UISlider 制作的声音显示效果

简单地演示效果，直接在入口类实现

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

    UISlider *slider = [[UISlider alloc] init];
    slider.center = CGPointMake(160, 400);
    slider.bounds = CGRectMake(0, 0, 240, 20);
    slider.tag = 100;
    slider.minimumValue = 0;
    slider.maximumValue = 100;
    slider.minimumTrackTintColor = [UIColor greenColor]; //已经滑过的颜色
    slider.maximumTrackTintColor = [UIColor blueColor];//滑动条的颜色
    slider.value = 30;
    [slider addTarget:self action:@selector(changeVoice:) forControlEvents:UIControlEventValueChanged];
    [self.window addSubview:slider];

    _imageView = [[UIImageView alloc] init];
    _imageView.center = CGPointMake(20, 400);
    _imageView.bounds = CGRectMake(0, 0, 20, 20);
    _imageView.image = [UIImage imageNamed:@"mid.png"];
    [self.window addSubview:_imageView];

//    [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:@selector(addValue:) userInfo:slider repeats:YES];

    UIButton *btn = [UIButton buttonWithType:UIButtonTypeSystem];
    btn.frame = CGRectMake(0, 0, 20, 20);
    [_imageView addSubview:btn];
    _imageView.userInteractionEnabled = YES;
    [btn addTarget:self action:@selector(voiceChange) forControlEvents:UIControlEventTouchUpInside];
    return YES;
}

//定时器方法，声音自动提高,但这时虽然滑动条的值发生变化，但是并不触发方法
- (void)addValue:(NSTimer *)timer
{
    UISlider *slider = (UISlider *)[timer userInfo];
    if (slider.value < 30)
    {
        slider.value += 0.1;
    }
}

//声音的高低可又图标表示出来
- (void)changeVoice:(UISlider *)slider
{
    if (slider.value == 0)
    {
        _imageView.image = [UIImage imageNamed:@"none.png"];
        return;
    }
    if (slider.value < 30)
    {
        _imageView.image = [UIImage imageNamed:@"low.png"];
        return;
    }
    if (slider.value < 60)
    {
        _imageView.image = [UIImage imageNamed:@"mid.png"];
        return;
    }
    if (slider.value <= 100)
    {
        _imageView.image = [UIImage imageNamed:@"high.png"];
    }
}

//当声音不为 0 的时候，点击声音图标总是将声音置 0，当再次点击图标的时候，声音恢复
- (void)voiceChange
{
    UISlider *slider = (UISlider *)[self.window viewWithTag:100];
    static int count = 0;
    count ++;
    if (count % 2 != 0)
    {
        _voiceValue = slider.value;  //记住上次的声音
        slider.value = 0;
    }
    else
    {
        if (slider.value != 0) //在回复声音之前已经将声音调节不再为0，则使用递归
        {
            [self voiceChange];
            count = 0;
        }
        slider.value = _voiceValue;
    }
}

@end

代码中的定时器本来是像模拟一下让声音自动提升的效果，演示的时候才知道这样并不可以，想了想，滑动条应该是需要与用户交互才能显示它存在的意义。