Java - 使用大量 RAM 的 GUI 时钟? [英] Java - GUI clock using large amounts of RAM?
问题描述
我用 Java 为桌面小部件制作了一个小时钟(该小部件还包括许多其他功能).我检查了任务管理器中的应用程序 RAM 使用情况,以查看时钟使用了 700+ MB 的 RAM.我禁用了时钟,RAM 使用量下降到大约 60 MB.这是时钟代码:
I made a little clock for a desktop widget in Java(the widget includes many other features as well). I checked the applications RAM usage in task manager to see that the clock was using 700+ MB of RAM. I disabled the clock and the RAM usage went down to about 60 MB. Here is the clocks code:
final int timeRun = 0;
new Thread()
{
public void run()
{
while(timeRun == 0)
{
Calendar cal = new GregorianCalendar();
int hour = cal.get(Calendar.HOUR);
int min = cal.get(Calendar.MINUTE);
int sec = cal.get(Calendar.SECOND);
int AM_PM = cal.get(Calendar.AM_PM);
String day_night = "";
if (AM_PM == 1){
day_night = "PM";
}else{
day_night = "AM";
}
String time = hour + ":" + min + ":" + sec + " " + day_night;
Clock.setText(time);
}
}
}.start();
为什么要使用这么多内存?我该如何解决?
Why is it using so much RAM? How could I fix it?
推荐答案
- 将更新次数减少到所需的最低限度
- 尽可能减少临时对象的数量
- 确保对 UI 的所有更新都是在主 UI 线程(Swing 的事件调度线程)的上下文中进行的
看看:
例如...
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ClockMeBaby {
public static void main(String[] args) {
new ClockMeBaby();
}
public ClockMeBaby() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public static class TestPane extends JPanel {
protected static final DateFormat CLOCK_FORMAT = new SimpleDateFormat("hh:mm:ss a");
private JLabel clock;
public TestPane() {
setLayout(new GridBagLayout());
clock = new JLabel("...");
clock.setFont(clock.getFont().deriveFont(Font.BOLD, 64f));
add(clock);
updateClock();
Timer timer = new Timer(500, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
updateClock();
}
});
timer.start();
}
protected void updateClock() {
clock.setText(CLOCK_FORMAT.format(System.currentTimeMillis()));
}
}
}
SwingTimer
使用 500
毫秒延迟的原因是为了确保我们保持同步,否则您的时钟可能会与 UI 的其余部分不同步"更新因为你错过了第二个边界.如果这对您不重要,您可以使用 1000
毫秒延迟来代替
The reason the SwingTimer
uses a 500
millisecond delay is to ensure we remain in sync, otherwise your clock might update "out of sync" with the rest of the UI because you've missed a second boundry. If this is not important to you, you could us 1000
millisecond delay instead
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