GWT ScrollPanel, bottom scrollbar is not scrollable

If I create a ScrollPanel like this:

p开发者_如何学JAVAublic class BoardPanel extends ScrollPanel {

    public BoardPanel(Game game) {

        AbsolutePanel abs = new AbsolutePanel();

        setHeight("100px");
        setWidth("100px");
        setAlwaysShowScrollBars(true);
        abs.add(new Image(game.getMap().getImageUrl()));
        add(abs);  
    }
}

I got my picture with a scrollbar on the right, which is scrollable. The bottom one is only shown, if I use setAlwaysShowScrollBars(true); My question is, how can I get the bottom one scrollable? It is just grey.

If the bottom one is shown only if you use the setAlwaysShowScrollBars(true) then it most probably means the image is being fully displayed and there is nothing left to scroll

public class BoardPanel extends ScrollPanel {
AbsolutePanel abs = new AbsolutePanel();

private GameCtrl gameCtrl;

public BoardPanel(Game game) {
    setSize("100px", "100px");
    abs.add(new Image(game.getMap().getImageUrl()));
    abs.setPixelSize(768,576);
    add(abs);
    for (Player player : game.getPlayerList()) {
        drawRobot(player);
    }
}

I have fixed it, your hint was right, because he thinks that the whole image is displayed. If I set the size of the AbsolutePanel, the bottom scrollbar appears and it looks like it should.