View as weak reference

Summary: Keep a weak reference of the view instead of a strong reference.

Reviewed By: LukeDefeo

Differential Revision: D39575312

fbshipit-source-id: ae8df7d089b29ea3b1cf960a6ae020ed5a9c3648

android/src/main/java/com/facebook/flipper/plugins/uidebugger/observers/DecorViewTreeObserver.kt

@@ -12,6 +12,7 @@ import android.view.View
 import android.view.ViewTreeObserver
 import com.facebook.flipper.plugins.uidebugger.LogTag
 import com.facebook.flipper.plugins.uidebugger.core.Context
+import java.lang.ref.WeakReference
 
 typealias DecorView = View
 
@@ -20,19 +21,20 @@ class DecorViewObserver(val context: Context) : TreeObserver<DecorView>() {
 
   val throttleTimeMs = 500
 
-  // should this be a weak reference?
-  private var nodeRef: View? = null
+  private var nodeRef: WeakReference<View>? = null
   private var listener: ViewTreeObserver.OnPreDrawListener? = null
 
   override val type = "DecorView"
 
   override fun subscribe(node: Any) {
-
     node as View
-    nodeRef = node
+    nodeRef = WeakReference(node)
 
     Log.i(LogTag, "Subscribing to decor view changes")
 
+    // TODO: there's a problem with this. Some future changes may have been
+    // ignored and not sent. Need to keep track of the last one, always and react
+    // accordingly.
     listener =
         object : ViewTreeObserver.OnPreDrawListener {
           var lastSend = 0L
@@ -53,7 +55,7 @@ class DecorViewObserver(val context: Context) : TreeObserver<DecorView>() {
     Log.i(LogTag, "Unsubscribing from decor view changes")
 
     listener.let {
-      nodeRef?.viewTreeObserver?.removeOnPreDrawListener(it)
+      nodeRef?.get()?.viewTreeObserver?.removeOnPreDrawListener(it)
       listener = null
       nodeRef = null
     }
@@ -66,7 +68,7 @@ object DecorViewTreeObserverBuilder : TreeObserverBuilder<DecorView> {
   }
 
   override fun build(context: Context): TreeObserver<DecorView> {
-    Log.i(LogTag, "Building decor view observer")
+    Log.i(LogTag, "Building DecorView observer")
     return DecorViewObserver(context)
   }
 }