Add support for injectedJavaScriptBeforeContentLoaded on Android

android/src/main/java/com/reactnativecommunity/webview/RNCWebViewManager.java

@@ -392,6 +392,11 @@ public class RNCWebViewManager extends SimpleViewManager<WebView> {
     ((RNCWebView) view).setInjectedJavaScript(injectedJavaScript);
   }
 
+  @ReactProp(name = "injectedJavaScriptBeforeContentLoaded")
+  public void setInjectedJavaScriptBeforeContentLoaded(WebView view, @Nullable String injectedJavaScriptBeforeContentLoaded) {
+    ((RNCWebView) view).setInjectedJavaScriptBeforeContentLoaded(injectedJavaScriptBeforeContentLoaded);
+  }
+
   @ReactProp(name = "messagingEnabled")
   public void setMessagingEnabled(WebView view, boolean enabled) {
     ((RNCWebView) view).setMessagingEnabled(enabled);
@@ -702,6 +707,7 @@ public class RNCWebViewManager extends SimpleViewManager<WebView> {
   protected static class RNCWebViewClient extends WebViewClient {
 
     protected boolean mLastLoadFailed = false;
+    protected boolean mIsFirstLoad = true;
     protected @Nullable
     ReadableArray mUrlPrefixesForDefaultIntent;
 
@@ -723,6 +729,12 @@ public class RNCWebViewManager extends SimpleViewManager<WebView> {
       super.onPageStarted(webView, url, favicon);
       mLastLoadFailed = false;
 
+      if (mIsFirstLoad) {
+        RNCWebView reactWebView = (RNCWebView) webView;
+        reactWebView.callInjectedJavaScriptBeforeContentLoaded();  
+      }
+      mIsFirstLoad = false;      
+
       dispatchEvent(
         webView,
         new TopLoadingStartEvent(
@@ -961,6 +973,8 @@ public class RNCWebViewManager extends SimpleViewManager<WebView> {
   protected static class RNCWebView extends WebView implements LifecycleEventListener {
     protected @Nullable
     String injectedJS;
+    protected @Nullable
+    String injectedJSBeforeContentLoaded;
     protected boolean messagingEnabled = false;
     protected @Nullable
     RNCWebViewClient mRNCWebViewClient;
@@ -1034,6 +1048,10 @@ public class RNCWebViewManager extends SimpleViewManager<WebView> {
       injectedJS = js;
     }
 
+    public void setInjectedJavaScriptBeforeContentLoaded(@Nullable String js) {
+      injectedJSBeforeContentLoaded = js;
+    }
+
     protected RNCWebViewBridge createRNCWebViewBridge(RNCWebView webView) {
       return new RNCWebViewBridge(webView);
     }
@@ -1075,6 +1093,14 @@ public class RNCWebViewManager extends SimpleViewManager<WebView> {
       }
     }
 
+    public void callInjectedJavaScriptBeforeContentLoaded() {
+      if (getSettings().getJavaScriptEnabled() &&
+      injectedJSBeforeContentLoaded != null &&
+      !TextUtils.isEmpty(injectedJSBeforeContentLoaded)) {
+        evaluateJavascriptWithFallback("(function() {\n" + injectedJSBeforeContentLoaded + ";\n})();");
+      }
+    }
+
     public void onMessage(String message) {
       if (mRNCWebViewClient != null) {
         WebView webView = this;