Having troubles moving sprite across the screen using the arrow keys?

[CookieMonster]

Hi I'm having trouble with moving the sprite across the screen, the sprite move but it's not smooth. For example when I press the right arrow key the sprite moves on the spot, but shifts right after the 'loop'. I don't know how to explain this but i hope you understand

this is my code:

Turing:

%Declare Variables var chars : array char of boolean var pics : array 0 .. 6 of int var sprite, standR, standRID, standL, standLID : int var x,y : int x:=200 y:=200 %Initialize standing sprite standRID := Pic.FileNew ("standR.bmp") standR := Sprite.New (standRID) standLID := Pic.FileNew ("standL.bmp") standL := Sprite.New (standLID) %Starting picture Sprite.SetPosition (standL, x,y, true) Sprite.Show (standL) % %For each key press repeat % loop     Input.KeyDown (chars)     %         %     %If the user presses the right arrow key     %     if chars (KEY_RIGHT_ARROW) then         %         %Hides the standing still sprite         %         Sprite.Hide (standR)         Sprite.Hide (standL)         %         % Loading each picture into the array         %         for i : 1 .. 7                 x := x + 5             pics (i - 1) := Pic.FileNew ("right" + intstr (i) + ".bmp")                            delay (20)             if Error.Last not= 0 then                 put "Error loading image: ", Error.LastMsg                 return                         end if         end for         sprite := Sprite.New (pics (0))         %         %Animate picture         %         for i : 1 .. 10             Sprite.ChangePic (sprite, pics (i mod 6))             Sprite.SetPosition (sprite, x,y, true)             Sprite.Show (sprite)             delay (80)         end for         Sprite.Free (sprite)         Sprite.SetPosition (standR, x,y, true)         Sprite.Show (standR)     end if     %     %If the user presses the left arrow key     %     if chars (KEY_LEFT_ARROW) then         %         %Hides the standing still sprite         %         Sprite.Hide (standL)         Sprite.Hide (standR)         %         % Loading each picture into the array         %         for i : 1 .. 7         x := x - 5             pics (i - 1) := Pic.FileNew ("left" + intstr (i) + ".bmp")             if Error.Last not= 0 then                 put "Error loading image: ", Error.LastMsg                 return             end if         end for         sprite := Sprite.New (pics (0))         Sprite.SetPosition (sprite, x,y, true)         Sprite.Show (sprite)         %         %Animate picture         %         for i : 1 .. 10             Sprite.ChangePic (sprite, pics (i mod 6))             delay (80)         end for         Sprite.Free (sprite)         Sprite.SetPosition (standL, x,y, true)         Sprite.Show (standL)     end if     %     end loop

What's wrong with it? D:

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Mod Edit:
Please wrap you code in either of the following in order to preserve whitespace (indentation) and to highlight the syntax.

code:

[syntax="turing"] ... code ... [/syntax] [code] ... code ... [/code ]

[Zren]

You should only be drawing one complete picture (frame) for each iteration of the main game loop. I'll provide an example after this next bit.

Since having animations play as you move is slightly more complicated, let's first work our way up to that point.

Step 1: Draw a black box.
Step 2: Have that box react to keyboard input.
Step 3: Replace black box with 1 static/unchanging picture.
Step 4: Change the picture according to which direction the "box" is moving in. Make him face left/right/up/down etc.

To do step 4, instead of doing like you are doing:

Turing:

loop     if chars (KEY_LEFT_ARROW) then         for i : 1 .. 10             characterX -= moveSpeed % Move character left             % Draw sprite i         end for     end for end loop

Try and break up where you process your game logic and where you draw things. This will help you make your games more complicated later on.

Turing:

loop     % Input     Input.Keydown(chars)         % Logic     % Have previous game state react to input.     if chars (KEY_LEFT_ARROW) then         characterX -= moveSpeed % Move character left         characterState = "face left"     elsif chars (KEY_RIGHT_ARROW) then         elsif ...         else         % Standing     end for         % Draw     picturePath := characterState + ".png" % Eg: "face left.png"     picId := Pic.FileNew(picturePath)     Pic.Draw(picId, ...)     Pic.Free(picId)         % Frame Rate Control     delay(...) end loop

Note that loading a picture, then freeing it every frame is extremely inefficient, but it will make it much easier to do reach our final goal without learning about arrays/hashmaps.


Alright, lets check our goal.

Step ?: Play animations as the character moves.

For your goal, you have to distinguish when you're currently holding the button down (to continue the animation) and when you first press the button down (to change and start a new animation) and when you release that button (to change back the standing animation).

Step 5: Distinguish when the key was just pressed down.

For this, we need to remember the last keyboard state. To do this, just make another variable to store it into before updating it.

You're going to need to default the values of chars and charsLast before starting the loop, so that you don't get errors stating when you try charsLast := chars.

Turing:

% Initialize Input.Keydown(chars) Input.Keydown(charsLast) loop     % Input     charsLast := chars % Remember last keyboard state     Input.Keydown(chars)         % Logic     if charsLast (KEY_LEFT_ARROW) and chars (KEY_LEFT_ARROW) then         % Still holding down the key     elsif not charsLast (KEY_LEFT_ARROW) and chars (KEY_LEFT_ARROW) then         % Just pressed the key     elsif charsLast (KEY_LEFT_ARROW) and not chars (KEY_LEFT_ARROW) then         % Just released the key     end if end loop

Since doing this code for all 4 arrow keys will seem repetitive, with the only thing changing between them being the placement of the not, making things harder to read. I suggest using functions.

Turing:

function KeyPushedDown (c : char) : boolean     result not charsLast (c) and chars (c) end KeyPushedDown ... loop     ...         % Logic     if KeyHeldDown (KEY_LEFT_ARROW) then         % Still holding down the key     elsif KeyPushedDown(KEY_LEFT_ARROW) then         % Just pressed the key     elsif KeyReleased(KEY_LEFT_ARROW) then         % Just released the key     end if end loop

Step 6: Use a variable to represent which picture in the animation we're on.

Eg:

Turing:

characterState := "walk left" characterStateFrame := 2 picturePath := characterState + characterStateFrame + ".png" % "walk left2.png"

We then increment that variable (characterStateFrame) every frame. We should also reset it to 0 (the start of the animation) whenever we change animations (whenever characterState is changed).

/mini tutorial