按下键时使用计时器 [英] Use a timer when a key is pressed
本文介绍了按下键时使用计时器的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
过去一周的搜索并没有为试图弄清楚如何做到这一点提供任何有用的帮助。当用户按下退格键时，它将保存游戏。我将其设置为在顶部显示一个小框，上面显示 Saving ..（保存..），我希望它在此处停留约2秒钟。我可以使用以下代码在按下按钮时显示它：
The past week of searching has not brought up any working help for trying to figure out how to do this. When a user presses the backspace, it saves the game. I set it up that it shows a little box at the top that says "Saving.." and I want that to stay up there for about 2 seconds. I can get it to show up while the button is being pressed with this code:
if (key.save) {
font = new Font(null, 0, 16);
g.setFont(font);
g.setColor(Color.DARK_GRAY);
g.fillRect(getWidth() / 2 - 40, -1, 80, 35);
g.setColor(Color.BLACK);
g.drawRect(getWidth() / 2 - 40, -1, 80, 35);
g.setColor(Color.white);
g.drawString("Saving..", getWidth() / 2 - 30, 22);
}
但是此代码不起作用，甚至不会显示该框在顶部：
But this code won't work, it won't even display the box at the top:
if (key.save) {
ActionListener action = new ActionListener() {
public void actionPerformed(ActionEvent e) {
Font font = new Font(null, 0, 16);
g.setFont(font);
g.setColor(Color.DARK_GRAY);
g.fillRect(getWidth() / 2 - 40, -1, 80, 35);
g.setColor(Color.BLACK);
g.drawRect(getWidth() / 2 - 40, -1, 80, 35);
g.setColor(Color.white);
g.drawString("Saving..", getWidth() / 2 - 30, 22);
}
};
timer = new Timer(0, action);
timer.start();
}
推荐答案
这是使用
基本思想是存在一个中央绘制循环，该循环负责根据什么来更新UI的当前状态。您要渲染。这意味着对UI的任何更改都必须经过这个中央循环。
The basic idea is there is a central paint loop that is responsible for updating the current state of the UI based on what you want to render. This means that any changes to the UI must go through this central loop.
此示例仅使用Swing，但该概念应易于翻译。
This example just uses Swing, but the concept should be easy to translate.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class QuickPaint01 {
public static void main(String[] args) {
new QuickPaint01();
}
public QuickPaint01() {
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 TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel implements Environment {
private List<Drawable> drawables;
public TestPane() {
drawables = new ArrayList<>(25);
Timer update = new Timer(40, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
Drawable[] draws = drawables.toArray(new Drawable[drawables.size()]);
for (Drawable drawable : draws) {
if (drawable instanceof Moveable) {
((Moveable)drawable).update(TestPane.this);
}
}
repaint();
}
});
update.setCoalesce(true);
update.setRepeats(true);
update.start();
drawables.add(new Ball());
}
@Override
public void add(Drawable drawable) {
drawables.add(drawable);
}
@Override
public void remove(Drawable drawable) {
drawables.remove(drawable);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
for (Drawable drawable : drawables) {
drawable.draw(this, g2d);
}
g2d.dispose();
}
}
public interface Environment {
public Dimension getSize();
public void add(Drawable drawable);
public void remove(Drawable drawable);
}
public interface Drawable {
public void draw(Environment env, Graphics2D g);
}
public interface Moveable extends Drawable {
public void update(Environment env);
}
public class Ball implements Moveable {
private int radius = 20;
private int x = 0;
private int y = 0;
private int xDelta = 4;
private Shape shape;
public Ball() {
shape = new Ellipse2D.Float(0, 0, radius, radius);
}
@Override
public void update(Environment env) {
x += xDelta;
if (x + radius > env.getSize().width) {
x = env.getSize().width - radius;
xDelta *= -1;
env.add(new Message(env, "<< Bounce", 1));
} else if (x < 0) {
x = 0;
xDelta *= -1;
env.add(new Message(env, "Bounce >> ", 1));
}
y = (env.getSize().height - radius) / 2;
}
@Override
public void draw(Environment env, Graphics2D g) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.translate(x, y);
g2d.setColor(Color.BLUE);
g2d.fill(shape);
g2d.dispose();
}
}
public class Message implements Drawable {
private Environment environment;
private String message;
private int delay;
public Message(Environment environment, String message, int delay) {
this.environment = environment;
this.message = message;
this.delay = delay;
Timer timer = new Timer(delay * 1000, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
Message.this.environment.remove(Message.this);
}
});
timer.start();
}
@Override
public void draw(Environment env, Graphics2D g) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(Color.RED);
FontMetrics fm = g2d.getFontMetrics();
g2d.drawString(message, env.getSize().width - fm.stringWidth(message), 0 + fm.getAscent());
g2d.dispose();
}
}
}
这篇关于按下键时使用计时器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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