatically followed by UI update
+     * @param synchronousBindPage The page to bind first. Can pass -1 to use the current page.
      */
-    public void forceReload() {
+    public void forceReload(int synchronousBindPage) {
         synchronized (mLock) {
             // Stop any existing loaders first, so they don't set mModelLoaded to true later
             stopLoader();
@@ -387,7 +392,10 @@ public class LauncherModel extends BroadcastReceiver
         // the next time launcher starts
         Callbacks callbacks = getCallback();
         if (callbacks != null) {
-            startLoader(callbacks.getCurrentWorkspaceScreen());
+            if (synchronousBindPage < 0) {
+                synchronousBindPage = callbacks.getCurrentWorkspaceScreen();
+            }
+            startLoader(synchronousBindPage);
         }
     }
 

src/com/android/launcher3/model/BaseLoaderResults.java

@@ -177,7 +177,7 @@ public abstract class BaseLoaderResults {
             public void run() {
                 Callbacks callbacks = mCallbacks.get();
                 if (callbacks != null) {
-                    callbacks.finishBindingItems(currentScreen);
+                    callbacks.finishBindingItems(mPageToBindFirst);
                 }
             }
         };

src/com/android/launcher3/model/ModelWriter.java

@@ -349,12 +349,12 @@ public class ModelWriter {
         mDeleteRunnables.clear();
     }
 
-    public void abortDelete() {
+    public void abortDelete(int pageToBindFirst) {
         mPreparingToUndo = false;
         mDeleteRunnables.clear();
         // We do a full reload here instead of just a rebind because Folders change their internal
         // state when dragging an item out, which clobbers the rebind unless we load from the DB.
-        mModel.forceReload();
+        mModel.forceReload(pageToBindFirst);
     }
 
     private class UpdateItemRunnable extends UpdateItemBaseRunnable {