im developing an app for android via c#(xamarin.visual studio)
, the problem is that i have some task to do that running in other threads , and when it should update the layout it should call Activity.RunOnUIThread
, everything it's working well but the thread dont wait this method to finnish and continue executing the rest withuout waiting.
The question is : How to wait for RunOnUIThread
to finish and after that continue executing rest of the commands of the task. ?
public void start(int threadCounter)
{
for (int i = 0; i < threadCounter; i++)
{
Thread thread1 = new Thread(new ThreadStart(RunScanTcp));
thread1.Start();
}
}
public void RunScanTcp()
{
int port;
//while there are more ports to scan
while ((port = portList.NextPort()) != -1)
{
count = port;
Thread.Sleep(1000); //lets be a good citizen to the cpu
Console.WriteLine("Current Port Count : " + count.ToString());
try
{
Connect(host, port, tcpTimeout);
}
catch
{
continue;
}
Activity.RunOnUiThread(() =>
{
mdata.Add(new data() { titulli = "Port : " + port, sekuenca = "Sequence : ", ttl = "Connection Sucessfull !", madhesia = "", koha = "Time : " });
mAdapter.NotifyItemInserted(mdata.Count() - 1);
if (ndaluar == false)
{
mRecyclerView.ScrollToPosition(mdata.Count() - 1);
}
}); // in that point i want to wait this to finish and than continue below...
Console.WriteLine("TCP Port {0} is open ", port);
}
First of all you should avoid creating new Threads
.
In you case you must use ThreadPool.QueueUserWorkItem
to enqueue the CPU bound operation.
Then you could use a ManualResetEventSlim
or TaskCompletionSource
to synchronize the the UI thread
and the Worker Thread.
Example:
// mre is used to block and release threads manually. It is
// created in the unsignaled state.
ManualResetEventSlim mre = new ManualResetEventSlim(false);
RunOnUiThread(() =>
{
// Update UI here.
// Release Manual reset event.
mre.Set();
});
// Wait until UI operations end.
mre.Wait();
In your specific case:
for (int i = 0; i < threadCounter; i++)
{
ThreadPool.QueueUserWorkItem(RunScanTcp);
}
private void RunScanTcp(object stateInfo)
{
// Do CPU bound operation here.
var a = 100;
while (--a != 0)
{
// mre is used to block and release threads manually. It is
// created in the unsignaled state.
ManualResetEventSlim mre = new ManualResetEventSlim(false);
Activity.RunOnUiThread(() =>
{
// Update UI here.
// Release Manual reset event.
mre.Set();
});
// Wait until UI operation ends.
mre.WaitOne();
}
}
If you prefer to use TaskCompletionSource
you could use an alternative approach:
private async void RunScanTcp(object stateInfo)
{
// Do CPU bound operation here.
var a = 100;
while (--a != 0)
{
// using TaskCompletionSource
var tcs = new TaskCompletionSource<bool>();
RunOnUiThread(() =>
{
// Update UI here.
// Set result
tcs.TrySetResult(true);
});
// Wait until UI operationds.
tcs.Task.Wait();
}
}