[英]Cannot access a nonstatic member of outer type… via nested type
为什么会出现此错误?
错误CS0038:无法
JsonFeedParserTabs.MainActivity' via nested type
JsonFeedParserTabs.MainActivity.SampleTabFragment'(CS0038)(JsonFeedParserTabs)访问外部类型JsonFeedParserTabs.MainActivity' via nested type
的非静态成员
我试图将带有json数据的ListView放在选项卡中。
这是我的代码:
using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using System.Threading.Tasks;
using System.Net.Http;
using Newtonsoft.Json;
using System.Linq;
namespace JsonFeedParserTabs
{
[Activity (Label = "Feed Reader", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
ListView listView;
// ProgressBar progressBar;
RootObject result;
string url = "http://javatechig.com/api/get_category_posts/?dev=1&slug=android";
protected override void OnCreate (Bundle bundle)
{
base.OnCreate (bundle);
// Set our view from the "main" layout resource.
SetContentView (Resource.Layout.Main);
this.ActionBar.NavigationMode = ActionBarNavigationMode.Tabs;
AddTab (" Tab 1", new SampleTabFragment ());
// AddTab (" Tab 2", new SampleTabFragment2 ());
if (bundle != null)
this.ActionBar.SelectTab(this.ActionBar.GetTabAt(bundle.GetInt("tab")));
}
protected override void OnSaveInstanceState(Bundle outState)
{
outState.PutInt("tab", this.ActionBar.SelectedNavigationIndex);
base.OnSaveInstanceState(outState);
}
void AddTab (string tabText, Fragment view)
{
var tab = this.ActionBar.NewTab ();
tab.SetText (tabText);
// Must set event handler before adding tab.
tab.TabSelected += delegate(object sender, ActionBar.TabEventArgs e) {
var fragment = this.FragmentManager.FindFragmentById(Resource.Id.fragmentContainer);
if (fragment != null)
e.FragmentTransaction.Remove(fragment);
e.FragmentTransaction.Add (Resource.Id.fragmentContainer, view);
};
tab.TabUnselected += delegate(object sender, ActionBar.TabEventArgs e) {
e.FragmentTransaction.Remove(view);
};
this.ActionBar.AddTab (tab);
}
class SampleTabFragment : Fragment
{
public override View OnCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
base.OnCreateView (inflater, container, savedInstanceState);
var view = inflater.Inflate (Resource.Layout.Tab, container, false);
// Initializing listView.
listView = view.FindViewById<ListView> (Resource.Id.listView); // <-- Error!
listView.ItemClick += OnListItemClick; // <-- Error!
// progressBar = view.FindViewById<ProgressBar> (Resource.Id.progressBar);
//
// // Showing loading progressBar.
// progressBar.Visibility = ViewStates.Visible;
// Download and display data in url.
downloadJsonFeedAsync (url); // <-- Error!
return view;
}
}
// class SampleTabFragment2 : Fragment
// {
// public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
// {
// base.OnCreateView(inflater, container, savedInstanceState);
//
// var view = inflater.Inflate(Resource.Layout.Tab, container, false);
// var sampleTextView = view.FindViewById<TextView>(Resource.Id.sampleTextView);
//
// sampleTextView.Text = "Sample fragment text 2.";
//
// return view;
// }
// }
public async void downloadJsonFeedAsync(String url)
{
var httpClient = new HttpClient();
Task<string> contentsTask = httpClient.GetStringAsync(url);
// Await! control returns to the caller and the task continues to run on another thread.
string content = await contentsTask;
Console.Out.WriteLine("Response Body: \r\n {0}", content);
// Convert string to JSON object.
result = Newtonsoft.Json.JsonConvert.DeserializeObject<RootObject> (content);
// Update listview.
RunOnUiThread (() => {
listView.Adapter = new CustomListAdapter(this, result.posts);
// progressBar.Visibility = ViewStates.Gone;
});
}
void OnListItemClick(object sender, AdapterView.ItemClickEventArgs e)
{
Post item = result.posts.ElementAt (e.Position);
// Passing object form one activity to other.
Intent i = new Intent(Application.Context, typeof(FeedDetailsActivity));
i.PutExtra("item", JsonConvert.SerializeObject(item));
StartActivity(i);
}
}
}
我陷入困境,需要帮助,任何想法我做错了什么以及该怎么做? 谢谢!
好的,它现在可以工作,但是我认为可能会有更好的方法来做到这一点。
using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using System.Threading.Tasks;
using System.Net.Http;
using Newtonsoft.Json;
using System.Linq;
namespace JsonFeedParserTabs
{
[Activity (Label = "Feed Reader", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
ListView listView;
// ProgressBar progressBar;
RootObject result;
string url = "http://javatechig.com/api/get_category_posts/?dev=1&slug=android";
protected override void OnCreate (Bundle bundle)
{
base.OnCreate (bundle);
// Set our view from the "main" layout resource.
SetContentView (Resource.Layout.Main);
this.ActionBar.NavigationMode = ActionBarNavigationMode.Tabs;
AddTab (" Tab 1", new SampleTabFragment (this));
// AddTab (" Tab 2", new SampleTabFragment2 ());
if (bundle != null)
this.ActionBar.SelectTab(this.ActionBar.GetTabAt(bundle.GetInt("tab")));
}
protected override void OnSaveInstanceState(Bundle outState)
{
outState.PutInt("tab", this.ActionBar.SelectedNavigationIndex);
base.OnSaveInstanceState(outState);
}
void AddTab (string tabText, Fragment view)
{
var tab = this.ActionBar.NewTab ();
tab.SetText (tabText);
// Must set event handler before adding tab.
tab.TabSelected += delegate(object sender, ActionBar.TabEventArgs e) {
var fragment = this.FragmentManager.FindFragmentById(Resource.Id.fragmentContainer);
if (fragment != null)
e.FragmentTransaction.Remove(fragment);
e.FragmentTransaction.Add (Resource.Id.fragmentContainer, view);
};
tab.TabUnselected += delegate(object sender, ActionBar.TabEventArgs e) {
e.FragmentTransaction.Remove(view);
};
this.ActionBar.AddTab (tab);
}
class SampleTabFragment : Fragment
{
private MainActivity context;
public SampleTabFragment(MainActivity _context) : base()
{
this.context = _context;
}
public override View OnCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
base.OnCreateView (inflater, container, savedInstanceState);
var view = inflater.Inflate (Resource.Layout.Tab, container, false);
// Initializing listView.
context.listView = view.FindViewById<ListView> (Resource.Id.listView);
context.listView.ItemClick += context.OnListItemClick;
// progressBar = view.FindViewById<ProgressBar> (Resource.Id.progressBar);
//
// // Showing loading progressBar.
// progressBar.Visibility = ViewStates.Visible;
// Download and display data in url.
context.downloadJsonFeedAsync (context.url);
return view;
}
}
// class SampleTabFragment2 : Fragment
// {
// public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
// {
// base.OnCreateView(inflater, container, savedInstanceState);
//
// var view = inflater.Inflate(Resource.Layout.Tab, container, false);
// var sampleTextView = view.FindViewById<TextView>(Resource.Id.sampleTextView);
//
// sampleTextView.Text = "Sample fragment text 2.";
//
// return view;
// }
// }
public async void downloadJsonFeedAsync(String url)
{
var httpClient = new HttpClient();
Task<string> contentsTask = httpClient.GetStringAsync(url);
// Await! control returns to the caller and the task continues to run on another thread.
string content = await contentsTask;
Console.Out.WriteLine("Response Body: \r\n {0}", content);
// Convert string to JSON object.
result = Newtonsoft.Json.JsonConvert.DeserializeObject<RootObject> (content);
// Update listview.
RunOnUiThread (() => {
listView.Adapter = new CustomListAdapter(this, result.posts);
// progressBar.Visibility = ViewStates.Gone;
});
}
void OnListItemClick(object sender, AdapterView.ItemClickEventArgs e)
{
Post item = result.posts.ElementAt (e.Position);
// Passing object form one activity to other.
Intent i = new Intent(Application.Context, typeof(FeedDetailsActivity));
i.PutExtra("item", JsonConvert.SerializeObject(item));
StartActivity(i);
}
}
}
它正在告诉您确切它不能做什么。 该MainActivity
成员不是从内声明的片段类型的访问MainActivity
类型。 因此,当您尝试调用downloadJsonFeedAsync (url);
它失败,因为它不是静态(类)方法。 片段(尽管在类型中声明了)在MainActivity
类型的实例中不存在。
除非有令人信服的理由让它们保留在MainActivity类型内,否则我将其移出。 然后,他们还应该引用MainActivity类型,以便可以在其上调用downloadJsonFeedAsync(string)
。
无关紧要的是(我很欣赏这是不受欢迎的评论:)),您可能需要考虑使用MVVM模式。 看起来您正在混合演示文稿,应用程序控制和业务数据。 如果此应用程序扩展到一页或两页之外,则可以轻松地分担责任。
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