ObservableMapAdapter: Based on an observable TreeMap

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/android/ObservableMapAdapter.java

@@ -0,0 +1,111 @@
+package com.wireguard.android;
+
+import android.content.Context;
+import android.databinding.DataBindingUtil;
+import android.databinding.ObservableMap;
+import android.databinding.ViewDataBinding;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.BaseAdapter;
+import android.widget.ListAdapter;
+
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
+import java.util.Collections;
+
+/**
+ * A generic ListAdapter backed by a TreeMap that adds observability.
+ */
+
+class ObservableMapAdapter<K extends Comparable<K>, V> extends BaseAdapter implements ListAdapter {
+    private ArrayList<K> keys;
+    private final int layoutId;
+    private final LayoutInflater layoutInflater;
+    private ObservableSortedMap<K, V> map;
+    private final OnMapChangedCallback<K, V> callback = new OnMapChangedCallback<>(this);
+
+    ObservableMapAdapter(final Context context, final int layoutId,
+                         final ObservableSortedMap<K, V> map) {
+        layoutInflater = LayoutInflater.from(context);
+        this.layoutId = layoutId;
+        setMap(map);
+    }
+
+    @Override
+    public int getCount() {
+        return map != null ? map.size() : 0;
+    }
+
+    @Override
+    public V getItem(final int position) {
+        if (map == null || position < 0 || position >= map.size())
+            return null;
+        return map.get(getKeys().get(position));
+    }
+
+    @Override
+    public long getItemId(final int position) {
+        if (map == null || position < 0 || position >= map.size())
+            return -1;
+        return getKeys().get(position).hashCode();
+    }
+
+    public int getItemPosition(final K key) {
+        if (map == null)
+            return -1;
+        return Collections.binarySearch(getKeys(), key);
+    }
+
+    private ArrayList<K> getKeys() {
+        if (keys == null)
+            keys = new ArrayList<>(map.keySet());
+        return keys;
+    }
+
+    @Override
+    public View getView(final int position, final View convertView, final ViewGroup parent) {
+        ViewDataBinding binding = DataBindingUtil.getBinding(convertView);
+        if (binding == null)
+            binding = DataBindingUtil.inflate(layoutInflater, layoutId, parent, false);
+        binding.setVariable(BR.item, getItem(position));
+        binding.executePendingBindings();
+        return binding.getRoot();
+    }
+
+    @Override
+    public boolean hasStableIds() {
+        return true;
+    }
+
+    public void setMap(final ObservableSortedMap<K, V> newMap) {
+        if (map != null)
+            map.removeOnMapChangedCallback(callback);
+        keys = null;
+        map = newMap;
+        if (map != null) {
+            map.addOnMapChangedCallback(callback);
+        }
+    }
+
+    private static class OnMapChangedCallback<K extends Comparable<K>, V>
+            extends ObservableMap.OnMapChangedCallback<ObservableSortedMap<K, V>, K, V> {
+
+        private final WeakReference<ObservableMapAdapter<K, V>> weakAdapter;
+
+        private OnMapChangedCallback(final ObservableMapAdapter<K, V> adapter) {
+            weakAdapter = new WeakReference<>(adapter);
+        }
+
+        @Override
+        public void onMapChanged(final ObservableSortedMap<K, V> sender, final K key) {
+            final ObservableMapAdapter<K, V> adapter = weakAdapter.get();
+            if (adapter != null) {
+                adapter.keys = null;
+                adapter.notifyDataSetChanged();
+            } else {
+                sender.removeOnMapChangedCallback(this);
+            }
+        }
+    }
+}

app/src/main/java/com/wireguard/android/ObservableSortedMap.java

@@ -0,0 +1,12 @@
+package com.wireguard.android;
+
+import android.databinding.ObservableMap;
+
+import java.util.SortedMap;
+
+/**
+ * Interface for maps that are both observable and sorted.
+ */
+
+public interface ObservableSortedMap<K, V> extends ObservableMap<K, V>, SortedMap<K, V> {
+}

app/src/main/java/com/wireguard/android/ObservableTreeMap.java

@@ -0,0 +1,67 @@
+package com.wireguard.android;
+
+import android.databinding.MapChangeRegistry;
+import android.databinding.ObservableMap;
+import android.support.annotation.NonNull;
+
+import java.util.Iterator;
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * Observable version of a TreeMap. Only notifies for changes made through methods, not iterators or
+ * views. This behavior is in line with that of ObservableArrayMap.
+ */
+
+public class ObservableTreeMap<K, V> extends TreeMap<K, V> implements ObservableSortedMap<K, V> {
+    private transient MapChangeRegistry listeners;
+
+    @Override
+    public void clear() {
+        super.clear();
+        notifyChange(null);
+    }
+
+    @Override
+    public void addOnMapChangedCallback(
+            final OnMapChangedCallback<? extends ObservableMap<K, V>, K, V> listener) {
+        if (listeners == null)
+            listeners = new MapChangeRegistry();
+        listeners.add(listener);
+    }
+
+    private void notifyChange(final K key) {
+        if (listeners != null)
+            listeners.notifyChange(this, key);
+    }
+
+    @Override
+    public V put(final K key, final V value) {
+        final V oldValue = super.put(key, value);
+        notifyChange(key);
+        return oldValue;
+    }
+
+    @Override
+    public void putAll(@NonNull final Map<? extends K, ? extends V> map) {
+        super.putAll(map);
+        for (final K key : map.keySet())
+            notifyChange(key);
+    }
+
+    @Override
+    public V remove(final Object key) {
+        final V oldValue = super.remove(key);
+        @SuppressWarnings("unchecked")
+        final K k = (K) key;
+        notifyChange(k);
+        return oldValue;
+    }
+
+    @Override
+    public void removeOnMapChangedCallback(
+            final OnMapChangedCallback<? extends ObservableMap<K, V>, K, V> listener) {
+        if (listeners != null)
+            listeners.remove(listener);
+    }
+}