如何知道JScrollBar是否已到达JScrollPane的底部? [英] How to know if a JScrollBar has reached the bottom of the JScrollPane?

问题描述

我想知道是否有办法知道JScrollBar(在我的情况下为垂直)何时到达其包含JScrollPane的底部.

I'd like to know if there is a way to know when a JScrollBar (vertical in my case) has reached the bottom of his containing JScrollPane.

起初，我虽然在滚动条上使用了AdjustmentListener，但是我不知道如何解释JScrollBar的value属性.另外，我不确定是否正确理解maximum的含义，以及是否可以使用该值来获取所需的信息.

At first i have though of using an AdjustmentListener on the scroll bar but i don't know how to interpret the value attribute of the JScrollBar. Also i'm not sure to properly understand what the maximum represents and if i can use with the value to get the information i need.

修改:

scrollPane.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() {
    @Override
    public void adjustmentValueChanged(AdjustmentEvent ae) {
        System.out.println("Value: " + scrollPane.getVerticalScrollBar().getValue() + " Max: " + scrollPane.getVerticalScrollBar().getMaximum());
    }
}

推荐答案

您必须在计算中添加滚动条的范围.我在下面的示例中将代码添加到您的代码中.

You have to add the extent of the scrollbar to your calculation. I added the code into your code in the example below.

scrollPane.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() {
    @Override
    public void adjustmentValueChanged(AdjustmentEvent ae) {
        int extent = scrollPane.getVerticalScrollBar().getModel().getExtent();
        System.out.println("Value: " + (scrollPane.getVerticalScrollBar().getValue()+extent) + " Max: " + scrollPane.getVerticalScrollBar().getMaximum());
    }
});

两种替代实现(部分对Kleopatra做出反应)

scrollPane.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() {

    @Override
    public void adjustmentValueChanged(AdjustmentEvent event) {
        JScrollBar scrollBar = (JScrollBar) event.getAdjustable();
        int extent = scrollBar.getModel().getExtent();
        System.out.println("1. Value: " + (scrollBar.getValue() + extent) + " Max: " + scrollBar.getMaximum());

    }
});

或通过模型

scrollPane.getVerticalScrollBar().getModel().addChangeListener(new ChangeListener() {

    @Override
    public void stateChanged(ChangeEvent event) {
        BoundedRangeModel model = (BoundedRangeModel) event.getSource();
        int extent = model.getExtent();
        int maximum = model.getMaximum();
        int value = model.getValue();

        System.out.println("2. Value: " + (value + extent) + " Max: " + maximum);

    }
});

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