iOS开发 - 滑动控制屏幕亮度和系统音量（附加AVAudioPlayer基本用法和Masonry简单使用）

    //获得当前屏幕亮度
    light = [UIScreen mainScreen].brightness;
    light = 0.5f;
    //直接赋值或者使用set方法皆可
    [UIScreen mainScreen].brightness = light;

MPMusicPlayerController *mpVC = [MPMusicPlayerController applicationMusicPlayer];
//获得系统当前音量
voice = _mpVC.volume;
voice = 0.5f;
//改变系统音量
_mpVC.volume = voice;

- (void)leftSwipGes:(UIPanGestureRecognizer *)leftSwip
{
    //滑动方法获取到当前位置的y坐标
    leftCurrentY = [leftSwip translationInView:leftView].y;
    NSLog(@"left");
    //当前坐标大于上一次移动的坐标，为向下滑动
    if (leftCurrentY > leftLastY) {
        if (light > 0) {
            //向下滑动屏幕变暗，亮度下降
            light = light - 0.01;
        }
        else{
            //当亮度为0时固定为0，禁止为负值
            light = 0;
        }
    }
    else
    {
        if (light < 1) {
            //向上滑动亮度增加
            light = light + 0.01;
        }
        else{
            //当亮度为1时固定为1，禁止大于1
            light = 1;
        }
    }
    //设置屏幕亮度
    [UIScreen mainScreen].brightness = light;
    //当前位置的上一次移动的位置y坐标
    leftLastY = leftCurrentY;
}
//此处除参数外原理一样，不再额外注释
- (void)rightSwipGes:(UIPanGestureRecognizer *)rightSwip
{
    NSLog(@"right");
    rightCurrentY = [rightSwip translationInView:rightView].y;
    if (rightCurrentY > rightLastY) {
        if (voice > 0) {
            voice = voice - 0.01;
        }
        else{
            voice = 0;
        }
    }
    else
    {
        if (voice < 1) {
            voice = voice + 0.01;
        }
        else{
            voice = 1;
        }
    }
    //设置系统音量
    _mpVC.volume = voice;
    rightLastY = rightCurrentY;
}

//从budle路径下读取音频文件,这个文件名是你的歌曲名字,mp3是你的音频格式
    NSString *string = [[NSBundle mainBundle] pathForResource:@"夜空中最亮的星" ofType:@"mp3"];
    NSString *playUrl = [string stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];  //转码成UTF-8  否则可能会出现错误
    //把音频文件转换成url格式
    NSURL *url = [NSURL URLWithString:playUrl];
    //初始化音频类 并且添加播放文件
    _avAudioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:nil];
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
    //设置初始音量大小
    _avAudioPlayer.volume = voice;
    //设置音乐播放次数  -1为一直循环
    _avAudioPlayer.numberOfLoops = -1;
    //预播放
    [_avAudioPlayer prepareToPlay];
    [_avAudioPlayer play];

    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];