From 1fde677cfc8abc1b0c300077da5286810b51b924 Mon Sep 17 00:00:00 2001
From: Listen <listenzz@163.com>
Date: Tue, 15 Jan 2019 20:42:13 -0800
Subject: [PATCH] Remove duplicated `OnGlobalLayoutListener` to improve
 performance (#22849)

Summary:
We are writing a native navigation library. When there are more than a dozen `ReactRootView` in the application, the application will be very stuck. It doesn't improve much, even if we remove the invisible ReactRootView from the View hierarchy temporarily.

After debugging, we found that we were not able to remove `OnGlobalLayoutListener` in `onDetachedFromWindow` because  this listener was added twice. One is in `onAttachedToWindow` and the other is in `attachToReactInstanceManager`.

We added the following code by inheriting ReactRootView.

```java
    Override
    protected void onAttachedToWindow() {
        try {
            Method method = ReactRootView.class.getDeclaredMethod("getCustomGlobalLayoutListener");
            method.setAccessible(true);
            // remove duplicated GlobalLayoutListener
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                getViewTreeObserver().removeOnGlobalLayoutListener((ViewTreeObserver.OnGlobalLayoutListener) method.invoke(this));
            } else {
                getViewTreeObserver().removeGlobalOnLayoutListener((ViewTreeObserver.OnGlobalLayoutListener) method.invoke(this));
            }
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        super.onAttachedToWindow();
    }
```

It turns out that there is no pressure even if  opening hundreds of pages that contain ReactRootView (remove ReactRootView from the View hierarchy temporarily in the invisible pages).

Changelog:
----------

[Android] [Fixed] - Remove duplicated `OnGlobalLayoutListener` to improve performance.
Pull Request resolved: https://github.com/facebook/react-native/pull/22849

Differential Revision: D13682818

Pulled By: hramos

fbshipit-source-id: 1f1bc8cd5fc4e01a1bc2f2a4784822b4eae92fdc
---
 .../java/com/facebook/react/ReactRootView.java    | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/ReactAndroid/src/main/java/com/facebook/react/ReactRootView.java b/ReactAndroid/src/main/java/com/facebook/react/ReactRootView.java
index 8441065aa95..0a98d47bc2d 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/ReactRootView.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/ReactRootView.java
@@ -308,6 +308,7 @@ public class ReactRootView extends SizeMonitoringFrameLayout
   protected void onAttachedToWindow() {
     super.onAttachedToWindow();
     if (mIsAttachedToInstance) {
+      removeOnGlobalLayoutListener();
       getViewTreeObserver().addOnGlobalLayoutListener(getCustomGlobalLayoutListener());
     }
   }
@@ -316,11 +317,15 @@ public class ReactRootView extends SizeMonitoringFrameLayout
   protected void onDetachedFromWindow() {
     super.onDetachedFromWindow();
     if (mIsAttachedToInstance) {
-      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
-        getViewTreeObserver().removeOnGlobalLayoutListener(getCustomGlobalLayoutListener());
-      } else {
-        getViewTreeObserver().removeGlobalOnLayoutListener(getCustomGlobalLayoutListener());
-      }
+      removeOnGlobalLayoutListener();
+    }
+  }
+
+  private void removeOnGlobalLayoutListener() {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
+      getViewTreeObserver().removeOnGlobalLayoutListener(getCustomGlobalLayoutListener());
+    } else {
+      getViewTreeObserver().removeGlobalOnLayoutListener(getCustomGlobalLayoutListener());
     }
   }