Java布局不显示组件（有时） [英] Java Layout not showing components (sometimes)

问题描述

我正在为我的学生写一个MathQuiz，包括用于渲染的JLatexMath和用于蜂鸣器的jinput。问题是，当我启动程序时，有时（就像每四次一样），没有任何组件可见。它们在调整JFrame大小后出现。
首先我在考虑jinput或jlatexMath库中的Bugs，但即使使用这个最小代码我也会得到相同的错误：

I'm writing a MathQuiz for my pupils including JLatexMath for rendering and jinput for the buzzers. The problem is, that sometimes (like every fourth time) when I start the program, none of the components are visible. They appear after resizing the JFrame. First I was thinking of Bugs in the jinput or jlatexMath libraries, but I do get the same Error even with this minimal Code:

public class Shell extends JFrame{

  private JButton button1;
  private JButton button2;
  private Formula formula;

  public Shell() {
    super("blaBla");
    this.setSize(800, 600);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
    this.setLayout(new BoxLayout(this.getContentPane(), BoxLayout.Y_AXIS));
    Box b = Box.createHorizontalBox();
    button1 = new JButton(" ");
    button1.setEnabled(false);
    b.add(button1);
    b.add(Box.createHorizontalGlue());
    button2 = new JButton(" ");
    button2.setEnabled(false);
    b.add(button2);
    add(b);
    JPanel formulaPanel = new JPanel();
    add(Box.createVerticalStrut(20));
    add(formulaPanel);
  } 

  public static void main(String[] args) {
    Shell s = new Shell();
  }
}

有什么问题，代码？

推荐答案

首先将 setVisible（true）; 移至构造函数的末尾。

Start by moving setVisible(true); to the end of the constructor.

而不是在这里......

Instead of been here...

public Shell() {
    super("blaBla");
    this.setSize(800, 600);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
    //...
} 

将它移到这里......

Move it here...

public Shell() {
    super("blaBla");
    //...
    add(Box.createVerticalStrut(20));
    add(formulaPanel);
    setVisible(true);
} 

为了防止任何其他可能的图形故障，你应该始终从你的UI开始在事件调度线程中，请参阅初始线程以获取更多详细信息

To protect against any other possible graphical glitches, you should always start you UI's from within the Event Dispatching Thread, see Initial Threads for more details

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