android [nfc]: Add ReactExtensions.kt

From MainActivity.kt and from notifications/NotifyReact.kt.

We'll move some more of this kind of React-extending code here soon.

Author: chrisbobbe

android/app/src/main/java/com/zulipmobile/MainActivity.kt

@@ -6,26 +6,11 @@ import android.os.Bundle
 import android.webkit.WebView
 import com.facebook.react.ReactActivity
 import com.facebook.react.ReactActivityDelegate
-import com.facebook.react.ReactApplication
 import com.facebook.react.ReactRootView
-import com.facebook.react.bridge.ReactContext
 import com.zulipmobile.notifications.*
 import com.zulipmobile.sharing.handleSend
 import expo.modules.ReactActivityDelegateWrapper
 
-// A convenience shortcut.
-fun ReactApplication.tryGetReactContext(): ReactContext? =
-    this.reactNativeHost.tryGetReactInstanceManager()?.currentReactContext
-
-/**
- * Like `.application`, but with a more specific type.
- *
- * This expresses the invariant that a ReactActivity's application
- * should always be a ReactApplication.
- */
-val ReactActivity.reactApplication: ReactApplication
-    get() = application as ReactApplication
-
 open class MainActivity : ReactActivity() {
     /**
      * Returns the name of the main component registered from JavaScript.

android/app/src/main/java/com/zulipmobile/ReactExtensions.kt

@@ -0,0 +1,30 @@
+package com.zulipmobile
+
+import com.facebook.react.ReactActivity
+import com.facebook.react.ReactApplication
+import com.facebook.react.ReactInstanceManager
+import com.facebook.react.ReactNativeHost
+import com.facebook.react.bridge.ReactContext
+
+/**
+ * Like getReactInstanceManager, but just return what exists; avoid trying to create.
+ *
+ * When there isn't already an instance manager, if we call
+ * getReactInstanceManager it'll try to create one... which asserts we're
+ * on the UI thread, which isn't true if e.g. we got here from a Service.
+ */
+fun ReactNativeHost.tryGetReactInstanceManager(): ReactInstanceManager? =
+    if (this.hasInstance()) this.reactInstanceManager else null
+
+// A convenience shortcut.
+fun ReactApplication.tryGetReactContext(): ReactContext? =
+    this.reactNativeHost.tryGetReactInstanceManager()?.currentReactContext
+
+/**
+ * Like `.application`, but with a more specific type.
+ *
+ * This expresses the invariant that a ReactActivity's application
+ * should always be a ReactApplication.
+ */
+val ReactActivity.reactApplication: ReactApplication
+    get() = application as ReactApplication

android/app/src/main/java/com/zulipmobile/notifications/NotifyReact.kt

@@ -4,8 +4,6 @@ package com.zulipmobile.notifications
 
 import android.os.Bundle
 import android.util.Log
-import com.facebook.react.ReactInstanceManager
-import com.facebook.react.ReactNativeHost
 import com.facebook.react.bridge.Arguments
 import com.facebook.react.bridge.ReactContext
 import com.facebook.react.common.LifecycleState
@@ -18,16 +16,6 @@ import com.facebook.react.modules.core.DeviceEventManagerModule
  * TODO: Replace this with a fresh implementation based on RN upstream docs.
  */
 
-/**
- * Like getReactInstanceManager, but just return what exists; avoid trying to create.
- *
- * When there isn't already an instance manager, if we call
- * getReactInstanceManager it'll try to create one... which asserts we're
- * on the UI thread, which isn't true if e.g. we got here from a Service.
- */
-fun ReactNativeHost.tryGetReactInstanceManager(): ReactInstanceManager? =
-    if (this.hasInstance()) this.reactInstanceManager else null
-
 /**
  * A distillation of ReactContext.getLifecycleState() and related information.
  *