基于BarrageRender自定义弹幕动画
BarrageRender目前已更新到2.0.1,自定义弹幕的机制有改变，本篇文章的代码在2.0.1下不起作用，如果想按照本文中用的方法，请使用1.9.1版本的BarrageRender。后续会更新2.0.1版本下的自定义弹幕
BarrageRender 是iOS上一个非常出名的弹幕渲染开源框架,其可以让我们在App中非常方便的集成弹幕功能，其作者在代码中提供了两种方式的弹幕动画，
BarrageFloatSprite和BarrageWalkSprite。可以说移动和浮动这两种动画方式基本上已经满足了大部分App的需求，但是仍然有部分App需要在弹幕的展现形式上更加的自由，例如各大直播平台的礼物弹幕。笔者将在这篇文章中分享自己在BarrageRender的基础上编写自定义礼物弹幕的过程。
博客地址
先展示效果
弹幕效果
再介绍BarrageWalkSprite原理
BarrageWalkSprite和本文将要实现的自定义Sprite有一定的关联性，所以就通过分析BarrageWalkSprite的源码来展示BarrageRender渲染弹幕的原理，另外一个BarrageFloatSprite的渲染方式稍有不同，但是如果你能搞清楚BarrageWalkSprite的原理，理解FloatSprite的渲染方式也是很轻松的。
弹幕的初始位置
BarrageRender在BarrageDispatcher的调度下触发activeWithContext方法，而在此方法中，BarrageRender调用了Sprite的originInBounds:withSprite方法来确定每个精灵的初始位置
- (void)activeWithContext:(NSDictionary *)context
{
CGRect rect = [[context objectForKey:kBarrageRendererContextCanvasBounds]CGRectValue];
NSArray * sprites = [context objectForKey:kBarrageRendererContextRelatedSpirts];
NSTimeInterval timestamp = [[context objectForKey:kBarrageRendererContextTimestamp]doubleValue];
_timestamp = timestamp;
_view = [self bindingView];
[self configView];
[_view sizeToFit];
if (!CGSizeEqualToSize(_mandatorySize, CGSizeZero)) {
_view.frame = CGRectMake(0, 0, _mandatorySize.width, _mandatorySize.height);
}
_origin = [self originInBounds:rect withSprites:sprites];
_view.frame = CGRectMake(_origin.x, _origin.y, self.size.width, self.size.height);
}
BarrageWalkSpirte在originInBounds:withSprite方法中,根据当前屏幕上已经存在的Sprite来计算自己的初始位置。
- (CGPoint)originInBounds:(CGRect)rect withSprites:(NSArray *)sprites
{
// 获取同方向精灵
NSMutableArray * synclasticSprites = [[NSMutableArray alloc]initWithCapacity:sprites.count];
for (BarrageWalkSprite * sprite in sprites) {
if (sprite.direction == _direction && sprite.side == self.side) { // 找寻同道中人
[synclasticSprites addObject:sprite];
}
}
static BOOL const AVAERAGE_STRATEGY = YES; // YES:条纹平均精灵策略(体验会好一些); NO:最快时间策略
NSTimeInterval stripMaxActiveTimes[STRIP_NUM]={0}; // 每一条网格 已有精灵中最后退出屏幕的时间
NSUInteger stripSpriteNumbers[STRIP_NUM]={0}; // 每一条网格 包含精灵的数目
NSUInteger stripNum = MIN(STRIP_NUM, MAX(self.trackNumber, 1)); // between (1,STRIP_NUM)
CGFloat stripHeight = rect.size.height/stripNum; // 水平条高度
CGFloat stripWidth = rect.size.width/stripNum; // 竖直条宽度
BOOL oritation = _direction == BarrageWalkDirectionL2R || _direction == BarrageWalkDirectionR2L; // 方向, YES代表水平弹幕
BOOL rotation = self.side == [self defaultSideWithDirection:_direction];
/// 计算数据结构,便于应用算法
NSUInteger overlandStripNum = 1; // 横跨网格条数目
if (oritation) { // 水平
overlandStripNum = (NSUInteger)ceil((double)self.size.height/stripHeight);
}
else // 竖直
{
overlandStripNum = (NSUInteger)ceil((double)self.size.width/stripWidth);
}
/// 当前精灵需要的时间,左边碰到边界, 不是真实的活跃时间
NSTimeInterval maxActiveTime = oritation?rect.size.width/self.speed:rect.size.height/self.speed;
NSUInteger availableFrom = 0;
NSUInteger leastActiveTimeStrip = 0; // 最小时间的行
NSUInteger leastActiveSpriteStrip = 0; // 最小网格的行
for (NSUInteger i = 0; i < stripNum; i++) {
//寻找当前行里包含的sprites
CGFloat stripFrom = i * (oritation?stripHeight:stripWidth);
CGFloat stripTo = stripFrom + (oritation?stripHeight:stripWidth);
if (!rotation) {
CGFloat preStripFrom = stripFrom;
stripFrom = (oritation?rect.size.height:rect.size.width) - stripTo;
stripTo = (oritation?rect.size.height:rect.size.width) - preStripFrom;
}
CGFloat lastDistanceAllOut = YES;
for (BarrageWalkSprite * sprite in synclasticSprites) {
CGFloat spriteFrom = oritation?sprite.origin.y:sprite.origin.x;
CGFloat spriteTo = spriteFrom + (oritation?sprite.size.height:sprite.size.width);
if ((spriteTo-spriteFrom)+(stripTo-stripFrom)>MAX(stripTo-spriteFrom, spriteTo-stripFrom)) { // 在条条里
stripSpriteNumbers[i]++;
NSTimeInterval activeTime = [sprite estimateActiveTime];
if (activeTime > stripMaxActiveTimes[i]){ // 获取最慢的那个
stripMaxActiveTimes[i] = activeTime;
CGFloat distance = oritation?fabs(sprite.position.x-sprite.origin.x):fabs(sprite.position.y-sprite.origin.y);
lastDistanceAllOut = distance > (oritation?sprite.size.width:sprite.size.height);
}
}
}
if (stripMaxActiveTimes[i]>maxActiveTime || !lastDistanceAllOut) {
availableFrom = i+1;
}
else if (i - availableFrom >= overlandStripNum - 1){
break; // eureka!
}
if (i <= stripNum - overlandStripNum) {
if (stripMaxActiveTimes[i] < stripMaxActiveTimes[leastActiveTimeStrip]) {
leastActiveTimeStrip = i;
}
if (stripSpriteNumbers[i] < stripSpriteNumbers[leastActiveSpriteStrip]) {
leastActiveSpriteStrip = i;
}
}
}
if (availableFrom > stripNum - overlandStripNum) { // 那就是没有找到喽
availableFrom = AVAERAGE_STRATEGY?leastActiveSpriteStrip:leastActiveTimeStrip; // 使用最小个数 or 使用最短时间
}
CGPoint origin = CGPointZero;
if (oritation) { // 水平
_destination.y = origin.y = (rotation?stripHeight*availableFrom:rect.size.height-stripHeight * availableFrom-self.size.height)+rect.origin.y;
origin.x = (self.direction == BarrageWalkDirectionL2R)?rect.origin.x - self.size.width:rect.origin.x + rect.size.width;
_destination.x = (self.direction == BarrageWalkDirectionL2R)?rect.origin.x + rect.size.width:rect.origin.x - self.size.width;
}
else
{
_destination.x = origin.x = (rotation?stripWidth*availableFrom:rect.size.width-stripWidth*availableFrom -self.size.width)+rect.origin.x;
origin.y = (self.direction == BarrageWalkDirectionT2B)?rect.origin.y - self.size.height:rect.origin.y + rect.size.height;
_destination.y = (self.direction == BarrageWalkDirectionT2B)?rect.origin.y + rect.size.height:rect.origin.y - self.size.height;
}
return origin;
}
代码虽然很长，但是主要就是为了实现下面几个逻辑:
1. BarrageWalkSprite先获取了同方向的所有精灵
2. 根据屏幕轨道的frame范围找到每一个轨道内的所有精灵
3. 在同一轨道内的所有精灵中找到存活时间最长的精灵(速度最慢)
4. 判断速度最慢的那个精灵的尾部是否已经完全进入弹幕显示区域
5. 如果速度最慢的精灵尾部已经进入弹幕显示区域，则可以确定自己的可以紧跟在后面出现，如果还没有完全进入弹幕显示区域，则继续在下一个轨道获取合适的位置
6. 根据计算得到的自己可以出现的轨道，加上该轨道上最后一个精灵的位置，得到自己的起始位置
弹幕的运动轨迹
BarrageRender绘制每个精灵的运动轨迹的方式非常简单，在BarrageRender中，内置的时钟引擎BarrageClock负责在间隔时间内调用所有已经激活精灵基类BarrageSprite中的updateWithTime方法。
- (void)initClock
{
__weak id weakSelf = self;
_clock = [BarrageClock clockWithHandler:^(NSTimeInterval time){
BarrageRenderer * strongSelf = weakSelf;
strongSelf->_time = time;
[strongSelf update];
}];
}
/// 每个刷新周期执行一次
- (void)update
{
[_dispatcher dispatchSprites]; // 分发精灵
for (BarrageSprite * sprite in _dispatcher.activeSprites) {
[sprite updateWithTime:_time];
}
}
而在BarrageSprite的updateWithTime方法中, 每个精灵重新更改了自身的frame属性，以此来达到动画位移的效果。其中_valid属性是Sprite存活的唯一标志，标记为NO之后，Sprite就会从队列中彻底移除
//BarrageSprite
- (void)updateWithTime:(NSTimeInterval)time
{
_valid = [self validWithTime:time];
_view.frame = [self rectWithTime:time];
}
BarrageWalkSprite通过属性speed来实时改变自己的frame位置,同时计算剩下的destination和speed来算出自己的存活时间以用来标记valid属性
//BarrageWalkSprite
- (BOOL)validWithTime:(NSTimeInterval)time
{
return [self estimateActiveTime] > 0;
}
- (NSTimeInterval)estimateActiveTime
{
CGFloat activeDistance = 0;
switch (_direction) {
case BarrageWalkDirectionR2L:
activeDistance = self.position.x - _destination.x;
break;
case BarrageWalkDirectionL2R:
activeDistance = _destination.x - self.position.x;
break;
case BarrageWalkDirectionT2B:
activeDistance = _destination.y - self.position.y;
break;
case BarrageWalkDirectionB2T:
activeDistance = self.position.y - _destination.y;
default:
break;
}
return activeDistance/self.speed;
}
- (CGRect)rectWithTime:(NSTimeInterval)time
{
CGFloat X = self.destination.x - self.origin.x;
CGFloat Y = self.destination.y - self.origin.y;
CGFloat L = sqrt(X*X + Y*Y);
NSTimeInterval duration = time - self.timestamp;
CGPoint position = CGPointMake(self.origin.x + duration * self.speed * X/L, self.origin.y + duration * self.speed * Y/L);
return CGRectMake(position.x, position.y, self.size.width, self.size.height);
}
弹幕终点
BarrageWalkSprite的终点计算很简单，弹幕的显示的距离加上Sprite自身的宽度就是整个精灵需要位移的距离，这个destination的计算已经体现在了起点位置的获取当中
CGPoint origin = CGPointZero;
if (oritation) { // 水平
_destination.y = origin.y = (rotation?stripHeight*availableFrom:rect.size.height-stripHeight * availableFrom-self.size.height)+rect.origin.y;
origin.x = (self.direction == BarrageWalkDirectionL2R)?rect.origin.x - self.size.width:rect.origin.x + rect.size.width;
_destination.x = (self.direction == BarrageWalkDirectionL2R)?rect.origin.x + rect.size.width:rect.origin.x - self.size.width;
}
else
{
_destination.x = origin.x = (rotation?stripWidth*availableFrom:rect.size.width-stripWidth*availableFrom -self.size.width)+rect.origin.x;
origin.y = (self.direction == BarrageWalkDirectionT2B)?rect.origin.y - self.size.height:rect.origin.y + rect.size.height;
_destination.y = (self.direction == BarrageWalkDirectionT2B)?rect.origin.y + rect.size.height:rect.origin.y - self.size.height;
}
return origin;
自定义Sprite
BarrageBubblingSprite的运动轨迹和BarrageWalkSprite有很多重合之处，所以自定义的BarrageBubblingSprite直接继承BarrageWalkSprite以获取其direction,side,speed,trackNumber等多个属性，当然还需要另外加上加速度speedUp和停留时间stay属性
@interface BarrrageBubblingSprite : BarrageWalkSprite
@property (nonatomic,assign) CGFloat speedUp; //加速度
@property (nonatomic,assign) CGFloat stay; //到达终点后的停留时间
@end
起点位置
BubblingSprite的起点位置的获取逻辑和WalkSprite的起点逻辑类似，不同的地方在于:
- 即使轨道内最慢的那个精灵已经完全进入弹幕显示区域，只要该精灵仍然存活，就不能紧跟其后,而是要另外找寻其他轨道
- 当所有轨道都已经有精灵占据的时候，找到存活时间最短的那个精灵，通过将其的stay属性设置为0让其直接消失，然后让自己占据该精灵所在轨道
- (CGPoint)originInBounds:(CGRect)rect withSprites:(NSArray *)sprites
{
// 获取同方向精灵
NSMutableArray * synclasticSprites = [[NSMutableArray alloc]initWithCapacity:sprites.count];
for (BarrageWalkSprite * sprite in sprites) {
if (sprite.direction == self.direction && sprite.side == self.side) { // 找寻同道中人
[synclasticSprites addObject:sprite];
}
}
NSUInteger stripNum = MIN(STRIP_NUM, MAX(self.trackNumber, 1)); // between (1,STRIP_NUM)
CGFloat stripHeight = rect.size.height/stripNum; // 水平条高度
CGFloat stripWidth = rect.size.width/stripNum; // 竖直条宽度
BOOL oritation = self.direction == BarrageWalkDirectionL2R || self.direction == BarrageWalkDirectionR2L; // 方向, YES代表水平弹幕
BOOL rotation = self.side == [self defaultSideWithDirection:self.direction];
/// 计算数据结构,便于应用算法
NSUInteger overlandStripNum = 1; // 横跨网格条数目
if (oritation) { // 水平
overlandStripNum = (NSUInteger)ceil((double)self.size.height/stripHeight);
}
else // 竖直
{
overlandStripNum = (NSUInteger)ceil((double)self.size.width/stripWidth);
}
NSUInteger availableFrom = 0;
BarrrageBubblingSprite* lastTimeSprite = self;
NSInteger lastSpriteIndex = 0;
for (NSUInteger i = 0; i < stripNum; i++) {
//寻找当前行里包含的sprites
CGFloat stripFrom = i * (oritation?stripHeight:stripWidth);
CGFloat stripTo = stripFrom + (oritation?stripHeight:stripWidth);
if (!rotation) {
CGFloat preStripFrom = stripFrom;
stripFrom = (oritation?rect.size.height:rect.size.width) - stripTo;
stripTo = (oritation?rect.size.height:rect.size.width) - preStripFrom;
}
CGFloat exsitSprite = NO;
for (BarrrageBubblingSprite * sprite in synclasticSprites) {
CGFloat spriteFrom = oritation?sprite.origin.y:sprite.origin.x;
CGFloat spriteTo = spriteFrom + (oritation?sprite.size.height:sprite.size.width);
if ((spriteTo-spriteFrom)+(stripTo-stripFrom)>MAX(stripTo-spriteFrom, spriteTo-stripFrom)) { // 在条条里
exsitSprite = YES;
if (sprite.timestamp < lastTimeSprite.timestamp){
lastTimeSprite = sprite;
lastSpriteIndex = i;
}
break;
}
}
if (exsitSprite) {
availableFrom = i+1;
}else{ //第一行就是空的
break;
}
}
if (availableFrom == stripNum) { // 超出最大的轨道数，挤掉最上层精灵
availableFrom = lastSpriteIndex;
lastTimeSprite.stay = 0;
}
CGPoint origin = CGPointZero;
if (oritation) { // 水平
_destination.y = origin.y = (rotation?stripHeight*availableFrom:rect.size.height-stripHeight * availableFrom-self.size.height)+rect.origin.y;
origin.x = (self.direction == BarrageWalkDirectionL2R)?rect.origin.x - self.size.width:rect.origin.x + rect.size.width;
_destination.x = (self.direction == BarrageWalkDirectionL2R)?rect.origin.x + rect.size.width - self.size.width :rect.origin.x + self.size.width;
}
else
{
_destination.x = origin.x = (rotation?stripWidth*availableFrom:rect.size.width-stripWidth*availableFrom -self.size.width)+rect.origin.x;
origin.y = (self.direction == BarrageWalkDirectionT2B)?rect.origin.y - self.size.height:rect.origin.y + rect.size.height;
_destination.y = (self.direction == BarrageWalkDirectionT2B)?rect.origin.y + rect.size.height - self.size.height:rect.origin.y + self.size.height;
}
return origin;
运动轨迹
BarrageBubblingSprite的运动轨迹和BarrageWalkSprite的运动轨迹不同的地方在于，BarrageWalkSprite是匀速前进，二BarrageBubblingSprite是加速前进，这样，在计算某个时段Sprite的位置就需要考虑加速度的存在。
- (CGRect)rectWithTime:(NSTimeInterval)time{
CGFloat X = self.destination.x - self.origin.x;
CGFloat Y = self.destination.y - self.origin.y;
CGFloat L = sqrt(X*X + Y*Y);
NSTimeInterval duration = time - self.timestamp;
CGPoint position = CGPointMake(self.origin.x + duration * self.speed * X/L, self.origin.y + duration * self.speed * Y/L);
if (position.x >= self.destination.x) {
position.x = self.destination.x;
}else{
self.destinationStamp = time;
self.speed = duration*self.speedUp;
}
if(position.y >= self.destination.y) {
position.y = self.destination.y;
}else{
self.destinationStamp = time;
self.speed = duration*self.speedUp;
}
return CGRectMake(position.x, position.y, self.size.width, self.size.height);
}
在存活时间上，与BarrageWalkSprite不同的地方在于，BarrageWalkSprite在位移到终点的时候消失，而BarrageBubblingSprite在到达终点之后仍然需要停留stay的时间。这里引入了currentStamp和destinationStamp时间戳用于来计算stay时间是否已经到达。
//计算精灵的剩余存活时间
- (double)countTimeByDistance:(CGFloat)distance{
CGFloat a = 0.5*self.speedUp;
CGFloat b = self.speed;
CGFloat c = -distance;
CGFloat delt = sqrt(b*b - 4*a*c);
double t = (-b+delt)/(2*a);
return t;
}
- (NSTimeInterval)estimateActiveTime
{
CGFloat activeDistance = 0;
switch (self.direction) {
case BarrageWalkDirectionR2L:
activeDistance = self.position.x - _destination.x;
break;
case BarrageWalkDirectionL2R:
activeDistance = _destination.x - self.position.x;
break;
case BarrageWalkDirectionT2B:
activeDistance = _destination.y - self.position.y;
break;
case BarrageWalkDirectionB2T:
activeDistance = self.position.y - _destination.y;
default:
break;
}
NSTimeInterval leftTime = 0.0;
CGFloat time = [self countTimeByDistance:activeDistance];
if (time > 0){
leftTime = time + self.stay;
}else{
leftTime = self.stay - (self.currentStamp - self.destinationStamp);
}
return leftTime;
}
- (BOOL)validWithTime:(NSTimeInterval)time{
self.currentStamp = time;
return [self estimateActiveTime] > 0;
}
自定义弹幕样式
类似BarrageWalkImageSprite，我们也通过继承BarrageSpirte的bindingView 来将自定义的弹幕view返回给BarrageRender
完整代码
BarrageRender-BubblingSprite