如何检测iframe何时开始加载新网址并显示加载图片或gif，以避免iframe加载时间

Question

如何检测页面上的iframe开始加载新页面，以及由于加载时间太长，如何显示加载GIF和图像的加载持续时间。我搜索了同样的答案，但没有一个对我有用。我还根据构建版本将RenderPriority设置为HIGH和setLayerType，但加载时间仍然很长。

我的webview代码

var cts = new CancellationTokenSource();

var parallelOptions = new ParallelOptions() { MaxDegreeOfParallelism = 8, CancellationToken = cts.Token };
Parallel.For(0, int.MaxValue, parallelOptions, (i) =>
{
    var guid = Guid.NewGuid().ToString();
    var four = guid.ElementAt(14);
    var ab89 = guid.ElementAt(19);

    if (four != '4') cts.Cancel();
    if (ab89 != 'a' && ab89 != 'b' && ab89 != '8' && ab89 != '9') cts.Cancel();

    if ((i % 100000) == 0 && i < (int.MaxValue / 8))
    {
        Console.WriteLine($"{i * 8:n}"); // roughly   
    }
});

activity_main.xml

public class MainActivity extends AppCompatActivity {
private WebView webView = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    this.webView = (WebView) findViewById(R.id.webview);
    WebSettings webSettings = webView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    webSettings.setRenderPriority(WebSettings.RenderPriority.HIGH);
    webSettings.setCacheMode(WebSettings.LOAD_NO_CACHE);
    if (Build.VERSION.SDK_INT >= 19) {
        webView.setLayerType(View.LAYER_TYPE_HARDWARE, null);
    }
    else {
        webView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    }
    MyWebViewClient webViewClient = new MyWebViewClient();
    webView.setWebViewClient(new WebViewClient());
    webView.loadUrl("https://www.example.com");

}


@Override

public boolean onKeyDown(final int keyCode, final KeyEvent event) {

    if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack()) {
        webView.goBack();
        return true;
    }

    return super.onKeyDown(keyCode, event);
}

private class MyWebViewClient extends WebViewClient {


    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {

        if(Uri.parse(url).getHost().endsWith(".com")) {


            return false;
        }

        Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
        view.getContext().startActivity(intent);
        return true;
    }
}
  }