CODEWITHSUNDEEP
javaswingpaintcomponent
zephos2014
zephos2014

Reputation: 331

Swing rendering... does it always have to be repaint() and paintComponent()?

In my program I am using Swing windows for my GUI, and I know that I'm supposed to use repaint and paintComponent methods to render swing components. I also have several custom class objects that need to be rendered inside the main window. For the sake of understanding, my program is a game that will have moving objects that need to be rendered 60 times per second.

In a game development tutorial I watched, the guy used a Jframe with Canvas, but he didn't use the paintComponent method. He simply made his own render() methods to draw all the graphics using graphics context he obtained from creating a bufferStrategy.

So if that works (which it does), why does everyone say to use the paintComponent methods and what exactly is the difference between them?

If I were to use the paintComponent way of doing things, how would I use bufferStrategy with that?

Upvotes: 0

Views: 1843

Answers (1)

MadProgrammer
MadProgrammer

Reputation: 347184

In a game development tutorial I watched, the guy used a Jframe with Canvas, but he didn't use the paintComponent method. He simply made his own render() methods to draw all the graphics using graphics context he obtained from creating a bufferStrategy.

Canvas is an AWT component, using a BufferStrategy, you take over the painting process and become responsible for update the Graphics context and scheduling it's push to the hardware/screen.

This is commonly known as "active painting", as you are constantly (one would assume at a constant frame rate), updating the buffer.

Swing uses a passive paint process, so you never know when a paint process might occur. Swing has it's own mechanisms for determining what should be repainted and when. Using repaint, you make a request to these mechanisms that your component be repainted, but there is no guarantee that a paint cycle will be initiated because of it.

If you use any Swing component for you painting, you MUST use repaint and paintComponent, as the Swing is responsible for providing the context onto which you can paint.

If you want to use Canvas, then you can use a BufferStrategy instead.

Essentially, they are different approaches to painting. Remember though, if you use a BufferStrategy, you lose ALL of the Swing API, you CAN NOT use Swing components with this approach, as they are not designed to work this way...

Upvotes: 3

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