Java SWT - 禁用按钮上的图像

Question

I use Buttons with Images in my SWT Gui and from time to time I have to disable them.

This lets SWT create an automatic disabled image from the colored image I placed previously on the button, and the disabled icon really does not really look pretty. I would like to place my own disabled image on the button, but I don't find a way to do this.

Is there one?

Answer 1

You can't subclass Button so you need to do it at the time you enabled/disable the button. I couldn't find the SWT -> Windows Event mapping ID to invoke addListener on the button to make it more generic.

public static void main(String[] args) throws Exception
{
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.setLayout(new GridLayout(1, true));

    final Image image1 = new Image(null, new FileInputStream(
            "C:\\tmp\\enabled.png"));
    final Image image2 = new Image(null, new FileInputStream(
            "C:\\tmp\\disabled.png"));

    final Button button= new Button(shell, SWT.NONE);
    button.setText("Hello World SWT");
    button.setImage(image1);
    button.pack();

    final Button cb = new Button(shell, SWT.CHECK);
    cb.setText("Check me");
    cb.addSelectionListener(new SelectionAdapter()
    {
        @Override
        public void widgetSelected(SelectionEvent event)
        {
            button.setEnabled(!cb.getSelection());
            if (button.isEnabled())
                button.setImage(image1);
            else
                button.setImage(image2);
        }
    });

    shell.pack();
    shell.open();
    while (!shell.isDisposed())
    {
        if (!display.readAndDispatch())
            display.sleep();
    }
    display.dispose();
}

Answer 2

One other tip which may or may not save you a lot of trouble. Make sure the alpha levels on your image go all the way to zero for the transparent portions, especially near the edges, and the standard default disabled look may look a lot better.

Answer 3

I fixed my problem by modifying the Button class itself. It caches the disabled images now and reuses them when needed.