Button 如何在屏幕宽度和高度范围内对Unity按钮进行简单的拖放

我是一名android开发人员，现在正在尝试使用unity。我试图用下面的代码在按钮上进行简单的拖放，但当我拖动到极限时，按钮就会丢失，我需要在屏幕宽度和高度范围内进行拖动，并且仅当我拖动按钮时进行。因此，我对Unity是新手，我需要您的指导。我从Unity论坛获得以下代码

public class UserInterface : MonoBehaviour {
public Rect playerPositionRect = new Rect(0, 151, 200, 50);
private Vector2 currentDrag = new Vector2();

void Start () {

}

void Update () {

}

void OnGUI(){
    GUI.Box (playerPositionRect, "MyButton" );

    Vector2 screenMousePosition = new Vector2(Input.mousePosition.x, Screen.height - Input.mousePosition.y);
    if (currentDrag.sqrMagnitude != 0 || playerPositionRect.Contains(screenMousePosition)) {
        if (Input.GetMouseButtonDown(0)) {
            currentDrag = screenMousePosition;
        } else if (Input.GetMouseButton(0)) {
            playerPositionRect.x += (screenMousePosition.x - currentDrag.x);
            playerPositionRect.y += (screenMousePosition.y - currentDrag.y);

            currentDrag = screenMousePosition;
        } else {
            currentDrag.x = 0;
            currentDrag.y = 0;
        }
    }
 }
}

---

移动按钮后，您需要确保其仍在屏幕内。屏幕边缘是屏幕。宽度，屏幕。高度，0和0，如果它在外面，我们就把它移回去。当我们在屏幕的右侧和底部时，我们还需要调整按钮的高度和宽度

else if (Input.GetMouseButton(0)) {
  playerPositionRect.x += (screenMousePosition.x - currentDrag.x);
  playerPositionRect.y += (screenMousePosition.y - currentDrag.y);

  playerPositionRect.x = Mathf.Clamp(playerPositionRect.x, 0, Screen.width - playerPositionRect.width);
  playerPositionRect.y = Mathf.Clamp(playerPositionRect.y, 0, Screen.height - playerPositionRect.height);

  currentDrag = screenMousePosition;
}

如果值超出范围，则Clamp只会剪切该值，因此，例如-5的x值将为0，或者10000000的值将为Screen.width-playerPositionRect.width