NullPointerException in CookieSyncManager.createInstance in AsyncTask

问题

I have a class that extends from AysncTask. Inside the doInBackground method I want to update the cookies, so I have:

CookieSyncManager.createInstance(context);      // <<<<<<<<<<<<<<<<<<
CookieManager cookieManager = CookieManager.getInstance();
cookieManager.setCookie(cookie.getDomain(), cookieString); 
CookieSyncManager.getInstance().sync();

But I get java.lang.NullPointerException in the first line.

So, the question is:

• Why could be causing this ?
• Do I need to create it in another activity, and just used it in this activity ? how ? why ?

---

Notes:

• I know that my context is not null, I checked that.
• I can't have an onCreate method on an AsyncTask. To do this.

---

Here is the stack-trace:

  java.lang.NullPointerException
    at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:101)
    at android.webkit.JniUtil.setContext(JniUtil.java:53)
    at android.webkit.CookieSyncManager.createInstance(CookieSyncManager.java:89)
    at com.t.m.library.HttpRequest.doInBackground(HttpRequest.java:129)
    at com.t.m.library.HttpRequest.doInBackground(HttpRequest.java:1)
    at android.os.AsyncTask$2.call(AsyncTask.java:287)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
    at java.lang.Thread.run(Thread.java:856)

---

This is my doInBackground method:

request = new HttpGet(this.url);
request.addHeader("Accept", "application/json");
request.addHeader("Authorization", this.basicAuthentication);
HttpParams httpParams = new BasicHttpParams();
HttpProtocolParams.setVersion(httpParams, HttpVersion.HTTP_1_1);
HttpClient httpclient = null;
httpclient = new DefaultHttpClient(httpParams);

HttpResponse response = httpclient.execute(request);


// The content from the requested URL along with headers, etc.
HttpEntity entity = response.getEntity();
String responseBody = EntityUtils.toString(entity, "UTF-8");

CookieSyncManager.createInstance(context);
CookieManager cookieManager = CookieManager.getInstance();
cookieManager.setCookie(cookie.getDomain(), cookieString); 
CookieSyncManager.getInstance().sync();

回答1:

I call it in Application's onCreate() passing the application as context

回答2:

I've never used CookieSyncManager, but from what I can see in the docs may be you should not use it within a Thread because its already creating one:

A separate thread saves the cookies between, driven by a timer.

• You should call createInstance when the application starts, usually in onCreate()
• getInstance().startSync() In Activity.onResume()
• And getInstance().stopSync() in Activity.onPause()

Here you have an example

Hope this help.

来源：https://stackoverflow.com/questions/23813034/nullpointerexception-in-cookiesyncmanager-createinstance-in-asynctask