Name
thread()
Description
Processing sketches follow a specific sequence of steps: setup()
first, followed by draw() over and over and over again in a loop. A
thread is also a series of steps with a beginning, a middle, and an end. A
Processing sketch is a single thread, often referred to as the "Animation"
thread. Other threads' sequences, however, can run independently of the
main animation loop. In fact, you can launch any number of threads at one
time, and they will all run concurrently.
You cannot draw to the screen from a function called by thread().
Because it runs independently, the code will not be synchronized to the
animation thread, causing strange or at least inconsistent results. Use
thread() to load files or do other tasks that take time. When the
task is finished, set a variable that indicates the task is complete, and
check that from inside your draw() method.
Processing uses threads quite often, such as with library functions like
captureEvent() and movieEvent(). These functions are
triggered by a different thread running behind the scenes, and they alert
Processing whenever they have something to report. This is useful when you
need to perform a task that takes too long and would slow down the main
animation's frame rate, such as grabbing data from the network. If a
separate thread gets stuck or has an error, the entire program won't grind
to a halt, since the error only stops that individual thread.
Writing your own thread can be a complex endeavor that involves extending
the Java Thread
class. However, the thread() method is a quick and dirty way to
implement a simple thread in Processing. By passing in a String that
matches the name of a function declared elsewhere in the sketch, Processing
will execute that function in a separate thread.
Examples
String time = ""; void setup() { size(100, 100); } void draw() { background(0); // Every 30 frames request new data if (frameCount % 30 == 0) { thread("requestData"); } text(time, 10, 50); } // This happens as a separate thread and can take as long as it wants void requestData() { JSONObject json = loadJSONObject("http://time.jsontest.com/"); time = json.getString("time"); }
Syntax
thread(name)
Parameters
name(String)name of the function to be executed in a separate thread
Return
void
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