java组织。日食swt。小部件。组，这个类可以被滚动吗

Question

类org.eclipse.swt.widgets.Group继承自Composite，后者继承自Scrollable。但是，当我调用继承的方法getVerticalScrollBar()时，它总是返回null

是否可以使Group可滚动？如果可能，怎么做

顺便说一句，Group包含许多org.eclipse.swt.widgets.Button.Button样式为SWT.CHECK

Answer 1

SWT的Javadoc表示：

Returns the receiver's vertical scroll bar if it has one, and null if it does not.

如果用户使窗口/对话框变小，则会出现滚动条。只有这样，方法getVerticalScrollBar()和getHorizontalScrollBar()才会返回非空值。在这个问题上，您必须始终检查null。这就是SWT的建造方式

编辑：尝试在Composite或Shell上调用getVerticalScrollBar()方法

Answer 2

我认为你不能让Group本身滚动。但是，我通过在Group中添加一个^{}实现了相同的效果：

group = new Group(parent, SWT.NONE);
group.setText("Images: ");
group.setLayout(new FillLayout());

ScrolledComposite comp = new ScrolledComposite(group, SWT.V_SCROLL | SWT.H_SCROLL);
comp.setLayout(new FillLayout());

Composite innerComp = new Composite(comp, SWT.NONE);
innerComp.setLayout(new FillLayout());

comp.setContent(innerComp);
comp.setExpandHorizontal(true);
comp.setExpandVertical(true);

之后，您可以将Button添加到Composite{}。可能需要在ScrolledComposite上使用setMinHeight(int height)和setMinWidth(int width)

编辑

下面是一个小的工作示例。如果减小窗口的大小，您将看到滚动条将出现：

public static void main(String[] args)
{
    Display display = Display.getDefault();
    Shell shell = new Shell(display);

    shell.setLayout(new FillLayout());

    Group imageGroup = new Group(shell, SWT.V_SCROLL | SWT.H_SCROLL);
    imageGroup.setText("Images: ");
    imageGroup.setLayout(new FillLayout());

    ScrolledComposite frontComp = new ScrolledComposite(imageGroup, SWT.V_SCROLL | SWT.H_SCROLL);
    Composite innerFrontComp = new Composite(frontComp, SWT.NONE);
    frontComp.setLayout(new FillLayout());

    innerFrontComp.setLayout(new FillLayout());

    new Button(innerFrontComp, SWT.CHECK).setText("Button");
    new Button(innerFrontComp, SWT.CHECK).setText("Button");
    new Button(innerFrontComp, SWT.CHECK).setText("Button");
    new Button(innerFrontComp, SWT.CHECK).setText("Button");
    new Button(innerFrontComp, SWT.CHECK).setText("Button");
    new Button(innerFrontComp, SWT.CHECK).setText("Button");
    new Button(innerFrontComp, SWT.CHECK).setText("Button");
    new Button(innerFrontComp, SWT.CHECK).setText("Button");

    frontComp.setMinHeight(innerFrontComp.computeSize(SWT.DEFAULT, SWT.DEFAULT).y);
    frontComp.setMinWidth(innerFrontComp.computeSize(SWT.DEFAULT, SWT.DEFAULT).x);
    frontComp.setContent(innerFrontComp);
    frontComp.setExpandHorizontal(true);
    frontComp.setExpandVertical(true);

    shell.pack();
    shell.open();

    while(!shell.isDisposed())
    {
        if(!display.readAndDispatch())
            display.sleep();
    }
}