Java动画：旋转图像

Question

我有一个非常简单的Java动画任务。我需要创建一个基本的“财富之轮小程序”。基本上显示的是一个轮子和一个按钮。当按下该按钮时，我希望它选择一个随机的度数（例如在720-3600的范围内）并旋转许多度数的轮子。然后，我将使用一些逻辑将该学位数转换为货币价值。我的问题是在动画中，如何让图像以恒定的速度旋转x度？有没有摆动功能？非常感谢您的帮助，除此之外，我现在不需要了解关于Java动画的其他任何信息。

Answer 1

我打算假设您了解如何旋转图像一次。如果你不这样做，你可以通过快速的谷歌搜索找到。

你需要的是一个为你旋转它的后台进程。它的工作原理是这样的：

/** 
* Warning - this class is UNSYNCHRONIZED! 
*/ 
public class RotatableImage { 
    Image image; 
    float currentDegrees; 

    public RotateableImage(Image image) { 
     this.image = image; 
     this.currentDegrees = 0.0f; 
     this.remainingDegrees = 0.0f; 
    } 

    public void paintOn(Graphics g) { 
     //put your code to rotate the image once in here, using current degrees as your rotation 
    } 

    public void spin(float additionalDegrees) { 
     setSpin(currentDegrees + additionalDegrees); 
    } 

    public void setSpin(float newDegrees) { 
     currentDegrees += additionalDegrees; 
     while(currentDegrees < 0f) currentDegrees += 360f; 
     while(currentDegrees >= 360f) currentDegrees -= 360f; 
    } 

} 

public class ImageSpinner implements Runnable { 
    RotateableImage image; 
    final float totalDegrees; 
    float degrees; 
    float speed; // in degrees per second 
    public ImageSpinner(RotatableImage image, float degrees, float speed) { 
     this.image = image; 
     this.degrees = degrees; 
     this.totalDegrees = degrees; 
     this.speed = speed; 
    } 

    public void run() { 
     // assume about 40 frames per second, and that the it doesn't matter if it isn't exact 
     int fps = 40; 
     while(Math.abs(degrees) > Math.abs(speed/fps)) { // how close is the degrees to 0? 
      float degreesToRotate = speed/fps; 
      image.spin(degreesToRotate); 
      degrees -= degreesToRotate; 
      /* sleep will always wait at least 1000/fps before recalcing 
       but you have no guarantee that it won't take forever! If you absolutely 
       require better timing, this isn't the solution for you */ 
      try { Thread.sleep(1000/fps); } catch(InterruptedException e) { /* swallow */ } 
     } 
     image.setSpin(totalDegrees); // this might need to be 360 - totalDegrees, not sure 
    } 

}