我有一个名为PopUp的类，它是一个JPanel，当激活时，根据中心给出的参数扩展到给定的大小和位置，并在点击时以相同的方式收缩。
出于某种原因，当PopUp正在扩展和收缩时，共享相同JPanel的动画会加速。我在我使用过PopUp课程的两个程序中见过这个。
以下是我认为的相关代码：
/**
* The {@code PopUp} class is a JPanel that expands to the rectangle
* created from the given x, y, width and height that expands from
* the center of the rectangle.
* <p>
* Here is an example of how the {@code PopUp} object can be initialized:
* <blockquote><pre>
* PopUp pu = new PopUp(25, 25, 575, 575, 25, Color.GRAY);
* </pre></blockquote>
* <p>
* The class {@code PopUp} includes methods for drawing the pop-up;
* choosing whether the pop-up is expanding or not; getting the
* percentage that the pop-up is expanded; and getting the maximum x, y,
* width, and height
*
* @author Gigi Bayte 2
*/
public class PopUp extends JPanel implements MouseListener {
private static final long serialVersionUID = 1L;
/**
* Expanded x coordinate
*/
private double x;
/**
* Expanded y coordinate
*/
private double y;
/**
* Expanded width value
*/
private double width;
/**
* Expanded height value
*/
private double height;
/**
* Number of steps until fully expanded
*/
private int steps;
/**
* This divided by steps is the percentage the pop-up is expanded
*/
private int expansionStage = 0;
/**
* Whether or not the pop-up is expansing
*/
private boolean isExpanding = false;
/**
* Color of the pop-up
*/
private Color color;
/**
* The rectangle that represents the bounds of the pop-up
*/
private Rectangle2D popUp;
/**
* Initializes a newly created {@code PopUp} with a uniform color
* @param x The x coordinate of the expanded pop-up
* @param y The y coordinate of the expanded pop-up
* @param w The width of the expanded pop-up
* @param h The height of the expanded pop-up
* @param expansionSteps The number of steps until fully expanded
* @param popUpColor The color of the pop-up
*/
public PopUp(double x, double y, double w, double h, int expansionSteps, Color popUpColor) {
this.x = x;
this.y = y;
width = w;
height = h;
color = popUpColor;
steps = expansionSteps;
popUp = new Rectangle2D.Double(0, 0, width, height);
addMouseListener(this);
}
/**
* Draws the pop-up
* @param g Graphics object from paintComponent
*/
public final void draw(Graphics g) {
if(isExpanding)
expansionStage = Math.min(expansionStage + 1, steps);
else
expansionStage = Math.max(expansionStage - 1, 0);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
AffineTransform trans = new AffineTransform();
trans.translate(x + width/2 * (1 - (double) expansionStage/steps), y + height/2 * (1 - (double) expansionStage/steps));
trans.scale((double) expansionStage/steps, (double) expansionStage/steps);
setBounds((int) trans.getTranslateX(), (int) trans.getTranslateY(), (int) (width * expansionStage/steps), (int) (height * expansionStage/steps));
g2d.setColor(color);
Shape transformed = trans.createTransformedShape(popUp);
g2d.fill(transformed);
}
/**
* Sets whether the pop-up is expanding or not
* @param expanding Whether or not the pop-up should expand
*/
public final void setExpanding(boolean expanding) {
isExpanding = expanding;
}
@Override
public final void mouseClicked(MouseEvent e) {
isExpanding = false;
}
}
这是一个要运行的测试类：
public class Test extends JPanel implements ActionListener, MouseListener {
private static final long serialVersionUID = 1L;
private static PopUp popUp;
private int stringX = 610;
private int stringCounter = 0;
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setSize(600, 600);
Test t = new Test();
t.setBounds(0, 0, 600, 600);
frame.add(t);
t.setVisible(true);
Timer timer = new Timer(5, t);
popUp = new PopUp(100, 100, 400, 400, 100, Color.WHITE);
frame.add(popUp);
popUp.setVisible(true);
timer.start();
frame.addMouseListener(t);
frame.setLayout(null);
frame.setUndecorated(true);
frame.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent e) {
repaint();
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLACK);
g.fillRect(0, 0, 600, 600);
popUp.draw(g);
g.setColor(Color.WHITE);
g.drawString("This is a test", stringX, 580);
if(++stringCounter % 3 == 0) {
--stringX;
stringCounter = 0;
}
if(stringX == -10 - g.getFontMetrics().stringWidth("This is a test"))
stringX = 610;
}
@Override
public void mouseClicked(MouseEvent e) {
popUp.setExpanding(!popUp.getExpanding());
}
@Override
public void mousePressed(MouseEvent e) {}
@Override
public void mouseReleased(MouseEvent e) {}
@Override
public void mouseEntered(MouseEvent e) {}
@Override
public void mouseExited(MouseEvent e) {}
}
从上面的示例中可以看出，每次弹出窗口扩展或收缩时，从右向左滚动的文本都会加速。
答案 0 :(得分：2)
这是接收调用paintComponent()的重复更新事件时的预期行为;调整此AnimationTest的大小以重现效果。
为什么重复更新事件确实会导致这种情况？它背后的逻辑是什么？
draw()方法中对setBounds()的每次调用都会使组件层次结构无效。“ Component API可确保
当层次结构失效时，例如在更改组件边界或向容器添加/删除组件之后，必须通过最顶层调用的
Container.validate()方法验证整个层次结构。层次结构的无效容器。
因为validate()方法“可能是一个非常耗时的操作，”你可以“推迟层次结构的验证，直到一组与布局相关的操作完成，”当你展示here时;或者您可以使用javax.swing.Timer来说明动画，图示为here。
答案 1 :(得分：1)
好吧，我发现了问题。罪魁祸首就在这里：
router.post('/authenticate', function(req, res, next){
User.findOne({username: req.body.username}, function(err, user){
//handling errors
if(!bcrypt.compareSync(req.body.password, user.password)){
return res.status(401).json({
success: false,
message: 'Invalid login credentials!'
});
}
const token = jwt.sign({user: user}, 'secret', {expiresIn: 7200});
res.status(200).json({
success: true,
message: 'Successfully logged in',
token: token,
userId: user._id
});
});
});
显然，快速连续地将JPanel缩放到不同的大小会导致一些速度变形，原因我不知道。我很欣赏这个答案的编辑，并对这种现象有更好的解释。
我只是为JPanel设置了一个静态大小，让图形完成剩下的工作。