在Java中显示图像时出现内存泄漏（？）

Question

today I kinda fiddled around with image opening/scaling/displaying in Java and wrote a bit of code to open an Image File, scale it randomly and display it for a short time.

The problem is: After displaying it for like 100-1000 times, the used memory of my "javaw.exe" grows and grows, it even reached 1 GB of memory space.

I dont know where the memory leak in my code is since the only memory eating things are my picures and there are only 2 (the original image and the one who is getting scaled, which is always assigned to the same variable(temp) so the "older" ones should be picked off by the GC), maybe you guys could have a look over it, its pretty simple.

1) You choose an image from your hard drive

2) It gets scaled randomly

3) Its displayed for a short amount of time and then disappears

4) go to 2)

To scale the image I used this library: http://www.thebuzzmedia.com/software/imgscalr-java-image-scaling-library/

import java.awt.image.BufferedImage;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;

import org.imgscalr.Scalr;

public static void main(String[] args) throws IOException, InterruptedException {


    JFileChooser chooser = new JFileChooser();
    chooser.showOpenDialog(null);

    BufferedImage originalImage = ImageIO.read(chooser.getSelectedFile());
    BufferedImage temp;


    while(true){

        int width = (int) ((Math.random()*1000)+1); 
        int height = (int) ((Math.random()*1000)+1);

        Thread.sleep(1000);

        temp = Scalr.resize(originalImage,Scalr.Mode.FIT_EXACT, width, height);


        showImage(temp, 800);

    }

}

static void showImage(BufferedImage v,long length) throws InterruptedException {


    JFrame frame = new JFrame();
    frame.add(new JLabel(new ImageIcon(v)));
    frame.setSize(v.getWidth(), v.getHeight());

    frame.setVisible(true);
    Thread.sleep(length);
    frame.setVisible(false);


}

This is my first time posting here, so please ask questions if I am unclear

thanks in advance!

EDIT: I monitored the memory javaw.exe is needing

1 picture displayed: 75M 100 pictures displayed: 330M 1000 pictures displayed: 2,4G

EDIT 2:

I now have applied your helpful advice but I still have a growing amount of memory and my Images arent displayed anymore.. The JFrames are empty.

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

import org.imgscalr.Scalr;

public class App {

    public static void main(String[] args) throws IOException, InterruptedException {


        JFileChooser chooser = new JFileChooser();
        chooser.showOpenDialog(null);

        BufferedImage originalImage = ImageIO.read(chooser.getSelectedFile());
        BufferedImage temp;

        JFrame frame = new JFrame();


        while(true){

            int width = (int) ((Math.random()*1000)+1); 
            int height = (int) ((Math.random()*1000)+1);

            Thread.sleep(1000);

            temp = Scalr.resize(originalImage,Scalr.Mode.FIT_EXACT, width, height);


            showImage(temp, 500, frame);

        }

    }

    static void showImage(BufferedImage v,long length, JFrame frame) throws InterruptedException {

        SwingUtilities.invokeLater(
                () -> {


                    frame.removeAll();
                    frame.revalidate();
                    frame.repaint();

                    frame.add(new JLabel(new ImageIcon(v)));
                    frame.setSize(v.getWidth(), v.getHeight());

                    frame.setVisible(true);
                    try {
                        Thread.sleep(length);
                    } catch (Exception e) {}
                    frame.setVisible(false);

                    frame.dispose();
                });



    }

}

Maybe I put your advice in the wrong places in my code.

Answer 1

You might want to try

originalImage.flush();
originalImage = null;
temp.flush();
temp = null;

but there is no guarantee when your image will get garbage collected

Apart from that you should also consider clearing and reusing the same JFrame.

removeAll();//or remove the previous JLabel
revalidate();
repaint();

Also the proper way to display a JFrame is by using the SwingUtilities invokeLater method to make sure this "job" is placed on the Event Dispatch Thread (EDT).

 // schedule this for the event dispatch thread (edt)
 SwingUtilities.invokeLater(yourJFrame);

Answer 2

The code below should do what you want. I used a Timer instead of Thread.sleep. You're tying up the EDT. I also just draw the image in the container. You should probably use a JPanel instead (add it to the JFrame and override its paintComponent method). I also cleaned up the methods a little.

import java.awt.image.BufferedImage;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.Graphics;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

import org.imgscalr.Scalr;

public class App extends JFrame implements ActionListener{

        BufferedImage originalImage = null;
        BufferedImage temp = null;
        JFileChooser chooser = null;

        public App(){

                setVisible(true);
        }

        public static void main(String[] args) throws IOException, InterruptedException {


                SwingUtilities.invokeLater(
                                () -> {
                                        App app = new App();

                                        Timer timer = new Timer(1000, app);
                                        timer.start();

                                });

        }

        @Override
        public void actionPerformed(ActionEvent ae){
                if(null == chooser){
                        chooser = new JFileChooser();
                        chooser.showOpenDialog(this);
                        loadImage();
                }
                showImage();
                repaint();
        }

        @Override
        public void paint(Graphics g){
                super.paint(g);
                if(null == temp){
                        return;
                }
                g.drawImage(temp, 0, 0, null);
        }

        public void loadImage(){

                try{
                        originalImage = ImageIO.read(chooser.getSelectedFile());
                } catch(IOException ioe){
                        ioe.printStackTrace();
                }
        }

        public void showImage() {
                int width = (int) ((Math.random()*1000)+1); 
                int height = (int) ((Math.random()*1000)+1);
                temp = Scalr.resize(originalImage,Scalr.Mode.BEST_FIT_BOTH, width, height);
                setSize(width, height);
        }
}