1 files changed, 140 insertions, 0 deletions
diff --git a/ui/src/main/java/com/wireguard/android/databinding/ItemChangeListener.java b/ui/src/main/java/com/wireguard/android/databinding/ItemChangeListener.java
new file mode 100644
index 00000000..e7303eae
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/databinding/ItemChangeListener.java
@@ -0,0 +1,140 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.databinding;
+
+import androidx.databinding.DataBindingUtil;
+import androidx.databinding.ObservableList;
+import androidx.databinding.ViewDataBinding;
+import androidx.annotation.Nullable;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import com.wireguard.android.BR;
+
+import java.lang.ref.WeakReference;
+import java.util.Objects;
+
+/**
+ * Helper class for binding an ObservableList to the children of a ViewGroup.
+ */
+
+class ItemChangeListener<T> {
+    private final OnListChangedCallback<T> callback = new OnListChangedCallback<>(this);
+    private final ViewGroup container;
+    private final int layoutId;
+    private final LayoutInflater layoutInflater;
+    @Nullable private ObservableList<T> list;
+
+    ItemChangeListener(final ViewGroup container, final int layoutId) {
+        this.container = container;
+        this.layoutId = layoutId;
+        layoutInflater = LayoutInflater.from(container.getContext());
+    }
+
+    private View getView(final int position, @Nullable final View convertView) {
+        ViewDataBinding binding = convertView != null ? DataBindingUtil.getBinding(convertView) : null;
+        if (binding == null) {
+            binding = DataBindingUtil.inflate(layoutInflater, layoutId, container, false);
+        }
+
+        Objects.requireNonNull(list, "Trying to get a view while list is still null");
+
+        binding.setVariable(BR.collection, list);
+        binding.setVariable(BR.item, list.get(position));
+        binding.executePendingBindings();
+        return binding.getRoot();
+    }
+
+    void setList(@Nullable final ObservableList<T> newList) {
+        if (list != null)
+            list.removeOnListChangedCallback(callback);
+        list = newList;
+        if (list != null) {
+            list.addOnListChangedCallback(callback);
+            callback.onChanged(list);
+        } else {
+            container.removeAllViews();
+        }
+    }
+
+    private static final class OnListChangedCallback<T>
+            extends ObservableList.OnListChangedCallback<ObservableList<T>> {
+
+        private final WeakReference<ItemChangeListener<T>> weakListener;
+
+        private OnListChangedCallback(final ItemChangeListener<T> listener) {
+            weakListener = new WeakReference<>(listener);
+        }
+
+        @Override
+        public void onChanged(final ObservableList<T> sender) {
+            final ItemChangeListener<T> listener = weakListener.get();
+            if (listener != null) {
+                // TODO: recycle views
+                listener.container.removeAllViews();
+                for (int i = 0; i < sender.size(); ++i)
+                    listener.container.addView(listener.getView(i, null));
+            } else {
+                sender.removeOnListChangedCallback(this);
+            }
+        }
+
+        @Override
+        public void onItemRangeChanged(final ObservableList<T> sender, final int positionStart,
+                                       final int itemCount) {
+            final ItemChangeListener<T> listener = weakListener.get();
+            if (listener != null) {
+                for (int i = positionStart; i < positionStart + itemCount; ++i) {
+                    final View child = listener.container.getChildAt(i);
+                    listener.container.removeViewAt(i);
+                    listener.container.addView(listener.getView(i, child));
+                }
+            } else {
+                sender.removeOnListChangedCallback(this);
+            }
+        }
+
+        @Override
+        public void onItemRangeInserted(final ObservableList<T> sender, final int positionStart,
+                                        final int itemCount) {
+            final ItemChangeListener<T> listener = weakListener.get();
+            if (listener != null) {
+                for (int i = positionStart; i < positionStart + itemCount; ++i)
+                    listener.container.addView(listener.getView(i, null));
+            } else {
+                sender.removeOnListChangedCallback(this);
+            }
+        }
+
+        @Override
+        public void onItemRangeMoved(final ObservableList<T> sender, final int fromPosition,
+                                     final int toPosition, final int itemCount) {
+            final ItemChangeListener<T> listener = weakListener.get();
+            if (listener != null) {
+                final View[] views = new View[itemCount];
+                for (int i = 0; i < itemCount; ++i)
+                    views[i] = listener.container.getChildAt(fromPosition + i);
+                listener.container.removeViews(fromPosition, itemCount);
+                for (int i = 0; i < itemCount; ++i)
+                    listener.container.addView(views[i], toPosition + i);
+            } else {
+                sender.removeOnListChangedCallback(this);
+            }
+        }
+
+        @Override
+        public void onItemRangeRemoved(final ObservableList<T> sender, final int positionStart,
+                                       final int itemCount) {
+            final ItemChangeListener<T> listener = weakListener.get();
+            if (listener != null) {
+                listener.container.removeViews(positionStart, itemCount);
+            } else {
+                sender.removeOnListChangedCallback(this);
+            }
+        }
+    }
+}