android - Fatal Exception: java.lang.NullPointerException at MainFragment -

recently found out application crashes on devices. here crash:

java.lang.nullpointerexception    @ com.zippyshare.search.free.fragment.mainfragment$3.loadfromassetswhite(mainfragment.java:501)    @ com.zippyshare.search.free.fragment.mainfragment$3.shouldinterceptrequest(mainfragment.java:477)    @ android.webkit.callbackproxy.shouldinterceptrequest(callbackproxy.java:1463)    @ android.webkit.browserframe.shouldinterceptrequest(browserframe.java:964)    @ android.webkit.jwebcorejavabridge.nativeservicefuncptrqueue(jwebcorejavabridge.java)    @ android.webkit.jwebcorejavabridge.handlemessage(jwebcorejavabridge.java:113)    @ android.os.handler.dispatchmessage(handler.java:99)    @ android.os.looper.loop(looper.java:177)    @ android.webkit.webviewcore$webcorethread.run(webviewcore.java:1133)    @ java.lang.thread.run(thread.java:856) 

here crashing coode:

    private webresourceresponse loadfromassetswhite(string assetpath, string mimetype, string encoding){  501 line ------>assetmanager assetmanager = getactivity().getassets();                 inputstream input;                 try {                     input = assetmanager.open("search-white.png");                     return new webresourceresponse(mimetype, encoding, input);                 } catch (ioexception e) {                     log.e("web-app", "error loading " + assetpath + " assets: " +                             e.getmessage(), e);                 }                 return null;             } 

and here call method:

if (webviewurl != null && webviewurl.contains("results.html")) {                             return loadfromassetsblack("", "", "");                         } else {     477 line--------------->return loadfromassetswhite("", "", "");                         } 

full webviewclient code:

        webview.setwebviewclient(new webviewclient()             {                 private boolean msuccess = true;                  @suppresswarnings("deprecation")                 @override                 public webresourceresponse shouldinterceptrequest(webview view, string url) {                     logcat.d("resource(pre) url: "+url);                     if (url.contains("adcash.com")){                         return new webresourceresponse("text/plain", "utf-8",                                 new bytearrayinputstream("".getbytes()));                     } else if (url.equals("search_box_icon.png")) {                         isurlready = false;                         webviewurl = null;                         try {                             mainactivity.mainactivity.runonuithread(new runnable() {                                 @override                                 public void run() {                                     webviewurl = webview.geturl();                                     isurlready = true;                                 }                             });                          } catch (exception ex) {                             ex.printstacktrace();                             isurlready = true;                         }                         while(!isurlready);                         isurlready = false;                         if (webviewurl != null && webviewurl.contains("results.html")) {                             return loadfromassetsblack("", "", "");                         } else {                             return loadfromassetswhite("", "", "");                         }                     }                      logcat.d("resource(post) url: "+url);                     return super.shouldinterceptrequest(view, url);                 }     private webresourceresponse loadfromassetsblack(string assetpath, string mimetype, string encoding){                      assetmanager assetmanager = getactivity().getassets();                     inputstream input;                     try {                         input = assetmanager.open("search-black.png");                         return new webresourceresponse(mimetype, encoding, input);                     } catch (ioexception e) {                         log.e("web-app", "error loading " + assetpath + " assets: " +                                 e.getmessage(), e);                     }                     return null;                 }        private webresourceresponse loadfromassetswhite(string assetpath, string mimetype, string encoding){              assetmanager assetmanager = getactivity().getassets();             inputstream input;             try {                 input = assetmanager.open("search-white.png");                 return new webresourceresponse(mimetype, encoding, input);             } catch (ioexception e) {                 log.e("web-app", "error loading " + assetpath + " assets: " +                         e.getmessage(), e);             }             return null;         } 

if need more details, can check crashalytics report: http://crashes.to/s/e0975fe822c thank in advance help.

fix suggested @chandra:

private webresourceresponse loadfromassetswhite(string assetpath, string mimetype, string encoding){             context context = getactivity();             if(context == null) {                 context = mainactivity.mainactivity;             }             assetmanager assetmanager = context.getassets();             inputstream input;             try {                 input = assetmanager.open("search-white.png");                 return new webresourceresponse(mimetype, encoding, input);             } catch (ioexception e) {                 log.e("web-app", "error loading " + assetpath + " assets: " +                         e.getmessage(), e);             }             return null;         }