Add "RemoveItemAtIndex" block to ListView (#2789)

---------
Co-authored-by: Evan W. Patton <ewpatton@mit.edu>

appinventor/appengine/src/com/google/appinventor/client/youngandroid/YoungAndroidFormUpgrader.java

@@ -1430,6 +1430,10 @@ public final class YoungAndroidFormUpgrader {
       // Added ...
       srcCompVersion = 6;
     }
+    if (srcCompVersion < 7) {
+      // Added RemoveItemAtIndex method
+      srcCompVersion = 7;
+    }
     return srcCompVersion;
   }
 

appinventor/blocklyeditor/src/versioning.js

@@ -2413,7 +2413,10 @@ Blockly.Versioning.AllUpgradeMaps =
     5: "noUpgrade",
     // AI2:
     // - Added ...
-    6: "noUpgrade"
+    6: "noUpgrade",
+    // AI2:
+    // - Added RemoveItemAtList method
+    7: "noUpgrade"
 
   }, // End ListView upgraders
 

appinventor/components-ios/src/ErrorMessages.swift

@@ -128,6 +128,9 @@ import Foundation
   // ImageBot Errors
   case ERROR_IMAGEBOT_ERROR = 4300
 
+  // ListView Errors
+  case ERROR_LISTVIEW_INDEX_OUT_OF_BOUNDS = 4601
+
   // CloudDB Errors
   case ERROR_EMPTY_CLOUDDB_PROPERTY = 104001
   case ERROR_CLOUDDB_JSON_MALFORMED = 104002
@@ -353,6 +356,10 @@ import Foundation
     case .ERROR_IMAGEBOT_ERROR:
       return "Error from the ImageBot code: %d %@"
 
+    // ListView Errors
+    case .ERROR_LISTVIEW_INDEX_OUT_OF_BOUNDS:
+      return "The index %d is out of bounds for the list view."
+
     // iOS Specific Errors
     case .ERROR_IOS_INSTALLING_URLS_NOT_SUPPORTED:
       return "Installing packages from URLs is not supported on iOS"

appinventor/components-ios/src/ListView.swift

@@ -332,6 +332,23 @@ open class ListView: ViewComponent, AbstractMethodsForViewComponent,
     }
   }
 
+  // MARK: Methods
+
+  @objc open func RemoveItemAtIndex(_ index: Int32) {
+    if index < 1 || index > max(_listData.count, _elements.count) {
+      _container?.form?.dispatchErrorOccurredEvent(self, "RemoveItemAtIndex",
+           ErrorMessage.ERROR_LISTVIEW_INDEX_OUT_OF_BOUNDS, index)
+      return
+    }
+    if _listData.count >= index {
+      _listData.remove(at: Int(index - 1))
+    }
+    if _elements.count >= index {
+      _elements.remove(at: Int(index - 1))
+    }
+    _view.reloadData()
+  }
+
   // MARK: Events
 
   @objc open func AfterPicking() {

appinventor/components/src/com/google/appinventor/components/common/YaVersion.java

@@ -584,6 +584,7 @@ public class YaVersion {
   // - TEXTTOSPEEECH_COMPONENT_VERSION was incremented to 6
   // - TINYDB_COMPONENT_VERSION was incremented to 3
   // For YOUNG_ANDROID_VERSION 225:
+  // - LISTVIEW_COMPONENT_VERSION was incremented to 7
   // - WEB_COMPONENT_VERSION was incremented to 9
   public static final int YOUNG_ANDROID_VERSION = 225;
 
@@ -1145,7 +1146,9 @@ public class YaVersion {
   // - Added SelectionColor Property
   // For LISTVIEW_COMPONENT_VERSION 6:
   // - Added ...
-  public static final int LISTVIEW_COMPONENT_VERSION = 6;
+  // For LISTVIEW_COMPONENT_VERSION 7:
+  // - Added RemoveItemAtIndex method
+  public static final int LISTVIEW_COMPONENT_VERSION = 7;
 
   // For LOCATIONSENSOR_COMPONENT_VERSION 2:
   // - The TimeInterval and DistanceInterval properties were added.

appinventor/components/src/com/google/appinventor/components/runtime/ListAdapterWithRecyclerView.java

@@ -143,7 +143,7 @@ public class ListAdapterWithRecyclerView
     Arrays.fill(isVisible, Boolean.TRUE);
   }
 
-  public ListAdapterWithRecyclerView(ComponentContainer container, YailList stringItems, int textMainColor, float textMainSize, String textMainFont, int backgroundColor, int selectionColor) {
+  public ListAdapterWithRecyclerView(ComponentContainer container, List<String> stringItems, int textMainColor, float textMainSize, String textMainFont, int backgroundColor, int selectionColor) {
     // Legacy Support
     this.container = container;
     this.textMainSize = textMainSize;
@@ -167,8 +167,7 @@ public class ListAdapterWithRecyclerView
     // Build the list of strings into a list of dictionaries
     this.items = new ArrayList<>();
     // YailList is 1-indexed
-    for(int i = 1; i <= stringItems.size(); ++i) {
-      String itemString = YailList.YailListElementToString(stringItems.get(i));
+    for(String itemString : stringItems) {
       YailDictionary itemDict = new YailDictionary();
       itemDict.put(Component.LISTVIEW_KEY_MAIN_TEXT, itemString);
       this.items.add(itemDict);

appinventor/components/src/com/google/appinventor/components/runtime/ListView.java

@@ -80,7 +80,7 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
 
   private RecyclerView recyclerView;
   private ListAdapterWithRecyclerView listAdapterWithRecyclerView;
-  private YailList stringItems;
+  private List<String> stringItems;
   private List<YailDictionary> dictItems;
   private int selectionIndex;
   private String selection;
@@ -122,7 +122,7 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
 
     super(container);
     this.container = container;
-    stringItems = YailList.makeEmptyList();
+    stringItems = new ArrayList<>();
     dictItems = new ArrayList<>();
 
     linearLayout = new LinearLayout(container.$context());
@@ -286,7 +286,7 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
           category = PropertyCategory.BEHAVIOR)
   public void Elements(YailList itemsList) {
     dictItems.clear();
-    stringItems = YailList.makeEmptyList();
+    stringItems = new ArrayList<>();
     if (itemsList.size() > 0) {
       Object firstitem = itemsList.getObject(0);
       // Check to see if this is a list of strings (backward compatibility) or a list of Dictionaries
@@ -307,7 +307,7 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
         }
       } else {
         // Support legacy single-string ListViews
-        stringItems = ElementsUtil.elements(itemsList, "Listview");
+        stringItems = ElementsUtil.elementsStrings(itemsList, "ListView");
       }
     }
     setAdapterData();
@@ -324,7 +324,7 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
     if (dictItems.size() > 0) {
       return YailList.makeList(dictItems);
     } else {
-      return stringItems;
+      return ElementsUtil.makeYailListFromList(stringItems);
     }
   }
 
@@ -340,7 +340,7 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
           "such as: Cheese,Fruit,Bacon,Radish. Each word before the comma will be an element in the " +
           "list.", category = PropertyCategory.BEHAVIOR)
   public void ElementsFromString(String itemstring) {
-    stringItems = ElementsUtil.elementsFromString(itemstring);
+    stringItems = ElementsUtil.elementsListFromString(itemstring);
     setAdapterData();
   }
 
@@ -409,13 +409,13 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
           category = PropertyCategory.BEHAVIOR)
   public void SelectionIndex(int index) {
     if (!dictItems.isEmpty()) {
-      selectionIndex = ElementsUtil.selectionIndex(index, YailList.makeList(dictItems));
+      selectionIndex = ElementsUtil.selectionIndexInStringList(index, YailList.makeList(dictItems));
       selection = dictItems.get(selectionIndex - 1).get(Component.LISTVIEW_KEY_MAIN_TEXT).toString();
       selectionDetailText = ElementsUtil.toStringEmptyIfNull(dictItems.get(selectionIndex - 1).get(Component.LISTVIEW_KEY_DESCRIPTION).toString());
     } else {
-      selectionIndex = ElementsUtil.selectionIndex(index, stringItems);
+      selectionIndex = ElementsUtil.selectionIndexInStringList(index, stringItems);
       // Now, we need to change Selection to correspond to SelectionIndex.
-      selection = ElementsUtil.setSelectionFromIndex(index, stringItems);
+      selection = ElementsUtil.setSelectionFromIndexInStringList(index, stringItems);
       selectionDetailText = "";
     }
     if (listAdapterWithRecyclerView != null) {
@@ -423,6 +423,26 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
     }
   }
 
+  /**
+   * Removes Item from list at a given index
+   */
+  @SimpleFunction(
+      description = "Removes Item from list at a given index")
+  public void RemoveItemAtIndex(int index) {
+    if (index < 1 || index > Math.max(dictItems.size(), stringItems.size())) {
+      container.$form().dispatchErrorOccurredEvent(this, "RemoveItemAtIndex",
+          ErrorMessages.ERROR_LISTVIEW_INDEX_OUT_OF_BOUNDS, index);
+      return;
+    }
+    if (dictItems.size() >= index) {
+      dictItems.remove(index - 1);
+    }
+    if (stringItems.size() >= index) {
+      stringItems.remove(index - 1);
+    }
+    setAdapterData();
+  }
+
   /**
    * Returns the text in the `ListView` at the position of {@link #SelectionIndex(int)}.
    */
@@ -456,7 +476,7 @@ public final class ListView extends AndroidViewComponent implements AdapterView.
         selectionIndex = 0;
       }
     } else {
-      selectionIndex = ElementsUtil.setSelectedIndexFromValue(value, stringItems);
+      selectionIndex = ElementsUtil.setSelectedIndexFromValueInStringList(value, stringItems);
     }
     SelectionIndex(selectionIndex);
   }

appinventor/components/src/com/google/appinventor/components/runtime/util/ElementsUtil.java

@@ -10,6 +10,8 @@ import com.google.appinventor.components.runtime.errors.YailRuntimeError;
 import org.json.JSONObject;
 
 import java.util.List;
+import java.util.Arrays;  
+import java.util.ArrayList;  
 
 /**
  * Utilities for Components that display a number of options on Screen such as ListPicker,
@@ -26,6 +28,81 @@ public class ElementsUtil {
     return items;
   }
 
+  /** Check a Yail list of items to verify that they are all strings
+   *
+   * @param itemList
+   * @param componentName
+   * @return the original list
+   */
+  public static List<String> elementsStrings(YailList itemList, String componentName){
+    Object[] objects = itemList.toStringArray();
+    for (int i = 0; i < objects.length; i++) {
+      if (!(objects[i] instanceof String)) {
+        throw new YailRuntimeError("Items passed to " + componentName + " must be Strings",
+            "Error");
+      }
+    }
+    // this is not changing itemlist.  it's just checking that the items are strings
+    String[] strings = (String[]) objects;
+    List<String> ans = new ArrayList<>(Arrays.asList(strings));
+    return ans;
+  }
+
+  /**
+   * Returns a list of string from a comma-separated string
+   * @param itemString
+   * @return items
+   */
+  public static List<String> elementsListFromString(String itemString){
+    List<String> items;
+    if (itemString.length() > 0) {
+      String[] words = itemString.split(" *, *");
+      items = new ArrayList<>(Arrays.asList(words));
+    } else {
+      items = new ArrayList();
+    }
+    return items;
+  }
+
+  /**
+   * Converts a List of string to YailList
+   * @param stringItems
+   * @return YailList
+   */
+  public static YailList makeYailListFromList(List<String> stringItems) {
+    if (stringItems == null || stringItems.size() == 0) return YailList.makeEmptyList();
+    return YailList.makeList(stringItems);
+  }
+
+  public static int selectionIndexInStringList(int index, List<String> items){
+    if (index < 0 || index >= items.size()) {
+      return 0;
+    } else {
+      return index;
+    }
+  }
+
+  public static String setSelectionFromIndexInStringList(int index, List<String> items){
+    if (index < 0 || index >= items.size()) {
+      return "";
+    }
+    return items.get(index);
+  }
+
+  public static int setSelectedIndexFromValueInStringList(String value, List<String> items){
+    // Now, we need to change SelectionIndex to correspond to Selection.
+    // If multiple Selections have the same SelectionIndex, use the first.
+    // If none do, arbitrarily set the SelectionIndex to its default value
+    // of 0.
+    for (int i = 0; i < items.size(); i++) {
+      // The comparison is case-sensitive to be consistent with yail-equal?.
+      if (items.get(i).equals(value)) {
+        return i;
+      }
+    }
+    return 0;
+  }
+
  /** Check a Yail list of items to verify that they are all strings and
   *
   * @param itemList

appinventor/components/src/com/google/appinventor/components/runtime/util/ErrorMessages.java

@@ -310,7 +310,10 @@ public final class ErrorMessages {
   // FilePicker Errors
   public static final int ERROR_FILEPICKER_NO_URI_RETURNED = 4501;
 
-  // Start the next group of errors at 4600
+  // ListView Errors
+  public static final int ERROR_LISTVIEW_INDEX_OUT_OF_BOUNDS = 4601;
+
+  // Start the next group of errors at 4700
 
   // Mapping of error numbers to error message format strings.
   private static final Map<Integer, String> errorMessages;
@@ -756,6 +759,10 @@ public final class ErrorMessages {
 
     // FilePicker Errors
     errorMessages.put(ERROR_FILEPICKER_NO_URI_RETURNED, "No URI returned to FilePicker");
+
+    // ListView Errors
+    errorMessages.put(ERROR_LISTVIEW_INDEX_OUT_OF_BOUNDS,
+        "The index %d is out of bounds for the list view.");
   }
 
   private ErrorMessages() {

appinventor/docs/html/reference/components/userinterface.html

@@ -740,6 +740,8 @@ Valid values for the month field are 1-12 and 1-31 for the day field.</dd>
   <dd>Get the Main Text of a ListView element.</dd>
   <dt id="ListView.Refresh" class="method"><i></i> Refresh()</dt>
   <dd>Reload the ListView to reflect any changes in the data.</dd>
+  <dt id="ListView.RemoveItemAtIndex" class="method"><i></i> RemoveItemAtIndex(<em class="number">index</em>)</dt>
+  <dd>Removes Item from list at a given index</dd>
 </dl>
 
 <h2 id="Notifier">Notifier</h2>

appinventor/docs/markdown/reference/components/userinterface.md

@@ -787,6 +787,9 @@ This is a visible component that displays a list of text and image elements in y
 {:id="ListView.Refresh" class="method"} <i/> Refresh()
 : Reload the ListView to reflect any changes in the data.
 
+{:id="ListView.RemoveItemAtIndex" class="method"} <i/> RemoveItemAtIndex(*index*{:.number})
+: Removes Item from list at a given index
+
 ## Notifier  {#Notifier}
 
 The Notifier component displays alert messages and creates Android log entries through