解決方案：
定義injectedJavaScript
(function() {
var originalPostMessage = window.postMessage;
var patchedPostMessage = function(message, targetOrigin, transfer) {
originalPostMessage(message, targetOrigin, transfer);
};
patchedPostMessage.toString = function() {
return String(Object.hasOwnProperty).replace('hasOwnProperty', 'postMessage');
};
window.postMessage = patchedPostMessage;
})();
<WebView injectedJavaScript={patchPostMessageJsCode} />
這樣就可以解決window.postMessage的問題了