[英]RunWorkerCompleted fired before async void Dowork event
我正在使用背景工进行BLE RSSI级别测试。
我的问题是RunWorkerCompleted事件在DoWork完成操作之前立即被触发。
DoWork事件的大多数操作是创建广告观察程序,并等待来自低功耗蓝牙设备的信号。 信号电平将从主线程进行更新,结果的处理将在后台工作程序中进行。
这是我给背景工作者打电话的时候:
...
worker = new BackgroundWorker();
worker.DoWork += callTestBLE;
worker.RunWorkerCompleted += worker_RunWorkerCompleted;
worker.RunWorkerAsync(RSSI_Label);
}
事件处理程序:
private async void callTestBLE(object sender, DoWorkEventArgs e)
{
BluetoothLEAdvertisementWatcher watcher1 ;
BluetoothLEAdvertisementFilter advertisementFilter1;
int rssiRetries1 = RSSIRETRIES;
RssiValue = "";
advertisementFilter1 = new BluetoothLEAdvertisementFilter();
try
{
advertisementFilter1.Advertisement.LocalName = myUswm.getAdvetrismentName();
checkRSSI = true;
}
catch (Exception) { checkRSSI = false; return; }
watcher1 = new BluetoothLEAdvertisementWatcher(advertisementFilter);
watcher1.ScanningMode = BluetoothLEScanningMode.Active;
watcher1.Received += OnAdvertisementReceived;
// Wait 5 seconds to make sure the device is really out of range
watcher1.SignalStrengthFilter.OutOfRangeTimeout = TimeSpan.FromMilliseconds(5000);
watcher1.SignalStrengthFilter.SamplingInterval = TimeSpan.FromMilliseconds(2000);
try
{
watcher1.Start();
await testBLEAsync();
if (myUswm.getConnectionStatus() == DISCONNECTED)
{
checkNextUUTClick(new object(), new RoutedEventArgs()); return;
}
for (int i = 0; i < 5; i++)
{
// if (RssiSamplesNum <= 0 || --rssiRetries < 0)
if (RssiSamplesNum <= 0 || --rssiRetries1 < 0)
{
//serviceList.Clear();
watcher1.Stop();
rssiRetries1 = RSSIRETRIES;
RssiSamplesNum1 = numOfAdvertismentSamples;
break;
}
else
{
((Label)e.Argument).Content = RssiValue;
/*RSSI_Label.Dispatcher.Invoke(new Action(() =>
{ RSSI_Label.Content = RssiValue; }));*/
}
Thread.Sleep(2000);
}
}
catch (Exception err) { }
}
private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
finalizeBleTest();
}
谢谢你的帮助!
这里的问题与async
和await
。 BackgroundWorker有点过时了,不支持异步代码。 因此,当您等待testBLEAsync
调用时, callTestBLE
方法完成,并且此时您已调用RunWorkerCompleted
事件,而实际代码继续在后台运行。
因此,最简单的解决方案是从代码中完全删除async
/ await
,一切都将按预期工作,或者,您也可以使用任务和任务延续来重写代码。
我同意BackgroundWorker
与async
/ await
不兼容的另一个答案。 但是,我不同意最简单的解决方案是删除async
,而使用BackgroundWorker
。 IMO的高级解决方案(也导致更简单的代码)是删除BackgroundWorker
,而支持async
; 具体来说, 用高级Task.Run
替换过时的BackgroundWorker
:
// `worker` is now `Task`.
await Task.Run(() => callTestBLE());
finalizeBleTest();
其中callTestBLE
的签名是async Task
,而不是async void
。
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