java 在 JScrollPane 上设置滚动条
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Setting Scroll Bar on a JScrollPane
提问by twolfe18
I have this JTextPane(wrapped in a JScrollPane) that is backed by a HTMLEditorKit. The contents of the JTextPaneis simple HTML with some images (local files) embedded using img tags. The problem is that when you load the the JTextPane, it takes a split second to load and then it comes up with the scroll bar at the bottom of the page. If I do:
我有这个JTextPane（包裹在 a 中JScrollPane）由HTMLEditorKit. 的内容JTextPane是简单的 HTML，其中使用 img 标签嵌入了一些图像（本地文件）。问题是，当您加载 时，加载JTextPane需要一瞬间，然后它会在页面底部出现滚动条。如果我做：
JTextPane text = new JTextPane();
JScrollPane scroll = new JScrollPane(text);
// do some set up...
scroll.getVerticalScrollBar().setValue(0);
it sets the scroll bar momentarily and then another thead (presumably that is in charge of loading the images) comes and knocks the scroll bar back to the bottom. I tried adding:
它会暂时设置滚动条，然后另一个thead（大概是负责加载图像）出现并将滚动条敲回底部。我尝试添加：
((AbstractDocument)text.getDocument()).setAsynchronousLoadPriority(-1);
but that did not fix it. Is there any way to get an event from either text.getDocument()or textthat will notify me when the pane is finished loading so that I can set the scroll bar then? The alternative is that I set up another thread to wait a second or so, and then set the scroll bar, but this is a bad hack.
但这并没有解决它。有没有办法从任一得到一个事件text.getDocument()或text当窗格完成加载，这样我可以设置滚动条，然后会通知我吗？另一种方法是我设置另一个线程等待一秒钟左右，然后设置滚动条，但这是一个糟糕的技巧。
Your suggestions?
你的建议？
回答by Spyder
Have you tried using invokeLater?
您是否尝试过使用 invokeLater？
final JScrollPane scroll = new JScrollPane(text);
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
scroll.getVerticalScrollBar().setValue(0);
}
});
If that doesn't work, digging into the image views is pretty tough so my next step would be to track down why the scrollbar is changing:
如果这不起作用，深入研究图像视图非常困难，所以我的下一步将是追踪滚动条发生变化的原因：
scroll.setVerticalScrollbar(new JScrollBar() {
public void setValue(int value) {
new Exception().printStackTrace();
super.setValue(value);
}
});
You could also use a debugger in the setValue() method instead of just printing the stack trace.
您还可以在 setValue() 方法中使用调试器，而不仅仅是打印堆栈跟踪。
回答by phil294
The following solved the problem for me, after 50 minutes of despair:
经过50分钟的绝望，以下为我解决了问题：
JTextPane.grabFocus();
JTextPane.setCaretPosition(20);
回答by Savvas Dalkitsis
Is your app single threaded by any chance? If it is you can request a list of running threads and get notified when they finish and then set the scrollbar value. Is that an option?
你的应用程序是单线程的吗？如果是，您可以请求正在运行的线程列表并在它们完成时得到通知，然后设置滚动条值。这是一个选择吗？
Or you can provide an ImageObserver to every image loaded and set the position of the scrollbar when all images are reported loaded?
或者您可以为每个加载的图像提供一个 ImageObserver 并在报告所有图像加载时设置滚动条的位置？
