Java 2d 方向鼠标点旋转
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Java 2d rotation in direction mouse point
提问by 36redsoxfan
So far I have a java app where I draw a circle(player) and then draw a green rectangle on top(gun barrel). I have it so when the player moves, the barrel follows with it. I want it to find where the mouse is pointing and then rotate the barrel accordingly. For an example of what I mean look at this video I found http://www.youtube.com/watch?v=8W7WSkQq5SUSee how the player image reacts when he moves the mouse around?
到目前为止，我有一个 Java 应用程序，我在其中绘制了一个圆圈（玩家），然后在顶部（枪管）绘制了一个绿色矩形。我有它，所以当玩家移动时，枪管随之而来。我希望它找到鼠标指向的位置，然后相应地旋转桶。举个例子，看看这个视频，我发现http://www.youtube.com/watch?v=8W7WSkQq5SU看看当玩家移动鼠标时播放器图像如何反应？
Here's an image of what the game looks like so far:
这是到目前为止游戏的样子：
So how do I rotate it like this? Btw I don't like using affinetransform or Graphics2D rotation. I was hoping for a better way. Thanks
那么我如何像这样旋转它？顺便说一句，我不喜欢使用仿射变换或 Graphics2D 旋转。我希望有更好的方法。谢谢
回答by Zong
Using the Graphics2Drotation method is indeed the easiest way. Here's a simple implementation:
使用Graphics2D旋转方法确实是最简单的方法。这是一个简单的实现：
int centerX = width / 2;
int centerY = height / 2;
double angle = Math.atan2(centerY - mouseY, centerX - mouseX) - Math.PI / 2;
((Graphics2D)g).rotate(angle, centerX, centerY);
g.fillRect(...); // draw your rectangle
If you want to remove the rotation when you're done so you can continue drawing normally, use:
如果要在完成后删除旋转以便可以继续正常绘制，请使用：
Graphics2D g2d = (Graphics2D)g;
AffineTransform transform = g2d.getTransform();
g2d.rotate(angle, centerX, centerY);
g2d.fillRect(...); // draw your rectangle
g2d.setTransform(transform);
It's a good idea to just use Graphics2Danyway for anti-aliasing, etc.
Graphics2D无论如何，将其用于抗锯齿等是个好主意。
回答by MadProgrammer
Using AffineTransform, sorry, only way I know how :P
使用AffineTransform，抱歉，只有我知道如何使用 :P
public class RotatePane extends javax.swing.JPanel {
private BufferedImage img;
private Point mousePoint;
/**
* Creates new form RotatePane
*/
public RotatePane() {
try {
img = ImageIO.read(getClass().getResource("/MT02.png"));
} catch (IOException ex) {
ex.printStackTrace();
}
addMouseMotionListener(new MouseAdapter() {
@Override
public void mouseMoved(MouseEvent e) {
mousePoint = e.getPoint();
repaint();
}
});
}
@Override
public Dimension getPreferredSize() {
return new Dimension(img.getWidth(), img.getHeight());
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
double rotation = 0f;
int width = getWidth() - 1;
int height = getHeight() - 1;
if (mousePoint != null) {
int x = width / 2;
int y = height / 2;
int deltaX = mousePoint.x - x;
int deltaY = mousePoint.y - y;
rotation = -Math.atan2(deltaX, deltaY);
rotation = Math.toDegrees(rotation) + 180;
}
int x = (width - img.getWidth()) / 2;
int y = (height - img.getHeight()) / 2;
g2d.rotate(Math.toRadians(rotation), width / 2, height / 2);
g2d.drawImage(img, x, y, this);
x = width / 2;
y = height / 2;
g2d.setStroke(new BasicStroke(3));
g2d.setColor(Color.RED);
g2d.drawLine(x, y, x, y - height / 4);
g2d.dispose();
}
}
Will produce this effect
会产生这种效果
The red line (point out from the center) will want to follow the cursor.
红线（从中心点出来）将要跟随光标。
