怎么用三个slider控制同页面的label的背景颜色

Question

用滚动条可以实时改变label的背景色。。假设三个slider，一个控制红色，一个控制绿色，一个控制蓝色

Answer 1

• (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view.

  UILabel *redLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 300, 70, 30)];
  redLabel.text = @"红色控制";
  [self.view addSubview:redLabel];
  [redLabel release];
  UISlider *redSlide = [[UISlider alloc] initWithFrame:CGRectMake(90, 300, 200, 30)];
  redSlide.maximumValue = 1;
  redSlide.minimumValue =0;
  [redSlide addTarget:self action:@selector(changeRed:) forControlEvents:(UIControlEventValueChanged)];

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

  UILabel *greenLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 360, 70, 30)];
  greenLabel.text = @"绿色控制";
  [self.view addSubview:greenLabel];
  [greenLabel release];
  UISlider *GreenSlide = [[UISlider alloc] initWithFrame:CGRectMake(90, 360, 200, 30)];
  GreenSlide.maximumValue = 1;
  GreenSlide.minimumValue =0;
  [GreenSlide addTarget:self action:@selector(changeGreen:) forControlEvents:(UIControlEventValueChanged)];

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

  UILabel *blueLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 420, 70, 30)];
  blueLabel.text = @"蓝色控制";
  [self.view addSubview:blueLabel];
  [blueLabel release];
  UISlider *BlueSlide = [[UISlider alloc] initWithFrame:CGRectMake(90, 420, 200, 30)];
  BlueSlide.maximumValue = 1;
  BlueSlide.minimumValue =0;
  [BlueSlide addTarget:self action:@selector(changeBlue:) forControlEvents:(UIControlEventValueChanged)];

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

  self.redColor = arc4random()%256/255.0;
  self.greenColor = arc4random()%256/255.0;
  self.blueColor = arc4random()%256/255.0;

  self.view.backgroundColor = [UIColor colorWithRed:_redColor green:_greenColor blue:_blueColor alpha:1];

}

• (CGFloat)changeRed:(UISlider *)slide{

  _redColor = slide.value;
  // 第一种方法,直接设置
  // self.view.backgroundColor = [UIColor colorWithRed:_redColor green:_greenColor blue:_blueColor alpha:1];

  //第二种方法,声明一个返回函数,返回slide.value
  return _redColor;

}

• (CGFloat)changeGreen:(UISlider *)slide{
  _greenColor = slide.value;
  // self.view.backgroundColor = [UIColor colorWithRed:_redColor green:_greenColor blue:_blueColor alpha:1];
  return _greenColor;
  }

• (CGFloat)changeBlue:(UISlider *)slide{

  _blueColor = slide.value;
  // self.view.backgroundColor = [UIColor colorWithRed:_redColor green:_greenColor blue:_blueColor alpha:1];
  return _blueColor;
  }

• (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.

}