C# - 防止圖片框離開邊界

Question

我有一個名為 player 的圖片框和 4 個在游戲開始時充當邊界的圖片框。 如果按下某個鍵，我將執行以下代碼：

private void HorrorForm_KeyDown(object sender, KeyEventArgs e)
        {
            int x = player.Location.X;
            int y = player.Location.Y;

            if (e.KeyCode == Keys.D)
                x += 7;
            if (e.KeyCode == Keys.A)
                x -= 7;
            if (e.KeyCode == Keys.S)
                y += 7;
            if (e.KeyCode == Keys.W)
                y -= 7;

            if (player.Bounds.IntersectsWith(openspot1.Bounds) || player.Bounds.IntersectsWith(openspot2.Bounds) || player.Bounds.IntersectsWith(openspot3.Bounds) || player.Bounds.IntersectsWith(openspot4.Bounds))
            {
                player.Location = new Point(player.Location.X - 1, player.Location.Y - 1);
            }

            player.Location = new Point(x, y);
        }

我如何移動玩家但阻止他離開邊界？

Answer 1

有一種觀點認為您的代碼不正確，至少我是這么認為的。

1. 你總是將玩家移動到他的新位置。 你確實檢查他是否觸及邊界。 如果他觸及邊界，您將他向上移動 1 個像素，向左移動 1 個像素，然后將他移動到所選方向的 7 個像素。 因此，在檢查他是否觸及邊界的if內部，您必須中斷並且不要執行設置新位置的其余代碼。 簡單的return; 會做的工作。

2. 如果按下某個鍵，您將執行邊界檢查，如果玩家未觸及邊界，您將移動玩家。 這是錯誤的順序。 您必須檢查玩家在移動后是否會觸及邊界，並且只有當他不會觸及邊界時才會移動他。 否則你會把他移到邊界內，再也不會把他弄出來。

所以這是您的代碼，並進行了一些更正：

private void HorrorForm_KeyDown(object sender, KeyEventArgs e)
{
    int x = player.Location.X;
    int y = player.Location.Y;

    if (e.KeyCode == Keys.D)
        x += 7;
    if (e.KeyCode == Keys.A)
        x -= 7;
    if (e.KeyCode == Keys.S)
        y += 7;
    if (e.KeyCode == Keys.W)
        y -= 7;

    var tempPlayerPosition= player.Bounds; // get the players position and remember it temporary
    tempPlayerPosition.X = x; // change the players temporary pisition to the new one that it will have after the move
    tempPlayerPosition.Y = y;

    //check if the play would touch the boundyries if we use the new temporary pisition
    if (tempPlayerPosition.IntersectsWith(openspot1.Bounds) || 
        tempPlayerPosition.IntersectsWith(openspot2.Bounds) || 
        tempPlayerPosition.IntersectsWith(openspot3.Bounds) || 
        tempPlayerPosition.IntersectsWith(openspot4.Bounds))
    {
        return; //if he would touch the boundary, then do nothing
    }

    player.Location = new Point(x, y); //if he would not touch the boundary, move him to his new location
}

但也許你也想

• 如果按下的鍵不是 W、S、A 或 D，則防止您的代碼被執行（即使他沒有更改任何值）。
• 使用switch而不是if這使它更具可讀性。
• 不是每次都寫數字 7，而是使用局部變量，因此如果將來要更改此值，您只需更改一個值。

所以我的建議是這樣的：

private void HorrorForm_KeyDown(object sender, KeyEventArgs e)
{    
    var oneStep = 7; // define the amount of pixel the player will be moved
    var tempPlayerPosition = player.Bounds;// get the players position and remember it temporary

    switch (e.KeyCode) // check which key was presses
    {
        case Keys.D:
            tempPlayerPosition.X += oneStep; // move right
            break;
        case Keys.A:
            tempPlayerPosition.X -= oneStep; // move left
            break;
        case Keys.S:
            tempPlayerPosition.Y += oneStep; // move down
            break;
        case Keys.W:
            tempPlayerPosition.Y -= oneStep; // move up
            break;
         default: // you may wan't to do nothing if there any other key presses...
            return;
    }

    //check if the play would touch the boundyries if we use the new temporary pisition
    if (tempPlayerPosition.IntersectsWith(openspot1.Bounds) || 
        tempPlayerPosition.IntersectsWith(openspot2.Bounds) || 
        tempPlayerPosition.IntersectsWith(openspot3.Bounds) || 
        tempPlayerPosition.IntersectsWith(openspot4.Bounds))
    {
        return; //if he would touch the boundary, then do nothing
    }

    player.Location = new Point(tempPlayerPosition.X, tempPlayerPosition.Y);   //if he would not touch the boundary, move him to his new location
}

這對你有幫助嗎？