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First of all, I already did ask this in SFML forums but they couldn't help, they actually copied my code and it worked perfectly, even with someone with the same OS as me (Windows 8)

I'm currently reading the SFML Game Development book, in the first chapter, when movement is introduced, I encountered some problems, I spawn a white circle in the centre of the window, now If i press any directional arrow, the circle keeps going in the other direction till I press it, and then it gets back to normal, and horizontal and vertical ones are seperate.

Example: I start "Game", press up, the circle keeps going down, i hold up, the circle stands still, I release, it keeps going down, I press down, it stops, now it responds normally to both keys, it will happen again with the right and left, it gets fixed after the initial error, but I wish to know how I can remove it

#include <SFML/Graphics.hpp>
using namespace sf;

class Game
{
    public:Game();
        void run();

    private:
        void processEvents();
        void update(Time);
        void render();
        void handlePlayerInput(Keyboard::Key,bool);

        bool mIsMovingUp, mIsMovingRight, mIsMovingLeft, mIsMovingDown;
        float playerSpeed;
        Time TimePerFrame;


    private:
        RenderWindow mWindow;
        CircleShape mPlayer;
};

Game::Game():mWindow(VideoMode(640, 480), "SFML Application"),mPlayer(), playerSpeed(20.f), TimePerFrame(seconds(1.f / 60.f))
{
    mPlayer.setRadius(20.f);
    mPlayer.setPosition(220.f, 220.f);
    mPlayer.setFillColor(Color::White);
}

void Game::handlePlayerInput(Keyboard::Key key, bool isPressed)
{
    if (key == Keyboard::W || key == Keyboard::Up)
        mIsMovingUp = isPressed;
    else if (key == Keyboard::S || key == Keyboard::Down)
        mIsMovingDown = isPressed;
    else if (key == Keyboard::A || key == Keyboard::Left)
        mIsMovingLeft = isPressed;
    else if (key == Keyboard::D || key == Keyboard::Right)
        mIsMovingRight = isPressed;
}

void Game::run()
{
    Clock clock;
    Time timeSinceLastUpdate = Time::Zero;
    while (mWindow.isOpen())
    {
        processEvents();
        timeSinceLastUpdate += clock.restart();
        while (timeSinceLastUpdate > TimePerFrame)
        {
            timeSinceLastUpdate -= TimePerFrame;
            processEvents();
            update(TimePerFrame);
        }
    render();
    }
}

void Game::processEvents()
{
    Event event;
    while (mWindow.pollEvent(event))
    {
        switch (event.type)
        {
            case Event::KeyPressed:
                handlePlayerInput(event.key.code, true);
                break;
            case sf::Event::KeyReleased:
                handlePlayerInput(event.key.code, false);
                break;
            case sf::Event::Closed:
                mWindow.close();
                break;
        }
    }
}

void Game::update(Time deltaTime)
{
    Vector2f movement(0.f, 0.f);
    if (mIsMovingUp)
        movement.y -= playerSpeed;
    if (mIsMovingDown)
        movement.y += playerSpeed;
    if (mIsMovingLeft)
        movement.x -= playerSpeed;
    if (mIsMovingRight)
        movement.x += playerSpeed;

    mPlayer.move(movement * deltaTime.asSeconds());
}

void Game::render()
{
    mWindow.clear();
    mWindow.draw(mPlayer);
    mWindow.display();
}

int main()
{
    Game game;
    game.run();
}
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1 に答える 1

2

答え：

デフォルトでは、これらの変数は次のようになっている必要がありますtrue。

bool mIsMovingUp, mIsMovingRight, mIsMovingLeft, mIsMovingDown;

ではGame::Game()、それらをすべて false として宣言します。それはあなたの問題を解決するはずです。

説明：

つまり、mIsMovingUpと down がmIsMovingDown trueのとき、静止しています。押し上げて離すと、つくmIsMovingUp falseけどそのままなmIsMovingDownのでボールが動くmIsMovingDown。を押して離すとmIsMovingDown、 になりmIsMovingDown false、両方falseになり、動きが止まります。isMovingLeftと についても同じですisMovingRight。

于 2013-07-27T18:59:46.997 に答える