Add support for async callbacks in ReactFindViewUtil

Reviewed By: AaaChiuuu

Differential Revision: D4841500

fbshipit-source-id: 16620d72bd636ad13085c15c38862e16da6c42d2

ReactAndroid/src/androidTest/java/com/facebook/react/tests/NativeIdTestCase.java

@@ -37,9 +37,28 @@ public class NativeIdTestCase extends ReactAppInstrumentationTestCase {
     "TextInput",
     "View");
 
+  private boolean mViewFound;
+
+  @Override
+  protected void setUp() throws Exception {
+    mViewFound = false;
+    ReactFindViewUtil.addViewListener(new ReactFindViewUtil.OnViewFoundListener() {
+      @Override
+      public String getNativeId() {
+        return viewTags.get(0);
+      }
+
+      @Override
+      public void onViewFound(View view) {
+        mViewFound = true;
+      }
+    });
+    super.setUp();
+  }
+
   public void testPropertyIsSetForViews() {
     for (String nativeId : viewTags) {
-      View viewWithTag = ReactFindViewUtil.findViewByNativeId(
+      View viewWithTag = ReactFindViewUtil.findView(
         getActivity().getRootView(),
         nativeId);
       assertNotNull(
@@ -47,4 +66,28 @@ public class NativeIdTestCase extends ReactAppInstrumentationTestCase {
         viewWithTag);
     }
   }
+
+  public void testViewListener() {
+    assertTrue("OnViewFound callback was never invoked", mViewFound);
+  }
+
+  public void testFindView() {
+    mViewFound = false;
+    ReactFindViewUtil.findView(
+      getActivity().getRootView(),
+      new ReactFindViewUtil.OnViewFoundListener() {
+        @Override
+        public String getNativeId() {
+          return viewTags.get(0);
+        }
+
+        @Override
+        public void onViewFound(View view) {
+          mViewFound = true;
+        }
+      });
+    assertTrue(
+      "OnViewFound callback should have successfully been invoked synchronously",
+      mViewFound);
+  }
 }

ReactAndroid/src/main/java/com/facebook/react/uimanager/BUCK

@@ -26,6 +26,7 @@ android_library(
         react_native_target("java/com/facebook/react/modules/i18nmanager:i18nmanager"),
         react_native_target("java/com/facebook/react/touch:touch"),
         react_native_target("java/com/facebook/react/uimanager/annotations:annotations"),
+        react_native_target("java/com/facebook/react/uimanager/util:util"),
         react_native_target("res:uimanager"),
     ],
 )

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

@@ -5,9 +5,11 @@ package com.facebook.react.uimanager;
 import android.graphics.Color;
 import android.os.Build;
 import android.view.View;
+
 import com.facebook.react.R;
 import com.facebook.react.bridge.ReadableArray;
 import com.facebook.react.uimanager.annotations.ReactProp;
+import com.facebook.react.uimanager.util.ReactFindViewUtil;
 
 /**
  * Base class that should be suitable for the majority of subclasses of {@link ViewManager}.
@@ -96,6 +98,7 @@ public abstract class BaseViewManager<T extends View, C extends LayoutShadowNode
   @ReactProp(name = PROP_NATIVE_ID)
   public void setNativeId(T view, String nativeId) {
     view.setTag(R.id.view_tag_native_id, nativeId);
+    ReactFindViewUtil.notifyViewRendered(view);
   }
 
   @ReactProp(name = PROP_ACCESSIBILITY_LABEL)

ReactAndroid/src/main/java/com/facebook/react/uimanager/util/ReactFindViewUtil.java

@@ -4,6 +4,10 @@ package com.facebook.react.uimanager.util;
 
 import javax.annotation.Nullable;
 
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
 import android.view.View;
 import android.view.ViewGroup;
 
@@ -14,25 +18,98 @@ import com.facebook.react.R;
  */
 public class ReactFindViewUtil {
 
+  private static final List<OnViewFoundListener> mOnViewFoundListeners = new ArrayList<>();
+
   /**
-   * Finds a view that is tagged with {@param nativeId} as its `nativeID` prop
+   * Callback to be invoked when a react native view has been found
    */
-  public static @Nullable View findViewByNativeId(View view, String nativeId) {
+  public interface OnViewFoundListener {
-    Object tag = view.getTag(R.id.view_tag_native_id);
+
-    if (tag instanceof String && tag.equals(nativeId)) {
+    /**
-      return view;
+     * Returns the native id of the view of interest
+     */
+    String getNativeId();
+
+    /**
+     * Called when the view has been found
+     * @param view
+     */
+    void onViewFound(View view);
   }
 
-    if (view instanceof ViewGroup) {
+  /**
-      ViewGroup viewGroup = (ViewGroup) view;
+   * Finds a view that is tagged with {@param nativeId} as its nativeID prop
+   * under the {@param root} view hierarchy. Returns the view if found, null otherwise.
+   * @param root root of the view hierarchy from which to find the view
+   */
+  public static @Nullable View findView(View root, String nativeId) {
+    String tag = getNativeId(root);
+    if (tag != null && tag.equals(nativeId)) {
+      return root;
+    }
+
+    if (root instanceof ViewGroup) {
+      ViewGroup viewGroup = (ViewGroup) root;
       for (int i = 0; i < viewGroup.getChildCount(); i++) {
-        View v = findViewByNativeId(viewGroup.getChildAt(i), nativeId);
+        View view = findView(viewGroup.getChildAt(i), nativeId);
-        if (v != null) {
+        if (view != null) {
-          return v;
+          return view;
         }
       }
     }
 
     return null;
   }
+
+  /**
+   * Finds a view tagged with {@param onViewFoundListener}'s nativeID in the given {@param root}
+   * view hierarchy. If the view does not exist yet due to React Native's async layout, a listener
+   * will be added. When the view is found, the {@param onViewFoundListener} will be invoked.
+   * @param root root of the view hierarchy from which to find the view
+   */
+  public static void findView(View root, OnViewFoundListener onViewFoundListener) {
+    View view = findView(root, onViewFoundListener.getNativeId());
+    if (view != null) {
+      onViewFoundListener.onViewFound(view);
+    }
+    addViewListener(onViewFoundListener);
+  }
+
+  /**
+   * Registers an OnViewFoundListener to be invoked when a view with a matching nativeID is found.
+   * Remove this listener using removeViewListener() if it's no longer needed.
+   */
+  public static void addViewListener(OnViewFoundListener onViewFoundListener) {
+    mOnViewFoundListeners.add(onViewFoundListener);
+  }
+
+  /**
+   * Removes an OnViewFoundListener previously registered with addViewListener().
+   */
+  public static void removeViewListener(OnViewFoundListener onViewFoundListener) {
+    mOnViewFoundListeners.remove(onViewFoundListener);
+  }
+
+  /**
+   * Invokes any listeners that are listening on this {@param view}'s native id
+   */
+  public static void notifyViewRendered(View view) {
+    String nativeId = getNativeId(view);
+    if (nativeId == null) {
+      return;
+    }
+    Iterator<OnViewFoundListener> iterator = mOnViewFoundListeners.iterator();
+    while (iterator.hasNext()) {
+      OnViewFoundListener listener = iterator.next();
+      if (nativeId != null && nativeId.equals(listener.getNativeId())) {
+        listener.onViewFound(view);
+        iterator.remove();
+      }
+    }
+  }
+
+  private static @Nullable String getNativeId(View view) {
+    Object tag = view.getTag(R.id.view_tag_native_id);
+    return tag instanceof String ? (String) tag : null;
+  }
 }