e615. finding the next focusable component.txt

这里面包含了一百多个JAVA源文件

public Component findNextFocus() {
        // Find focus owner
        Component c = KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner();
        Container root = c == null ? null : c.getFocusCycleRootAncestor();
    
        if (root != null) {
            FocusTraversalPolicy policy = root.getFocusTraversalPolicy();
            Component nextFocus = policy.getComponentAfter(root, c);
            if (nextFocus == null) {
                nextFocus = policy.getDefaultComponent(root);
            }
            return nextFocus;
        }
        return null;
    }
    
    public Component findPrevFocus() {
        // Find focus owner
        Component c = KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner();
        Container root = c == null ? null : c.getFocusCycleRootAncestor();
    
        if (root != null) {
            FocusTraversalPolicy policy = root.getFocusTraversalPolicy();
            Component prevFocus = policy.getComponentBefore(root, c);
            if (prevFocus == null) {
                prevFocus = policy.getDefaultComponent(root);
            }
            return prevFocus;
        }
        return null;
    }

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