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SWT 用户控件设计决策

发布于 2024-11-30 14:11:34 字数 298 浏览 1 评论 0原文

假设问题：

为了制作自定义复合小部件，我必须将 Composite 子类化，这个 SWT 设计决策怎么样？这真的明智吗？

如果 SWT 有一个像 Win Forms 之类的 UserControl 类不是更好吗？

当我对 Composite 进行子类化时，我的自定义小部件将获得 Composite 接口，即使它不打算被客户端用作 Composite。这有点糟糕。对于某些 SWT 小部件（例如 Spinner）也是如此。

有没有好的办法解决这个问题？

而且，最有趣的是：有人知道这个设计决定的动机吗？

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巾帼英雄 2024-12-07 14:11:34

您可以查看 org.eclipse.swt.custom.CCombo 的源代码，了解 SWT 如何在内部处理此问题，因为 CCombo 扩展自 Composite< /代码>。以下是他们处理 setLayout() 的方式，例如：

/**
 * Sets the layout which is associated with the receiver to be
 * the argument which may be null.
 * <p>
 * Note: No Layout can be set on this Control because it already
 * manages the size and position of its children.
 * </p>
 *
 * @param layout the receiver's new layout or null
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void setLayout (Layout layout) {
    checkWidget ();
    return;
}

You could look at the source code for org.eclipse.swt.custom.CCombo to see how SWT deals with this problem internally, as CCombo extends from Composite. Here's how they handle setLayout(), for example:

/**
 * Sets the layout which is associated with the receiver to be
 * the argument which may be null.
 * <p>
 * Note: No Layout can be set on this Control because it already
 * manages the size and position of its children.
 * </p>
 *
 * @param layout the receiver's new layout or null
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void setLayout (Layout layout) {
    checkWidget ();
    return;
}

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空气里的味道 2024-12-07 14:11:34

您可以创建自己的 NonCompositeUserControl 类：

public class NonCompositeUserControl extends Composite {
    @Override
    public void setLayout(Layout layout) {
        throw new UnsupportedOperationException("This control is not really a composite")
    }
    // similarly for other methods
}

You could create your own NonCompositeUserControl class:

public class NonCompositeUserControl extends Composite {
    @Override
    public void setLayout(Layout layout) {
        throw new UnsupportedOperationException("This control is not really a composite")
    }
    // similarly for other methods
}

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