title: android: WebView canGoBack() Error
body: <p>I'm following (<a href="http://developer.android.com/guide/webapps/webview.html" rel="nofollow">Building Web Apps in WebView</a>) tutorial, but I have problem with (Navigating web page history) I'm runing it on my device and I click on a link but when I click the back button the application shuts down:</p>
  
  <p>That's my activity:</p>
  
  <pre><code>public class MainActivity extends Activity {
  
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
  
      WebView myWebView = (WebView) findViewById(R.id.webView1);
      myWebView.setWebViewClient(new MyWebViewClient());
      myWebView.setWebViewClient(new WebViewClient());
      WebSettings webSettings = myWebView.getSettings();
      webSettings.setJavaScriptEnabled(true);
      myWebView.loadUrl("http://www.google.com");
  }
  
  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
      getMenuInflater().inflate(R.menu.activity_main, menu);
      return true;
  }
  
  private class MyWebViewClient extends WebViewClient {
      @Override
      public boolean shouldOverrideUrlLoading(WebView view, String url) {
          if (Uri.parse(url).getHost().equals("www.example.com")) {
              // This is my web site, so do not override; let my WebView load the page
              return false;
          }
          // Otherwise, the link is not for a page on my site, so launch another Activity that handles URLs
          Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
          startActivity(intent);
          return true;
      }
  }
  
  @Override
  public boolean onKeyDown(int keyCode, KeyEvent event) {
      WebView myWebView = null;
      // Check if the key event was the Back button and if there's history
      if ((keyCode == KeyEvent.KEYCODE_BACK) &amp;&amp; myWebView.canGoBack()) {
          myWebView.goBack();
          return true;
      }
      // If it wasn't the Back key or there's no web page history, bubble up to the default
      // system behavior (probably exit the activity)
      return super.onKeyDown(keyCode, event);
  }
  </code></pre>
  
  <p>}</p>