Add ability to dump a Native View Hierarchy

Differential Revision: D3411095

fbshipit-source-id: cc7e26eea63b0146250177c2e1b780ecc03da02f

ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewHierarchyDumper.java

@@ -0,0 +1,52 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.uimanager;
+
+import javax.annotation.Nullable;
+
+import android.view.View;
+import android.view.ViewGroup;
+
+import com.facebook.react.bridge.UiThreadUtil;
+
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+public class ViewHierarchyDumper {
+
+  public static @Nullable JSONObject toJSON(@Nullable View view) {
+    UiThreadUtil.assertOnUiThread();
+    if (view == null) {
+      return null;
+    }
+    JSONObject result = new JSONObject();
+    try {
+      result.put("class", view.getClass().getSimpleName());
+      Object tag = view.getTag();
+      if (tag != null && tag instanceof String) {
+        result.put("id", tag);
+      }
+      if (view instanceof ViewGroup) {
+        ViewGroup viewGroup = (ViewGroup) view;
+        if (viewGroup.getChildCount() > 0) {
+          JSONArray children = new JSONArray();
+          for (int i = 0; i < viewGroup.getChildCount(); i++) {
+            children.put(i, toJSON(viewGroup.getChildAt(i)));
+          }
+          result.put("children", children);
+        }
+      }
+    } catch (JSONException ex) {
+      return null;
+    }
+    return result;
+  }
+}