我是Java新手，我正在尝试设置一个简单的计时器，我熟悉set_interval，因为有JavaScript和ActionScript的经验，
我还不熟悉课程，所以我很容易感到困惑，我知道我需要设置一个新的Timer，然后设置一个TimerTask，但我不明白正是为了做到这一点，即使我现在正在查看文档..
所以我创建了一个Applet，这是我的init方法：
public void init() {
TimerTask myTask;
Timer myTimer;
myTimer.schedule(myTask,5000);
}
如何实际设置任务代码？ 我希望它能做类似
的事情g.drawString("Display some text with changing variables here",10,10);
答案 0 :(得分：2)
无论你想表演什么。绘图或smwhat，只需定义任务并在其中实现代码。
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);
}
//.....
}
}
答案 1 :(得分：2)
正如许多精彩的Stackoverflow用户所说，这里正确的想法是使用javax.swing.TImer。这是一个小代码片段供您使用。请问任何超出您掌握的问题，我会尽力提供相关信息。
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);
}
}
答案 2 :(得分：1)
Example as you expected in this link
计时器将在我们的应用程序中永久运行，直到应用程序关闭或当没有更多工作可用于分配或安排时。
TimerTask - 这是一项具有一些基于时间或持续时间运行的功能的任务。
在计时器中，我们会指定 TimerTask 运行特定的持续时间或在特定时间内开始运行。
请了解其工作原理，然后通过applet或其他任何方式申请
1，GCTask类扩展了TimerTask类并实现了run（）方法。
2，在TimerDemo程序中，实例化Timer对象和GCTask对象。
3，使用Timer对象，使用Timer类的schedule（）方法调度任务对象，在5秒延迟后执行，然后每5秒继续执行一次。
4，main（）中的无限while循环实例化SimpleObject类型的对象（其定义如下），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 ***");
}
}
答案 3 :(得分：1)
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。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();
}
}