Question

我有一个警报对话框，其中包含用户可能要作为构建器项目访问的网站名称的数组。现在的名字是Facebook，我希望当通过DialogClick事件处理程序单击该项目时在类中声明的WebView加载Facebook网址，但是我在类中声明的所有变量（包括Webview）对该DialogClick事件处理程序不可见，想我应该尝试一个函数指针或委托，但卡住了请帮助... 警报对话框的C＃代码以及侦听下面点击的项目的方法

  class Internet : AppCompatActivity,Android.Webkit.IDownloadListener, GestureDetector.IOnGestureListener, BottomNavigationView.IOnNavigationItemSelectedListener, IDialogInterfaceOnClickListener
    {
        WebView webview;
        protected override void OnCreate(Bundle savedInstanceState)
        {

            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            SetContentView(Resource.Layout.Browser);
//webview definition
    webview=this.FindViewById<WebView>(Resource.Id.webview1); 
   //Button that shows the dialog on click
    Button f=this.FindViewById<Button>(Resource.Id.button1);
        f.Click +=show;
         }
  //Method to build and show alert dialog
private void show(object sender, EventArgs e){
 string[] items = new string[5] { "Facebook", "Google", "Instagram", "Twitter","Reddit" };

Android.Support.V7.App.AlertDialog.Builder builder =new Android.Support.V7.App.AlertDialog.Builder(this);
                    builder.SetTitle("Menu Items");
                    builder.SetIcon(Resource.Drawable.avatar);
//This function pointer in here called handler is the one that handles the dialog click event 
                    builder.SetItems(items, handler);
                    });
                    dialog.Show();
}
//Handler method to take care of an item clicked on the dialog
 EventHandler<DialogClickEventArgs> handler = (s, o) => {
            // save off selected event
            switch (o.Which)
            {
                case 0:
                    
                    Toast.MakeText(Application.Context, "You tapped on facebook", ToastLength.Short).Show();
                    //Tried to make variable webview load facebook url but the variable is invisible to this scope
                    break;

                case 1:
                    Toast.MakeText(Application.Context, "You tapped on Google", ToastLength.Short).Show();
                    break;
                case 4:
                    Toast.MakeText(Application.Context, "You tapped on Reddit", ToastLength.Short).Show();
                    break;
            }
              

        };
}

我需要使该类中声明的所有webview变量在此方法中可见的代码，或者使该Webview可见的另一种方法的有效函数指针可以为我加载网址

Answer 1

您可以用另一种方式定义处理程序：

class Internet : AppCompatActivity
{
    public WebView webview;
   
    EventHandler<DialogClickEventArgs> handler { get; set; }

    protected override void OnCreate(Bundle savedInstanceState)
    {

        base.OnCreate(savedInstanceState);
        Xamarin.Essentials.Platform.Init(this, savedInstanceState);

        handler += test;
    }

    public void test(object sender, DialogClickEventArgs e)
    {

        switch (e.Which)
        {
            case 0:

                Toast.MakeText(Application.Context, "You tapped on facebook", ToastLength.Short).Show();
                //Tried to make variable webview load facebook url but the variable is invisible to this scope
                webview.LoadUrl("123");

                break;

            case 1:
                Toast.MakeText(Application.Context, "You tapped on Google", ToastLength.Short).Show();
                break;
            case 4:
                Toast.MakeText(Application.Context, "You tapped on Reddit", ToastLength.Short).Show();
                break;
        }
    }
}

从DialogClick事件处理程序方法中调用另一个方法

1 个答案: