In Delphi, you can use the Synchronize method of the TThread class to synchronize a thread with the main GUI thread. The Synchronize method allows you to execute a method in the context of the main GUI thread, while the current thread waits. This is useful when you need to update the GUI from a worker thread, as the GUI can only be updated from the main thread.
Here is an example of how to use the Synchronize method to update a label on a form from a worker thread
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type TWorkerThread = class(TThread) private FLabel: TLabel; protected procedure Execute; override; public constructor Create(ALabel TLabel); end; constructor TWorkerThread.Create(ALabel TLabel); begin inherited Create(False); FLabel := ALabel; end; procedure TWorkerThread.Execute; begin //Do some work in the thread ... //Update the label on the form Synchronize( procedure begin FLabel.Caption := ‘Thread completed’; end ); end; //To create and start the thread var WorkerThread: TWorkerThread; begin WorkerThread := TWorkerThread.Create(Label1); WorkerThread.Start; end; |
Alternatively, you can use the TThread.Queue method to queue a method for execution in the context of the main GUI thread. The Queue method does not wait for the method to be executed, so it is useful when you need to update the GUI asynchronously from a worker thread.
Here is an example of how to use the Queue method to update a label on a form from a worker thread
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type TWorkerThread = class(TThread) private FLabel: TLabel; protected procedure Execute; override; public constructor Create(ALabel TLabel); end; constructor TWorkerThread.Create(ALabel TLabel); begin inherited Create(False); FLabel := ALabel; end; procedure TWorkerThread.Execute; begin //Do some work in the thread ... //Queue the update of the label on the form TThread.Queue(nil, procedure begin FLabel.Caption := ‘Thread completed’; end ); end; //To create and start the thread var WorkerThread: TWorkerThread; begin WorkerThread := TWorkerThread.Create(Label1); WorkerThread.Start; end; |
It is important to note that when using either the Synchronize or Queue method, you should not access GUI components directly from the worker thread. Instead, you should pass the necessary data to the main thread for processing.
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