`opaque` means don&#39;t draw _anything_ underneath, even if you are transparent.

The background color&#39;s alpha only affects the background color&#39;s transparency, not anything else drawn on the view.

`alpha` affects everything drawn on the view.

---

The opaque property can give you a speed increase - if you know that your view will _never_ have transparency you can set this to `YES` and when iOS renders your view it can make some performance optimisations and render it faster. If this is set to `NO` iOS will have to blend your view with the view underneath, even if it doesn&#39;t happen to contain any transparency.

The alpha will also affect the alpha of the backround color i.e. if the background color is 0.5 transparent and the alpha is also 0.5, this has the effect of making the background view&#39;s alpha 0.25 (0.5 * 0.5).


To the very good [answer](https://stackoverflow.com/a/8520656/1656515) by deanWombourne it&#39;s worth to add that, unless you don&#39;t draw your own content using the drawRect: method, the opaque property has no effect.

[Apple&#39;s doc](https://developer.apple.com/reference/uikit/uiview/1622622-opaque):
&gt; You only need to set a value for the opaque property in subclasses of
&gt; UIView that ***draw their own content*** using the drawRect: method. The
&gt; opaque property ***has no effect in system-provided classes*** such as
&gt; UIButton, UILabel, UITableViewCell, and so on.

If you draw your own content, keep in mind, that opaque is just a hint

&gt; This property provides a ***hint to the drawing system*** as to how it
&gt; should treat the view.

and some more guidelines from the same Apple&#39;s doc:
&gt; If the view is opaque and either does not fill its bounds or contains
&gt; wholly or partially transparent content, the results are
&gt; unpredictable. You should always set the value of this property to NO
&gt; if the view is fully or partially transparent.

I am wondering what the `atomically:` parameter stands for in the `writeToFile:atomically:` method (`-[NSArray writeToFile:atomically:]` for example). It is common to pass `YES` for `atomically:`, but I don&#39;t know what it means.

writeToFile:atomically: what does atomically mean?

To state it in a general form, I&#39;m looking for a way to join several points with a **gradient color line** using **matplotlib**, and I&#39;m not finding it anywhere.
To be more specific, I&#39;m plotting a 2D random walk with a one color line. But, as the points have a relevant sequence, I would like to look at the plot and see where the data has moved. A gradient colored line would do the trick. Or a line with gradually changing transparency.

I&#39;m just trying to improve the vizualization of my data. Check out this beautiful image produced by the ggplot2 package of R. I&#39;m looking for the same in matplotlib. Thanks.

![enter image description here][1]


  [1]: http://i.stack.imgur.com/7sNmT.png

How to plot a gradient color line in matplotlib?

How do `opaque` `alpha` and the opacity of the background work together for a UIView and what are the differences between them?


![UIView](http://i.minus.com/jb2IP8TXbYTxKr.png)

UIView: opaque vs. alpha vs. opacity

<p>How do <code>opaque</code> <code>alpha</code> and the opacity of the background work together for a UIView and what are the differences between them?</p>
<p><img src="http://i.minus.com/jb2IP8TXbYTxKr.png" alt="UIView"></p>


I&#39;m currently working on an app that uses the &quot;ChalkboardSE-Regular&quot; font and my deployment target is 4.0+.  This font was not available in 4.1 but it is supported in 4.3.  What would be the best way to go about checking if the font exists and if it does not, use another supported font on the &lt;4.1 versions of iOS. [UIFont familyName] returns a list of these fonts &quot;Chalkboard SE&quot;

Thanks in advance!

T

How to check if a font is available in version of iOS?

I want to perform some action when UISwitch changes its state, thus is set on or off. How do I do this? I need to pass two objects as parameters. 

It&#39;s created in code, thus not using xib.

How to call an action when UISwitch changes state?

Is it possible to design interfaces in landscape with Interface Builder? Others with the same question apparently were able to do so with an arrow at the top right of any selected view, but I see no such arrow. A picture would be helpful. (Note: I am using storyboards, not xibs.)

Designing in landscape with Storyboards

How to change the default color(blue) of a UISwitch?

How to change the UISwitch default color(blue)

I want my users to be able to download a PDF file and have the browser treat it as a file, not just display it (i.e. it has a filename, user gets option to save, etc.).  The following header seems to work well for this everywhere except for iOS:

    Content-Disposition: attachment; filename=file.pdf

iOS just ignores this and displays the image or document.  No big deal, you might think, except I&#39;m doing this in a hidden IFRAME as part of my download page, so the document is never even seen, and it looks like the download failed.

What&#39;s the best way to handle this in a cross-browser compatible manner?  Does iOS just ignore this header?  I can&#39;t find any spec or mention of this anywhere.  

Do I need to check for iOS in request headers and serve the response differently?  I was hoping to avoid this.  Thanks.

P.S. Any other helpful tips related to downloading files etc. in iOS web browsers are appreciated.

CLARIFICATION:  This regarding a regular web site browsed by the mobile Safari browser.  Not a native app.

HTTP &quot;Content-Disposition: attachment&quot; and downloading files on iOS web browser

I&#39;m customizing a `UITableView`. I want to hide the line separating on the *last* cell ... can i do this?

I know I can do `tableView.separatorStyle = UITableViewCellStyle.None` but that would affect *all* the cells of the tableView. I want it to only affect my last cell.

Hide separator line on one UITableViewCell

For better re-usability I want to create a table view outside of my Storyboard.

Now when I create a `UITableView` based ViewController with Nib in Xcode I get the default TableView in the nib file. However, I am not able in Interface Builder to add prototype cells like I am in my Storyboard.

Is it currently not possible to add prototype cells in a nib or am I missing something.

Thanks very much for any help.

Prototype Cells in a nib instead of a storyboard

I have an NSArray that I want to filter out certain objects using an NSPredicate, I was hoping I could use NOT IN since I saw that I can easily do an IN.

So I have my array:

    self.categoriesList

Then I get the values I want to remove:

    NSArray *parentIDs = [self.cateoriesList valueForKeyPath:@&quot;@distinctUnionOfObjects.ParentCategoryID&quot;];

This gives me a list of ParentCategoryID&#39;s for categories I DO NOT want to display, so I figure I can use an NSPredicate to remove them:

    self.cateoriesList = [self.cateoriesList filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@&quot;CategoryID NOT IN %@&quot;,parentIDs]];

This fails:

    reason: &#39;Unable to parse the format string &quot;CategoryID NOT IN %@&quot;&#39;

If I wanted to use just IN that works perfectly of course.
 

NSArray with NSPredicate using NOT IN

I&#39;m trying to implement AQRecorder.h class from SpeakHere Apple Xcode project example, but even I rename my implementation class to ext. `*.mm` and put line with `#import &quot;AQRecorder.h&quot;` still getting error `&quot;Unknown type name &#39;class&#39;; did you mean &#39;Class&#39;?&quot;` and many others.
Which according to me means that it is not recognized as C++ class.

Any help will be appreciated.

Unknown type name &#39;class&#39;; did you mean &#39;Class&#39;?

I need to get the country location of a iOS device.

I&#39;ve been trying to use CoreLocation with MKReverseGeocoder. However this seems to return erraneous quite frequently. And I only need the country, no need for streets and such.

How can this be done in a more stable way?

Get device location (only country) in iOS

Ideally, i would want the entire interface to have a **custom styling** that is seen on the ios (itouch / ipad) or android equivalent with the virtual keyboard present. See below for more details.

A custom set CSS hacking rules to be active, when the keyboard is &quot;present&quot;, is also an acceptable solution.

Targets both androids and ios, on a website (HTML/JavaScript/CSS)
Also note that the layout inside is: **&quot;fluid&quot;.**

**Edit:** This was more design, then text; So the changes are not disorientating. At the lowest level, I just desire a design change with and without the virtual keys **(Perhaps just a background change).** 

**The question on which, this is a good or bad design idea, is debatable. However, I feel is irrelevant to the question. For such an exploit can have uses more then text (such as games, or interactive media).**

**Hence the bounty:** Despite no longer needing the answer for the project I was working on (an alternative design was used). I still believe this question can benefit from being answered.

**Default Behavior** 

                           +--------+ 
                           |        |
    +------------+       +-+-hidden-+-+   &lt;- ~50% hidden
    | +--------+ |       | +--------+ |
    | |        | |       | |visible | |
    | |        | |   \   | |        | |   &lt;- ~50% visible
    | |  100%  | |  ==&gt;  | +--------+ |
    | |        | |   /   | |virtual | |
    | |        | |       | |  keys  | |
    | +--------+ |       | +--------+ |
    +------------+       +------------+

**Desired Behavior** 


    +------------+       +------------+   
    | +--------+ |       | +--------+ |
    | |        | |       | |visible | |   &lt;- 100% visible (example styling)
    | |        | |   \   | |        | |      Custom Styling
    | |  100%  | |  ==&gt;  | +--------+ |
    | |        | |   /   | |virtual | |
    | |        | |       | |  keys  | |
    | +--------+ |       | +--------+ |
    +------------+       +------------+


screen styling when virtual keyboard is active

I have a `UIView` with 4 buttons on it and another `UIView` on top of the buttons view.  The top most view contains a `UIImageView` with a `UITapGestureRecognizer` on it.

The behavoir I am trying to create is that when the user taps the `UIImageView` it toggles between being small in the bottom right hand corner of the screen and animating to become larger.  When it is large I want the buttons on the bottom view to be disabled and when it is small and in the bottom right hand corner I want the touches to be passed through to the buttons and for them to work as normal.  I am almost there but I cannot get the touches to pass through to the buttons unless I disable the `UserInteractions` of the top view.

I have this in my `initWithFrame:` of the top view:

    // Add a gesture recognizer to the image view
    UITapGestureRecognizer *tapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageTapped:)];
    tapGestureRecognizer.cancelsTouchesInView = NO;
    [imageView addGestureRecognizer:tapGestureRecognizer];
    [tapGestureRecognizer release];

and I this is my `imageTapped:` method:

    - (void) imageTapped:(UITapGestureRecognizer *) gestureRecognizer {
    	// Toggle between expanding and contracting the image
    	if (expanded) {
    		[self contractAnimated:YES];
    		expanded = NO;
            gestureRecognizer.cancelsTouchesInView = NO;
            self.userInteractionEnabled = NO;
            self.exclusiveTouch = NO;
    	}
    	else {
    		[self expandAnimated:YES];
    		expanded = YES;
            gestureRecognizer.cancelsTouchesInView = NO;
            self.userInteractionEnabled = YES;
            self.exclusiveTouch = YES;
    	}
    }

 With the above code, when the image is large the buttons are inactive, when I touch the image it shrinks and the buttons become active.  However, the small image doesn&#39;t receive the touches and therefore wont expand.

If I set `self.userInteractionEnabled = YES` in both cases, then the image expands and contracts when touched but the buttons never receive touches and act as though disabled.

Is there away to get the image to expand and contract when touched but for the buttons underneath to only receive touches if the image is in its contracted state?  Am I doing something stupid here and missing something obvious?

I am going absolutely mad trying to get this to work so any help would be appreciated,

Dave

**UPDATE:**

For further testing I overrode the `touchesBegan:` and `touchesCancelled:` methods and called their super implementations on my view containing the UIImageView.  With the code above, the `touchesCancelled:` is never called and the `touchesBegan:` is always called.

So it would appear that the view is getting the touches, they are just not passed to the view underneath.

**UPDATE**

Is this because of the way the responder chain works?  My view hierarchy looks like this:

    VC - View1
         -View2
          -imageView1 (has tapGestureRecogniser)
          -imageView2
         -View3
          -button1
          -button2

I think the OS first does a hitTest as says View2 is in front so should get all the touches and these are never passed on to View3 unless userInteractions is set to NO for View2, in which case the imageView1 is also prevented from receiving touches.  Is this how it works and is there a way for View2 to pass through it&#39;s touches to View3?

  

Passing through touches to UIViews underneath

I am currently making an app that will have multiple timers, which are basically all the same. 

I want to create a custom class that uses all of the code for the timers as well as the layout/animations, so I can have 5 identical timers that operate independently of each other. 

I created the layout using IB (xcode 4.2) and all the code for the timers is currently just in the viewcontroller class.

I am having difficulty wrapping my brain around how to encapsulate everything into a custom class and then add it to the viewcontroller, any help would be much appreciated.

How do I create a custom iOS view class and instantiate multiple copies of it (in IB)?

I want to use a view throughout multiple viewcontrollers in a storyboard. Thus, I thought about designing the view in an external xib so changes are reflected in every viewcontroller. But how can one load a view from a external xib in a storyboard and is it even possible? If thats not the case, what other alternatives are availble to suit the situation abouve?

Load view from an external xib file in storyboard

I am trying to add a drop shadow to views that are layered on top of one another, the views collapse allowing content in other views to be seen, in this vein i want to keep `view.clipsToBounds` ON so that when the views collapse their content is clipped.

This seems to have made it difficult for me to add a drop shadow to the layers as when i turn `clipsToBounds` ON the shadows are clipped also.

I have been trying to manipulate `view.frame` and `view.bounds` in order to add a drop shadow to the frame but allow the bounds to be large enough to encompass it, however I have had no luck with this.

Here is the code I am using to add a Shadow (this only works with `clipsToBounds` OFF as shown)

    view.clipsToBounds = NO;
    view.layer.shadowColor = [[UIColor blackColor] CGColor];
    view.layer.shadowOffset = CGSizeMake(0,5);
    view.layer.shadowOpacity = 0.5;

Here is a screenshot of the shadow being applied to the top lightest grey layer. Hopefully this gives an idea of how my content will overlap if `clipsToBounds` is OFF.

![Shadow Application.][1]


  [1]: http://i.stack.imgur.com/CeyVz.png

How can I add a shadow to my `UIView` and keep my content clipped?

Edit: Just wanted to add that I have also played around with using background images with shadows on, which does work well, however I would still like to know the best coded solution for this.

What&#39;s the best way to add a drop shadow to my UIView

I&#39;m trying to rotate a `UIImageView` 360 degrees, and have looked at several tutorials online. I could get none of them working, without the `UIView` either stopping, or jumping to a new position.

* How can I achieve this?

The latest thing I&#39;ve tried is:

    [UIView animateWithDuration:1.0
						  delay:0.0
						options:0
					 animations:^{
						 imageToMove.transform = CGAffineTransformMakeRotation(M_PI);
					 } 
					 completion:^(BOOL finished){
						 NSLog(@&quot;Done!&quot;);
					 }];

But if I use 2*pi, it doesn&#39;t move at all (since it&#39;s the same position). If I try to do just pi (180 degrees), it works, but if I call the method again, it rotates backwards.

**EDIT**:

    [UIView animateWithDuration:1.0
						  delay:0.0
						options:0
					 animations:^{
						 [UIView setAnimationRepeatCount:HUGE_VALF];
						 [UIView setAnimationBeginsFromCurrentState:YES];
						 imageToMove.transform = CGAffineTransformMakeRotation(M_PI);
					 } 
					 completion:^(BOOL finished){
						 NSLog(@&quot;Done!&quot;);
					 }];

doesn&#39;t work either. It goes to `180` degrees, pauses for a split second, then resets back to `0` degrees before it starts again.


Content Type	Original Author	Original Content on Stackoverflow
Question	Besi	View Question on Stackoverflow
Solution 1 - Iphone	deanWombourne	View Answer on Stackoverflow
Solution 2 - Iphone	Mikolaj	View Answer on Stackoverflow

UIView: opaque vs. alpha vs. opacity

Iphone Problem Overview

Iphone Solutions

Solution 1 - Iphone

Solution 2 - Iphone

How to plot a gradient color line in matplotlib?

writeToFile:atomically: what does atomically mean?

Attributions