NotRunning ThenĪs the Thread runs, it updates the ArrayPosition property on the window. The position in the array is stored as a property of the window (ArrayPosition) as is the maximum value of the array (ArraySize): The thread loops through an array (with a pause in the middle). Here is an example of the Run event handler of a thread that was added to a window.
Xojo program will not run update#
Rather than having your thread update a Progress Bar directly, a Timer periodically get the progress value from the thread and then the Timer (which runs on the main application UI thread) updates the Progress Bar. If you have a thread that needs to update user interface in some way, such as updating a Progress Bar, you should instead use a Timer as an intermediary. Should a thread access a UI element your app will raise a ThreadAccessingUIException. You can manage this by using a CriticalSection, Semaphore or Mutex to prevent multiple threads from trying to access the same shared resource.īecause of operating system restrictions, threads can not directly access or manipulate any user interface element. This can cause issues and unwanted exceptions. An example would be that a thread tries to open a file for writing that another thread has already opened for writing. Sometimes you may have a resource (data or a file, for example) that needs to be used by multiple threads that are all currently running. A thread can be Running (0), Waiting (1), Suspended (2), Sleeping (3) or NotRunning (4). You can check the thread state any time using the State property. Finally you can kill a thread, which terminates it.Įach of these actions changes the state of the thread. If you suspend a thread, it stays suspended until you specifically resume it. It will automatically wake itself when the time has elapsed. When you sleep a thread, you specify the amount of time (in milliseconds) for the thread to sleep. Threads can be slept, suspended, resumed and killed. So your thread is running 3 times more often than the main thread.
This means your thread will get 75 of the 100 time units and the main thread will get only 25. If you change your thread’s priority to 15 then the time unit split is calculated the same, but results in more time units for your thread: But what if you want your thread to run more often because it is doing some heavy processing? In this case you would increase its priority. This means that the main thread runs 50 times and your thread runs 50 times. If both the main thread and your thread have a priority of 5 then the time unit split is calculated like this: This is the same priority as the main application thread, so if you leave your thread at 5 it will have the same amount of time allocated to it as the main thread.įor example, presume there are 100 "units" of thread time available. You can also force context switches by calling Application.YieldToNextThread or by calling Application.SleepCurrentThread.īy default a thread has a priority of 5. Context switches are expensive, so the Thread Scheduler always tries to avoid them. A thread actually yields to another thread when the Thread Scheduler decides that its timeslice has expired.
However, a thread does not necessarily yield time at every loop boundary even though it has an opportunity to do so. Threads can yield time to other threads each time they execute a looping construct such as For, While, and Do.
Xojo program will not run code#
To start a thread you call its Run method, which calls the code in the Run event handler. Anything you call from the thread is considered part of the thread and also runs in the background. The code that you want to run in the thread is placed in the Run event handler. You can do this by dragging a Thread from the Library onto a window, web page or to the Navigator. To create a thread, first you need to add a Thread object to your project (iOS projects use ).
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