Java Canvas repaint() is flickering

问题

So I finally got a Canvas to work the way I want it but it flickers constantly, repaint() is run 20 times a second and the flicking does lessen when I make it run 10 times a second.

package pd.data;

import java.awt.BorderLayout;

import javax.swing.JFrame;
import javax.swing.JPanel;

import pd.areas.MainMenu;

@SuppressWarnings("serial")
public class Main extends JFrame implements Runnable {

    private JPanel contentPane = new JPanel();

    private Thread gameThread = new Thread(this);
    public boolean running = false;



    @SuppressWarnings("unused")
    private int current = PDU.PD_MAIN_MENU;
    private MainMenu mainmenu;

    public Main() {main.setTitle("PD");
        main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        main.setLocation(SPU.screenWidth / 2 - SPU.windowSize.width / 2,
                SPU.screenHeight / 2 - SPU.windowSize.height / 2);
        main.setResizable(false);
        main.setVisible(true);
        contentPane.setLayout(new BorderLayout(0, 0));
        contentPane.setPreferredSize(SPU.windowSize);
        main.setContentPane(contentPane);
        main.pack();
        mainmenu = new MainMenu();

        contentPane.add(mainmenu, BorderLayout.CENTER);
        this.gameThread.start();
    }

    @Override
    public void run() {
        running = true;
        while (running) {
            {
                mainmenu.repaint();
            }
            try {
                Thread.sleep(SPU.TSU);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }
    public static void main(String[] args) {
        new Main();
    }
}

And below is my MainMenu class:

package pd.areas;

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;

import javax.imageio.ImageIO;

@SuppressWarnings("serial")
public class MainMenu extends Canvas{

    BufferedImage img = null;
    public MainMenu() {
        this.setBackground(Color.BLACK);

    }
    public void paint(Graphics graphics){

        try {
            img = ImageIO.read(this.getClass().getResource(
                    "/image.png"));
        } catch (IOException e1) {
            e1.printStackTrace();
        }
        graphics.drawImage(img, this.getWidth() / 2 - img.getWidth()/2, 50, null);
    }

}

Although the flicker is actually a nice effect, it's going to effect the whole canvas and not just the image I'm guessing, how can I fix the flicker?

回答1:

Don't use java.awt.Canvas. Use a JPanel instead.
Draw in the JPanel's paintComponent method.
Don't forget to call your super's painting method which for paintComponent would be super.paintComponent(graphics)
Never try to read in an image from within any painting method. That will slow down painting and make your program seem unresponsive. Why keep reading in the same image over and over again anyway? Read it in once and save it to a variable.

来源：https://stackoverflow.com/questions/29424960/java-canvas-repaint-is-flickering

标签

java

canvas

repaint

flicker