Promise based evaluateJavascript result

README.md

@@ -104,7 +104,8 @@ var WebViewAndroidExample = React.createClass({
     },
     evaluateJavascript: function(data) {
       // evaluates javascript directly on the webview instance
-      this.refs.webViewAndroidSample.evaluateJavascript(data);
+      this.refs.webViewAndroidSample.evaluateJavascript(data)
+        .then(res => console.log(res));
     },
     injectJavaScript: function(script) {
       // executes JavaScript immediately in web view

android/build.gradle

@@ -14,4 +14,5 @@ android {
 
 dependencies {
     compile 'com.facebook.react:react-native:+'
+    compile 'com.google.code.gson:gson:2.8.5'
 }

android/src/main/java/com/burnweb/rnwebview/RNWebViewManager.java

@@ -32,7 +32,6 @@ public class RNWebViewManager extends SimpleViewManager<RNWebView> {
     public static final int POST_MESSAGE = 5;
     public static final int INJECT_JAVASCRIPT = 6;
     public static final int SHOULD_OVERRIDE_WITH_RESULT = 7;
-    public static final int EVALUATE_JAVASCRIPT = 8;
 
     private static final String HTML_MIME_TYPE = "text/html";
 
@@ -193,7 +192,6 @@ Map<String, Integer> getCommandsMap() {
                 "injectJavaScript", INJECT_JAVASCRIPT,
                 "shouldOverrideWithResult", SHOULD_OVERRIDE_WITH_RESULT
         );
-        map.put("evaluateJavascript", EVALUATE_JAVASCRIPT);
 
         return map;
     }
@@ -238,11 +236,6 @@ public void receiveCommand(RNWebView view, int commandId, @Nullable ReadableArra
             case SHOULD_OVERRIDE_WITH_RESULT:
                 view.shouldOverrideWithResult(view, args);
                 break;
-            case EVALUATE_JAVASCRIPT:
-                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
-                    view.evaluateJavascript(args.getString(0), null);
-                }
-                break;
         }
     }
 

android/src/main/java/com/burnweb/rnwebview/RNWebViewModule.java

@@ -12,13 +12,24 @@
 import android.os.Build;
 import android.os.Bundle;
 import android.util.Log;
+import android.view.View;
 import android.webkit.JsResult;
 import android.webkit.ValueCallback;
 import android.webkit.WebChromeClient;
 
 import com.facebook.react.bridge.ActivityEventListener;
 import com.facebook.react.bridge.ReactApplicationContext;
 import com.facebook.react.bridge.ReactContextBaseJavaModule;
+import com.facebook.react.bridge.Promise;
+import com.facebook.react.bridge.ReactMethod;
+
+import com.facebook.react.uimanager.UIManagerModule;
+import com.facebook.react.uimanager.UIBlock;
+import com.facebook.react.uimanager.NativeViewHierarchyManager;
+
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonToken;
+import java.io.StringReader;
 
 public class RNWebViewModule extends ReactContextBaseJavaModule implements ActivityEventListener {
 
@@ -171,4 +182,61 @@ public void onActivityResult(Activity activity, int requestCode, int resultCode,
 
     public void onNewIntent(Intent intent) {}
 
+    public interface RNWebViewHandler {
+        void handle(RNWebView result);
+    }
+
+    @ReactMethod
+    public void evaluateJavascript(final String data, final int viewId, final Promise promise) {
+        withRNWebView(viewId, promise, new RNWebViewHandler() {
+            @Override
+            public void handle(RNWebView view) {
+                view.evaluateJavascript(data, new ValueCallback<String>() {
+                    @Override
+                    public void onReceiveValue(String value) {
+                        JsonReader reader = new JsonReader(new StringReader(value));
+
+                        reader.setLenient(true);
+
+                        try {
+                            if(reader.peek() != JsonToken.NULL && reader.peek() == JsonToken.STRING) {
+                                String msg = reader.nextString();
+                                promise.resolve(msg);
+                            } else {
+                                promise.resolve(value);
+                            }
+                        } catch (Exception e) {
+                            Log.e(REACT_CLASS, "Unparsable evaluate javascript result");
+                            promise.reject(e.toString());
+                        } finally {
+                            try {
+                                reader.close();
+                            } catch (Exception e) {
+                                // NOOP
+                                promise.reject(e.toString());
+                            }
+                        }
+                    }
+                });
+            }
+        });
+    }
+
+    private void withRNWebView(final int viewId, final Promise promise, final RNWebViewHandler handler) {
+        UIManagerModule uiManager = getReactApplicationContext().getNativeModule(UIManagerModule.class);
+        uiManager.addUIBlock(new UIBlock() {
+            @Override
+            public void execute(NativeViewHierarchyManager nativeViewHierarchyManager) {
+                View view = nativeViewHierarchyManager.resolveView(viewId);
+                if (view instanceof RNWebView) {
+                    RNWebView myView = (RNWebView) view;
+                    handler.handle(myView);
+                }
+                else {
+                    promise.reject("RNWebView", "Unexpected view type");
+                }
+            }
+        });
+    }
+
 }

index.android.js

@@ -84,13 +84,6 @@ var WebViewAndroid = createClass({
       null
     );
   },
-  evaluateJavascript: function(data) {
-    RCTUIManager.dispatchViewManagerCommand(
-      this._getWebViewHandle(),
-      RCTUIManager.RNWebViewAndroid.Commands.evaluateJavascript,
-      [String(data)]
-    );
-  },
   postMessage: function(data) {
     RCTUIManager.dispatchViewManagerCommand(
       this._getWebViewHandle(),
@@ -105,6 +98,9 @@ var WebViewAndroid = createClass({
       [data]
     );
   },
+  evaluateJavascript: function(data) {
+    return NativeModules.RNWebViewAndroidModule.evaluateJavascript(data, this._getWebViewHandle());
+  },
   render: function() {
     return (
       <RNWebViewAndroid