我对 java 还很陌生,我刚刚开始编写这个愚蠢的小程序作为 GUI 测试。它应该做的是有 12 个按钮,将它们全部设置为白色,连续将 3 个随机按钮设置为黑色,再次将所有按钮设置回白色,等待一秒钟,然后重复。问题是,我似乎无法重复它。每次我尝试在使随机按钮变黑的代码部分周围放置 while 或 for 循环时,它根本不会运行。它不会给出任何错误,并且进程本身确实会运行,但不会出现任何窗口。这是该类的代码(减去导入语句):
public class testingness extends JFrame {
JButton one, two, three, four, five, six, seven, eight, nine, ten, eleven,
twelve;
JPanel panel;
testingness(String title) {
super(title);
this.init();
this.setSize(800, 800);
this.setLocationRelativeTo(null);
this.setVisible(true);
}
void init() {
panel = new JPanel();
panel.setLayout(new GridLayout(3, 4));
one = new JButton();
one.setBackground(Color.white);
two = new JButton();
two.setBackground(Color.white);
three = new JButton();
three.setBackground(Color.white);
four = new JButton();
four.setBackground(Color.white);
five = new JButton();
five.setBackground(Color.white);
six = new JButton();
six.setBackground(Color.white);
seven = new JButton();
seven.setBackground(Color.white);
eight = new JButton();
eight.setBackground(Color.white);
nine = new JButton();
nine.setBackground(Color.white);
ten = new JButton();
ten.setBackground(Color.white);
eleven = new JButton();
eleven.setBackground(Color.white);
twelve = new JButton();
twelve.setBackground(Color.white);
panel.add(one);
panel.add(two);
panel.add(three);
panel.add(four);
panel.add(five);
panel.add(six);
panel.add(seven);
panel.add(eight);
panel.add(nine);
panel.add(ten);
panel.add(eleven);
panel.add(twelve);
this.add(panel);
while (true) {
randomness();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public void randomness() {
for (int timesdone = 0; timesdone < 4; timesdone++) {
panel.update(panel.getGraphics());
Random r = new Random();
int rand = r.nextInt(12);
if (rand == 0) {
one.setBackground(Color.black);
} else if (rand == 1) {
two.setBackground(Color.black);
} else if (rand == 2) {
three.setBackground(Color.black);
} else if (rand == 3) {
four.setBackground(Color.black);
} else if (rand == 4) {
five.setBackground(Color.black);
} else if (rand == 5) {
six.setBackground(Color.black);
} else if (rand == 6) {
seven.setBackground(Color.black);
} else if (rand == 7) {
eight.setBackground(Color.black);
} else if (rand == 8) {
nine.setBackground(Color.black);
} else if (rand == 9) {
ten.setBackground(Color.black);
} else if (rand == 10) {
eleven.setBackground(Color.black);
} else if (rand == 11) {
twelve.setBackground(Color.black);
}
one.setBackground(Color.white);
two.setBackground(Color.white);
three.setBackground(Color.white);
four.setBackground(Color.white);
five.setBackground(Color.white);
six.setBackground(Color.white);
seven.setBackground(Color.white);
eight.setBackground(Color.white);
nine.setBackground(Color.white);
ten.setBackground(Color.white);
eleven.setBackground(Color.white);
twelve.setBackground(Color.white);
}
}
}
我在这里做错了什么?
最佳答案
Swing 是单线程环境。要求所有对 UI 的交互和修改都在事件调度线程的上下文中进行。
EDT 负责处理重绘请求和传入事件等事务
任何阻止 EDT 的操作都会阻止它处理这些事件并更新屏幕。
在您的代码中,您正在执行此操作...
while (true) {
randomness();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
这可能会阻止 EDT,从而阻止其更新屏幕。
同样,你也在这样做......
for (int timesdone = 0; timesdone < 4; timesdone++) {
/*...*/
}
这同样会阻止 EDT,阻止它更新屏幕...
此外,这个 panel.update(panel.getGraphics());
是一个非常糟糕的主意。在 Swing 中,您无法控制绘制过程,这由 RepaintManager
决定。您可以提出更新/重绘请求,但由 RepaintManager
决定更新/重绘内容和时间。然后,这些请求将发布到 EDT...如果被阻止,将不会执行任何操作。
getGraphics
也可以返回 null
,这绝不是漂亮的...
要解决您的问题,您需要将“等待”时间转移到某种后台进程,该后台进程准备好后,需要告诉 UI 相应地更改其状态...
您可以使用Thread
,但这意味着您需要负责将所有调用重新同步回 EDT,这很困惑并且几乎没有带来任何开销。
您可以使用 SwingWorker
,但它并不真正适合您手头的任务
更好的解决方案是使用 javax.swing.Timer
,它将在指定的延迟后重复触发 actionPerformed
事件,就像在美国东部夏令时间。
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Flashy01 {
public static void main(String[] args) {
new Flashy01();
}
public Flashy01() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new FlashPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class FlashPane extends JPanel {
private final BigButton one, two, three, four, five, six, seven, eight, nine, ten, eleven,
twelve;
private final JPanel panel;
private final Random random;
private int timesDone;
public FlashPane() {
panel = new JPanel();
panel.setLayout(new GridLayout(3, 4));
one = new BigButton();
one.setBackground(Color.white);
two = new BigButton();
two.setBackground(Color.white);
three = new BigButton();
three.setBackground(Color.white);
four = new BigButton();
four.setBackground(Color.white);
five = new BigButton();
five.setBackground(Color.white);
six = new BigButton();
six.setBackground(Color.white);
seven = new BigButton();
seven.setBackground(Color.white);
eight = new BigButton();
eight.setBackground(Color.white);
nine = new BigButton();
nine.setBackground(Color.white);
ten = new BigButton();
ten.setBackground(Color.white);
eleven = new BigButton();
eleven.setBackground(Color.white);
twelve = new BigButton();
twelve.setBackground(Color.white);
panel.add(one);
panel.add(two);
panel.add(three);
panel.add(four);
panel.add(five);
panel.add(six);
panel.add(seven);
panel.add(eight);
panel.add(nine);
panel.add(ten);
panel.add(eleven);
panel.add(twelve);
this.add(panel);
random = new Random();
Timer timer = new Timer(1000, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
randomness();
}
});
timer.start();
}
public void randomness() {
int rand = random.nextInt(12);
timesDone++;
if (timesDone % 5 != 0) {
if (rand == 0) {
one.setBackground(Color.black);
} else if (rand == 1) {
two.setBackground(Color.black);
} else if (rand == 2) {
three.setBackground(Color.black);
} else if (rand == 3) {
four.setBackground(Color.black);
} else if (rand == 4) {
five.setBackground(Color.black);
} else if (rand == 5) {
six.setBackground(Color.black);
} else if (rand == 6) {
seven.setBackground(Color.black);
} else if (rand == 7) {
eight.setBackground(Color.black);
} else if (rand == 8) {
nine.setBackground(Color.black);
} else if (rand == 9) {
ten.setBackground(Color.black);
} else if (rand == 10) {
eleven.setBackground(Color.black);
} else if (rand == 11) {
twelve.setBackground(Color.black);
}
} else {
one.setBackground(Color.white);
two.setBackground(Color.white);
three.setBackground(Color.white);
four.setBackground(Color.white);
five.setBackground(Color.white);
six.setBackground(Color.white);
seven.setBackground(Color.white);
eight.setBackground(Color.white);
nine.setBackground(Color.white);
ten.setBackground(Color.white);
eleven.setBackground(Color.white);
twelve.setBackground(Color.white);
}
}
}
public class BigButton extends JButton {
@Override
public Dimension getPreferredSize() {
return new Dimension(20, 20);
}
}
}
看看...
了解更多详情...
关于java - GUI 中的循环问题 (java),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18304643/