數據加載時顯示進度條

Question

我想在數據加載和數據加載時顯示進度條我想隱藏進度條。

對於測試目的，我剛剛添加了10秒，它的工作原理。

private async Task ProgressBarAsync() 
{ 
    _isProgressVisible = true; 
    RaisePropertyChanged(() => IsProgressVisible); 

    await Task.Delay(TimeSpan.FromSeconds(10)).ConfigureAwait(false); 

    isProgressVisible = false; 
    RaisePropertyChanged(() => IsProgressVisible); 
} 

然而，在下面的實際代碼，不顯示進度條。

private async Task RefreshStudentList() 
{ 
    //display progressbar 
    _isProgressVisible = true; 
    RaisePropertyChanged(() => IsProgressVisible); 

    // load data 
    var task = _studentService.GetStudentAsync(); 
    await task; 
    Students = new ObservableCollection<StudentViewModel>(task.Result.ConvertAll(x => new ClassViewModel(x))); 

    //hide progressbar 
    _isProgressVisible = false; 
    RaisePropertyChanged(() => IsProgressVisible); 
} 

Answer 1

試試這個使用InvokeOnMainThread：

private async Task RefreshStudentList() 
{ 
    //display progressbar 
    _isProgressVisible = true; 
    InvokeOnMainThread(() => RaisePropertyChanged(() => IsProgressVisible)); 

    // load data 
    var data = await _studentService.GetStudentAsync(); 
    Students = new ObservableCollection<StudentViewModel> 
     (data.ConvertAll(x => new ClassViewModel(x))); 

    //hide progressbar 
    _isProgressVisible = false; 
    InvokeOnMainThread(() => RaisePropertyChanged(() => IsProgressVisible)); 
}