android webview 返回键监听

@Overridepublic boolean onKeyDown(int keyCode, KeyEvent event) {    if ((keyCode == KeyEvent.KEYCODE_BACK) ) {        if (webview.canGoBack())        {            webview.goBack(); //goBack()表示返回WebView的上一页面            return true;        }else        {            finish();            return true;        }    }    return false;}