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@using System.Timers
@implements IDisposable
@inject IJSRuntime js
<a
class=@(isLoading || errorTimer.Enabled ? "disabled" : "")
@attributes=Attributes
@onclick=Trigger>
@if(errorTimer.Enabled) {
@("Error!")
} else if(isLoading) {
@(LoadingText + "...")
} else {
@Text
}
</a>
@code {
[Parameter]
public Func<Task> OnClick { get; set; }
[Parameter]
public string Text{ get; set; }
[Parameter]
public string LoadingText { get; set; }
private Dictionary<string, object?> Attributes => new() {
["disabled"] = isLoading,
};
private Timer loadingTimer;
private Timer errorTimer;
private object triggerLock = new();
private bool isRunning = false;
private bool isLoading = false;
protected override void OnInitialized() {
loadingTimer = new(50) {
AutoReset = false
};
loadingTimer.Elapsed += LoadingTimerElapsed;
errorTimer = new(1000) {
AutoReset = false
};
errorTimer.Elapsed += ErrorTimerElapsed;
}
// Most link-click actions (e.g. triggering dialogs, page
// navigation, etc) complete very quickly (under 50ms).
// Triggering a render cycle to show a loading animation is
// usually pointless as doing so would waste resources and
// appear less seemless to the user who will see brief
// flickering while the browser quickly recalculates it's
// layout twice. To that end, a timer is used to only render
// the loading animation on the link if the delegate task
// takes longer than 50ms
private void LoadingTimerElapsed(object? sender, EventArgs e) {
lock(triggerLock) {
if(isRunning)
isLoading = true;
InvokeAsync(() => StateHasChanged());
}
}
private void ErrorTimerElapsed(object? sender, EventArgs e) =>
InvokeAsync(() => StateHasChanged());
private async Task Trigger() {
lock(triggerLock) {
if(isRunning)
return;
isRunning = true;
loadingTimer.Start();
}
bool error = false;
try {
await Task.Run(OnClick);
} catch {
error = true;
} finally {
lock(triggerLock) {
loadingTimer.Stop();
isRunning = false;
isLoading = false;
}
}
if(error)
errorTimer.Start();
await InvokeAsync(() => StateHasChanged());
}
public void Dispose() =>
loadingTimer.Dispose();
}
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