在JScrollPane的

Question

这段代码显示的JLayeredPane显示我波形内滚动窗格：

var scrollPane = new JScrollPane 
var waveform = new Waveform(trackModel) // JPanel with waveform 

scrollPane.setViewportView(waveform) 

，这表明我的ScrollPane只是一个灰色的背景：

var scrollPane = new JScrollPane 
var layeredPane = new JLayeredPane 
var waveform = new Waveform(trackModel) // JPanel with waveform 

layeredPane.add(waveform, JLayeredPane.DEFAULT_LAYER) 
layeredPane.setPreferredSize(trackModel.getSize()) 
scrollPane.setViewportView(layeredPane) 

我不知道为什么波形（波形不会显示扩展JPanel）。下面是详细信息：

System.out.println("waveform visibility: " + waveform.isVisible) 
System.out.println("layeredPane visibility: " + layeredPane.isVisible) 
System.out.println("scrollPane visibility: " + scrollPane.isVisible) 

System.out.println("waveform dimensions: " + waveform.getPreferredSize.width + "/" + waveform.getPreferredSize.height) 
System.out.println("layeredPane dimensions: " + layeredPane.getPreferredSize.width + "/" + layeredPane.getPreferredSize.height) 
System.out.println("scrollPane dimensions: " + scrollPane.getPreferredSize.width + "/" + scrollPane.getPreferredSize.height) 

System.out.println("waveform dimensions: " + waveform.getWidth + "/" + waveform.getHeight) 
System.out.println("layeredPane dimensions: " + layeredPane.getWidth + "/" + layeredPane.getHeight) 
System.out.println("scrollPane dimensions: " + scrollPane.getWidth + "/" + scrollPane.getHeight) 

和输出：

waveform visibility: true 
layeredPane visibility: true 
scrollPane visibility: true 
waveform dimensions: 40315/200 
layeredPane dimensions: 40315/200 
scrollPane dimensions: 40318/203 
waveform dimensions: 0/0 
layeredPane dimensions: 0/0 
scrollPane dimensions: 0/0 

Answer 1

SOLUTION

我改变了setPreferredSize波形来的setSize。现在它可以工作。