Drawing Shapes outside paintComponent() (java)

Question

I'm new to graphics in java and am having difficulty grasping the whole concept of drawing all your graphics from one method (paintComponent ()). I was just curious to see if we can draw graphics outside the paintComponent. Is that even possible? is it possible to write a line in the main method like: fillRect(100,100, 500,400); and have it draw a rectangle? If it is possible, is it conventional according to Java?

Basically, I'm asking if you can draw graphics outside the paintComponent class and is it conventional.

Answer 1

You can draw to a BufferedImage , but if you want it drawn on the screen then generally, you'll need to use paintComponent . You can pass the instance of Graphics which is passed into paintComponent to other classes which can do more complex operations, but you should never maintain a reference that instance or try painting outside of a paint cycle context.

See Painting in AWT and Swing and Performing Custom Painting for more details

If you need more control over the paint process you could also use a BufferStrategy

See BufferStrategy and BufferCapabilities for more details

Things you should know:

• Swing uses a "passive rendering" approach, this means that painting occurs when the paint system decides it needs to be done. This is why you MUST perform your painting within the context of a paint cycle (ie - in the paintComponent method)
• BufferStrategy uses a "active rendering" approach, which gives you complete control of the painting process, but it's not capable of painting Swing components