org.eclipse.swt.SWTException: Subclassing not allowed

错误: org.eclipse.swt.SWTException: Subclassing not allowed

[img]http://dl.iteye.com/upload/attachment/362293/c513312c-2456-32f8-95a4-1a381dbcdb5f.jpg[/img]

创建一个继承Shell的类BorderTextShell后出错
因为在BorderTextShell构造方法中,

super(display, style);

要调用父类构造方法:

public Shell (Display display, int style) {
	this (display, null, style, 0, false);
}

Shell (Display display, Shell parent, int style, int /*long*/ handle, boolean embedded) {
	super ();
	checkSubclass ();
	...
}

其中,checkSubclass ()方法继承自Decoration类,用来验证子类是否存在于org.eclipse.swt.widgets包内.
若不在此包内,则报错.

解决办法:
1. package org.eclipse.swt.widgets;
2. 重写checkSubclass ()方法,方法体为空.即在子类中添加:

protected void checkSubclass()
	{

	}

3. 在类中声明Shell类的一个实例.(OO原则: 多用组合,少用继承)