ImportKeys: Use cache for Highlighter

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/adapter/ImportKeysAdapterBinding.java

@@ -9,6 +9,7 @@ import android.widget.TextView;
 import org.sufficientlysecure.keychain.R;
 import org.sufficientlysecure.keychain.ui.util.Highlighter;
 import org.sufficientlysecure.keychain.ui.util.KeyFormattingUtils;
+import org.sufficientlysecure.keychain.util.LruCache;
 
 public class ImportKeysAdapterBinding {
 
@@ -25,7 +26,7 @@ public class ImportKeysAdapterBinding {
         if (secret) {
             userId = resources.getString(R.string.secret_key) + " " + userId;
         } else {
-            Highlighter highlighter = new Highlighter(context, query);
+            Highlighter highlighter = getHighlighter(context, query);
             userId = highlighter.highlight(userId);
         }
         textView.setText(userId);
@@ -46,7 +47,7 @@ public class ImportKeysAdapterBinding {
         if (userEmail == null)
             userEmail = "";
 
-        Highlighter highlighter = new Highlighter(context, query);
+        Highlighter highlighter = getHighlighter(context, query);
         textView.setText(highlighter.highlight(userEmail));
 
         if (revokedOrExpired) {
@@ -69,4 +70,16 @@ public class ImportKeysAdapterBinding {
         textView.setText(KeyFormattingUtils.beautifyKeyIdWithPrefix(keyId));
     }
 
+    private static LruCache<String, Highlighter> highlighterCache = new LruCache<>(1);
+
+    private static Highlighter getHighlighter(Context context, String query) {
+        Highlighter highlighter = highlighterCache.get(query);
+        if (highlighter == null) {
+            highlighter = new Highlighter(context, query);
+            highlighterCache.put(query, highlighter);
+        }
+
+        return highlighter;
+    }
+
 }

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/LruCache.java

@@ -0,0 +1,22 @@
+package org.sufficientlysecure.keychain.util;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+
+// Source: http://stackoverflow.com/a/1953516
+public class LruCache<A, B> extends LinkedHashMap<A, B> {
+
+    private final int maxEntries;
+
+    public LruCache(final int maxEntries) {
+        super(maxEntries + 1, 1.0f, true);
+        this.maxEntries = maxEntries;
+    }
+
+    @Override
+    protected boolean removeEldestEntry(final Map.Entry<A, B> eldest) {
+        return super.size() > maxEntries;
+    }
+
+}