How to use

getExtension

method

in

com.mikepenz.fastadapter.FastAdapter

public ActionModeHelper(FastAdapter<Item> fastAdapter, int cabMenu, ActionMode.Callback callback) {
  this.mFastAdapter = fastAdapter;
  this.mCabMenu = cabMenu;
  this.mCallback = callback;
  this.mInternalCallback = new ActionBarCallBack();
  this.mSelectExtension = fastAdapter.getExtension(SelectExtension.class);
  if (mSelectExtension == null) {
    throw new IllegalStateException("The provided FastAdapter requires the `SelectExtension` or `withSelectable(true)`");
  }
}

public ActionModeHelper(FastAdapter<Item> fastAdapter, int cabMenu, ActionItemClickedListener actionItemClickedListener) {
  this.mFastAdapter = fastAdapter;
  this.mCabMenu = cabMenu;
  this.mInternalCallback = new ActionBarCallBack();
  this.actionItemClickedListener = actionItemClickedListener;
  this.mSelectExtension = fastAdapter.getExtension(SelectExtension.class);
  if (mSelectExtension == null) {
    throw new IllegalStateException("The provided FastAdapter requires the `SelectExtension` or `withSelectable(true)`");
  }
}

/**
 * Uses Reflection to collapse all items if this adapter uses expandable items
 *
 * @param fastAdapter
 */
private static void collapseIfPossible(FastAdapter fastAdapter) {
  try {
    Class c = Class.forName("com.mikepenz.fastadapter.expandable.ExpandableExtension");
    if (c != null) {
      IAdapterExtension extension = fastAdapter.getExtension(c);
      if (extension != null) {
        Method method = extension.getClass().getMethod("collapse");
        method.invoke(extension);
      }
    }
  } catch (Exception ignored) {
    //
  }
}

  @Override
  public boolean apply(@NonNull IAdapter lastParentAdapter, int lastParentPosition, @NonNull IItem item, int position) {
    if (position != -1) {
      SelectExtension extension = (SelectExtension) adapter.getExtension(SelectExtension.class);
      if (extension != null) {
        extension.deselect(position);
      }
    } else {
      item.withSetSelected(false);
    }
    return true;
  }
}, false);

/**
 * counts the selected items in the adapter underneath an expandable item, recursively
 *
 * @param adapter the adapter instance
 * @param header  the header who's selected children should be counted
 * @return number of selected items underneath the header
 */
public static <T extends IItem & IExpandable> int countSelectedSubItems(final FastAdapter adapter, T header) {
  SelectExtension extension = (SelectExtension) adapter.getExtension(SelectExtension.class);
  if (extension != null) {
    Set<IItem> selections = extension.getSelectedItems();
    return countSelectedSubItems(selections, header);
  }
  return 0;
}

public boolean setSelectionAtPosition(int position, boolean fireOnClick) {
  if (mDrawerBuilder.mRecyclerView != null) {
    SelectExtension<IDrawerItem> select = getAdapter().getExtension(SelectExtension.class);
    if (select != null) {
      select.deselect();
      select.select(position, false);
      notifySelect(position, fireOnClick);
    }
  }
  return false;
}

/**
 * deselects all selections
 */
public void deselect() {
  SelectExtension<Item> selectExtension = mFastAdapter.getExtension(SelectExtension.class);
  if (selectExtension == null) {
    return;
  }
  for (Item item : AdapterUtil.getAllItems(mFastAdapter)) {
    selectExtension.deselect(item);
  }
  mFastAdapter.notifyDataSetChanged();
}

/**
 * select all items
 *
 * @param considerSelectableFlag true if the select method should not select an item if its not selectable
 */
public void select(boolean considerSelectableFlag) {
  SelectExtension<Item> selectExtension = mFastAdapter.getExtension(SelectExtension.class);
  if (selectExtension == null) {
    return;
  }
  for (Item item : AdapterUtil.getAllItems(mFastAdapter)) {
    selectExtension.select(item, considerSelectableFlag);
  }
  mFastAdapter.notifyDataSetChanged();
}

  @Override
  public boolean apply(@NonNull IAdapter lastParentAdapter, int lastParentPosition, @NonNull IItem item, int position) {
    if (item.getIdentifier() == identifier) {
      if (position != -1) {
        SelectExtension extension = (SelectExtension) adapter.getExtension(SelectExtension.class);
        if (extension != null) {
          if (select) {
            extension.select(position);
          } else {
            extension.deselect(position);
          }
        }
      } else {
        item.withSetSelected(select);
      }
      return true;
    }
    return false;
  }
}, true);

@Test
public void select() throws Exception {
  itemAdapter.set(TestDataGenerator.genTestItemList(100));
  SelectExtension<TestItem> selectExtension = adapter.getExtension(SelectExtension.class);
  assertThat(selectExtension).isEqualTo(this.selectExtension);
  assertThat(selectExtension.getSelectedItems().size()).isEqualTo(0);
  assertThat(selectExtension.getSelections().size()).isEqualTo(0);
  selectExtension.select(10);
  assertThat(selectExtension.getSelectedItems().size()).isEqualTo(1);
  assertThat(selectExtension.getSelectedItems().iterator().next().getIdentifier()).isEqualTo(10);
  assertThat(selectExtension.getSelections().size()).isEqualTo(1);
  assertThat(selectExtension.getSelections().iterator().next()).isEqualTo(10);
}

/**
 * set the current selection in the drawer
 * NOTE: This will trigger onDrawerItemSelected without a view if you pass fireOnClick = true;
 *
 * @param identifier  the identifier to search for
 * @param fireOnClick true if the click listener should be called
 */
public void setSelection(long identifier, boolean fireOnClick) {
  SelectExtension<IDrawerItem> select = getAdapter().getExtension(SelectExtension.class);
  if (select != null) {
    select.deselect();
    select.selectByIdentifier(identifier, false, true);
    //we also have to call the general notify
    Pair<IDrawerItem, Integer> res = getAdapter().getItemById(identifier);
    if (res != null) {
      Integer position = res.second;
      notifySelect(position != null ? position : -1, fireOnClick);
    }
  }
}

for (int i = 0; i < subItems; i++) {
  if (((IItem) header.getSubItems().get(i)).isSelectable()) {
    SelectExtension extension = (SelectExtension) adapter.getExtension(SelectExtension.class);
    if (extension != null) {
      if (select) {

mFastAdapter.withMultiSelect(true);
mFastAdapter.withSelectOnLongClick(false);
selectExtension = mFastAdapter.getExtension(SelectExtension.class);