Provide filter when there are many options

platform_tools/android/apps/viewer/src/main/java/org/skia/viewer/OptionAdapter.java

Index: platform_tools/android/apps/viewer/src/main/java/org/skia/viewer/OptionAdapter.java
diff --git a/platform_tools/android/apps/viewer/src/main/java/org/skia/viewer/OptionAdapter.java b/platform_tools/android/apps/viewer/src/main/java/org/skia/viewer/OptionAdapter.java
new file mode 100644
index 0000000000000000000000000000000000000000..4fefb54d8dc73f515fad4e22627c25aa29759584
--- /dev/null
+++ b/platform_tools/android/apps/viewer/src/main/java/org/skia/viewer/OptionAdapter.java
@@ -0,0 +1,64 @@
+package org.skia.viewer;
+
+import android.content.Context;
+import android.widget.ArrayAdapter;
+import android.widget.Filter;
+import android.widget.Spinner;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class OptionAdapter extends ArrayAdapter<String> {
+    private String mCurrentOption;
+    private List<String> mOptions;
+    private Filter mFilter = null;
+    private Spinner mSpinner;
+
+    public OptionAdapter(Context context, int resource, List<String> options, Spinner spinner) {
+        super(context, resource);
+        addAll(options);
+        mOptions = options;
+        mSpinner = spinner;
+    }
+
+    public void setCurrentOption(String currentOption) {
+        this.mCurrentOption = currentOption;
+    }
+
+    private class OptionFilter extends Filter {
+
+        @Override
+        protected FilterResults performFiltering(CharSequence constraint) {
+            final String pattern = constraint.toString().toLowerCase();
+            ArrayList<String> filteredOptions = new ArrayList<>();
+            for(String option : mOptions) {
+                if (option.equals(mCurrentOption)
+                        || option.toLowerCase().indexOf(pattern) > -1) {
+                    filteredOptions.add(option);
+                }
+            }
+            FilterResults results = new FilterResults();
+            results.values = filteredOptions;
+            results.count = filteredOptions.size();
+            return results;
+        }
+
+        @Override
+        protected void publishResults(CharSequence constraint, FilterResults results) {
+            clear();
+            List<String> filteredOptions = (List<String>) results.values;
+            addAll(filteredOptions);
+            // We set the selection to the current option to avoid unwanted option selection change
+            mSpinner.setSelection(filteredOptions.indexOf(mCurrentOption));
+            notifyDataSetChanged();
+        }
+    }
+
+    @Override
+    public Filter getFilter() {
+        if (mFilter == null) {
+            mFilter = new OptionFilter();
+        }
+        return mFilter;
+    }
+}