如何检查JScrollPane中的JComponent是否对用户可见? [英] How to check whether JComponent inside JScrollPane is visible to a user?

问题描述

想象一下，您有一个JScrollPane并添加了许多JLabel或任何其他JComponent.

Imagine you have a JScrollPane and many JLabels or any other JComponents added to it.

您将如何检查某个组件是否对用户可见/部分可见/不可见?(滚动)

我曾经尝试过使用Google，但找不到简单的解决方案.是否有我缺少的现有方法，或者我们必须处理坐标和矩形比较?

I have tried to Google but could not find an easy solution. Is there some existing method I am missing or we have to deal with coordinates and rectangular comparison?

UPD:以下情况不适用于我.它似乎与JLabel.setVisible(true/false)有关，但不在JScrollPane内部

UPD: the following is not working in my case. It seem to relate to JLabel.setVisible(true/false) but not being inside JScrollPane

JLabel.isVisible();

推荐答案

看看JComponent java doc:

Have a look at JComponent java doc:

Rectangle r = child.getVisibleRect();
if (r.getSize().equals(child.getSize())) {
   // fully visible
} else if (r.isEmpty()) {
   // not visible
} else {
  // partly visible
}

修改

更改了不可见的使用Rectangle api的条件-感谢@mKorbel提醒我:-)

changed the condition for not-visible to use Rectangle api - thanks to @mKorbel for reminding me :-)

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