XNA - Mouse.Left Button gets executed more than once in Update

Question

I am making a Tic-Tac-Toe game. I need to check if a player is clicking on a square they have already clicked. Problem is error is shown in the first click itself. My update code is: ``` MouseState mouse = Mouse.GetState(); int x, y; int go = 0; if (mouse.LeftButton == ButtonState.Pressed) { showerror = 0; gamestate = 1; x = mouse.X; y = mouse.Y; int getx = x / squaresize; int gety = y / squaresize; for (int i = 0; i < 3; i++) { if (go == 1) { break; } for (int j = 0; j < 3; j++) { if (getx == i && gety == j) { if (storex[i, j] == 0) { showerror = 1; } go = 1; if (showerror != 1) { loc = i; loc2 = j; storex[i, j] = 0; break; } } } } } ``` `showerror` is set to 0 whenever left button is clicked. My matrix is a 3x3 matrix for storing information. If it is 0 that means it has been already clicked.So in the loop I check if `store[i,j] == 0` then set `showerror` to 1. Now in the draw function I made this call for showerror ``` spriteBatch.Begin(); if (showerror == 1) { spriteBatch.Draw(inv…

Accepted Answer

How to Fix:

Add a new global variable to store the mouse state from the previous frame:

```
MouseState oldMouseState;
```

At the very beginning (or end) of your update method, add this,

```
oldMouseState = mouse;
```

And replace

```
if (mouse.LeftButton == ButtonState.Pressed)
```

with

```
if (mouse.LeftButton == ButtonState.Pressed && oldMouseState.LeftButton == ButtonState.Released)
```

What this does is check if you made one click, having the key released then pressing, because sometimes you may hold the key for multiple frames.

To Recap:

By setting `oldMouseState` before you update the `currentMouseState` (Or after you are done with it), you garantee that `oldMouseState` will be one frame behind `currentMouseState`. Using this you can check if a button was down the previous frame, but not anymore, and handle input accordingly. A good idea to extend this is write some extension methods like `IsHolding()`, `IsClicking()`, etc.

In simple code:

```
private MouseState oldMouseState, currentMouseState;
protected override void Update(GameTime gameTime)
{
     oldMouseState = currentMouseState;
     currentMouseState = Mouse.GetState();
     //TODO: Update your code here
}
```

XNA - Mouse.Left Button gets executed more than once in Update

Solution

Problem