Determine the current position of an object in the context of drag and drop

Hello,

I have two different drag n drop fields. a and b.

When moving an a(cc) field and then releasing it, I want the X position to be the same as the mouse and the Y position to be set to 0.1. The b(cc) field should behave like a(cc) but snap to 0.3 in the y-direction.

Everything I tried so far didn't work.

Thx for your Help.

function minimalExample
dragging = [];
orPos = [];

global a;
global b;

global numberOfFields;

numberOfFields = 2;

f = figure('WindowButtonUpFcn',@dropObject,...
    'units','normalized',...
    'position', [0.1 0.2 0.35 0.5],...
    'WindowButtonMotionFcn',@moveObject);

for cc = 1:numberOfFields
    a(cc) = annotation('textbox',...
        'position',[(0.1*cc) 0.1 0.08 0.1],...
        'String', ['a # ' num2str(cc)],...
        'Tag', ['a' num2str(cc)],...
        'BackgroundColor',hsv2rgb([0.33 0.5 0.66]),...
        'ButtonDownFcn',@dragObject);
    b(cc) = annotation('textbox',...
        'position',[(0.1*cc) 0.3 0.08 0.1],...
        'String', ['b # ' num2str(cc)],...
        'Tag', ['a' num2str(cc)],...
        'BackgroundColor',hsv2rgb([0.0 0.5 0.66]),...
        'ButtonDownFcn',@dragObject);
end
    function dragObject(hObject,eventdata)
        dragging = hObject;
        orPos = get(gcf,'CurrentPoint');
    end
    function dropObject(hObject,eventdata)
        if ~isempty(dragging)
            newPos = get(gcf,'CurrentPoint');
            posDiff = newPos - orPos;
            set(dragging,'Position',get(dragging,'Position') + [posDiff(1:2) 0 0]);
            dragging = [];
        end
    end
    function moveObject(hObject,eventdata)
        if ~isempty(dragging)
            newPos = get(gcf,'CurrentPoint');
            posDiff = newPos - orPos;
            orPos = newPos;
            set(dragging,'Position',get(dragging,'Position') + [posDiff(1:2) 0 0]);
        end
    end
end

Answer 1

[Voss]

Basically, in the motion function and button up function, you have to check whether dragging is an element of a or of b and set the y-coordinate accordingly.

(It wasn't clear to me whether you want to constrain the y-coordinate the whole time the annotation is dragged or just when it is released, so I put the option to do it either way. See the variable do_move_freely.)

function minimalExample
dragging = [];
orPos = [];

do_move_freely = true; % move the object with the mouse, then snap when mouse button is released
% do_move_freely = false; % constrain the y-coordinate to 0.1 or 0.3 the entire time the object is being moved

global a;
global b;

global numberOfFields;

numberOfFields = 2;

f = figure('WindowButtonUpFcn',@dropObject,...
    'units','normalized',...
    'position', [0.1 0.2 0.35 0.5],...
    'WindowButtonMotionFcn',@moveObject);

for cc = 1:numberOfFields
    a(cc) = annotation('textbox',...
        'position',[(0.1*cc) 0.1 0.08 0.1],...
        'String', ['a # ' num2str(cc)],...
        'Tag', ['a' num2str(cc)],...
        'BackgroundColor',hsv2rgb([0.33 0.5 0.66]),...
        'ButtonDownFcn',@dragObject);
    b(cc) = annotation('textbox',...
        'position',[(0.1*cc) 0.3 0.08 0.1],...
        'String', ['b # ' num2str(cc)],...
        'Tag', ['a' num2str(cc)],...
        'BackgroundColor',hsv2rgb([0.0 0.5 0.66]),...
        'ButtonDownFcn',@dragObject);
end
    function dragObject(hObject,eventdata)
        dragging = hObject;
        orPos = get(gcf,'CurrentPoint');
    end
    function dropObject(hObject,eventdata)
        if ~isempty(dragging)
            newPos = get(gcf,'CurrentPoint');
            posDiff = newPos - orPos;
            setPos = get(dragging,'Position') + [posDiff(1:2) 0 0];
            if ismember(double(dragging),double(a))
                setPos(2) = 0.1;
            else
                setPos(2) = 0.3;
            end
            set(dragging,'Position',setPos);
            dragging = [];
        end
    end
    function moveObject(hObject,eventdata)
        if ~isempty(dragging)
            newPos = get(gcf,'CurrentPoint');
            posDiff = newPos - orPos;
            orPos = newPos;
            setPos = get(dragging,'Position') + [posDiff(1:2) 0 0];
            if ~do_move_freely
                if ismember(double(dragging),double(a))
                    setPos(2) = 0.1;
                else
                    setPos(2) = 0.3;
                end
            end
            set(dragging,'Position',setPos);
        end
    end
end

Answer 2

[Stefan]

Thx for your help.

By releasing the mousebutton (button up) x shuold be the same als the mouse and y should be 0.1 or 0.3

I was running the script at my PC but unfortunately its a little bit buggy:

Error using matlab.graphics.shape.TextBox/vertcat
Cannot convert double value 7.00012 to a handle

Error in ismember>ismemberClassTypes (line 429)
        ab = [a(:);b(:)];

Error in ismember>ismemberR2012a (line 204)
            lia = ismemberClassTypes(a,b);

Error in ismember (line 95)
        lia = ismemberR2012a(A,B);

Error in minimalExample2/dropObject (line 37)
            if ismember(dragging,a)
 
Error while evaluating Figure WindowButtonUpFcn.

And the dragged object sticks to the mouse coursor all the time.

[Voss]

Hmm. It works on my machine. Maybe try this:

function minimalExample
dragging = [];
orPos = [];

do_move_freely = true; % move the object with the mouse, then snap when mouse button is released
% do_move_freely = false; % constrain the y-coordinate to 0.1 or 0.3 the entire time the object is being moved

global a;
global b;

global numberOfFields;

numberOfFields = 2;

f = figure('WindowButtonUpFcn',@dropObject,...
    'units','normalized',...
    'position', [0.1 0.2 0.35 0.5],...
    'WindowButtonMotionFcn',@moveObject);

for cc = 1:numberOfFields
    a(cc) = annotation('textbox',...
        'position',[(0.1*cc) 0.1 0.08 0.1],...
        'String', ['a # ' num2str(cc)],...
        'Tag', ['a' num2str(cc)],...
        'BackgroundColor',hsv2rgb([0.33 0.5 0.66]),...
        'ButtonDownFcn',@dragObject);
    b(cc) = annotation('textbox',...
        'position',[(0.1*cc) 0.3 0.08 0.1],...
        'String', ['b # ' num2str(cc)],...
        'Tag', ['a' num2str(cc)],...
        'BackgroundColor',hsv2rgb([0.0 0.5 0.66]),...
        'ButtonDownFcn',@dragObject);
end
    function dragObject(hObject,eventdata)
        dragging = hObject;
        orPos = get(gcf,'CurrentPoint');
    end
    function dropObject(hObject,eventdata)
        if ~isempty(dragging)
            newPos = get(gcf,'CurrentPoint');
            posDiff = newPos - orPos;
            setPos = get(dragging,'Position') + [posDiff(1:2) 0 0];
            if ismember(double(dragging),double(a))
                setPos(2) = 0.1;
            else
                setPos(2) = 0.3;
            end
            set(dragging,'Position',setPos);
            dragging = [];
        end
    end
    function moveObject(hObject,eventdata)
        if ~isempty(dragging)
            newPos = get(gcf,'CurrentPoint');
            posDiff = newPos - orPos;
            orPos = newPos;
            setPos = get(dragging,'Position') + [posDiff(1:2) 0 0];
            if ~do_move_freely
                if ismember(double(dragging),double(a))
                    setPos(2) = 0.1;
                else
                    setPos(2) = 0.3;
                end
            end
            set(dragging,'Position',setPos);
        end
    end
end

[Voss]

Does that work? If so, please mark my answer as Accepted. If not, please post the problem and I'll see if I can fix it. Thanks!

[Stefan]

Thank you for your help.

Sorry for the late answer, sleep is important from time to time ^^

I was a little surprised to see where the first answer had gone. I have now tested the remaining answer again and am very satisfied.

Thank you very much.