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项目介绍：
1、绘制文本
使用core text可以将文本绘制在一个CGContextRef上，最后再通过UIGraphicsGetImageFromCurrentImageContext()生成图片，再将图片赋值给cell.contentView.layer，从而达到减少cell层级的目的。
绘制普通文本（譬如用户昵称）在context上，相关注释在代码里：
[Objective-C] 查看源文件 复制代码
- (void)drawInContext:(CGContextRef)context withPosition:(CGPoint)p andFont:(UIFont *)font andTextColor:(UIColor *)color andHeight:(float)height andWidth:(float)width lineBreakMode:(CTLineBreakMode)lineBreakMode {
CGSize size = CGSizeMake(width, height);
// 翻转坐标系
CGContextSetTextMatrix(context,CGAffineTransformIdentity);
CGContextTranslateCTM(context,0,height);
CGContextScaleCTM(context,1.0,-1.0);
NSMutableDictionary * attributes = [StringAttributes attributeFont:font andTextColor:color lineBreakMode:lineBreakMode];
// 创建绘制区域（路径）
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path,NULL,CGRectMake(p.x, height-p.y-size.height,(size.width),(size.height)));
// 创建AttributedString
NSMutableAttributedString *attributedStr = [[NSMutableAttributedString alloc] initWithString:self attributes:attributes];
CFAttributedStringRef attributedString = (__bridge CFAttributedStringRef)attributedStr;
// 绘制frame
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attributedString);
CTFrameRef ctframe = CTFramesetterCreateFrame(framesetter, CFRangeMake(0,0),path,NULL);
CTFrameDraw(ctframe,context);
CGPathRelease(path);
CFRelease(framesetter);
CFRelease(ctframe);
[[attributedStr mutableString] setString:@""];
CGContextSetTextMatrix(context,CGAffineTransformIdentity);
CGContextTranslateCTM(context,0, height);
CGContextScaleCTM(context,1.0,-1.0);
}
绘制朋友圈内容文本（带链接）在context上，这里我还没有去实现文本多了会折叠的效果，与上面普通文本不同的是这里需要创建带链接的AttributeString和CTLineRef的逐行绘制：
[Objective-C] 查看源文件 复制代码
- (NSMutableAttributedString *)highlightText:(NSMutableAttributedString *)coloredString{
// 创建带高亮的AttributedString
NSString* string = coloredString.string;
NSRange range = NSMakeRange(0,[string length]);
NSDataDetector *linkDetector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingTypeLink error:nil];
NSArray *matches = [linkDetector matchesInString:string options:0 range:range];
for(NSTextCheckingResult* match in matches) {
[self.ranges addObject:NSStringFromRange(match.range)];
UIColor *highlightColor = UIColorFromRGB(0x297bc1);
[coloredString addAttribute:(NSString*)kCTForegroundColorAttributeName
value:(id)highlightColor.CGColor range:match.range];
}
return coloredString;
}
- (void)drawFramesetter:(CTFramesetterRef)framesetter
attributedString:(NSAttributedString *)attributedString
textRange:(CFRange)textRange
inRect:(CGRect)rect
context:(CGContextRef)c {
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, rect);
CTFrameRef frame = CTFramesetterCreateFrame(framesetter, textRange, path, NULL);
CGFloat ContentHeight = CGRectGetHeight(rect);
CFArrayRef lines = CTFrameGetLines(frame);
NSInteger numberOfLines = CFArrayGetCount(lines);
CGPoint lineOrigins[numberOfLines];
CTFrameGetLineOrigins(frame, CFRangeMake(0, numberOfLines), lineOrigins);
// 遍历每一行
for (CFIndex lineIndex = 0; lineIndex < numberOfLines; lineIndex++) {
CGPoint lineOrigin = lineOrigins[lineIndex];
CTLineRef line = CFArrayGetValueAtIndex(lines, lineIndex);
CGFloat descent = 0.0f, ascent = 0.0f, lineLeading = 0.0f;
CTLineGetTypographicBounds((CTLineRef)line, &ascent, &descent, &lineLeading);
CGFloat penOffset = (CGFloat)CTLineGetPenOffsetForFlush(line, NSTextAlignmentLeft, rect.size.width);
CGFloat y = lineOrigin.y - descent - self.font.descender;
// 设置每一行位置
CGContextSetTextPosition(c, penOffset + self.xOffset, y - self.yOffset);
CTLineDraw(line, c);
// CTRunRef同一行中文本的不同样式，包括颜色、字体等，此处用途为处理链接高亮
CFArrayRef runs = CTLineGetGlyphRuns(line);
for (int j = 0; j < CFArrayGetCount(runs); j++) {
CGFloat runAscent, runDescent, lineLeading1;
CTRunRef run = CFArrayGetValueAtIndex(runs, j);
NSDictionary *attributes = (__bridge NSDictionary*)CTRunGetAttributes(run);
// 判断是不是链接
if (!CGColorEqualToColor((__bridge CGColorRef)([attributes valueForKey:@"CTForegroundColor"]), self.textColor.CGColor)) {
CFRange range = CTRunGetStringRange(run);
float offset = CTLineGetOffsetForStringIndex(line, range.location, NULL);
// 得到链接的CGRect
CGRect runRect;
runRect.size.width = CTRunGetTypographicBounds(run, CFRangeMake(0,0), &runAscent, &runDescent, &lineLeading1);
runRect.size.height = self.font.lineHeight;
runRect.origin.x = lineOrigin.x + offset+ self.xOffset;
runRect.origin.y = lineOrigin.y;
runRect.origin.y -= descent + self.yOffset;
// 因为坐标系被翻转，链接正常的坐标需要通过CGAffineTransform计算得到
CGAffineTransform transform = CGAffineTransformMakeTranslation(0, ContentHeight);
transform = CGAffineTransformScale(transform, 1.f, -1.f);
CGRect flipRect = CGRectApplyAffineTransform(runRect, transform);
// 保存是链接的CGRect
NSRange nRange = NSMakeRange(range.location, range.length);
self.framesDict[NSStringFromRange(nRange)] = [NSValue valueWithCGRect:flipRect];
// 保存同一条链接的不同CGRect，用于点击时背景色处理
for (NSString *rangeString in self.ranges) {
NSRange range = NSRangeFromString(rangeString);
if (NSLocationInRange(nRange.location, range)) {
NSMutableArray *array = self.relationDict[rangeString];
if (array) {
[array addObject:NSStringFromCGRect(flipRect)];
self.relationDict[rangeString] = array;
} else {
self.relationDict[rangeString] = [NSMutableArray arrayWithObject:NSStringFromCGRect(flipRect)];
}
}
}
}
}
}
CFRelease(frame);
CFRelease(path);
}
上述方法运用起来就是：
[Objective-C] 查看源文件 复制代码
- (void)fillData:(CGContextRef)context {
[self.nickname drawInContext:context withPosition:(CGPoint){kTextXOffset, kSpec} andFont:kNicknameFont
andTextColor:UIColorFromRGB(0x556c95) andHeight:self.nicknameSize.height
andWidth:self.nicknameSize.width lineBreakMode:kCTLineBreakByTruncatingTail];
[self.drawer setText:self.contentString context:context contentSize:self.contentSize
backgroundColor:[UIColor whiteColor] font:kContentTextFont textColor:[UIColor blackColor]
block:nil xOffset:kTextXOffset yOffset:kSpec * 2 + self.nicknameSize.height];
}
- (void)fillContents:(NSArray *)array {
UIGraphicsBeginImageContextWithOptions(CGSizeMake(self.size.width, self.size.height), YES, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
[UIColorFromRGB(0xffffff) set];
CGContextFillRect(context, CGRectMake(0, 0, self.size.width, self.size.height));
// 获取需要高亮的链接CGRect，并填充背景色
if (array) {
for (NSString *string in array) {
CGRect rect = CGRectFromString(string);
[UIColorFromRGB(0xe5e5e5) set];
CGContextFillRect(context, rect);
}
}
[self fillData:context];
UIImage *temp = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.contentView.layer.contents = (__bridge id _Nullable)(temp.CGImage);
}
这样就完成了文本的显示。
2、显示图片
图片包括用户头像和朋友圈的内容，这里只是将CALayer添加到contentView.layer上，具体做法是继承了CALayer，实现部分功能。
通过链接显示图片：
[Objective-C] 查看源文件 复制代码
- (void)setContentsWithURLString:(NSString *)urlString {
self.contents = (__bridge id _Nullable)([UIImage imageNamed:@"placeholder"].CGImage);
@weakify(self)
SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadImageWithURL:[NSURL URLWithString:urlString]
options:SDWebImageCacheMemoryOnly
progress:nil
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
if (image) {
@strongify(self)
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
if (!_observer) {
_observer = CFRunLoopObserverCreateWithHandler(kCFAllocatorDefault, kCFRunLoopBeforeWaiting | kCFRunLoopExit, false, POPAnimationApplyRunLoopOrder, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
self.contents = (__bridge id _Nullable)(image.CGImage);
});
if (_observer) {
CFRunLoopAddObserver(CFRunLoopGetMain(), _observer, kCFRunLoopCommonModes);
}
}
});
self.originImage = image;
}
}];
}
3、显示小视频
之前的一篇文章简单讲了怎么自己做一个播放器，这里就派上用场了。而显示小视频封面图片的CALayer同样在显示小视频的时候可以复用。
这里使用了NSOperationQueue来保障播放视频的流畅性，具体继承NSOperation的VideoDecodeOperation相关代码如下：
[Objective-C] 查看源文件 复制代码
- (void)main {
@autoreleasepool {
if (self.isCancelled) {
_newVideoFrameBlock = nil;
_decodeFinishedBlock = nil;
return;
}
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:[[NSURL alloc] initFileURLWithPath:self.filePath] options:nil];
NSError *error;
AVAssetReader* reader = [[AVAssetReader alloc] initWithAsset:asset error:&error];
if (error) {
return;
}
NSArray* videoTracks = [asset tracksWithMediaType:AVMediaTypeVideo];
AVAssetTrack* videoTrack = [videoTracks objectAtIndex:0];
// 视频播放时，m_pixelFormatType=kCVPixelFormatType_32BGRA
// 其他用途，如视频压缩，m_pixelFormatType=kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange
int m_pixelFormatType = kCVPixelFormatType_32BGRA;
NSDictionary* options = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt: (int)m_pixelFormatType]
forKey:(id)kCVPixelBufferPixelFormatTypeKey];
AVAssetReaderTrackOutput* videoReaderOutput = [[AVAssetReaderTrackOutput alloc]
initWithTrack:videoTrack outputSettings:options];
[reader addOutput:videoReaderOutput];
[reader startReading];
// 要确保nominalFrameRate>0，之前出现过android拍的0帧视频
if (self.isCancelled) {
_newVideoFrameBlock = nil;
_decodeFinishedBlock = nil;
return;
}
while ([reader status] == AVAssetReaderStatusReading && videoTrack.nominalFrameRate > 0) {
if (self.isCancelled) {
_newVideoFrameBlock = nil;
_decodeFinishedBlock = nil;
return;
}
CMSampleBufferRef sampleBuffer = [videoReaderOutput copyNextSampleBuffer];
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
// Lock the base address of the pixel buffer
CVPixelBufferLockBaseAddress(imageBuffer, 0);
// Get the number of bytes per row for the pixel buffer
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
// Get the pixel buffer width and height
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
//Generate image to edit`
unsigned char* pixel = (unsigned char *)CVPixelBufferGetBaseAddress(imageBuffer);
CGColorSpaceRef colorSpace=CGColorSpaceCreateDeviceRGB();
CGContextRef context=CGBitmapContextCreate(pixel, width, height, 8, bytesPerRow, colorSpace,
kCGBitmapByteOrder32Little|kCGImageAlphaPremultipliedFirst);
if (context != NULL) {
CGImageRef imageRef = CGBitmapContextCreateImage(context);
CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
CGColorSpaceRelease(colorSpace);
CGContextRelease(context);
// 解码图片
size_t width = CGImageGetWidth(imageRef);
size_t height = CGImageGetHeight(imageRef);
size_t bitsPerComponent = CGImageGetBitsPerComponent(imageRef);
// CGImageGetBytesPerRow() calculates incorrectly in iOS 5.0, so defer to CGBitmapContextCreate
size_t bytesPerRow = 0;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGColorSpaceModel colorSpaceModel = CGColorSpaceGetModel(colorSpace);
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
if (colorSpaceModel == kCGColorSpaceModelRGB) {
uint32_t alpha = (bitmapInfo & kCGBitmapAlphaInfoMask);
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wassign-enum"
if (alpha == kCGImageAlphaNone) {
bitmapInfo &= ~kCGBitmapAlphaInfoMask;
bitmapInfo |= kCGImageAlphaNoneSkipFirst;
} else if (!(alpha == kCGImageAlphaNoneSkipFirst || alpha == kCGImageAlphaNoneSkipLast)) {
bitmapInfo &= ~kCGBitmapAlphaInfoMask;
bitmapInfo |= kCGImageAlphaPremultipliedFirst;
}
#pragma clang diagnostic pop
}
CGContextRef context = CGBitmapContextCreate(NULL, width, height, bitsPerComponent,
bytesPerRow, colorSpace, bitmapInfo);
CGColorSpaceRelease(colorSpace);
if (!context) {
if (self.newVideoFrameBlock) {
dispatch_async(dispatch_get_main_queue(), ^{
if (self.isCancelled) {
_newVideoFrameBlock = nil;
_decodeFinishedBlock = nil;
return;
}
self.newVideoFrameBlock(imageRef, self.filePath);
CGImageRelease(imageRef);
});
}
} else {
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), imageRef);
CGImageRef inflatedImageRef = CGBitmapContextCreateImage(context);
CGContextRelease(context);
if (self.newVideoFrameBlock) {
dispatch_async(dispatch_get_main_queue(), ^{
if (self.isCancelled) {
_newVideoFrameBlock = nil;
_decodeFinishedBlock = nil;
return;
}
self.newVideoFrameBlock(inflatedImageRef, self.filePath);
CGImageRelease(inflatedImageRef);
});
}
CGImageRelease(imageRef);
}
if(sampleBuffer) {
CMSampleBufferInvalidate(sampleBuffer);
CFRelease(sampleBuffer);
sampleBuffer = NULL;
} else {
break;
}
}
[NSThread sleepForTimeInterval:CMTimeGetSeconds(videoTrack.minFrameDuration)];
}
if (self.isCancelled) {
_newVideoFrameBlock = nil;
_decodeFinishedBlock = nil;
return;
}
if (self.decodeFinishedBlock) {
self.decodeFinishedBlock(self.filePath);
}
}
}
解码图片是因为UIImage在界面需要显示的时候才开始解码，这样可能会造成主线程的卡顿，所以在子线程对其进行解压缩处理。
具体的使用：
[Objective-C] 查看源文件 复制代码
- (void)playVideoWithFilePath:(NSString *)filePath_ type:(NSString *)type {
@weakify(self)
[[VideoPlayerManager shareInstance] decodeVideo:filePath_
withVideoPerDataBlock:^(CGImageRef imageData, NSString *filePath) {
@strongify(self)
if ([type isEqualToString:@"video"]) {
if ([filePath isEqualToString:self.filePath]) {
[self.sources.firstObject
setContents:(__bridge id _Nullable)(imageData)];
}
}
} decodeFinishBlock:^(NSString *filePath){
[self playVideoWithFilePath:filePath type:type];
}];
}
4、其他
1、触摸交互是覆盖了以下方法实现：
[Objective-C] 查看源文件 复制代码
- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event - (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
2、页面上FPS的测量是使用了YYKit项目中的YYFPSLabel。
本文转自： 伯乐在线 – Hawk0620 github.com/hawk0620/PYQFeedDemo
DEMO 下载：
