spinning wheel for webview

I want to set 开发者_JS百科spinning wheel for the webview till when the page is loaded , i am using the following approach but its floating with following logcat errors . Please guide

public class Webview extends Activity {
  WebView mWebView;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    this.getWindow().requestFeature(Window.FEATURE_PROGRESS);


    // Makes Progress bar Visible



    getWindow().requestFeature(Window.FEATURE_PROGRESS);

    WebView mWebView = (WebView) findViewById(R.id.webview);

    mWebView.getSettings().setJavaScriptEnabled(true);

    final Activity activity = this;

    mWebView.setWebChromeClient(new WebChromeClient(){

             public void onProgressChanged(WebView view, int progress) {
                     activity.setTitle("Loading...");
                     activity.setProgress(progress * 100);
                        if(progress == 100)
                           activity.setTitle("My title");
                     }
    });

    mWebView.loadUrl("..........................");

    mWebView.setVerticalScrollBarEnabled(false);
    mWebView.setHorizontalScrollBarEnabled(false);

}

xml

<?xml version="1.0" encoding="utf-8"?>


    <WebView  xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/webview"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"

/>

logcat

07-10 17:49:18.785: DEBUG/AndroidRuntime(23772): Shutting down VM
07-10 17:49:18.785: WARN/dalvikvm(23772): threadid=3: thread exiting with uncaught exception (group=0x4001e390)
07-10 17:49:18.785: ERROR/AndroidRuntime(23772): Uncaught handler: thread main exiting due to uncaught exception
07-10 17:49:18.795: ERROR/AndroidRuntime(23772): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.droidnova.android.howto.optionmenu/com.droidnova.android.howto.optionmenu.Webview}: java.lang.NullPointerException
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2596)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2621)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.app.ActivityThread.access$2200(ActivityThread.java:126)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1932)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.os.Looper.loop(Looper.java:123)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.app.ActivityThread.main(ActivityThread.java:4595)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at java.lang.reflect.Method.invokeNative(Native Method)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at java.lang.reflect.Method.invoke(Method.java:521)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at dalvik.system.NativeStart.main(Native Method)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772): Caused by: java.lang.NullPointerException
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at com.droidnova.android.howto.optionmenu.Webview.onCreate(Webview.java:36)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2544)
07-10 17:49:18.795: ERROR/AndroidRuntime(23772):     ... 11 more

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I don't see it in your code - you should call setContentView before you can call findViewById, otherwise it will return null.

So if your xml is called main.xml, you should first call setContentView(R.layout.main);