Erase bouncing ball drawn on GUI so there is only one drawn ball on GUI at a time

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Dakota Nielsen 2021-5-28

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https://ww2.mathworks.cn/matlabcentral/answers/842345-erase-bouncing-ball-drawn-on-gui-so-there-is-only-one-drawn-ball-on-gui-at-a-time

评论： Jan 2021-5-28

Hey guys, I'm working on this quick project that has a ball bouncing off all the walls continously. I basically have everything running as I want it, but when I draw the ball on the GUI my old drawn balls stay on GUI as well. How could I delete it so there is only one ball drawn on the GUI at a time. This is what I have.

set(gca, 'XLim',[-10 10], 'YLim', [-10 10]);
cla
axis square
ball = animatedline('color' , 'r', 'Marker', 'o' , 'MarkerSize',12,'MarkerFaceColor','r');
theta = pi/6; % Sets Theta
V = 5; %Sets value of V
[x,y,t] = startBall(V,theta,ball); %Calls function to return x,y,t
xr = 10; % x right
xl = -10; % x left
yt = xr; % y top
yb = xl; % y bottom
function[x,y,t] = startBall(V,theta,ball)
    dt =0.1 ; % sets time as 0.1
    Vx = V * cos(theta);
    Vy = V * sin(theta);
    x0 = 0; %initial x position
    y0 = 0; %initial y position
    x = x0;
    y = y0;
    t = 0; % Time
    while 1 == 1
        if x(end) > 10 && y(end) > 10 || x(end) < -10 && y(end) < -10 %Condition of the ball hittin CORNER
            Vx = -1*Vx %Change Vx velocity from hitting corner
            Vy = -1 * Vy; %Change Vy velocity from hitting corner
        elseif x(end) > 10 || x(end) < -10 % Checks if Ball is hitting top or bottom
            Vx = -1 * Vx;
        elseif y(end) > 10 || y(end) < -10 %Checks if ball is hitting left or right
            Vy = -1 * Vy;
        end
        x(end + 1) = x(end) + Vx * dt; % UPDATES X VAL
        y(end + 1) = y(end) + Vy * dt; % UPDdATES Y VAL
        t(end + 1) = t(end) + dt; %UPDATES T VAL
        clearpoints(ball);
        addpoints(ball,x,y);
        drawnow;
        pause(.01)
    end
end

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Adam Danz 2021-5-28

I would just plot the ball once outside of the loop and then update its xdata & ydata values within the loop.

Jan 2021-5-28

在 MATLAB Online 中打开

Just a hint: This can be simplified:

        if x(end) > 10 && y(end) > 10 || x(end) < -10 && y(end) < -10 %Condition of the ball hittin CORNER
            Vx = -1*Vx %Change Vx velocity from hitting corner
            Vy = -1 * Vy; %Change Vy velocity from hitting corner
        elseif x(end) > 10 || x(end) < -10 % Checks if Ball is hitting top or bottom
            Vx = -1 * Vx;
        elseif y(end) > 10 || y(end) < -10 %Checks if ball is hitting left or right
            Vy = -1 * Vy;
        end

        if x(end) > 10 || x(end) < -10 % Checks if Ball is hitting top or bottom
            Vx = -Vx;
        end
        if y(end) > 10 || y(end) < -10 %Checks if ball is hitting left or right
            Vy = -Vy;
        end