Databases
StackOverflow2013
Postsdbo
POUIScrollView - Custom Map - Prevent marker subview on map from scaling with map
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POUIScrollView - Custom Map - Prevent marker subview on map from scaling with map
    primarykey
    data
    text
    <p>I have a custom map of a limited area, and have it set up to correctly show the users' location. The map is a 1600px square image within a UIScrollView.</p> <p>I have a crosshair image to show the current location of the user, which at zoomScale 1.0 is the desired size. When I pinch and zoom the scrollView, the crosshair scales with it. I would like to have the subview remain the same size on screen. </p> <p>I haven't been able to find any information on this, what would be the best way to go about this?</p> <p>If there is anything I can provide you with to help the answer, please let me know.</p> <p>Many thanks!</p> <p><strong>EDIT -</strong></p> <p>Having looked in to this further, there is a UIScrollViewDelegate method <code>- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale</code> which I tried using to take the marker's current center and size, then adjust, but this only scales at the end of the zoom. I would prefer to have the marker remain the same size while the user is zooming.</p> <p><strong>EDIT 2-</strong></p> <p>Cake has provided a great answer below, but I haven't been able to implement this in the way I imagined it would be.</p> <p>I have the UIImageView as a placeholder, with alpha set to 0. This placeholder moves around relative to the map to show the user location. This operates as I expect it to. Unfortunately, this resizes with the map, as it is a subview of the map (so it stays in place).</p> <p>Taking Cake's below answer, I have created the non-scaling crosshair image, and added it as a sibling subview to the scrollview. The maths, once Cake had pointed them out, were quite simple to get the new frame for the crosshair:</p> <pre><code> CGPoint ULPC = userLocationPlaceholder.center; float zs = scrollView.zoomScale; CGRect newFrame = CGRectMake(((ULPC.x * zs) - scrollView.contentOffset.x) - 20, ((ULPC.y * zs) - scrollView.contentOffset.y) - 20, 40, 40); </code></pre> <p>Where the image is 40points wide. This matches the centers perfectly.</p> <p>The problem I <em>now</em> have is that I cannot get the crosshair image to stay locked to the placeholder.</p> <p>I have tried using a self calling animation as such:</p> <pre><code>-(void)animeUserLocationAttachment { [UIView animateWithDuration:0.05 delay:0 options:(UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionCurveLinear ) animations:^{ userLocationDotContainer.frame = newFrame; } completion:^(BOOL finished){ // Call self [self animateUserLocationAttachment]; }]; } </code></pre> <p>As soon as I start scrolling/zooming, this locks the animation so that the crosshair just sits in place until I release the scrolling/zooming, then it correctly updates it's location.</p> <p>Is there any way I can get around this, or an alternative method I can apply?</p> <p>Many thanks</p> <p><strong>EDIT 3 -</strong></p> <p>I've re-accepted Cake's answer as it covers 90% of the issue. Further to his answer I have implemented the ScrollViewDelegate methods <code>scrollViewWillBeginDragging:</code> and<code>scrollViewWillBeginDecelerating:</code> to scale the placeholder to match the current size of the crosshair relative to the map, show the placeholder (that is a subview of the map image) and hide the crosshair image. The delegate method <code>scrollviewWillBeginZooming:withView:</code> does not show the placeholder because it scales with the map. As Cake recommends, I'll make a new question for this issue.</p> <p>The counterpart methods (<code>scrollViewDidEndZooming:withView:atScale:</code>, <code>scrollViewDidEndDragging:willDecelerate:</code> and -scrollViewDidEndDecelerating:`) all hide the placeholder, and re-show the crosshair.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USPete C
    1. USPete C
    plurals
    1. PL
      singulars
      1. LTLinked
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COIf you're still having trouble, try looking at this question: http://stackoverflow.com/q/11228200/1439815. It seems like this is similar to what you're trying to accomplish.
      singulars
      1. POUIScrollView - Custom Map - Prevent marker subview on map from scaling with map
      1. USDustin
    2. COI had a look at that, thanks for the link. I've still not got it working perfectly, In the mean time I am making the placeholder the same crosshair image, and when the view is scrolling/decelerating I resize the placeholder to the same as the crosshair, make it visible, and hide it until the motion is done. This works for movements where there is no change in scale. Right now I have it completely disappear while zooming is in progress. I would like to have it so that it scales with the zoom, but might have to settle for this.
      singulars
      1. POUIScrollView - Custom Map - Prevent marker subview on map from scaling with map
      1. USPete C
    3. COIt seems like maybe you should create a new question with the additional problems that have been raised.
      singulars
      1. POUIScrollView - Custom Map - Prevent marker subview on map from scaling with map
      1. USDustin
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload