<WebView android:id="@+id/Toweb"

     android:layout_width="fill_parent"

     android:layout_height="fill_parent" /> 

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        //WebView

        WebView browser=(WebView)findViewById(R.id.Toweb);

        browser.loadUrl("http://www.baidu.com");  

        //设置可自由缩放网页

        browser.getSettings().setSupportZoom(true);

        browser.getSettings().setBuiltInZoomControls(true);  

        // 如果页面中链接，如果希望点击链接继续在当前browser中响应，

        // 而不是新开Android的系统browser中响应该链接，必须覆盖webview的WebViewClient对象

        browser.setWebViewClient(new WebViewClient() {

            public boolean shouldOverrideUrlLoading(WebView view, String url)

            {

                //  重写此方法表明点击网页里面的链接还是在当前的webview里跳转，不跳到浏览器那边

                view.loadUrl(url);

                        return true;

            }

             });

    }  

    //go back

    @Override

    public boolean onKeyDown(int keyCode, KeyEvent event) {

        WebView browser=(WebView)findViewById(R.id.Toweb);

        // Check if the key event was the Back button and if there's history

        if ((keyCode == KeyEvent.KEYCODE_BACK) && browser.canGoBack()) {

            browser.goBack();

            return true;

        }

      //  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);

    }
    

    <!--添加该权限，webview可以访问网页-->

    <uses-permission android:name="android.permission.INTERNET"></uses-permission>