数据加载时显示进度条

Question

我想在数据加载和数据加载时显示进度条我想隐藏进度条。

对于测试目的，我刚刚添加了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，在下面的实际代码，不显示进度条。

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

试试这个使用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)); 
}