SWT技术咨询：如何从父复合组件移除子复合组件及相关问题

Hey there! Let's tackle your SWT Composite questions one by one—this is a common gotcha, so I’ll break it down clearly.

First, let's clarify what each of your attempted methods actually does, because that's probably where the confusion is:

• setVisible(false): This only hides the component visually, but it still exists in the parent's child list and takes up layout space. It's not removed.
• setExclude(true) (usually part of layout data like GridData.exclude): This tells the layout to ignore the component, but the component itself is still attached to the parent. Again, not a true removal.
• destroy(): This is the correct method to permanently remove and dispose of the child component. But here's the critical step you might have missed: after calling destroy(), you need to force the parent composite to re-layout, otherwise the visual change won't take effect!

Here's the working code example:

// Assume 'child' is the Composite you want to remove
child.destroy();
// Force the parent to recalculate and refresh its layout (recursively updates all children)
parent.layout(true);

If destroy() still didn't seem to do anything, check these common issues:

• Are you sure the child you're targeting is a direct child of the parent? Double-check if there's another nested Composite in between.
• Is the parent using a NullLayout? If so, components are positioned manually, and destroy() won't automatically clean up the visual space. Switch to a structured layout like GridLayout or FillLayout for predictable behavior.
• Is there other code re-adding the child component? For example, a listener or refresh loop that's recreating it without you noticing.

Absolutely! Adding multiple child Composites is straightforward—just make sure you set up the parent's layout first, add the children, then trigger a layout refresh.

Example code for adding multiple children:

// First, ensure the parent has a proper layout (GridLayout here, 2 columns)
parent.setLayout(new GridLayout(2, false));

// Create and add individual child Composites
Composite child1 = new Composite(parent, SWT.BORDER);
child1.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true)); // Makes it expand

Composite child2 = new Composite(parent, SWT.BORDER);
child2.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

// Refresh the parent's layout to show the new children
parent.layout(true);

For bulk additions, use a loop:

List<Composite> newChildren = new ArrayList<>();
for (int i = 0; i < 3; i++) {
    Composite child = new Composite(parent, SWT.BORDER);
    child.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
    newChildren.add(child);
}
// Always call layout after adding all children
parent.layout(true);

Pro tip: If the parent had old child components before, make sure to destroy them and refresh the layout first before adding new ones—this prevents layout conflicts and memory leaks.

内容的提问来源于stack exchange，提问作者Gabrial David