How to use the Segmented Control

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本文介绍如何在iOS应用中使用UISegmentedControl组件。通过创建视图控制器项目、添加标签和段控件，设置样式及目标动作，实现当用户选择不同选项时更新UI的功能。

Here is How You Use the Segmented Control [UISegmentedControl]

by MattjDrake on SEPTEMBER 15, 2009 in CODE TIPS

A segmented control displays a list of options that a user can choose from. Each segment sort of looks like a button; the segments remains “pressed” even after the user lifts his or her finger.

You can detect when a different segment is selected and also what corresponding value in an array (that you supply) is referenced by the selected segment. Here is an example of what a UISegmentedControl looks like:

Here Are the Steps To Use UISegmentedControl

Create A View Based XCode Project

Add A UILabel To the Controller:

#import "UseSegmentedControlViewController.h"
@implementation UseSegmentedControlViewController
UILabel *label;

- (void)viewDidLoad {
    [super viewDidLoad];

	//Create label
	label = [[UILabel alloc] init];
	label.frame = CGRectMake(10, 10, 300, 40);
	label.textAlignment = UITextAlignmentCenter;
	[self.view addSubview:label];

- (void)dealloc {
     [label release];
     [super dealloc];
}

@end

Create An Array:

	NSArray *itemArray = [NSArray arrayWithObjects: @"One", @"Two", @"Three", nil];

Create An Instance of UISegmentedControl:

	UISegmentedControl *segmentedControl = [[UISegmentedControl alloc] initWithItems:itemArray];

Customize the Control By Setting It’s Properties:

	segmentedControl.frame = CGRectMake(35, 200, 250, 50);
	segmentedControl.segmentedControlStyle = UISegmentedControlStylePlain;
	segmentedControl.selectedSegmentIndex = 1;

Set A Target and Action (The Code That Will Execute When The User Selects A New Segment):

	[segmentedControl addTarget:self
	                     action:@selector(pickOne:)
	           forControlEvents:UIControlEventValueChanged];

Add the Segmented Control to the view:

	[self.view addSubview:segmentedControl];
	[segmentedControl release];

Implement the Action:

- (void) pickOne:(id)sender{
    UISegmentedControl *segmentedControl = (UISegmentedControl *)sender;
    label.text = [segmentedControl titleForSegmentAtIndex: [segmentedControl selectedSegmentIndex]];
}

Release the UILabel in dealloc:

-(void)dealloc{
	[label release];
	[super dealloc];
}

Here Is the Complete Code For the UIViewController:

#import "UseSegmentedControlViewController.h"
@implementation UseSegmentedControlViewController
UILabel *label;

- (void)viewDidLoad {
    [super viewDidLoad];

	//Create label
	label = [[UILabel alloc] init];
	label.frame = CGRectMake(10, 10, 300, 40);
	label.textAlignment = UITextAlignmentCenter;
	[self.view addSubview:label]; 

	//Create the segmented control
	NSArray *itemArray = [NSArray arrayWithObjects: @"One", @"Two", @"Three", nil];
	UISegmentedControl *segmentedControl = [[UISegmentedControl alloc] initWithItems:itemArray];
	segmentedControl.frame = CGRectMake(35, 200, 250, 50);
	segmentedControl.segmentedControlStyle = UISegmentedControlStylePlain;
	segmentedControl.selectedSegmentIndex = 1;
	[segmentedControl addTarget:self
	                     action:@selector(pickOne:)
	           forControlEvents:UIControlEventValueChanged];
	[self.view addSubview:segmentedControl];
	[segmentedControl release];

}

//Action method executes when user touches the button
- (void) pickOne:(id)sender{
    UISegmentedControl *segmentedControl = (UISegmentedControl *)sender;
    label.text = [segmentedControl titleForSegmentAtIndex: [segmentedControl selectedSegmentIndex]];
} 

- (void)dealloc {
     [label release];
     [super dealloc];
}

@end

Be Sure To Check Out the Header Files In XCode To See All Your Options

You can change the look and feel of the UISegmentedControl by altering the background color. You can use your own images and add/remove segments on the fly.