MATLAB: How to Move the Patches fluidly without Leaving a Marking of the Patch at the previous Location

keypressfcn

if true
  % code








end
clc
clear all
close all
if true
  % code
end
global y
global y1
global h_rec
global h_rec1
if true
  % code
end
h_fig=figure;
set(h_fig, 'KeyPressFcn', @kpfcn)
if true
  % code
end
axis([-10 10 -10 10])
if true
  % code
end
x=[2 2 4 4];
y=[2 4 2 4];
h_rec= patch(x,y,'k');
if true
  % code
end
x1=[2 4 2 4];
y1=[2 2 4 4];
h_rec1= patch(x1,y1,'k');
if true
  % code
end
refreshdata
function kpfcn(~, event)
global y
global y1
global h_rec
global h_rec1
if true
  % code
end
switch event.Key
  case 'uparrow'
  x=[2 2 4 4];
  x1=[2 4 2 4];
  y=y+[1 1 1 1];
  y1=y1+[1 1 1 1];
  h_rec=patch(x,y,'k')
  h_rec1=patch(x1,y1,'k')
    case 'downarrow'
        x=[2 2 4 4];
        x1=[2 4 2 4];
        y=y-[1 1 1 1];
        y1=y1-[1 1 1 1];
        h_rec=patch(x,y,'k')
        h_rec1=patch(x1,y1,'k')
if true
  % code
end
end
end

Best Answer

Do not patch() at the new location. Instead set the XData and YData properties of the existing patch object.

Alternatively, parent the patch im a hgtransform group, and each time you want to move it, change the transfom matrix of the group.

Related Solutions

MATLAB: I’m making a Pong Game and trying to set the limit of the y direction of the paddles to y max to 9 and y min to -9

David - it looks like you are using your kpfcn to move the paddles and are using the code

    if y5>9
      y5=9;
    end
    if y5<-5
      y5=-5;
    end
    if y6>5
      y6=5;
    end
    if y6<-9
      y6=-9;
    end

to control the positions of the paddles so that they don't exceed the minimum and maximum bounds of the gaming area. But this code is affecting variables y5 and y6 which are no longer relevant. They were only used when creating the initial positions of the paddles but since then are no longer used. It is the y1 and y2 arrays that control the positions of the paddles and so it is the elements within these arrays that you should be adding your checks to. For example, you could do

    function kpfcn(hObject,event)
        switch event.Key
          case 'uparrow'
              if max(y2) < 9
                  y2 = y2 + [1 1 1 1];
              end
          case 'downarrow'
              if min(y2) > -9
                  y2 = y2 - [1 1 1 1];
              end
          case 'w'
              if max(y1) < 9
                  y1 = y1 + [1 1 1 1];
              end      
          case 's'
              if min(y1) > -9
                  y1 = y1 - [1 1 1 1];
              end  
        end
        set(h_rec1, 'YData', y1)
        set(h_rec2, 'YData', y2)
    end

where we only adjust the position of the paddle if its maximum or minimum position (along the y-axis) allows for the paddle to be moved up or down. Note how I've removed the global variables which are not necessary if you nest this function within the parent function. That way the nested function has access to all local variables within the parent (and so you can remove the global qualifier from those variables). See nested functions for more details.

MATLAB: Is their an error with the keypressfcn because I want to move the patch up and down using the arrows, but I get errors saying, too many input arguments and Error while evaluating Figure KeyPressFcn.

Callbacks are automatically passed two parameters, namely the object being called back for, and some event data. You appear to need the event data. You need to define

 function kpfcn(hObject, event)

 function kpfcn(~, event)

You also have the difficulty that y is not defined in the scope of your function. If it were defined then you have the problem that your function computes two variables but does not do anything with them to change the graphics being displayed.

http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.28s.29.3F

https://www.mathworks.com/help/matlab/ref/refreshdata.html

Best Answer

Related Solutions

MATLAB: I’m making a Pong Game and trying to set the limit of the y direction of the paddles to y max to 9 and y min to -9

MATLAB: Is their an error with the keypressfcn because I want to move the patch up and down using the arrows, but I get errors saying, too many input arguments and Error while evaluating Figure KeyPressFcn.

Related Question