我是 Java 新手，我正在尝试设置一个我熟悉的简单计时器，set_interval因为我有 JavaScript 和 ActionScript 方面的经验，
我对类还不是很熟悉，所以很容易混淆，我知道我需要设置一个 new Timer，然后设置 a TimerTask，但是即使我正在查看文档，我也不知道该怎么做马上..
所以我创建了一个 Applet，这就是我的init方法：
public void init() {
TimerTask myTask;
Timer myTimer;
myTimer.schedule(myTask,5000);
}
我如何实际设置任务代码？我想让它做类似的事情
g.drawString("Display some text with changing variables here",10,10);
正如许多优秀的 Stackoverflow 用户所说，这里的正确想法是使用javax.swing.TImer。这是一个小代码片段，可以为您提供帮助。请提出任何超出您能力范围的问题，我也会尝试提供信息。
import java.awt.*;
import java.awt.event.*;
import java.util.Random;
import javax.swing.*;
public class DrawStringWithTimer
{
private final int WIDTH = 400;
private final int HEIGHT = 300;
private Timer timer;
private int x;
private int y;
private int counter;
private Random random;
private String[] messages = {
"Bingo, I am ON",
"Can you believe this !!",
"What else you thinking about ?",
"Ahha, seems like you are confused now !!",
"Lets Roll and Conquer :-)"
};
private CustomPanel contentPane;
private ActionListener timerAction = new ActionListener()
{
@Override
public void actionPerformed(ActionEvent ae)
{
if (counter == 5)
counter = 0;
/*
* Creating random numbers where
* x will be equal to zero or
* less than WIDTH and y will be
* equal to zero or less than HEIGHT.
* And we getting the value of the
* messages Array with counter variable
* and passing this to setValues function,
* so that it can trigger a repaint()
* request, since the state of the
* object has changed now.
*/
x = random.nextInt(WIDTH);
y = random.nextInt(HEIGHT);
contentPane.setValues(x, y, messages[counter]);
counter++;
}
};
public DrawStringWithTimer()
{
counter = 0;
x = y = 10;
random = new Random();
}
private void displayGUI()
{
JFrame frame = new JFrame("Drawing String Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
contentPane = new CustomPanel(WIDTH, HEIGHT);
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
/*
* javax.swing.Timer is what you need
* when dealing with Timer related
* task when using Swing.
* For more info visit the link
* as specified by @trashgod, in the
* comments.
* Two arguments to the constructor
* specify as the delay and the
* ActionListener associated with
* this Timer Object.
*/
timer = new Timer(2000, timerAction);
timer.start();
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
@Override
public void run()
{
new DrawStringWithTimer().displayGUI();
}
});
}
}
class CustomPanel extends JPanel
{
private final int GAP = 10;
private int width;
private int height;
private int x;
private int y;
private String message = "";
public CustomPanel(int w, int h)
{
width = w;
height = h;
setOpaque(true);
setBackground(Color.WHITE);
setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
}
public void setValues(int x, int y, String msg)
{
this.x = x;
this.y = y;
message = msg;
/*
* As the state of the variables will change,
* repaint() will call the paintComponent()
* method indirectly by Swing itself.
*/
repaint();
}
@Override
public Dimension getPreferredSize()
{
return (new Dimension(width, height));
}
@Override
protected void paintComponent(Graphics g)
{
/*
* Below line is used to draw the JPanel
* in the usual Java way first.
*/
super.paintComponent(g);
/*
* This line is used to draw the dynamic
* String at the given location.
*/
g.drawString(message, x, y);
}
}
无论您想执行什么，即绘图或smwhat，只需定义任务并实现其中的代码。
import javax.swing.*;
import java.awt.*;
import java.util.Timer;
import java.util.TimerTask;
public class TimerApplet extends JApplet {
String someText;
int count = 0;
public TimerApplet() {
Timer time = new Timer();
Сalculate calculate = new Сalculate();
time.schedule(calculate, 1 * 1000, 1000);
}
class Сalculate extends TimerTask {
@Override
public void run() {
count++;
System.out.println("working.. "+count);
someText = "Display some text with changing variables here.." +count;
repaint();
}
}
//This is how do you actually code.
@Override
public void paint(Graphics g)//Paint method to display our message
{
// super.paint(g); flickering
Graphics2D g2d = (Graphics2D)g;
g2d.setColor(Color.WHITE);
g2d.fillRect(0, 0, getWidth(), getHeight());
if (someText != null) {
g2d.setColor(Color.BLACK);
g2d.drawString(someText,10,10);
}
//.....
}
}
我在我的小应用程序中发现了同样的问题，我知道我的解决方案不是最好的，但它很简单。只需在自定义内部类中使用两个自变化参数即可。这是我的代码。
final static Random random = new Random();
....//other codes
static class MyTimerTask extends TimerTask {
int index_x = random.nextInt(50);
int index_y = random.nextInt(50);
@Override
public void run() {
System.out.println("Display some text with changing variables here: " + index_x + "," + index_y);
index_x = random.nextInt(50);
index_y = random.nextInt(50);
System.gc();
}
public static MyTimerTask getInstance() {
return new MyTimerTask();
}
}
计时器将在我们的应用程序中永远运行，直到应用程序关闭或当没有更多作业可分配或调度时。
TimerTask - 这是具有某些功能的任务，该功能将根据时间或持续时间运行。
在Timer中，我们将分配TimerTask以运行特定的持续时间或在特定的持续时间开始运行。
请了解它是如何工作的，然后适用于小程序或任何其他
1、GCTask类扩展了TimerTask类，实现了run()方法。
2、在TimerDemo程序中，实例化了一个Timer对象和一个GCTask对象。
3、使用Timer对象，使用Timer类的schedule()方法调度任务对象延迟5秒后执行，然后每隔5秒继续执行。
4、main() 中的无限while 循环实例化了SimpleObject 类型的对象（其定义如下），这些对象可立即用于垃圾回收。
import java.util.TimerTask;
public class GCTask extends TimerTask
{
public void run()
{
System.out.println("Running the scheduled task...");
System.gc();
}
}
import java.util.Timer;
public class TimerDemo
{
public static void main(String [] args)
{
Timer timer = new Timer();
GCTask task = new GCTask();
timer.schedule(task, 5000, 5000);
int counter = 1;
while(true)
{
new SimpleObject("Object" + counter++);
try
{
Thread.sleep(500);
}
catch(InterruptedException e) {}
}
}
}
public class SimpleObject
{
private String name;
public SimpleObject(String n)
{
System.out.println("Instantiating " + n);
name = n;
}
public void finalize()
{
System.out.println("*** " + name + " is getting garbage collected ***");
}
}