ObservableMapAdapter: Based on an observable TreeMap

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2017-08-17 02:40:05 -05:00
parent 5023c937ad
commit 97149fff3f
3 changed files with 190 additions and 0 deletions
@@ -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);
+            }
+        }
+    }
+}