Android: cargando la URL en la vista web desde la pantalla en blanco de la pantalla web por primera vez

You have not set any url in outside your MuCountDown Class that's why you are getting error. It means you have to give

mWebView.loadUrl("http://stackoverflow.com"); 

atleast one URL inside your Gif_First class.

Use el código a continuación,

mTimer.start();
mWebView = (WebView) findViewById(R.id.webviewActionView);
mWebView.loadUrl("http://stackoverflow.com");
mWebView.getSettings().setJavaScriptEnabled(true);

syntax " CountDownTimer(start time, intervel time) " .. replace the code mTimer = new CountDownTimer(10000, 1000) en lugar de mTimer = new CountDownTimer(0, 1000) hope it will work. happy coding...

Use this custom :

private class MyCountDown extends CountDownTimer
 {
long duration, interval;
public MyCountDown(long millisInFuture, long countDownInterval) {
    super(millisInFuture, countDownInterval);
    // TODO Auto-generated constructor stub
    duration = millisInFuture;
    interval = countDownInterval;
    start();
}

@Override
public void onFinish() {

}

@Override
public void onTick(long duration) {

}   
}

public class Gif_First extends Activity {

WebView mWebView;
CountDownTimer mTimer;

@SuppressLint("SetJavaScriptEnabled")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
        WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.animation);

mTimer = new MyCountDown(10000, 1000);
mWebView = (WebView) findViewById(R.id.webviewActionView);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.setWebViewClient(new WebSliderWebViewClient() {
    @Override
    public void onPageFinished(WebView view, String url) {
        super.onPageFinished(mWebView, url);
        //Toast.makeText(getApplicationContext(), "Done!",
            //  Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onReceivedError(WebView view, int errorCode,
            String description, String failingUrl) {
        Toast.makeText(getApplicationContext(),
                "Oh no! " + description, Toast.LENGTH_SHORT).show();
    }
});
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK) && mWebView.canGoBack()) {
    mWebView.goBack();
    return true;
}
return super.onKeyDown(keyCode, event);
 }

private class WebSliderWebViewClient extends WebViewClient {
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
    view.loadUrl(url);
    return true;
}
}

public void onPause() {
super.onPause();
mTimer.cancel();
}

class MyCountDown extends CountDownTimer
{
 long duration, interval;
 private String[] myArray = {
            "http://i.share.pho.to/efe195fd_o.gif",
            "http://i.share.pho.to/cf478918_o.gif",
            "http://i.share.pho.to/5ae5a0a9_o.gif",
            "http://i.share.pho.to/17d0c96f_o.gif",
            "http://i.share.pho.to/d2139e2d_o.gif" };
 int currentIndex = 0;
 public MyCountDown(long millisInFuture, long countDownInterval) {
  super(millisInFuture, countDownInterval);
  // TODO Auto-generated constructor stub
  duration = millisInFuture;
  interval = countDownInterval;
  start();
 }

 @Override
 public void onFinish() {
  if (currentIndex < myArray.length) {
            mWebView.loadUrl(myArray[currentIndex]);
            currentIndex++;
        } else {
            currentIndex = 0;
            if (currentIndex < myArray.length)
                mWebView.loadUrl(myArray[currentIndex]);
            currentIndex++; 
        }
 }

 @Override
 public void onTick(long duration) {

 }   
}
}

There are possible reasons causing "WebView goes blank after finish loading page":

1. If your WebView part defined in the layout xml file has dimensions like
   

   android: layout_width = "wrap_content"
   

   or

   android: layout_height = "wrap_content"
   

   Then after the page is loaded, the content is defined and WebView tries to "wrap" it, thus in some cases reduces the view's dimensions into 0dp and make your WebView invisible. Solution: change all those into fill_parent

   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   

2. This may be caused by an SSL certification error. Try this:

   public void onReceivedSslError(WebView view, SslErrorHandler handler, SslError error) {
       handler.proceed();
   }