如果您想要以设定的时间间隔安排更新,javax.swing.Timer
会为其提供Swing集成服务。 Timer
定期在EDT上运行其任务,而没有显式循环。 (明确的循环会阻止EDT处理事件,这会冻结UI,我更深入地解释了here)。
最终在Swing中做任何类型的绘画,你仍然会做两件事:
- 覆盖
paintComponent
做你的绘画。
- 根据需要调用
repaint
以请求使您的图形可见。 (Swing通常只在需要时才重新绘制,例如当某个其他程序的窗口经过Swing组件顶部时)。
如果您正在做这两件事,那么您可能做得很对。 Swing并没有真正具有动画的高级API。它的设计主要是考虑绘制GUI组件。它当然可以做一些好的事情,但是你必须从头开始编写一个组件,就像你正在做的那样。
Painting in AWT and Swing涵盖了一些'幕后'的东西,如果你没有书签。
您可能会查看JavaFX。我个人不太了解它,但它应该更适合动画。
作为一种优化,可以做的一件事就是在单独的图像上绘制图像,然后在paintComponent
上将图像绘制到面板上。如果绘画很长时,这是特别有用的:重绘可以由系统调度,以便在发生更多控制时保持重绘。
如果您未绘制图像,则需要用对象构建模型,并在paintComponent
内每次绘制所有模型。
这里画上一个形象的例子:
import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
/**
* Holding left-click draws, and
* right-clicking cycles the color.
*/
class PaintAnyTime {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new PaintAnyTime();
}
});
}
Color[] colors = {Color.red, Color.blue, Color.black};
int currentColor = 0;
BufferedImage img = new BufferedImage(256, 256, BufferedImage.TYPE_INT_ARGB);
Graphics2D imgG2 = img.createGraphics();
JFrame frame = new JFrame("Paint Any Time");
JPanel panel = new JPanel() {
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Creating a copy of the Graphics
// so any reconfiguration we do on
// it doesn't interfere with what
// Swing is doing.
Graphics2D g2 = (Graphics2D) g.create();
// Drawing the image.
int w = img.getWidth();
int h = img.getHeight();
g2.drawImage(img, 0, 0, w, h, null);
// Drawing a swatch.
Color color = colors[currentColor];
g2.setColor(color);
g2.fillRect(0, 0, 16, 16);
g2.setColor(Color.black);
g2.drawRect(-1, -1, 17, 17);
// At the end, we dispose the
// Graphics copy we've created
g2.dispose();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(img.getWidth(), img.getHeight());
}
};
MouseAdapter drawer = new MouseAdapter() {
boolean rButtonDown;
Point prev;
@Override
public void mousePressed(MouseEvent e) {
if (SwingUtilities.isLeftMouseButton(e)) {
prev = e.getPoint();
}
if (SwingUtilities.isRightMouseButton(e) && !rButtonDown) {
// (This just behaves a little better
// than using the mouseClicked event.)
rButtonDown = true;
currentColor = (currentColor + 1) % colors.length;
panel.repaint();
}
}
@Override
public void mouseDragged(MouseEvent e) {
if (prev != null) {
Point next = e.getPoint();
Color color = colors[currentColor];
// We can safely paint to the
// image any time we want to.
imgG2.setColor(color);
imgG2.drawLine(prev.x, prev.y, next.x, next.y);
// We just need to repaint the
// panel to make sure the
// changes are visible
// immediately.
panel.repaint();
prev = next;
}
}
@Override
public void mouseReleased(MouseEvent e) {
if (SwingUtilities.isLeftMouseButton(e)) {
prev = null;
}
if (SwingUtilities.isRightMouseButton(e)) {
rButtonDown = false;
}
}
};
PaintAnyTime() {
// RenderingHints let you specify
// options such as antialiasing.
imgG2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
imgG2.setStroke(new BasicStroke(3));
//
panel.setBackground(Color.white);
panel.addMouseListener(drawer);
panel.addMouseMotionListener(drawer);
Cursor cursor =
Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR);
panel.setCursor(cursor);
frame.setContentPane(panel);
frame.pack();
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
如果程序是长时间运行并重新绘制可能同时发生,也可使用双缓冲。将图像与所显示的图像分开进行绘制。然后,当绘图程序完成时,图像引用被交换,因此更新是无缝的。例如,您通常应该对游戏使用双缓冲。双缓冲可防止图像以部分状态显示。例如,如果您在游戏循环中使用后台线程(而不是Timer
),并且重绘发生在游戏正在进行绘画时,就可能发生这种情况。如果没有双缓冲,这种情况会导致闪烁或撕裂。
默认情况下,Swing组件是双缓冲区,所以如果所有绘图都在EDT上进行,则不需要自己编写双缓冲区逻辑。 Swing已经做到了。
这是一个较为复杂的例子显示了一个长时间运行的任务和缓冲交换:
import java.awt.*;
import javax.swing.*;
import java.awt.image.*;
import java.awt.event.*;
import java.util.*;
/**
* Left-click to spawn a new background
* painting task.
*/
class DoubleBuffer {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new DoubleBuffer();
}
});
}
final int width = 640;
final int height = 480;
BufferedImage createCompatibleImage() {
GraphicsConfiguration gc =
GraphicsEnvironment
.getLocalGraphicsEnvironment()
.getDefaultScreenDevice()
.getDefaultConfiguration();
// createCompatibleImage creates an image that is
// optimized for the display device.
// See http://docs.oracle.com/javase/8/docs/api/java/awt/GraphicsConfiguration.html#createCompatibleImage-int-int-int-
return gc.createCompatibleImage(width, height, Transparency.TRANSLUCENT);
}
// The front image is the one which is
// displayed in the panel.
BufferedImage front = createCompatibleImage();
// The back image is the one that gets
// painted to.
BufferedImage back = createCompatibleImage();
boolean isPainting = false;
final JFrame frame = new JFrame("Double Buffer");
final JPanel panel = new JPanel() {
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Scaling the image to fit the panel.
Dimension actualSize = getSize();
int w = actualSize.width;
int h = actualSize.height;
g.drawImage(front, 0, 0, w, h, null);
}
};
final MouseAdapter onClick = new MouseAdapter() {
@Override
public void mousePressed(MouseEvent e) {
if (!isPainting) {
isPainting = true;
new PaintTask(e.getPoint()).execute();
}
}
};
DoubleBuffer() {
panel.setPreferredSize(new Dimension(width, height));
panel.setBackground(Color.WHITE);
panel.addMouseListener(onClick);
frame.setContentPane(panel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
void swap() {
BufferedImage temp = front;
front = back;
back = temp;
}
class PaintTask extends SwingWorker<Void, Void> {
final Point pt;
PaintTask(Point pt) {
this.pt = pt;
}
@Override
public Void doInBackground() {
Random rand = new Random();
synchronized(DoubleBuffer.this) {
Graphics2D g2 = back.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,
RenderingHints.VALUE_STROKE_PURE);
g2.setBackground(new Color(0, true));
g2.clearRect(0, 0, width, height);
// (This computes pow(2, rand.nextInt(3) + 7).)
int depth = 1 << (rand.nextInt(3) + 7);
float hue = rand.nextInt(depth);
int radius = 1;
int c;
// This loop just draws concentric circles,
// starting from the inside and extending
// outwards until it hits the outside of
// the image.
do {
int rgb = Color.HSBtoRGB(hue/depth, 1, 1);
g2.setColor(new Color(rgb));
int x = pt.x - radius;
int y = pt.y - radius;
int d = radius * 2;
g2.drawOval(x, y, d, d);
++radius;
++hue;
c = (int) (radius * Math.cos(Math.PI/4));
} while (
(0 <= pt.x - c) || (pt.x + c < width)
|| (0 <= pt.y - c) || (pt.y + c < height)
);
g2.dispose();
back.flush();
return (Void) null;
}
}
@Override
public void done() {
// done() is completed on the EDT,
// so for this small program, this
// is the only place where synchronization
// is necessary.
// paintComponent will see the swap
// happen the next time it is called.
synchronized(DoubleBuffer.this) {
swap();
}
isPainting = false;
panel.repaint();
}
}
}
绘画程序只是打算画垃圾这需要很长的时间:
我不会看JavaFX,因为我时间不多,但谢谢。我正在做这两件事。此外,每次模拟更新时窗口都应该重新绘制,因此现在我可以不使用定时器。 – corazza
这是非常缓慢的,除非你手工加倍缓冲,FYI –
@DanielMurphy当然可以做出优化,但这不是问题。请注意,所有Swing组件默认都是双缓冲的,因此更优雅的优化方法是对图像执行自定义图像绘制,并在重新绘制的面板上绘制图像。没有必要加倍缓冲。 – Radiodef