Within OnCreate()
new Thread(new ThreadStart(() => {
this.RunOnUiThread(async () =>
{
await SetData(TodaysDate); ;
//await FindNotesForDay(TodaysDate, TodaysDate.AddDays(+6));
progress.Dismiss();
});
})).Start();
private async Task SetData(DateTime date)
{
await Task.Run(() =>
{
dicMyMap = null;
dicMyMap = new Dictionary<string, List<ClassInstance>>();
List<string> group = new List<string>();
group.Add("Monday");
group.Add("Tuesday");
group.Add("Wednesday");
group.Add("Thursday");
group.Add("Friday");
dicMyMap.Add(group[0], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
date = date.AddDays(+1);
dicMyMap.Add(group[1], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
date = date.AddDays(+1);
dicMyMap.Add(group[2], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
date = date.AddDays(+1);
dicMyMap.Add(group[3], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
date = date.AddDays(+1);
dicMyMap.Add(group[4], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
myAdapater = new ExpandableListViewAdapter(this, group, dicMyMap);
expandableListView.SetAdapter(myAdapater);
});
}
private List<ClassInstance> ListsPopulation(String date)
{
string sql = "SELECT * FROM lectures join groupConvert using (Groups) where StartDate = '" + date + "' AND Cohort = '" + User.Cohort + "' AND Year = '" + User.IntakeYear + "';";
List<ClassInstance> Temp = new List<ClassInstance>();
//Insert Header
Temp.Add(new ClassInstance("Start Time", "End Time", "Subject", "Location", "", ""));
using (MySqlCommand cmd = new MySqlCommand(sql, Connect.GetConnection()))
{
MySqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
ClassInstance c = new ClassInstance(reader["StartTime"].ToString(), reader["EndTime"].ToString(), reader["Theme"].ToString(), reader["Location"].ToString(), reader["Essential"].ToString(), reader["Notes"].ToString());
Temp.Add(c);
}
}
if (Temp.Count == 1)
{
Temp.Clear();
Temp.Add(new ClassInstance("No Classes", "", "", "", "", ""));
}
return Temp;
}
你好
我目前正在尝试从AWS上托管的数据库填充ListView。您可以想象加载需要一些时间。我的问题是我当前的代码抛出错误。抛出的错误是模棱两可的，只是表明程序崩溃了。
本质上我想做的很简单，我基本上只想在加载这些方法时显示一个对话框。
关于我的代码的任何建议都会非常好。
编辑：我已将错误消息缩小到代码的这个区域。在尝试使用线程之前，我能够加载此Activity，但是由于没有加载消息，用户看起来活动已经冻结而不是它正在加载的事实。
谢谢， 乔
答案 0 :(得分：0)
所以我设法修复上面的代码以正确运行。
如果您有任何反馈或意见，请告诉我，我希望有人认为这有帮助。
我完全错误地使用了Async方法，你也无法从oncreate调用Async方法，因为我确定你知道。我的解决方案的一部分是更改我使Async错误地返回void的所有方法（意味着它们是同步的）。
然后我创建了一个运行命令的线程，现在它们最终以正确的顺序运行：）。
在Thread中需要注意的是，受UI影响的任何元素都需要使用主UI线程运行它们，这也适用于它们调用的方法。
以下是为解决我遇到的问题而创建的代码区域
// Try catch attempt to catch all errors, the error dialog thrown within
//the catch is fairly simple
try
{
//Start loading spinner
var LoadingProgressDialog = ProgressDialog.Show(this, "Loading", "Loading", false);
//Start loading thread, this thread will carry out the functions
// in the order you requested
Thread LoadingThread = new Thread(() =>
{
//Line below only relevant to my code
StartMonday.Text = "Week Commencing On " + TodaysDate.ToLongDateString();
// Call this method first
SetData(TodaysDate);
// call this method second
FindNotesForWeek(TodaysDate, 7);
//Update the UI on the main thread but call third this will close the loading dialog message
RunOnUiThread(() => LoadingProgressDialog.Hide());
// End of thread
});
//Run the thread
LoadingThread.Start();
}
catch (Exception e)
{
var ErrorMessageDialog = ProgressDialog.Show(this, "Loading", e.ToString(), false);
}
以下是我的完整课程，供其他用户参考。我没有在此评论中将此代码描述为足够大
namespace MedicalHubApplication
{
[Activity(Label = "TimeTable", NoHistory = true)]
public class TimeTable : Activity
{
ClassInstance populateClass = new ClassInstance();
UserInstance User = new UserInstance();
GetConnectionClass Connect = new GetConnectionClass();
Dictionary<string, List<ClassInstance>> dicMyMap;
TextView DateHeaderTV;
TextView NoteHeaderTV;
ExpandableListViewAdapter myAdapater;
ExpandableListView expandableListView;
// Need Instance of List
NotesListViewAdapter myNoteAdapater;
ListView NotesListView;
ScrollView ScrollViewList;
TextView StartMonday;
Button SelectDateButton;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
// Create your application here
SetContentView(Resource.Layout.TimeTable);
expandableListView = FindViewById<ExpandableListView>(Resource.Id.ListViewExpanded);
StartMonday = FindViewById<TextView>(Resource.Id.TextViewStartDateMonday);
SelectDateButton = FindViewById<Button>(Resource.Id.SelectDateButton);
NotesListView = FindViewById<ListView>(Resource.Id.NotesListView);
DateHeaderTV = FindViewById<TextView>(Resource.Id.DateHeader);
NoteHeaderTV = FindViewById<TextView>(Resource.Id.NoteHeader);
ScrollViewList = FindViewById<ScrollView>(Resource.Id.ScrollView);
// Populate User
User = JsonConvert.DeserializeObject<UserInstance>(Intent.GetStringExtra("User"));
//Find Monday
DateTime TodaysDate = DateTime.Now;
while (TodaysDate.DayOfWeek != DayOfWeek.Monday) TodaysDate = TodaysDate.AddDays(-1);
try
{
var LoadingProgressDialog = ProgressDialog.Show(this, "Loading", "Loading", false);
Thread LoadingThread = new Thread(() =>
{
StartMonday.Text = "Week Commencing On " + TodaysDate.ToLongDateString();
SetData(TodaysDate);
FindNotesForWeek(TodaysDate, 7);
RunOnUiThread(() => LoadingProgressDialog.Hide());
});
LoadingThread.Start();
}
catch (Exception e)
{
var ErrorMessageDialog = ProgressDialog.Show(this, "Loading", e.ToString(), false);
}
SelectDateButton.Click += delegate
{
DateSelectOnClick();
};
}
private void DateSelectOnClick()
{
DatePickerFragment frag = DatePickerFragment.NewInstance(delegate (DateTime SelectedDate)
{
while (SelectedDate.DayOfWeek != DayOfWeek.Monday) SelectedDate = SelectedDate.AddDays(-1);
try
{
var LoadingProgressDialog = ProgressDialog.Show(this, "Loading", "Loading", false);
Thread LoadingThread = new Thread(() =>
{
RunOnUiThread(() => StartMonday.Text = "Week Commencing On " + SelectedDate.ToLongDateString());
SetData(SelectedDate);
FindNotesForWeek(SelectedDate, 7);
RunOnUiThread(() => LoadingProgressDialog.Hide());
});
LoadingThread.Start();
}
catch (Exception e)
{
var ErrorMessageDialog = ProgressDialog.Show(this, "Loading", e.ToString(), false);
}
});
frag.Show(FragmentManager, DatePickerFragment.TAG);
}
private void SetData(DateTime date)
{
dicMyMap = null;
dicMyMap = new Dictionary<string, List<ClassInstance>>();
List<string> group = new List<string>();
group.Add("Monday");
group.Add("Tuesday");
group.Add("Wednesday");
group.Add("Thursday");
group.Add("Friday");
dicMyMap.Add(group[0], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
date = date.AddDays(+1);
dicMyMap.Add(group[1], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
date = date.AddDays(+1);
dicMyMap.Add(group[2], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
date = date.AddDays(+1);
dicMyMap.Add(group[3], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
date = date.AddDays(+1);
dicMyMap.Add(group[4], ListsPopulation(date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)));
myAdapater = new ExpandableListViewAdapter(this, group, dicMyMap);
RunOnUiThread(() => expandableListView.SetAdapter(myAdapater));
}
private List<ClassInstance> ListsPopulation(String date)
{
string sql = "SELECT * FROM lectures join groupConvert using (Groups) where StartDate = '" + date + "' AND Cohort = '" + User.Cohort + "' AND Year = '" + User.IntakeYear + "';";
List<ClassInstance> Temp = new List<ClassInstance>();
//Insert Header
Temp.Add(new ClassInstance("Start Time", "End Time", "Subject", "Location", "", ""));
using (MySqlCommand cmd = new MySqlCommand(sql, Connect.GetConnection()))
{
MySqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
ClassInstance c = new ClassInstance(reader["StartTime"].ToString(), reader["EndTime"].ToString(), reader["Theme"].ToString(), reader["Location"].ToString(), reader["Essential"].ToString(), reader["Notes"].ToString());
Temp.Add(c);
}
}
if (Temp.Count == 1)
{
Temp.Clear();
Temp.Add(new ClassInstance("No Classes", "", "", "", "", ""));
}
return Temp;
}
private void FindNotesForWeek(DateTime StartDate, int DaysInMonth)
{
List<NotesInstance> WeekNotes = new List<NotesInstance>();
WeekNotes.AddRange(FindNotesForDay(StartDate, StartDate.AddDays(+DaysInMonth)));
if (WeekNotes.Count != 0)
{
RunOnUiThread(() => NoteHeaderTV.Visibility = ViewStates.Visible);
RunOnUiThread(() => NotesListView.Visibility = ViewStates.Visible);
RunOnUiThread(() => DateHeaderTV.Text = "Date:");
myNoteAdapater = new NotesListViewAdapter(this, WeekNotes);
RunOnUiThread(() => NotesListView.Adapter = myNoteAdapater);
}
else
{
RunOnUiThread(() => NoteHeaderTV.Visibility = ViewStates.Invisible);
RunOnUiThread(() => NotesListView.Visibility = ViewStates.Invisible);
RunOnUiThread(() => DateHeaderTV.Text = "No Notifications");
}
// Set up Adapter
myNoteAdapater = new NotesListViewAdapter(this, WeekNotes);
RunOnUiThread(() => NotesListView.Adapter = myNoteAdapater);
}
private List<NotesInstance> FindNotesForDay(DateTime StartDate, DateTime EndDate)
{
string sql = "SELECT * FROM Notes WHERE dates between '" + StartDate.ToString("yyyy-MM-dd") + "' AND '" + EndDate.ToString("yyyy-MM-dd") + "' AND yearGroup = '" + User.IntakeYear.ToString() + "';";
List<NotesInstance> Temp = new List<NotesInstance>();
using (MySqlCommand cmd = new MySqlCommand(sql, Connect.GetConnection()))
{
MySqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
NotesInstance c = new NotesInstance(reader.GetDateTime("dates").ToString("dd-MM-yyyy"), reader["Notes"].ToString());
Temp.Add(c);
}
}
return Temp;
}
}
}