これを試してください
mWebView.setWebChromeClient(new MyWebChromeClient());
mWebView.setFocusable(true);
mWebView.setFocusableInTouchMode(true);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setPluginsEnabled(true);
mWebView.getSettings().setRenderPriority(RenderPriority.HIGH);
mWebView.getSettings().setCacheMode(WebSettings.LOAD_NO_CACHE);
mWebView.getSettings().setDomStorageEnabled(true);
mWebView.getSettings().setDatabaseEnabled(true);
mWebView.getSettings().setAppCacheEnabled(true);
mWebView.setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY);
public class MyWebChromeClient extends WebChromeClient {
//Handle javascript alerts:
@Override
public boolean onJsAlert(WebView view, String url, String message, final android.webkit.JsResult result)
{
Log.d("alert", message);
Toast.makeText(context, message, 3000).show();
result.confirm();
return true;
};