NullPointerException con ProgressBar usando ActionBarCompat

Estoy usando ActionBarCompat en soporte-v7-r18. Al tratar de mostrar un progreso indeterminado, que funciona en Galaxy S3 Android 4.1.2, pero no en Galaxy Ace Android 2.3.3.

No puedo entender por qué.

El código que eleva la excepción:

@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ... final ActionBarActivity activity = this; content = (WebView) findViewById(R.id.webContent); content.setWebViewClient(new WebViewClient() { @Override public void onPageStarted(WebView view, String url, Bitmap favicon) { super.onPageStarted(view, url, favicon); activity.setSupportProgressBarIndeterminate(true); <=== Line 88 activity.setSupportProgressBarIndeterminateVisibility(true); } }

La excepción :

 FATAL EXCEPTION: main java.lang.NullPointerException at android.support.v7.app.ActionBarActivityDelegateBase.updateProgressBars(ActionBarActivityDelegateBase.java:508) at android.support.v7.app.ActionBarActivityDelegateBase.setSupportProgressBarIndeterminate(ActionBarActivityDelegateBase.java:469) at android.support.v7.app.ActionBarActivity.setSupportProgressBarIndeterminate(ActionBarActivity.java:282) at MyActivity.onPageStarted(MyActivityActivity.java:88) at android.webkit.CallbackProxy.handleMessage(CallbackProxy.java:266) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:123) at android.app.ActivityThread.main(ActivityThread.java:3687) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:507) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625) at dalvik.system.NativeStart.main(Native Method)

Añadir supportRequestWindowFeature(Window.FEATURE_PROGRESS); O supportRequestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS); To onCreate () antes de llamar a setContentView ().