java什么会导致Swing应用程序不一致地抛出空指针异常?
我有一个两类的项目,一个类读取一个文件,并对照网站检查所述文件中的每个条目,然后将返回数据发布到另一个文件中
如果返回数据为true(例如),则文件中的数据点会在屏幕上闪烁。这个功能很有效
我在while循环中通过下面的if语句调用它
if (!query.text().contains("unavailable") && !query.text().contains("at least 3 characters long to acquire.") && line != null) {
HitBox h = new HitBox(line); //GUI Class.
fos.write(query.text().getBytes());
fos.write("\n".getBytes());
fos.flush();
}
下面是我的GUI课程
import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.io.IOException;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JWindow;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.UIManager;
public class HitBox {
private Timer t;
JWindow frame = new JWindow();
public HitBox(String s) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager
.getSystemLookAndFeelClassName());
} catch (Exception ex) {
}
frame.setAlwaysOnTop(true);
t = new Timer(1000 * 5, new ActionListener() {
public void actionPerformed(ActionEvent e2) {
SwingUtilities.getWindowAncestor(frame.getComponent(0))
.dispose();
}
});
}
});
frame.setBackground(new Color(0, 0, 0, 0));
TranslucentPane tp = new TranslucentPane(s);
frame.setContentPane(tp);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
t.start();
}
}
class TranslucentPane extends JPanel {
public TranslucentPane(String s) {
add(new JLabel(s));
setOpaque(false);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setComposite(AlphaComposite.SrcOver.derive(0.85f));
g2d.setColor(getBackground());
g2d.fillRect(0, 0, getWidth(), getHeight());
}
}
这是使用同一组输入数据实现的,即使我重写web查询,只返回一个设置值,@a random point in runtime,会出现一个JWindow,会抛出一个null指针(@my call of the start method of my timer object)
这让我相信我错误地实现了计时器;我很感兴趣的是,对于一致的数据和返回,它抛出空指针的点是如何变化的
Exception in thread "main" java.lang.NullPointerException
at HitBox.<init>(HitBox.java:51)
at OriginalGangster.main(OriginalGangster.java:38)
# 1 楼答案
您没有在GUI线程上启动GUI。您需要将其移动到可运行状态,并确保在构建后启动计时器
例如
代码更新了