CODEWITHSUNDEEP
objective-ciosxcodecocoa-touchipad
user784625
user784625

Reputation: 1938

How can I draw dynamic rectangle on screen according to touchMove event on iOS

the rectangle will be considered two points, first point will be the touchBegan point, and on touchMove will be the second point, the rectangle will be dynamically drawn according to the user finger move, (like when you click one click on desktop and move the mouse you will get dynamically rectangle).

Thanks

Upvotes: 3

Views: 4606

Answers (2)

NSZombie
NSZombie

Reputation: 1867

Okay here is how you can draw your rect in touchesMoved (use @Nekto touchesBegan to store the starting point of your rect).

Let's assume you keep a reference on the UIView we are drawing and call it drawnView. In touchesBegan, we set the origin of the frame for drawnView

Here is touchesMoved :

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent*)event
{
    // We only take care of a single touch
    if ([touches count] == 1)
    {
        UITouch *touch = [touches anyObject];
        // Find the width and height of the rect
        CGRect drawnFrame = drawnView.frame
        drawnFrame.size.width = [touch locationInView:parentView].x - drawnFrame.origin.x
        drawnFrame.size.height = [touch locationInView:parentView].y - drawnFrame.origin.y
        [drawnView setFrame:drawnFrame];
    }
}

Don't copy paste that code, I didn't write it in Xcode or anything. It could have mistakes (for sure). But I hope it can help to find your solution. And be careful, I can't tell how it will behave if you drag your finger to the top, or to the left (negative values for height and width).

Upvotes: 4

Nekto
Nekto

Reputation: 17877

  1. You should define subclass of UIView, for example, DrawingView

  2. In DrawingView you should implement following methods:

    Save start point in method: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

    Redraw rect here - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event

    Hide rect (or save it) here - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event and here - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event

For example, in first method you could detect start point in following way: 

CGPoint startCornerOfYourRect;
for (UITouch *touch in touches)
{
    startCornerOfYourRect  = [touch locationInView:self];
    break;
}

Upvotes: 4

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