锁屏状态下展示音乐信息

• 音乐类项目将当前播放音乐信息展示到锁屏

#pragma mark - 生成锁屏界面的图片
- (void)generatorLockImage
{
    // 1.拿到当前歌曲的图片
    DXMusic *playingMusic = [DXMusicTool playingMusic];
    UIImage *currentImage = [UIImage imageNamed:playingMusic.icon];
    
    // 2.拿到三句歌词
    // 2.1.获取当前的歌词
    DXLrcline *currentLrc = self.lrclist[self.currentIndex];
    // 2.2.上一句歌词
    NSInteger previousIndex = self.currentIndex - 1;
    DXLrcline *prevousLrc = nil;
    if (previousIndex >= 0) {
        prevousLrc = self.lrclist[previousIndex];
    }
    // 2.3.下一句歌词
    NSInteger nextIndex = self.currentIndex + 1;
    DXLrcline *nextLrc = nil;
    if (nextIndex < self.lrclist.count) {
        nextLrc = self.lrclist[nextIndex];
    }
    
    // 3.生成水印图片
    // 3.1.获取上下文
    UIGraphicsBeginImageContext(currentImage.size);
    // 3.2.将图片画上去
    [currentImage drawInRect:CGRectMake(0, 0, currentImage.size.width, currentImage.size.height)];
    // 3.3.将歌词画到图片上
    CGFloat titleH = 25;
    NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];
    style.alignment = NSTextAlignmentCenter;
    NSDictionary *attributes1 = @{NSFontAttributeName : [UIFont systemFontOfSize:14.0],
                                  NSForegroundColorAttributeName : [UIColor lightGrayColor],
                                  NSParagraphStyleAttributeName : style};
    [prevousLrc.text drawInRect:CGRectMake(0, currentImage.size.height - titleH * 3, currentImage.size.width, titleH) withAttributes:attributes1];
    [nextLrc.text drawInRect:CGRectMake(0, currentImage.size.height - titleH, currentImage.size.width, titleH)  withAttributes:attributes1];
    
    NSDictionary *attributes2 = @{NSFontAttributeName : [UIFont systemFontOfSize:16.0],
                                  NSForegroundColorAttributeName : [UIColor whiteColor],
                                  NSParagraphStyleAttributeName : style};
    [currentLrc.text drawInRect:CGRectMake(0, currentImage.size.height - titleH * 2, currentImage.size.width, titleH)  withAttributes:attributes2];
    
    // 4.生成图片
    UIImage *lockImage = UIGraphicsGetImageFromCurrentImageContext();
    
    // 5.设置锁屏信息
    [self setupLockScreenInfoWithLockImage:lockImage];
    
    // 6.关闭
    UIGraphicsEndImageContext();
}

- (void)setupLockScreenInfoWithLockImage:(UIImage *)lockImage
{
    // 0.获取当前正在播放的歌曲
    DXMusic *playingMusic = [DXMusicTool playingMusic];
    
    // 1.获取锁屏界面中心
    MPNowPlayingInfoCenter *playingInfoCenter = [MPNowPlayingInfoCenter defaultCenter];
    
    // 2.设置展示的信息
    NSMutableDictionary *playingInfo = [NSMutableDictionary dictionary];
    [playingInfo setObject:playingMusic.name forKey:MPMediaItemPropertyAlbumTitle];
    [playingInfo setObject:playingMusic.singer forKey:MPMediaItemPropertyArtist];
    MPMediaItemArtwork *artWork = [[MPMediaItemArtwork alloc] initWithImage:lockImage];
    [playingInfo setObject:artWork forKey:MPMediaItemPropertyArtwork];
    [playingInfo setObject:@(self.duration) forKey:MPMediaItemPropertyPlaybackDuration];
    [playingInfo setObject:@(self.currentTime) forKey:MPNowPlayingInfoPropertyElapsedPlaybackTime];
    
    playingInfoCenter.nowPlayingInfo = playingInfo;
    
    // 3.让应用程序可以接受远程事件
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
}

// 监听锁屏控制事件
- (void)remoteControlReceivedWithEvent:(UIEvent *)event
{
    switch (event.subtype) {
        case UIEventSubtypeRemoteControlPlay:
        case UIEventSubtypeRemoteControlPause:
            [self playOrPause];
            break;
            
        case UIEventSubtypeRemoteControlNextTrack:
            [self next];
            break;
            
        case UIEventSubtypeRemoteControlPreviousTrack:
            [self previous];
            break;
            
        default:
            break;
    }
}

• 一个不错的开源项目 Jackdx/QQMusic