ios弹幕高效加载实现方式实例代码

#pragma mark - 获取数据源
- (void)loadData{
  // 获取plist全路径
  NSString *filePath = [[NSBundle mainBundle] pathForResource:@"barrage.plist" ofType:nil];
  // 从指定的路径中加载数据
  NSArray *array = [NSArray arrayWithContentsOfFile:filePath];

  // 遍历数组
  for (NSDictionary *dict in array) {
    // 字典转模型
    BAModle *barrageM = [BAModle barrageWithDict:dict];
    [self.danMus addObject:barrageM];
  }
}

#pragma mark - 触摸屏幕响应事件
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{

  // 获得一个随机整数
  NSInteger index = arc4random_uniform((u_int32_t)self.danMus.count);
  // 获得一个随机模型
  BAModle *danMu = self.danMus[index];
  // 根据模型生成图片
  BAImage *image = [self.danMuview imageWithBarrage:danMu];
  // 调整弹幕加载区域
  image.x = self.view.bounds.size.width;
  image.y = arc4random_uniform(self.danMuview.bounds.size.height - image.size.height);
  // 把图片加到弹幕view上
  [self.danMuview addImage:image]; 
}

#pragma mark - 绘制弹幕图片
- (BAImage *)imageWithBarrage:(BAModle *)danMu{
  // 开启绘图上下文
  //
  UIFont *font = [UIFont systemFontOfSize:13];
  // 头像
  CGFloat iconH = 30;
  CGFloat iconW = iconH;
  // 间距
  CGFloat marginX = 5;

  // 表情的尺寸
  CGFloat emotionW = 25;
  CGFloat emotionH = emotionW;
  // 计算用户名占据的区域
  CGSize nameSize = [danMu.userName boundingRectWithSize:CGSizeMake(MAXFLOAT, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:font} context:nil].size;
  // 计算内容占据的区域
  CGSize textSize = [danMu.text boundingRectWithSize:CGSizeMake(MAXFLOAT, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:font} context:nil].size;

  // 位图上下文的尺寸
  CGFloat contentH = iconH;
  CGFloat contentW = iconW + 4 * marginX + nameSize.width + textSize.width + danMu.emotions.count * emotionH;

  CGSize contextSize = CGSizeMake(contentW, contentH);
  UIGraphicsBeginImageContextWithOptions(contextSize, NO, 0.0);

  // 获得位图上下文
  CGContextRef ctx = UIGraphicsGetCurrentContext();
  // 将上下文保存到栈中
  CGContextSaveGState(ctx);
  // 1.绘制圆形区域
  CGRect iconFrame = CGRectMake(0, 0, iconW, iconH);
  // 绘制头像圆形
  CGContextAddEllipseInRect(ctx, iconFrame);
  // 超出圆形的要裁剪
  CGContextClip(ctx);
  // 2.绘制头像
  UIImage *icon = danMu.type ? [UIImage imageNamed:@"headImage_1"]:[UIImage imageNamed:@"headImage_2"];
  [icon drawInRect:iconFrame];
  // 将上下文出栈替换当前上下文
  CGContextRestoreGState(ctx);
  // 3.绘制背景图片
  CGFloat bgX = iconW + marginX;
  CGFloat bgY = 0;
  CGFloat bgW = contentW - bgX;
  CGFloat bgH = contentH;
  danMu.type ? [[UIColor orangeColor] set]:[[UIColor whiteColor] set];
  [[UIBezierPath bezierPathWithRoundedRect:CGRectMake(bgX, bgY, bgW, bgH) cornerRadius:20.0] fill];

  // 4.绘制用户名
  CGFloat nameX = bgX + marginX;
  CGFloat nameY = (contentH - nameSize.height) * 0.5;
  [danMu.userName drawAtPoint:CGPointMake(nameX, nameY) withAttributes:@{NSAttachmentAttributeName:font,NSForegroundColorAttributeName:danMu.type == NO ? [UIColor orangeColor]:[UIColor blackColor]}];

  // 5.绘制内容
  CGFloat textX = nameX + nameSize.width + marginX;
  CGFloat textY = nameY;
  [danMu.text drawAtPoint:CGPointMake(textX, textY) withAttributes:@{NSAttachmentAttributeName:font,NSForegroundColorAttributeName:danMu.type == NO ? [UIColor blackColor]:[UIColor whiteColor]}];

  // 6.绘制表情
  __block CGFloat emotionX = textX + textSize.width;
  CGFloat emotionY = (contentH - emotionH) * 0.5;
  [danMu.emotions enumerateObjectsUsingBlock:^(NSString *emotionName, NSUInteger idx, BOOL * _Nonnull stop) {
    // 加载表情图片
    UIImage *emotion = [UIImage imageNamed:emotionName];
    [emotion drawInRect:CGRectMake(emotionX, emotionY, emotionW, emotionH)];
    // 修改emotionX
    emotionX += emotionW;
  }];
  // 从位图上下文中获得绘制好的图片
  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

  return [[BAImage alloc] initWithCGImage:image.CGImage scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
}

#pragma mark - 添加定时器
- (void)addTimer{
  if (self.link) {
    return;
  }
  // 每秒执行60次回调
  CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(setNeedsDisplay)];
  // 将定时器添加到runLoop
  [link addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
  self.link = link;
}
#pragma mark - 绘制移动
- (void)drawRect:(CGRect)rect{

  for (BAImage *image in self.imageArray) {
    image.x -= 3;
    // 绘制图片
    [image drawAtPoint:CGPointMake(image.x, image.y)];
    // 判断图片是否超出屏幕
    if (image.x + image.size.width < 0) {
      [self.deleteImageArray addObject:image];
    }
  }
  // 移除超过屏幕的弹幕
  for (BAImage *image in self.deleteImageArray) {
    [self.imageArray removeObject:image];
  }
  [self.deleteImageArray removeAllObjects];
}