Android编程实现WebView添加进度条的方法

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical" >
 <ProgressBar
  android:id="@+id/pb"
  style="?android:attr/progressBarStyleHorizontal"
  android:layout_width="fill_parent"
  android:layout_height="8dip"
  android:indeterminateOnly="false"
  android:max="100"
  android:progressDrawable="@drawable/progress_bar_states" >
 </ProgressBar>
 <WebView
  android:id="@+id/webview"
  android:layout_width="match_parent"
  android:layout_height="match_parent" />
</LinearLayout>

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
 <item android:id="@android:id/background">
  <shape>
   <gradient
     android:startColor="#ff0000"
     android:centerColor="#ffa600"
     android:endColor="#ff5500"
   />
  </shape>
 </item>
 <item android:id="@android:id/secondaryProgress">
  <clip>
   <shape>
    <gradient
      android:startColor="#234"
      android:centerColor="#234"
      android:endColor="#a24"
    />
   </shape>
  </clip>
 </item>
 <item android:id="@android:id/progress">
  <clip>
   <shape>
    <gradient
     android:startColor="#33000001"
     android:centerColor="#40000000"
     android:endColor="#44000000"
    />
   </shape>
  </clip>
 </item>
</layer-list>

ProgressBar pb;
@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.xxx);
 pb = (ProgressBar) findViewById(R.id.pb);
 pb.setMax(100);
 WebView webView = (WebView) findViewById(R.id.webview);
 webView.getSettings().setJavaScriptEnabled(true);
 webView.getSettings().setSupportZoom(true);
 webView.getSettings().setBuiltInZoomControls(true);
 webView.setWebChromeClient(new WebViewClient() );
 webView.loadUrl("http://www.x.com");
}
private class WebViewClient extends WebChromeClient {
 @Override
 public void onProgressChanged(WebView view, int newProgress) {
  pb.setProgress(newProgress);
  if(newProgress==100){
   pb.setVisibility(View.GONE);
  }
  super.onProgressChanged(view, newProgress);
 }
}