Harden reflection

Summary:
Changelog: Fix theme reflection logging lot of errors if the APIs aren't accessible, see #1736

Harden theme reflection based on the comments in https://github.com/facebook/flipper/issues/1736

Reviewed By: jknoxville

Differential Revision: D32202434

fbshipit-source-id: 99178df56c91715f9eff1e4764ebc55b29ecb6f3

android/src/main/java/com/facebook/flipper/plugins/inspector/descriptors/utils/ContextDescriptorUtils.java

@@ -21,6 +21,7 @@ import java.util.Map;
 public final class ContextDescriptorUtils {
   private static String TAG = "ContextDescriptor";
 
+  private static boolean doneFieldDiscovery = false;
   private static Field sThemeImplField;
   private static Field sThemeImplThemeKeyField;
   private static Field sThemeImplAssetManagerField;
@@ -47,30 +48,61 @@ public final class ContextDescriptorUtils {
       final Object themeKey;
 
       // Nasty reflection to get a list of theme attributes that apply to this context.
-      if (sThemeImplField == null
-          || sThemeImplThemeKeyField == null
-          || sThemeKeyResIdField == null
-          || sThemeImplAssetManagerField == null) {
+      if (!doneFieldDiscovery) {
+        doneFieldDiscovery = true; // even if it fails, we don't want to retry
+        try {
           sThemeImplField = theme.getClass().getDeclaredField("mThemeImpl");
           sThemeImplField.setAccessible(true);
+        } catch (NoSuchFieldException e) {
+          // hardening against #1736
+          return builderMap;
+        }
 
         themeImpl = sThemeImplField.get(theme);
+        try {
           sThemeImplThemeKeyField = themeImpl.getClass().getDeclaredField("mKey");
           sThemeImplThemeKeyField.setAccessible(true);
+        } catch (NoSuchFieldException e) {
+          // hardening against #1736
+          return builderMap;
+        }
 
+        try {
           sThemeImplAssetManagerField = themeImpl.getClass().getDeclaredField("mAssets");
           sThemeImplAssetManagerField.setAccessible(true);
+        } catch (NoSuchFieldException e) {
+          // hardening against #1736
+          return builderMap;
+        }
 
+        try {
           sAssetManagerGetStyleAttributesMethod =
               assetManager.getClass().getDeclaredMethod("getStyleAttributes", int.class);
           sAssetManagerGetStyleAttributesMethod.setAccessible(true);
+        } catch (NoSuchMethodException e) {
+          // hardening against #1736
+          return builderMap;
+        }
 
         themeKey = sThemeImplThemeKeyField.get(themeImpl);
+        try {
           sThemeKeyResIdField = themeKey.getClass().getDeclaredField("mResId");
           sThemeKeyResIdField.setAccessible(true);
-      } else {
+        } catch (NoSuchFieldException e) {
+          // hardening against #1736
+          return builderMap;
+        }
+      } else if (sThemeImplField != null && sThemeImplThemeKeyField != null) {
         themeImpl = sThemeImplField.get(theme);
         themeKey = sThemeImplThemeKeyField.get(themeImpl);
+      } else {
+        themeKey = null;
+      }
+
+      if (sThemeKeyResIdField == null
+          || sAssetManagerGetStyleAttributesMethod == null
+          || themeKey == null) {
+        return builderMap;
       }
 
       int[] appliedThemeResIds = (int[]) sThemeKeyResIdField.get(themeKey);