在java swing中渲染问题

Question

I have a java application with a GUI running in ubuntu 16.04 using jre 1.7 and I got some rendering issues. The following code is not the application code but a simple test case.

import javax.swing.JComboBox;
import javax.swing.JFrame;

public class Test {


  public static void main(String[] args) {
    JFrame f = new JFrame();
    f.setSize(400,200);

    String[] s = {"test", "of", "rendering"};
    JComboBox<String> cs = new JComboBox<>(s);
    f.add(cs);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.pack();
    f.setVisible(true);

  }
}

The following images show the problem: I have 3 elements in the JcomboBox, however when I browse (either by the mouse or the keyboard) the display of the elements changes (which should not happen). The problem happens also in Jtree elements.

Any thoughts on this one. Thanks in advance.

Answer 1

I had the same problem as you, and I managed to get rid of this rather irritating bug by using the Oracle Java JDK 7 instead of OpenJDK 7 which seems to be having the above issue.

For me the issue is notable just by hovering over the different selections in a JComboBox . I did not have this problem using Windows so I figured switching versions of the Java JDK could give a different result.

The error is probably located somewhere inside the Swing repaint functions in OpenJDK as the repaint seems to be executed in the wrong thread. By extending the RepaintManager class overriding the addDirtyRegion(JComponent c, int x, int y, int w, int h) with an added print out of java.awt.EventQueue.isDispatchThread() I could check the thread used during the repaint.

The above function returned false multiple times when hovering inside the JComboBox using OpenJDK but true when using the Oracle JDK. I hope someone smarter than me can pinpoint the error exactly and report it, as I have not had the time figure it out or to do a source comparison between the JDK implementations.

PS there seems to be an issue installing Oracle JDK 7 at the moment on Ubuntu using APT, so I downloaded the RPM package, converted it to a deb package using alien by using this method - Oracle Java JDK 7 on Ubuntu Linux - Source or RPM Installation