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我试图解决这个问题，当我终于找到它背后的原因时 - 调用静态方法 get_mouse_x() 和 get_mouse_y() 根据调用位置返回不同的结果：如果它是从对象的 update() 方法调用的，它总是返回 0.0，而如果它从 draw() 方法调用，它返回有效的答案。

按钮类（出现问题的地方）：

public abstract class Button extends Drawable_object {
...
 @Override
public void update()
{
    super.update();
    mouseOver_last = mouseOver;

     mx = Game_logic.get_mouse_x();
     my = Game_logic.get_mouse_y();
     // for some reasons mx and my are always 0.0

    if ((mx <= x + ((double)width / 2))&&
       (mx >= x  - ((double)width / 2))&&
       (my >= y  - ((double)height / 2))&&
       (my <= y  + ((double)height / 2)))

    { mouseOver = true;}
    else mouseOver = false;
    ...
    }

@Override
public void draw(Graphics g)
{
    super.draw (g);
    g.drawString ("x - width / 2 = " + String.valueOf(x - width), 10, 30);
    g.drawString ("mouse_x = " + String.valueOf(Game_logic.get_mouse_x()), 10, 40);
    // at this point get_mouse_x() returns true result

    g.drawString ("x + width / 2 = " + String.valueOf(x + width), 10, 50);

    g.drawString ("y - width / 2 = " + String.valueOf(y - width), 200, 30);
    g.drawString ("mouse_y= " + String.valueOf(Game_logic.get_mouse_y()), 200, 40);
    // at this point get_mouse_y() returns true result

    g.drawString ("y + width / 2 = " + String.valueOf(y + width), 200, 50);

    g.drawString ("mouseOver = " + String.valueOf(mouseOver), 10, 80);
    ...
    }

...
}

鼠标坐标在 Board 类中使用 MouseAdapter 设置：

public class Board extends JPanel implements ActionListener {

...

 private class MAdapter2 extends MouseAdapter {
    @Override
    public void mouseMoved(MouseEvent e) {
        Game_logic.set_mouse_x(e.getX());
        Game_logic.set_mouse_y(e.getY());
    }

}

...

}

所有的东西都在同一个 Board 类中更新和绘制：

public void actionPerformed(ActionEvent e) {

update(); // calls update() method in every object
checkCollisions(); //checks collision
repaint(); // calls draw() method in every drawable object

}

那么为什么在对象的 update() 方法中调用 Game_logic.get_mouse_x() 和 Game_logic.get_mouse_y() 会返回 0.0 的值，而在对象的 draw() 方法中调用它们总是返回正确的值呢？

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0 回答 0