不通过Interface Builder创建更改背景色的范例

头文件：

 

#import <UIKit/UIKit.h>

@interface ColorViewController : UIViewController {
  UILabel *redValue, *greenValue, *blueValue;
  UISlider *redSlider, *greenSlider, *blueSlider;
}

@property(nonatomic, retain) UILabel *redValue;
@property(nonatomic, retain) UILabel *greenValue;
@property(nonatomic, retain) UILabel *blueValue;
@property(nonatomic, retain) UISlider *redSlider;
@property(nonatomic, retain) UISlider *greenSlider;
@property(nonatomic, retain) UISlider *blueSlider;

@end

 

实现文件：

 

#import "ColorViewController.h"

@implementation ColorViewController

@synthesize redValue, greenValue, blueValue;
@synthesize redSlider, greenSlider, blueSlider;

- (void)loadView {
  UIView *contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
  [contentView setBackgroundColor:[UIColor blackColor]];
  self.view = contentView;
  
  redValue = [[UILabel alloc] initWithFrame:CGRectMake(10, 30, 30, 20)];
  redValue.text = @"0";
  redValue.textColor = [UIColor redColor];
  redValue.backgroundColor = [UIColor blackColor];
  
  greenValue = [[UILabel alloc] initWithFrame:CGRectMake(10, 90, 30, 20)];
  greenValue.text = @"0";
  greenValue.textColor = [UIColor greenColor];
  greenValue.backgroundColor = [UIColor blackColor];
  
  blueValue = [[UILabel alloc] initWithFrame:CGRectMake(10, 150, 30, 20)];
  blueValue.text = @"0";
  blueValue.textColor = [UIColor blueColor];
  blueValue.backgroundColor = [UIColor blackColor];
  
  [self.view addSubview:redValue];
  [self.view addSubview:greenValue];
  [self.view addSubview:blueValue];
	
  [redValue release];
  [greenValue release];
  [blueValue release];
  
  [self.view addSubview:self.redSlider];
  [self.view addSubview:self.greenSlider];
  [self.view addSubview:self.blueSlider];
  
  [contentView release];
}

- (UISlider *)redSlider{
  if(redSlider == nil){
    redSlider = [[UISlider alloc] initWithFrame:CGRectMake(50, 30, 255, 20)];
    [redSlider addTarget:self action:@selector(changeColor) forControlEvents:UIControlEventValueChanged];
    redSlider.maximumValue = 255.0;
    redSlider.minimumValue = 0.0;
    redSlider.value = 0.0;
    redSlider.continuous = YES;
  }
  return redSlider;
}

- (UISlider *)greenSlider{
  if(greenSlider == nil){
    greenSlider = [[UISlider alloc] initWithFrame:CGRectMake(50, 90, 255, 20)];
    [greenSlider addTarget:self action:@selector(changeColor) forControlEvents:UIControlEventValueChanged];
    greenSlider.maximumValue = 255.0;
    greenSlider.minimumValue = 0.0;
    greenSlider.value = 0.0;
    greenSlider.continuous = YES;
  }
  return greenSlider;
}

- (UISlider *)blueSlider{
  if(blueSlider == nil){
    blueSlider = [[UISlider alloc] initWithFrame:CGRectMake(50, 150, 255, 20)];
    [blueSlider addTarget:self action:@selector(changeColor) forControlEvents:UIControlEventValueChanged];
    blueSlider.maximumValue = 255.0;
    blueSlider.minimumValue = 0.0;
    blueSlider.value = 0.0;
    blueSlider.continuous = YES;
  }
  return blueSlider;
}

- (void)changeColor{
  NSString *redStr = [[NSString alloc] initWithFormat:@"%d", (int)redSlider.value];
  NSString *greenStr = [[NSString alloc] initWithFormat:@"%d", (int)greenSlider.value];
  NSString *blueStr = [[NSString alloc] initWithFormat:@"%d", (int)blueSlider.value];
  redValue.text = redStr;
  greenValue.text = greenStr;
  blueValue.text = blueStr;
	
  self.view.backgroundColor = [UIColor colorWithRed:[redValue.text floatValue]/255.0 green:[greenValue.text floatValue]/255.0 blue:[blueValue.text floatValue]/255.0 alpha:1.0]; 
	
  [redStr release];
  [greenStr release];
  [blueStr release];
}

- (void)dealloc {
  [super dealloc];
  [redSlider release];
  [greenSlider release];
  [blueSlider release];
  
  redSlider = nil;
  greenSlider = nil;
  blueSlider = nil;
  
  [redValue release];
  [greenValue release];
  [blueValue release];
	
  redValue = nil;
  greenValue = nil;
  blueValue = nil;
}

@end

 

示例图：