Java: Using multiple Threads to paint simultaniously on a JPanel

Question

I have a JPanel on which I wish to have several threads painting "animations" on. An "animation" consists of a JLabel with an ImageIcon on it, which is being moved from one area of the screen to another area.

Now, problem is - I want several such animations to be portrayed on screen by those threads mentioned. Problem is - the JPanel's "paint()" method can only be trigged by one thread at a time - causing the animations to execute serially, instead of in a parallel way.

Any idea how to have several such animations on screen at the same time?

Answer 1

Swing is not thread-safe, thus it's simply not a supported use-case to do UI-related stuff from several threads simultaneously.

Go for the model-view-controller (MVC) pattern:

• Let all threads update a (thread safe) model.
• Whenever there is an update of the model, invoke repaint.
• repaint() will schedule the UI-thread to call the proper paint-methods.
• The paint-method should then simply read the state of the model, and draw the component accordingly.

Answer 2

It is impossible to use multiple threads to do what you want. Swing Toolkit is single threaded . The correct way to do it is to use one of the animation frameworks available:

• Trident animation framework
• TimingFramework