Difference between syncExec() and asyncExec() of Display class

Question

I\'m working on a plugin project in which I\'m using Eclipse background processing.
What\'s the difference between the syncExec() and asyncExec() methods of the Display

Answer 1

from Q: Why do I get the error "org.eclipse.swt.SWTException: Invalid thread access"?

To allow background threads to perform operations on objects belonging to the UI-thread, the methods syncExec(Runnable runnable) and asyncExec(Runnable runnable) of Display are used. These are the only methods in SWT that can be called from any thread. They allow a runnable to be executed by the UI-thread, either synchronously, causing the background thread to wait for the runnable to finish, or asynchronously allowing the background thread to continue execution without waiting for the result. A runnable that is executed using syncExec() most closely matches the equivalent direct call to the UI operation because a Java method call always waits for the result before proceeding, just like syncExec().

Answer 2

Adding to Tom Seidel's answer, here are examples of situations where you might want to use one or the other:

• Use asyncExec when you want to update something in the UI without caring about the results. For example updating a label or a progress bar.

• Use syncExec where the code following that method call needs to be sure that the UI is in a consistent state, or needs some data from the UI. For example getting some data from a user dialog. Or you update a widget and before doing anything else (e.g. another UI update) you want to know that the widget update has completed.

Answer 3

SWT implements single threaded UI model. In this model, only the UI-thread can invoke UI operations. If you try and access an SWT object from outside the UI-thread, you get the exception "org.eclipse.swt.SWTException: Invalid thread access". So to allow other threads to perform operations on objects belonging to the UI-thread, SWT provides syncExec and asyncExec methods.

This link may help you with an example