矩形应该在屏幕上移动但消失了

Question

所以我想做一个迷你 "tower defense" 游戏。现在，我目前的问题是我无法将图片框设置为 "shoot" 矩形 "bullet"

我在开头声明了这些变量

    Rectangle Bullet = new Rectangle(225, 400, 10, 25); //position of this shouldn't matter since it's not drawed instantly and it's later moved moved under the picturebox.
    private bool bulletIsActive = false;
    private int update_speed = 250;

此外，定时器被声明为 AFTER InitializeComponent();

        InitializeComponent();
        timer1.Interval = update_speed;
        timer1.Start();

我有用于按键的事件处理程序，而且我有（只包括 Keys.Space 因为其他的无关紧要。

private void Paaikkuna_KeyDown(object sender, KeyEventArgs e)
    {
            case Keys.Space:
                if(bulletIsActive == false)
                {
                    bulletIsActive = true; //set bool bullet to true and draw the bullet

                    Bullet.Location = new Point(playerX, playerY); //set bullet location at picturebox
                }
                break;

那我有Paaikkuna_paint（形式明显）

private void Paaikkuna_Paint(object sender, PaintEventArgs e)
    {
        if(bulletIsActive == true) //if bulletIsActive == true (Which happens when I press space, draw bullet)
        {
             e.Graphics.DrawRectangle(Pens.Blue, Bullet); 
        }

一切正常，当我按 space 并将 "tower"（图片框）移动到任一侧时，矩形就会在那里。但是问题来了

我的想法是使用 timer_tick 移动子弹，代码如下所示。它应该在每个计时器滴答声中移动 Bullet -10Y，但相反，它只是消失了。

        private void timer1_Tick(object sender, EventArgs e)
    {
        int bulletY = Bullet.Location.Y;
        int bulletX = Bullet.Location.X;

        if (bulletY>-10 && bulletIsActive == true) //checks if Bullet.Location.Y is >-10 (if not, it's not on screen and it can be "killed") and also if bullet == true
        {
            Bullet.Location = new Point(bulletX, bulletY - 10);
        }
        else
        {
            bulletIsActive = false;
        }

    }

TL;DR 矩形 "disappears" 即使坐标表明它应该在图片框上方的屏幕上向上移动。

我真的不知道为什么会这样，已经尝试了很多东西。

这里有完整代码http://pastebin.com/WVpLzxUT（如果你想看得更清楚）

Answer 1

如果 Bullet 是一个 Rectangle 并且您希望它在每个 Tick 的新坐标上绘制，您需要 Invalidate Control 它应该画在：

private void timer1_Tick(object sender, EventArgs e)
{
    int bulletY = Bullet.Location.Y;
    int bulletX = Bullet.Location.X;

    //checks if Bullet.Location.Y is >-10 
    //(if not, it's not on screen and it can be "killed") 
    //and also if bullet == true
    if (bulletY > -10 && bullet == true) 
    {
        Bullet.Location = new Point(bulletX, bulletY - 10);
        Paaikkuna.Invalidate();   // <-- trigger the paint event!
    }
    else
    {
        bullet = false;
    }

}

顺便说一句：您应该 1) 更好地命名它，例如 bulletIsActive，而不是 if (bullet == true) 和 2) 使用它具有的数据类型 bool：if (bulletIsActive)

矩形应该在屏幕上移动但消失了

Rectangle is supposed to move on the screen but disappears instead

.net

c#

drawing