android - Null Object Reference error when adding refresh listener to SwipeRefreshLayout for a WebView -

when add line of code

swipelayout.setonrefreshlistener(this); 

i error

void android.support.v4.widget.swiperefreshlayout.setonrefreshlistener (android.support.v4.widget.swiperefreshlayout$onrefreshlistener)' on null object reference 

mainactivity

import android.app.activity; import android.os.bundle; import android.os.handler; import android.view.keyevent; import android.view.window; import android.webkit.websettings; import android.webkit.webview; import android.webkit.webviewclient; import android.support.v4.widget.swiperefreshlayout;  public class mainactivity extends activity implements swiperefreshlayout.onrefreshlistener {     private webview mwebview;     private swiperefreshlayout swipelayout;      @override     public void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         getwindow().requestfeature(window.feature_no_title);         setcontentview(r.layout.main);         mwebview = new webview(this);          mwebview.loadurl("https://secure.tickspot.com");         mwebview.setwebviewclient(new webviewclient() {             @override             public boolean shouldoverrideurlloading(webview view, string url) {                 view.loadurl(url);                 return true;             }         });          websettings websettings = mwebview.getsettings();         websettings.setjavascriptenabled(true);          swipelayout = (swiperefreshlayout) findviewbyid(r.id.swipe_container);         swipelayout.setonrefreshlistener(this);     }      @override     public boolean onkeydown(final int keycode, final keyevent event) {         if ((keycode == keyevent.keycode_back) && mwebview.cangoback()) {             mwebview.goback();             return true;         }         return super.onkeydown(keycode, event);     }      @override     public void onrefresh() {         mwebview.reload();         new handler().postdelayed(new runnable() {             @override             public void run() {                 swipelayout.setrefreshing(false);             }         }, 1000);     }  } 

androidmanifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"     package="com.mkyong.android"     android:versioncode="1"     android:versionname="1.0" >     <uses-sdk android:minsdkversion="12" />     <uses-permission android:name="android.permission.internet" />     <application         android:hardwareaccelerated="true"         android:icon="@drawable/ic_launcher"         android:label="@string/app_name" >         <activity             android:label="@string/app_name"             android:id="@+id/main_activity"             android:name=".mainactivity" >             <intent-filter >                 <action android:name="android.intent.action.main" />                 <category android:name="android.intent.category.launcher" />             </intent-filter>         </activity>     </application> </manifest> 

im new android development , having trouble understanding error messages. help! if i'm doing else wrong, love feedback :)

edit

i moved swipe refresh layout code

layout/main.xml

<?xml version="1.0" encoding="utf-8"?> <android.support.v4.widget.swiperefreshlayout xmlns:android="http://schemas.android.com/apk/res/android"     android:id="@+id/swipe_container"     android:layout_width="fill_parent"     android:layout_height="fill_parent" > </android.support.v4.widget.swiperefreshlayout> 

i had change

mwebview = new webview(this);

to

mwebview = (webview) findviewbyid(r.id.webview);

and had add following between swiperefreshlayout xml in main.xml file.

   <webview android:layout_width="match_parent"         android:layout_height="match_parent"         android:id="@+id/webview"         android:layout_alignparenttop="true"/>