mWebView.setWebViewClient(new WebViewClient(){
 public boolean shouldOverrideUrlLoading(WebView view, String url) {
 view.loadUrl(url);
 return true;
 }
});

public boolean onKeyDown(int keyCode, KeyEvent event) {
 if ((keyCode == KeyEvent.KEYCODE_BACK) && mWebView.canGoBack()) {
  mWebView.goBack();
   return true;
 }
 return super.onKeyDown(keyCode, event);
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:background="@drawable/bg_main" >
 <RelativeLayout
 android:id="@+id/title"
 android:layout_width="fill_parent"
 android:layout_height="48dp"
 android:layout_alignParentTop="true"
 android:background="@drawable/bg_title"
 android:padding="0dp" >
 <TextView
  android:id="@+id/news"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_centerInParent="true"
  android:text="新浪微博"
  android:textSize="22sp"
  android:textColor="#ffffff"/>
 </RelativeLayout>
 <WebView
 android:id="@+id/web_view_pethome"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:layout_below="@+id/title"/>
 <ProgressBar
 android:id="@+id/progress_bar"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_centerInParent="true"
 android:visibility="gone" />
</RelativeLayout>

private void findViews() {
 mWebView = (WebView) findViewById(R.id.web_view_pethome);
 mProgressBar = (ProgressBar) findViewById(R.id.progress_bar);
}
private void setWebView() {
 // 调用loadUrl()方法进行加载内容
 mWebView.loadUrl(URL);
 // 设置WebView的属性，此时可以去执行JavaScript脚本
 mWebView.getSettings().setJavaScriptEnabled(true);
 // 设置缩放按钮
 mWebView.getSettings().setBuiltInZoomControls(true);
 mWebView.getSettings().setSupportZoom(true);
 mWebView.setWebViewClient(new WebViewClient() {
 public boolean shouldOverrideUrlLoading(WebView view, String url) {
  view.loadUrl(url);
  return true;
 }
 @Override
 public void onPageFinished(WebView view, String url) {
  Log.v("webview", "========onPageFinished=======");
  super.onPageFinished(view, url);
  mProgressBar.setVisibility(View.GONE);
 }
 @Override
 public void onPageStarted(WebView view, String url, Bitmap favicon) {
  Log.v("webview", "========onPageStarted=======");
  super.onPageStarted(view, url, favicon);
  mProgressBar.setVisibility(View.VISIBLE);
 }
 });
}
/**
 * 返回键监听事件
 */
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
 if ((keyCode == KeyEvent.KEYCODE_BACK)) {
 if (mWebView.canGoBack()) {
  mWebView.goBack();
 }
 return true;
 }
 return super.onKeyDown(keyCode, event);
}