Why does Android WebView sporadically not sending my session cookie?

Thanks justingrammens! That worked for me, I managed to share the cookie within my DefaultHttpClient requests and WebView activity:

//------- Native request activity
private DefaultHttpClient httpClient;
public static Cookie cookie = null;

//After Login
List<Cookie> cookies = httpClient.getCookieStore().getCookies();
for (int i = 0; i < cookies.size(); i++) {
    cookie = cookies.get(i);
}

//------- Web Browser activity
Cookie sessionCookie = myapp.cookie;
CookieSyncManager.createInstance(this);
CookieManager cookieManager = CookieManager.getInstance();
if (sessionCookie != null) {
    cookieManager.removeSessionCookie();
    String cookieString = sessionCookie.getName() + "=" + sessionCookie.getValue() + "; domain=" + sessionCookie.getDomain();
    cookieManager.setCookie(myapp.domain, cookieString);
    CookieSyncManager.getInstance().sync();
}   

I've spent the greater half of 3 hours working on a very similar issue. In my case I had a number of calls, that I made to a web service using a DefaulHttpClient and then I wanted to set the session and all other corresponding cookies in my WebView.

I don't know if this will solve your problem, since I don't know what your getCookie() method does, but in my case I actually had to call.

cookieManager.removeSessionCookie();

First to remove the session cookie and then re-add it. I was finding that when I tried to set the JSESSIONID cookie without first removing it, the value I wanted to set it to wasn't being save. Not sure if this will help you particular issue, but thought I'd share what I had found.

Couple of comments (at least for APIs >= 21) which I found out from my experience and gave me headaches:

1. http and https urls are different. Setting a cookie for http://www.example.com is different than setting a cookie for https://www.example.com
2. A slash in the end of the url can also make a difference. In my case https://www.example.com/ works but https://www.example.com does not work.
3. CookieManager.getInstance().setCookie is performing an asynchronous operation. So, if you load a url right away after you set it, it is not guaranteed that the cookies will have already been written. To prevent unexpected and unstable behaviours, use the CookieManager#setCookie(String url, String value, ValueCallback callback) (link) and start loading the url after the callback will be called.

I hope my two cents save some time from some people so you won't have to face the same problems like I did.

After some time researching I've gathered some pieces that made me get to this solution. Once that CookieSyncManager is deprecated, this may be the best way to set a specific cookie for a webview in Kotlin nowadays, you shouldn't need anything else.

private fun setCookie(){
    val webView = WebView(this) // this = context
    val cookieManager = CookieManager.getInstance()
    cookieManager.acceptCookie()

    val domain = "https://www.yourdomain.com/"

    webView.webViewClient = WebViewClient()
    webView.settings.javaScriptEnabled = true

    cookieManager.setCookie(domain,"$cookieKey=$cookieValue")
    cookieManager.setAcceptThirdPartyCookies(webView, true)

    webView.loadUrl(domain)
}

I have faced same problem and It will resolve this issue in all android versions

private void setCookie() {
    try {
        CookieSyncManager.createInstance(context);
        CookieManager cookieManager = CookieManager.getInstance();
        cookieManager.setAcceptCookie(true);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            cookieManager.setCookie(Constant.BASE_URL, getCookie(), value -> {
                String cookie = cookieManager.getCookie(Constant.BASE_URL);
                CookieManager.getInstance().flush();
                CustomLog.d("cookie", "cookie ------>" + cookie);
                setupWebView();
            });
        } else {
            cookieManager.setCookie(webUrl, getCookie());
            new Handler().postDelayed(this::setupWebView, 700);
            CookieSyncManager.getInstance().sync();
        }

    } catch (Exception e) {
        CustomLog.e(e);
    }
}

Note that it may be better use subdomains instead of usual URL. So, set .example.com instead of https://example.com/.

Thanks to Jody Jacobus Geers and others I wrote so:

if (savedInstanceState == null) {
    val cookieManager = CookieManager.getInstance()
    cookieManager.acceptCookie()
    val domain = ".example.com"
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        cookieManager.setCookie(domain, "token=$token") {
            view.webView.loadUrl(url)
        }
        cookieManager.setAcceptThirdPartyCookies(view.webView, true)
    } else {
        cookieManager.setCookie(domain, "token=$token")
        view.webView.loadUrl(url)
    }
} else {
    // Check whether we're recreating a previously destroyed instance.
    view.webView.restoreState(savedInstanceState)
}