LibGDX Window组件Cell异常问题咨询及潜在Bug排查

Let’s walk through common pitfalls and checks to figure out if this is a code oversight or a potential LibGDX edge case—since your logic worked before, state-related issues are the most likely culprit.

1. Watch for Layout Pass Conflicts #

When you call setVisible(false), make sure you’re not removing actors mid-layout cycle (like inside act() or layout() methods). LibGDX’s Table/Window relies on stable cell references during layout, and modifying the actor hierarchy at the wrong time can leave invalid Cell objects hanging around, causing exceptions.

• Fix: Use a flag to delay removal until the next safe cycle:

  private boolean shouldClearActors = false;
  
  @Override
  public void act(float delta) {
      super.act(delta);
      if (shouldClearActors) {
          clear(); // Properly cleans up cells and actors
          shouldClearActors = false;
      }
  }
  
  @Override
  public void setVisible(boolean visible) {
      super.setVisible(visible);
      if (!visible) shouldClearActors = true;
  }
  

2. Double-Check Your Actor Removal Method #

If you’re manually iterating over children to remove them, you might be skipping proper Cell cleanup. LibGDX’s built-in methods handle this better:

• Avoid this (may leave orphaned Cell references):

  for (Actor actor : getChildren()) {
      removeActor(actor);
  }
  

• Use this instead:

  removeAll(true); // `true` ensures actors are unparented and cells are cleaned
  // Or `clear()` if you don’t need to keep references to the removed actors
  

3. Rule Out Leaking Actor References #

If you reuse actors after removing them from the Information window, make sure they’re fully detached from their previous parent. An actor attached to two parents (even temporarily) can create conflicting Cell state.

• Quick check before reusing an actor:

  if (actor.getParent() != null) {
      actor.remove(); // Ensures full detachment from old parent/cell
  }
  

4. Test with a Minimal Reproducible Example #

Strip down your Information class to the bare bones to isolate the issue. If this simplified version throws the same exception, it’s worth investigating as a potential LibGDX bug. If not, the problem is in your full implementation’s extra logic.

Example minimal test class:

public class TestInfoWindow extends Window {
    public TestInfoWindow(String title, Skin skin) {
        super(title, skin);
        add(new Label("Initial Content", skin)).pad(10);
    }

    @Override
    public void setVisible(boolean visible) {
        super.setVisible(visible);
        if (!visible) {
            clear();
        } else {
            add(new Label("Refreshed Content", getSkin())).pad(10);
        }
    }
}

5. Check LibGDX Version Changes #

If you recently updated your LibGDX version, a change in Table/Window layout logic could be the cause. Roll back to the version where your code worked to confirm.

Before submitting a GitHub Issue, make sure you have:

• The full exception stack trace
• Your exact LibGDX version
• A minimal, runnable example that reproduces the issue

内容的提问来源于stack exchange，提问作者Ernesto Gonzalez