如何在GroupLayout中调整图像大小？

Question

I have an image which is displayed with a label in grouplayout.I want the image to be resized as the size of the window gets changed but label's getSize() always returns zero width and height which causes and exception to be thrown. here is relevant part of my code :

GroupLayout gl_panel_3 = new GroupLayout(panel_3);
    gl_panel_3.setHorizontalGroup(gl_panel_3.createParallelGroup(
            Alignment.LEADING).addGroup(
            gl_panel_3
                    .createSequentialGroup()
                    .addContainerGap()
                    .addComponent(logoPanel,GroupLayout.PREFERRED_SIZE,300,Short.MAX_VALUE)
                    .addComponent(topButtonPanel,
                            GroupLayout.PREFERRED_SIZE, 519,
                            GroupLayout.PREFERRED_SIZE).addContainerGap()));
    gl_panel_3.setVerticalGroup(gl_panel_3.createParallelGroup(
            Alignment.LEADING)
            .addComponent(logoPanel,GroupLayout.PREFERRED_SIZE,100,Short.MAX_VALUE)
            .addComponent(topButtonPanel,GroupLayout.PREFERRED_SIZE, 100, Short.MAX_VALUE));

JLabel label22 = new JLabel();


GroupLayout gl_logoPanel = new GroupLayout(logoPanel);
    gl_logoPanel.setHorizontalGroup(
        gl_logoPanel.createParallelGroup(Alignment.LEADING)
            .addGroup(gl_logoPanel.createSequentialGroup()
                .addComponent(logoLabel, GroupLayout.PREFERRED_SIZE, 122, GroupLayout.PREFERRED_SIZE)
                .addContainerGap(313, Short.MAX_VALUE))
    );
    gl_logoPanel.setVerticalGroup(
        gl_logoPanel.createParallelGroup(Alignment.LEADING)
            .addComponent(logoLabel, GroupLayout.DEFAULT_SIZE, 104, Short.MAX_VALUE)
    );

ImageIcon icon = new ImageIcon(getClass().getResource("/icons/noa_en/logo.png"));
    ImageIcon scaledinstance = new ImageIcon(icon.getImage().getScaledInstance(label22.getWidth(), label22.getWidth(), Image.SCALE_SMOOTH));
    label22.setIcon(scaledinstance);

I'm wondering how to do it in grouplayout,or if I have to change my layout manager?

Answer 1

but label's getSize() always returns zero width and height which causes and exception to be thrown.

Components only have a size once the GUI is visible.

I'm wondering how to do it in grouplayout,or if I have to change my layout manager?

GroupLayout is generally only used with an IDE because it is complicated to use. Most developers will code the GUI themselves and use various layout managers to achieve the desired layout.

In any case an Icon on a JLabel is always displayed at its actual size, so it doesn't matter what layout you use, the image size will not change.

However you can use Darryl's Stretch Icon which is designed to stretch/shrink depending on the space available for the label. I have no idea if it will work with a GroupLayout, but it does work with other layout managers that support dynamic sizing.