1 files changed, 168 insertions, 0 deletions
diff --git a/app/src/main/java/de/danoeh/antennapod/adapter/SelectableAdapter.java b/app/src/main/java/de/danoeh/antennapod/adapter/SelectableAdapter.java
new file mode 100644
index 000000000..670357d16
--- /dev/null
+++ b/app/src/main/java/de/danoeh/antennapod/adapter/SelectableAdapter.java
@@ -0,0 +1,168 @@
+package de.danoeh.antennapod.adapter;
+
+import android.app.Activity;
+import android.view.ActionMode;
+import android.view.Menu;
+import android.view.MenuInflater;
+import android.view.MenuItem;
+
+import androidx.recyclerview.widget.RecyclerView;
+
+import de.danoeh.antennapod.R;
+
+import java.util.HashSet;
+
+/**
+ * Used by Recyclerviews that need to provide ability to select items.
+ */
+abstract class SelectableAdapter<T extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<T> {
+    private ActionMode actionMode;
+    private final HashSet<Long> selectedIds = new HashSet<>();
+    private final Activity activity;
+    private OnEndSelectModeListener onEndSelectModeListener;
+
+    public SelectableAdapter(Activity activity) {
+        this.activity = activity;
+    }
+
+    public void startSelectMode(int pos) {
+        if (inActionMode()) {
+            endSelectMode();
+        }
+
+        selectedIds.clear();
+        selectedIds.add(getItemId(pos));
+        notifyDataSetChanged();
+
+        actionMode = activity.startActionMode(new ActionMode.Callback() {
+            @Override
+            public boolean onCreateActionMode(ActionMode mode, Menu menu) {
+                MenuInflater inflater = mode.getMenuInflater();
+                inflater.inflate(R.menu.multi_select_options, menu);
+                return true;
+            }
+
+            @Override
+            public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
+                updateTitle();
+                toggleSelectAllIcon(menu.findItem(R.id.select_toggle), false);
+                return false;
+            }
+
+            @Override
+            public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
+                if (item.getItemId() == R.id.select_toggle) {
+                    boolean allSelected = selectedIds.size() == getItemCount();
+                    setSelected(0, getItemCount(), !allSelected);
+                    toggleSelectAllIcon(item, !allSelected);
+                    updateTitle();
+                    return true;
+                }
+                return false;
+            }
+
+            @Override
+            public void onDestroyActionMode(ActionMode mode) {
+                callOnEndSelectMode();
+                actionMode = null;
+                selectedIds.clear();
+                notifyDataSetChanged();
+            }
+        });
+        updateTitle();
+    }
+
+    /**
+     * End action mode if currently in select mode, otherwise do nothing
+     */
+    public void endSelectMode() {
+        if (inActionMode()) {
+            callOnEndSelectMode();
+            actionMode.finish();
+        }
+    }
+
+    public boolean isSelected(int pos) {
+        return selectedIds.contains(getItemId(pos));
+    }
+
+    /**
+     * Set the selected state of item at given position
+     *
+     * @param pos      the position to select
+     * @param selected true for selected state and false for unselected
+     */
+    public void setSelected(int pos, boolean selected) {
+        if (selected) {
+            selectedIds.add(getItemId(pos));
+        } else {
+            selectedIds.remove(getItemId(pos));
+        }
+        updateTitle();
+    }
+
+    /**
+     * Set the selected state of item for a given range
+     *
+     * @param startPos start position of range, inclusive
+     * @param endPos   end position of range, inclusive
+     * @param selected indicates the selection state
+     * @throws IllegalArgumentException if start and end positions are not valid
+     */
+    public void setSelected(int startPos, int endPos, boolean selected) throws IllegalArgumentException {
+        for (int i = startPos; i < endPos && i < getItemCount(); i++) {
+            setSelected(i, selected);
+        }
+        notifyItemRangeChanged(startPos, (endPos - startPos));
+    }
+
+    protected void toggleSelection(int pos) {
+        setSelected(pos, !isSelected(pos));
+        notifyItemChanged(pos);
+
+        if (selectedIds.size() == 0) {
+            endSelectMode();
+        }
+    }
+
+    public boolean inActionMode() {
+        return actionMode != null;
+    }
+
+    public int getSelectedCount() {
+        return selectedIds.size();
+    }
+
+    private void toggleSelectAllIcon(MenuItem selectAllItem, boolean allSelected) {
+        if (allSelected) {
+            selectAllItem.setIcon(R.drawable.ic_select_none);
+            selectAllItem.setTitle(R.string.deselect_all_label);
+        } else {
+            selectAllItem.setIcon(R.drawable.ic_select_all);
+            selectAllItem.setTitle(R.string.select_all_label);
+        }
+    }
+
+    private void updateTitle() {
+        if (actionMode == null) {
+            return;
+        }
+        actionMode.setTitle(activity.getResources()
+                .getQuantityString(R.plurals.num_selected_label, selectedIds.size(),
+                selectedIds.size(), getItemCount()));
+    }
+
+    public void setOnEndSelectModeListener(OnEndSelectModeListener onEndSelectModeListener) {
+        this.onEndSelectModeListener = onEndSelectModeListener;
+    }
+
+    private void callOnEndSelectMode() {
+        if (onEndSelectModeListener != null) {
+            onEndSelectModeListener.onEndSelectMode();
+        }
+    }
+
+    public interface OnEndSelectModeListener {
+        void onEndSelectMode();
+    }
+}