User Interface Customization in iOS 5

做项目过程中，需要自定义一些控件外观，发现略微有些复杂，先记录下来，这些个性化的外观只是使用于IOS5.0，如[UISegmentedControl appearance];

appearance只有在IOS5里才可使用，如果你的部属环境是4.3的，则会报错。

To be successful on the App Store, your app needs to stand out. The vanilla user-interface “look and feel” provided by Apple just doesn’t cut it any more in a crowded market.

Many of the most popular apps on the App Store present standard iOS UI elements in a non-standard fashion:

• Twitter employs a custom UITabBar
• Instagram uses both a custom UITabBar and a custom UINavigationBar
• Epicurious for iPad customizes elements of the standard split-view interface

Create a cool custom user interface with iOS 5's new UIKit and UIAppearance APIs!

Prior to iOS 5, many developers had to take somewhat unconventional approaches to achieve these results. Although subclassing and overriding drawRect: was the recommended approach, many resorted to the dreaded “method swizzling”.

But with iOS 5, those dark days are over! iOS 5 has included many new APIs you can use to easily customize the appearance of various UIKit controls.

To illustrate some of these new APIs, in this tutorial we’re going to take a “plain vanilla” app about surfing trips and customize the UI to get a more “beach-themed” look-and-feel.

To get the most out of this tutorial, you need to know the basics of iOS development first. If you are new to iOS development, you should check out some of the other tutorials on this site first.

Getting Started

To begin, download the starter project. I’ve created a simple app for you to start with so we can focus on the meat of this tutorial – UIKit customization.

Once you open up the project, take a look around the code and XIBs. You’ll see that the primary view presents a list of our surfing trips, and the detail view allows us to capture more information about each trip individually.

With that context, Build & Run the app (Cmd-R) to see what we have to start with.

Huh. Yes, this app is functional, but it’s hardly representative of the fun one would expect to have on a surfing trip. Let’s survey the scene in more detail.

Let’s start with the detail page. Things look pretty standard there, eh?

A plain UIBarButtonItem on the UINavigationBar at the top, stock UITabBar elements at the bottom, and the following “standard” data entry components including the following:

• UILabels with “System” Helvetica fonts
• UITextField
• UISlider
• UISwitch
• UISegmentedControl

In this tutorial, we’ll completely customize the detail screen to give it some style, using the new APIs available in iOS 5. So with anidea of what’s in store, let’s convert this app from “zero” to “hero”.

Adding a Background Image

If you open up the Images folder in your project, you’ll see that we already have some images we can use to customize the UI included in the project – we just need to modify the code tomake use of them.

Inside the images folder is a file called bg_sand.png. We’re going to start our UI customization bymaking this the background image in the detail view.

Open DetailViewController.m and create a viewDidLoad method like this:

- (void)viewDidLoad {    [super viewDidLoad];    [[self view] setBackgroundColor:[UIColor colorWithPatternImage:[UIImage imageNamed:@"bg_sand"]]];}

If you aren’t familiar with this technique, you can actually make a “color” based on an image like you see here. This is an easy way to set the background of a view, because there’s no “backgroundImage” property, but there is a “backgroundColor” property!

Compile and run to verify that it worked:

I can feel the sand between our toes already!

Customizing UINavigationBar

If you look inside the images folder, you’ll see two images that we want to use to customize the navigation bar: surf_gradient_textured_32.png and surf_gradient_textured_44.png.

We want to repeat these from left to right across the navigation bar. there are two different heights because the height of the navigation bar shrinks when thephone goes into landscape.

iOS 5 offers two new APIs that can help us with this:

• UINavigationBar has a new backgroundImage property we can use to set a custom background image like this.
• UIImage has a new resizableImageWithCapInsets method we can use to create a resizable image. The cap insets allow you to specify the portions of the image that should not be repeated, such as if you have roundedcorners for a button on the edges that shouldn’t be repeated.

We could go into the detail view and use these new APIs to set the navigation bar’s background image directly. But then we’d have to go and do the same thing inside our list view, and any other views we might have in our app!

Obviously this would get old quick. Recognizing this, iOS 5 offers a cool new feature that allows us to customize user interface elements once, allowing it to “stand in” for other elements within the same level in the containment hierarchy.

So starting with the navigation bar, we’re going to use this concept of the “appearance proxy” to customize some elements that will be repeated throughout the app.

Let’s see how it looks. Inside SurfsUpAppDelegate.m, create a new method right above application:didFinishLaunchingWithOptions:

- (void)customizeAppearance{    // Create resizable images    UIImage *gradientImage44 = [[UIImage imageNamed:@"surf_gradient_textured_44"]        resizableImageWithCapInsets:UIEdgeInsetsMake(0, 0, 0, 0)];    UIImage *gradientImage32 = [[UIImage imageNamed:@"surf_gradient_textured_32"]        resizableImageWithCapInsets:UIEdgeInsetsMake(0, 0, 0, 0)];    // Set the background image for *all* UINavigationBars    [[UINavigationBar appearance] setBackgroundImage:gradientImage44        forBarMetrics:UIBarMetricsDefault];    [[UINavigationBar appearance] setBackgroundImage:gradientImage32        forBarMetrics:UIBarMetricsLandscapePhone];    // Customize the title text for *all* UINavigationBars    [[UINavigationBar appearance] setTitleTextAttributes:        [NSDictionary dictionaryWithObjectsAndKeys:            [UIColor colorWithRed:255.0/255.0 green:255.0/255.0 blue:255.0/255.0 alpha:1.0],            UITextAttributeTextColor,            [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.8],            UITextAttributeTextShadowColor,            [NSValue valueWithUIOffset:UIOffsetMake(0, -1)],            UITextAttributeTextShadowOffset,            [UIFont fontWithName:@"Arial-Bold" size:0.0],            UITextAttributeFont,            nil]];}

The first two lines create stretchable images using the resizableImageWithCapInsets method discussed earlier. Note that this method replaces stretchableImageWithLeftCapWidth:topCapHeight:, which is now deprecated.

For the cap insets, you basically specify the fixed region of a given image in top, left, bottom, right. What’s left is stretched over the remainder of the region to which the image is applied. In this particular image we want the whole thing stretched, so we pass 0 for all of the fixed caps.

The next two lines invoke the appearance proxy, designating these stretchable images as background images, for the bar metrics specified.

The last line stylizes the title that appears in our detail view. To do so, we pass a dictionary of title text attributes. The available keys include the following:

• UITextAttributeFont
• UITextAttributeTextColor
• UITextAttributeTextShadowColor
• UITextAttributeTextShadowOffset

Almost done – just add the line to call this method at the top of application:didFinishLaunchingWithOptions:

[self customizeAppearance];

Compile and run, and now you should see the navigation bar has the teal background image applied in both orientations, with stylized title text as well!

Customizing UIBarButtonItem

Open up the Images directory and look at button_textured_24.png and button_textured_30.png. We want to use these to customize the look and feel of the buttons that appear in the UINavigationBar.

Notice that we’re going to set up these button images as resizable images. It’s important to make them resizable because the button widths will vary depending on what text is inside.

For these buttons, we don’t want the 5 leftmost pixels to stretch, nor the 5 rightmost pixels, so we’ll set the left and right cap insets to 5. The pixels in between will repeat as much as is needed for the width of the button.

Let’s try this out! We’ll use the appearance proxy to customize all the UIBarButtonItems at once, like we did last time. Add the following code to the end of customizeAppearance:

UIImage *button30 = [[UIImage imageNamed:@"button_textured_30"]    resizableImageWithCapInsets:UIEdgeInsetsMake(0, 5, 0, 5)];UIImage *button24 = [[UIImage imageNamed:@"button_textured_24"]    resizableImageWithCapInsets:UIEdgeInsetsMake(0, 5, 0, 5)];[[UIBarButtonItem appearance] setBackgroundImage:button30 forState:UIControlStateNormal    barMetrics:UIBarMetricsDefault];[[UIBarButtonItem appearance] setBackgroundImage:button24 forState:UIControlStateNormal    barMetrics:UIBarMetricsLandscapePhone];[[UIBarButtonItem appearance] setTitleTextAttributes:    [NSDictionary dictionaryWithObjectsAndKeys:        [UIColor colorWithRed:220.0/255.0 green:104.0/255.0 blue:1.0/255.0 alpha:1.0],        UITextAttributeTextColor,        [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0],        UITextAttributeTextShadowColor,        [NSValue valueWithUIOffset:UIOffsetMake(0, 1)],        UITextAttributeTextShadowOffset,        [UIFont fontWithName:@"AmericanTypewriter" size:0.0],        UITextAttributeFont,        nil]    forState:UIControlStateNormal];

This looks familiar. We create the stretchable images for the buttons and set them as the background for both display in both portrait & landscape orientation. We then format the text to match the typewriter-style font you saw at the outset of the tutorial.

The “back” bar button item needs special customization, because it should look different – like it’s pointing backwards. Take a look at the images we’re going to use to see what I mean: Imagesbutton_back_textured_24.png and Imagesbutton_back_textured_30.png.

Add the following code at the bottom of customizeAppearance to take care of the back bar button item:

UIImage *buttonBack30 = [[UIImage imageNamed:@"button_back_textured_30"]    resizableImageWithCapInsets:UIEdgeInsetsMake(0, 13, 0, 5)];UIImage *buttonBack24 = [[UIImage imageNamed:@"button_back_textured_24"]    resizableImageWithCapInsets:UIEdgeInsetsMake(0, 12, 0, 5)];[[UIBarButtonItem appearance] setBackButtonBackgroundImage:buttonBack30    forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];[[UIBarButtonItem appearance] setBackButtonBackgroundImage:buttonBack24    forState:UIControlStateNormal barMetrics:UIBarMetricsLandscapePhone];

Note that we use different cap inset values because the back image has a wider left hand side that shouldn’t stretch. Also note that there is a separate property on UIBarButtonItem for “backButtonBackgroundImage” that we use here.

Compile and run, and you should now see some cool customized UIBarButtonItems in your UINavigationBar!

Customizing UITabBar

To customize a UITabBar, iOS 5 offers an API to let you change the background image of the toolbar, and the image to indicate the selected item. Take a look at Imagestab_bg.png and Imagestab_select_indicator.png to see the images we’ll use for these.

Although our mockups only depict one UITabBar, these will in all likelihood have the same appearance if others appear, so we’ll use the appearance proxy to customize this as well.

Add the following code to the bottom of customizeAppearance:

UIImage *tabBackground = [[UIImage imageNamed:@"tab_bg"]    resizableImageWithCapInsets:UIEdgeInsetsMake(0, 0, 0, 0)];[[UITabBar appearance] setBackgroundImage:tabBackground];[[UITabBar appearance] setSelectionIndicatorImage:        [UIImage imageNamed:@"tab_select_indicator"]];

Compile and run again…nice! The background and selected image are nice touches.

Note you can also specify “finished” and “unfinished” images if you wish to modify the manner in which the selected & unselected images appear.

Customizing UISlider

Open up Imagesslider_minimum.png, Imagesslider_maximum.png, and Imagesthumb.png to see the images that we’re going to use to customize the UISlider.

iOS 5 makes it ridiculously easy to customize the UISlider by just setting the “maximumTrackImage”, “minimumTrackImage”, and “thumbImage” properties of a UISlider.

Let’s try it out. Add the following code to the bottom of customizeAppearance:

UIImage *minImage = [[UIImage imageNamed:@"slider_minimum.png"]    resizableImageWithCapInsets:UIEdgeInsetsMake(0, 5, 0, 0)];UIImage *maxImage = [[UIImage imageNamed:@"slider_maximum.png"]    resizableImageWithCapInsets:UIEdgeInsetsMake(0, 5, 0, 0)];UIImage *thumbImage = [UIImage imageNamed:@"thumb.png"];[[UISlider appearance] setMaximumTrackImage:maxImage    forState:UIControlStateNormal];[[UISlider appearance] setMinimumTrackImage:minImage    forState:UIControlStateNormal];[[UISlider appearance] setThumbImage:thumbImage    forState:UIControlStateNormal];

Compile and run, and check out your cool and stylish UISlider!

Customizing UISegmentedControl

Now we’ll customize our segmented control. This component is a little bit more complicated, as we have both selected & unselected backgrounds, as well as varying states for the adjacent regions (e.g., selected on left, unselected on right; unselected on the left & selected on the right; unselected on both sides).

Take a look at the images we’ll use for this to see what I mean: Imagessegcontrol_sel.png, Imagessegcontrol_uns.png, Imagessegcontrol_sel-uns.png, and Imagessegcontrol_uns-uns.png.

Then add the code to make use of these to the bottom of customizeAppearance:

UIImage *segmentSelected =    [[UIImage imageNamed:@"segcontrol_sel.png"]        resizableImageWithCapInsets:UIEdgeInsetsMake(0, 15, 0, 15)];UIImage *segmentUnselected =    [[UIImage imageNamed:@"segcontrol_uns.png"]        resizableImageWithCapInsets:UIEdgeInsetsMake(0, 15, 0, 15)];UIImage *segmentSelectedUnselected =    [UIImage imageNamed:@"segcontrol_sel-uns.png"];UIImage *segUnselectedSelected =    [UIImage imageNamed:@"segcontrol_uns-sel.png"];UIImage *segmentUnselectedUnselected =    [UIImage imageNamed:@"segcontrol_uns-uns.png"];[[UISegmentedControl appearance] setBackgroundImage:segmentUnselected    forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];[[UISegmentedControl appearance] setBackgroundImage:segmentSelected    forState:UIControlStateSelected barMetrics:UIBarMetricsDefault];[[UISegmentedControl appearance] setDividerImage:segmentUnselectedUnselected    forLeftSegmentState:UIControlStateNormal    rightSegmentState:UIControlStateNormal    barMetrics:UIBarMetricsDefault];[[UISegmentedControl appearance] setDividerImage:segmentSelectedUnselected    forLeftSegmentState:UIControlStateSelected    rightSegmentState:UIControlStateNormal    barMetrics:UIBarMetricsDefault];[[UISegmentedControl appearance]    setDividerImage:segUnselectedSelected    forLeftSegmentState:UIControlStateNormal    rightSegmentState:UIControlStateSelected    barMetrics:UIBarMetricsDefault];

Compile and run, and now our UISegmentedControl has a completely different look!

Customizing UISwitch

At the time of writing this tutorial, there is no easy way to customize the artwork on a UISwitch. However (like many other controls) it is extremely easy to change its color via the tintColor property.

To ensure that we touch on a few different approaches to customization, we’ll customize the “onTintColor” parameter in code. You’ll note that in DetailViewController, we already have an IBOutlet – rentSwitch – wired to our switch in DetailView.xib.

So, add the following code to set the tint color in the viewDidLoad method of DetailViewController:

[rentSwitch setOnTintColor:[UIColor colorWithRed:0 green:175.0/255.0 blue:176.0/255.0 alpha:1.0]];

Compile and run, and check out your newly colored switch!

Things are looking pretty good, but we still have a couple of items outstanding. We need to update the labels and set the background of our custom UITextField.

Customizing UILabel

The labels are one part of the detail view we won’t customize via the appearance proxy. Open DetailView.xib so that we can edit them in Interface Builder. Start by selecting the first label (i.e., “Your name”) in the main view, the in the Utilities view (i.e., the right pane), select the Attributes Inspector and set the following:

• Font: Custom
• Family: American Typewriter
• Style: Regular
• Size: 16

Repeat this for the two remaining labels: “Experience Level” and “Rent a board?”.

Compile and run, and now your labels have a neat typewriter feel!

Customizing UITextField

Our UITextField has already been set to use UITextBorderStyleLine. Since we’re still in Interface Builder, let’s set the font to American Typewriter, Size 12, Regular. Now if you look at the Identity Inspector, you’ll see that the Custom Class has been defined as something other than UITextField – CustomTextField. If you look in the Navigator pane on the left, there is a group called Custom Views. Expand that, and you will see that we have a type called exactly that.

Right now the drawRect: method of our UITextField delegates to the superclass implementation. But in order to paint the teal background, we are going to override drawRect: as another customization technique.

Replace the call to super with the following code:

- (void)drawRect:(CGRect)rect{    UIImage *textFieldBackground = [[UIImage imageNamed:@"text_field_teal.png"] resizableImageWithCapInsets:UIEdgeInsetsMake(15.0, 5.0, 15.0, 5.0)];    [textFieldBackground drawInRect:[self bounds]];}

Here we create yet another stretchable image with appropriate insets, and draw it in the rectangle defined by the bounds of this view (i.e., our UITextField). Let’s Build & Run…

Congratulations – the detail view is complete!