如何在Java Swing中自动滚动到底部

Question

我有一个带有JScrollPane（根据需要有垂直滚动条）的简单JPanel。

事情被添加到JPanel（或从JPAnel中删除），当它超出面板底部时，我希望JScrollPane根据需要自动向下滚动到底部，或者如果某些组件离开面板则向上滚动。

我该怎么办？我猜我需要某种监听器，只要JPanel高度发生变化就会调用它？或者有什么像JScrollPanel.setAutoScroll(true)一样简单？

Answer 1

为面板添加/删除组件时，应调用面板上的revalidate（）以确保组件正确布局。

然后，如果你想滚动到底部，那么你应该可以使用：

JScrollBar sb = scrollPane.getVerticalScrollBar();
sb.setValue( sb.getMaximum() );

Answer 2

scrollPane.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() {  
        public void adjustmentValueChanged(AdjustmentEvent e) {  
            e.getAdjustable().setValue(e.getAdjustable().getMaximum());  
        }
    });

这将是最好的。来自JScrollPane and JList auto scroll

Answer 3

这就是我自动向上或向下滚动的方式：

/**
 * Scrolls a {@code scrollPane} all the way up or down.
 *
 * @param scrollPane the scrollPane that we want to scroll up or down
 * @param direction  we scroll up if this is {@link ScrollDirection#UP},
 *                   or down if it's {@link ScrollDirection#DOWN}
 */
public static void scroll(JScrollPane scrollPane, ScrollDirection direction) {
    JScrollBar verticalBar = scrollPane.getVerticalScrollBar();
    // If we want to scroll to the top, set this value to the minimum,
    // else to the maximum
    int topOrBottom = direction == ScrollDirection.UP ?
                      verticalBar.getMinimum() :
                      verticalBar.getMaximum();

    AdjustmentListener scroller = new AdjustmentListener() {
        @Override
        public void adjustmentValueChanged(AdjustmentEvent e) {
            Adjustable adjustable = e.getAdjustable();
            adjustable.setValue(topOrBottom);
            // We have to remove the listener, otherwise the
            // user would be unable to scroll afterwards
            verticalBar.removeAdjustmentListener(this);
        }
    };
    verticalBar.addAdjustmentListener(scroller);
}

public enum ScrollDirection {
    UP, DOWN
}