android webview find element doesn't work before Kitkat version

问题

I have a app which clicks automatically button by javascript. It works fine but before Kitkat versions find element doesn't work.

webView.setWebViewClient(new WebViewClient() {
    public void onPageFinished(WebView view, String url) {
        view.loadUrl("javascript:window.frames['top_level'].document.getElementById('enter_desktop').click();");
    }
});

Before Kitkat window.frames['top_level'].document.getElementById('enter_desktop') returns frame's src value not my element.Please help me? Thanks in advance!

来源：https://stackoverflow.com/questions/36256857/android-webview-find-element-doesnt-work-before-kitkat-version