CODEWITHSUNDEEP
javagraphicspaint
Docithe
Docithe

Reputation: 3

Java: Painting multiple objects to one frame

I've been working on a java game recently, and I have a lot of it figured out. One thing still plagues me, however. The way it's set up, a player moves across a background (the game board). Currently, every time the player moves, it repaints the whole frame, including the background. This causes a brief, yet annoying screen flicker whenever the player moves.

I've separated out my code to draw the background separately from the things that need to be repainted:

public void drawMap(Graphics pane) {...}

public void drawPlayer(Graphics pane) {...}

The problem is that I can't find a way to make the board stay on the screen when I use repaint(); , a necessity for the player to move. Any suggestions?

Upvotes: 0

Views: 1455

Answers (2)

dann.dev
dann.dev

Reputation: 2494

You should look into double buffering, basically you paint an image to the buffer, then paint the buffer. It should remove the flickering effect you are talking about. Below are a few helpful links:

http://docs.oracle.com/javase/tutorial/extra/fullscreen/doublebuf.html
http://content.gpwiki.org/index.php/Java:Tutorials:Double_Buffering
http://www.ecst.csuchico.edu/~amk/classes/csciOOP/double-buffering.html

Just comment if your having trouble understanding it.

UPDATE: I would also suggest you look in 'Killer game programming in java'. You can get a free ebook of one of the older versions. Some of it is a bit out dated, but the first few chapters about setting up a game loop and drawing to the screen etc are still very much relevant.

UPDATE 2: From the second link, try something like this:

private void drawStuff() { 
    BufferStrategy bf = this.getBufferStrategy();
    Graphics g = null;

  try {
    g = bf.getDrawGraphics();

       drawMap(g);
       drawPlayer(g);

  } finally {
    // It is best to dispose() a Graphics object when done with it.
    g.dispose();
  }

  // Shows the contents of the backbuffer on the screen.
  bf.show();

      //Tell the System to do the Drawing now, otherwise it can take a few extra ms until 
      //Drawing is done which looks very jerky
      Toolkit.getDefaultToolkit().sync();   
}

UPDATE 3: This post here gives a nice code sample that you can play with and adapt, that should give you the best idea on how to do double buffering

Upvotes: 1

Jan Henke
Jan Henke

Reputation: 875

I suggest to avoid redrawing everything with every change. Instead draw the whole frame at a fixed interval, e.g. every 50ms. Just keep the status of every element in a class and if something changes just change the data value. Due to the fixed redrawing interval the display will pick up any changes at the next redraw.

Upvotes: 0

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