所以我正在创建一个基本的应用程序，我希望在屏幕底部有一个 JLabel，它从左下角开始移动，动画风格，在设定的时间到右下角，和一个静态图像在中心。为此，我使用 BorderLayout 创建了一个带有 JPanel 的 JFrame。在 BorderLayout.CENTER 中添加了一个带有 ImageIcon 的 JLabel，在 BorderLayout.SOUTH 中添加了一个 JPanel。我的代码虽然仓促编写而且远非漂亮，但它是:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.BorderFactory;
public class GameWindow extends JPanel{
private static JLabel mainWindow, arrowLabel, arrowBox;
protected static JFrame frame;
protected static JPanel arrows;
public static int x = 600;
public GameWindow(){
mainWindow = new JLabel("Center");
arrowLabel = new JLabel("Moving");
arrows = new JPanel();
arrows.setSize(600, 100);
arrows.setLayout(null);
arrowBox = new JLabel("");
arrowBox.setBounds(0, 0, 150, 100);
arrowBox.setPreferredSize(new Dimension(150, 100));
arrowBox.setBorder(BorderFactory.createLineBorder(Color.black));
arrows.add(arrowBox);
this.setSize(600,600);
this.setLayout(new BorderLayout());
this.add(mainWindow, BorderLayout.CENTER);
this.add(arrows, BorderLayout.SOUTH);
}
public static void main(String[] args)
{
GameWindow g = new GameWindow();
frame = new JFrame("Sword Sword Revolution");
frame.add(g);
frame.setSize(600,600);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
Timer t = new Timer(1000, new ActionListener(){
@Override
public void actionPerformed(ActionEvent e) {
arrows.add(arrowLabel);
arrowLabel.setBounds(x, 100, 100, 100);
x-=50;
arrows.repaint();
frame.repaint();
}
});
t.start();
}
中间 JLabel 的 ImageIcon 看起来很好，带边框的空 JLabel 出现在底部，但我无法让带有箭头图像的第二个 JLabel 显示在屏幕上。最终我将更改为 scheduleAtFixedRate 以连续移动 JLabel，但现在我什至无法让图像出现在屏幕上。
我也知道我很可能无法为此使用 FlowLayout，因为我知道它不允许您设置组件的位置。我尝试使用空布局，但空布局不会出现带边框的空 JLabel。我几乎无法在框架的底部边缘辨认出边框的顶部，但即使使用 setLocation，我也无法让它出现在我想要的位置。
显然，我的思维过程存在缺陷，因此我们将不胜感激。
最佳答案
对于 Swing 应用程序，您对线程的使用完全错误。您不应尝试在后台线程中添加或删除组件，而应使用 Swing 计时器在 Swing 事件线程上执行此操作。
另外，你是什么意思:
I want to have a scrolling JLabel at the bottom of the screen
请说明您要达到的效果。
另外关于，
I also understand that I will most likely not be able to use FlowLayout for this, as I understand it does not allow you to set the location of your components. I tried using null layout, but with null layout the empty JLabel with a border does not appear. I can barely make out the top of the border at the bottom edge of the frame, but even with setLocation I cannot get it to appear where I want it to.
不，不要在这种情况下使用空布局。有更好的布局管理器可以帮助您以更清晰、更独立于平台的方式构建您的应用程序。
编辑 3
关于:
To clarify, at the bottom of the screen I want a JLabel at the far right corner, then in the swing timer, the JLabel will gradually move to the left until it leaves the screen. If I could get setLocation to work, the basic premise would be to have a variable x set to 600, and then every second decrement x by say 50 and then redraw the JLabel at the new location on the screen. Basic animation.
我会在屏幕底部创建一个 JPanel，用于保存 JLabel 或通过重写其 paintComponent(...) 方法来显示没有 JLabel 的图像。如果您将它用作容器，那么是的，它的布局应该为空，但 GUI 的其余部分不应该使用空布局。 Swing Timer 将简单地更改 JLabel 的位置，然后在其 JPanel/容器上调用 repaint()。如果你走后一条路线，你会在 JPanel 的 paintComponent(...) 方法中使用 g.drawImage(myImage, x, y) 绘制图像，而你的计时器会更改 x 和/或 y 并在绘图 JPanel 上调用 repaint()。
此外，您可能不想在计时器中继续添加 JLabel，而只是简单地移动已显示在 GUI 中的 JLabel。
另外，为了避免焦点问题，不要使用 KeyListener 来捕获击键输入，而是使用键绑定(bind)。 Google 会指导您阅读有关此构造的精彩教程。
编辑4
例如:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.EnumMap;
import javax.imageio.ImageIO;
import javax.swing.*;
@SuppressWarnings("serial")
public class AnimateExample extends JPanel {
public static final String DUKE_IMG_PATH =
"https://duke.kenai.com/iconSized/duke.gif";
private static final int PREF_W = 800;
private static final int PREF_H = 800;
private static final int TIMER_DELAY = 20;
private static final String KEY_DOWN = "key down";
private static final String KEY_RELEASE = "key release";
public static final int TRANSLATE_SCALE = 3;
private static final String BACKGROUND_STRING = "Use Arrow Keys to Move Image";
private static final Font BG_STRING_FONT = new Font(Font.SANS_SERIF,
Font.BOLD, 32);
private EnumMap<Direction, Boolean> dirMap =
new EnumMap<AnimateExample.Direction, Boolean>(Direction.class);
private BufferedImage image = null;
private int imgX = 0;
private int imgY = 0;
private int bgStringX;
private int bgStringY;
public AnimateExample() {
for (Direction dir : Direction.values()) {
dirMap.put(dir, Boolean.FALSE);
}
try {
URL imgUrl = new URL(DUKE_IMG_PATH);
image = ImageIO.read(imgUrl);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
new Timer(TIMER_DELAY, new TimerListener()).start();
// here we set up our key bindings
int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
InputMap inputMap = getInputMap(condition);
ActionMap actionMap = getActionMap();
for (final Direction dir : Direction.values()) {
// for the key down key stroke
KeyStroke keyStroke = KeyStroke.getKeyStroke(dir.getKeyCode(), 0,
false);
inputMap.put(keyStroke, dir.name() + KEY_DOWN);
actionMap.put(dir.name() + KEY_DOWN, new AbstractAction() {
@Override
public void actionPerformed(ActionEvent arg0) {
dirMap.put(dir, true);
}
});
// for the key release key stroke
keyStroke = KeyStroke.getKeyStroke(dir.getKeyCode(), 0, true);
inputMap.put(keyStroke, dir.name() + KEY_RELEASE);
actionMap.put(dir.name() + KEY_RELEASE, new AbstractAction() {
@Override
public void actionPerformed(ActionEvent arg0) {
dirMap.put(dir, false);
}
});
}
FontMetrics fontMetrics = getFontMetrics(BG_STRING_FONT);
int w = fontMetrics.stringWidth(BACKGROUND_STRING);
int h = fontMetrics.getHeight();
bgStringX = (PREF_W - w) / 2;
bgStringY = (PREF_H - h) / 2;
}
@Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g.setFont(BG_STRING_FONT);
g.setColor(Color.LIGHT_GRAY);
g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
g.drawString(BACKGROUND_STRING, bgStringX, bgStringY);
if (image != null) {
g.drawImage(image, imgX, imgY, this);
}
}
private class TimerListener implements ActionListener {
public void actionPerformed(java.awt.event.ActionEvent e) {
for (Direction dir : Direction.values()) {
if (dirMap.get(dir)) {
imgX += dir.getX() * TRANSLATE_SCALE;
imgY += dir.getY() * TRANSLATE_SCALE;
}
}
repaint();
};
}
enum Direction {
Up(KeyEvent.VK_UP, 0, -1), Down(KeyEvent.VK_DOWN, 0, 1), Left(
KeyEvent.VK_LEFT, -1, 0), Right(KeyEvent.VK_RIGHT, 1, 0);
private int keyCode;
private int x;
private int y;
private Direction(int keyCode, int x, int y) {
this.keyCode = keyCode;
this.x = x;
this.y = y;
}
public int getKeyCode() {
return keyCode;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
}
private static void createAndShowGui() {
AnimateExample mainPanel = new AnimateExample();
JFrame frame = new JFrame("Animate Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
这将创建此 GUI:
关于Java 动画 JLabel，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12545744/