一、后台有媒体播放器时：
当其他应用程序占用媒体播放器时，不能影响到后台的媒体音乐播放；
当你的应用程序中有相机要拍照时，不会影响到后台音乐程序的播放
// 当其他应用程序占用媒体播放器时，不能影响到后台的媒体音乐播放
NSError *error;
BOOL success = [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient error:&error];
if (!success) { //Handle error
AXLog(@"%@", [error localizedDescription]);
} else {
// Yay! It worked! 当你的应用程序中有相机要拍照时，不会影响到后台音乐程序的播放
AXLog(@"123456789");
}
二、屏幕常亮
/// 屏幕长亮
[[UIApplication sharedApplication] setIdleTimerDisabled:YES];
三、NSString 转换为 int64、int32 （微信支付时遇到）
// NSString 转换为 int64
UInt64 timeStamp = atoll([payItem.timestamp UTF8String]);
// NSString 转换为 int32
UInt32 timeStamp = atoi([payItem.timestamp UTF8String]);
四、float变量 值为NaN
“这种错误是在float经过函数运行出了不是数字的值，nan的意思就是not a number。
主要常见原因：
1.除以0
2.sizeWithFont的字符串为nil
3.数学函数不正确运算
解决方法除了排除根源所在之外，用函数isnan()也是不错的选择（至少在没有彻底解决以前）
如下:
float x = NAN;
if (!isnan(x)) {
view.frame = CGRectMake(x, 8, 10, 12);
}”
五、CFNetwork internal error
CFNetwork internal error (0xc01a:/BuildRoot/Library/Caches/com.apple.xbs/Sources/CFNetwork_Sim/CFNetwork-808.2.16/Loading/URLConnectionLoader.cpp:304)
访问的url地址不对 不存在等
六、获取网络图片大小
①阿里云OSS图片处理，链接：
https://help.aliyun.com/document_detail/44976.html?spm=5176.doc44975.6.952.aGGXXG
下面是iOS端获取，若是网络图片显示在UIImageView上，并且根据图片大小决定UIImageView长宽的话，直接让后台去做这件事
#define kHeadUrl @"http://image.xxxxx.com/" // 项目阿里云存储服务器地址
#define kSize_Image_Get @"x-oss-process=image/info"
+ (void)getImageSizePath:(NSString *)imagePath heightBlock:(ImgHeightBlock)heightBlock{
NSString *path = [NSString stringWithFormat:@"%@%@?%@",kHeadUrl,imagePath,kSize_Image_Get];
[NetWorkManager getOrPostWithType:Get withUrlString:path withParams:nil loadingImageArr:nil progress:^(float progress) {
} toShowView:nil success:^(NSDictionary *object) {
NSDictionary *wD = [object objectForKey:@"ImageWidth"];
NSDictionary *hD = [object objectForKey:@"ImageHeight"];
NSString *w = [wD objectForKey:@"value"];
NSString *h = [hD objectForKey:@"value"];
// CGFloat heightR = kWidth * [h floatValue] / [w floatValue];
if (heightBlock) {
// ... 根据项目所需自定义
}
} fail:^(NSError *error) {
AXLog(@"error : %@", error);
} showHUD:NO];
}
②NSData
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://xxx.jpg"]];
UIImage *image = [UIImage imageWithData:data];
AXLog(@"w = %f, h = %f",image.size.width,image.size.height);
③SDWebImage
[[[SDWebImageManager sharedManager] imageDownloader] downloadImageWithURL:[NSURL URLWithString:[AXUtils getImagePath:ad.img]] options:SDWebImageDownloaderIgnoreCachedResponse progress:^(NSInteger receivedSize, NSInteger expectedSize, NSURL * _Nullable targetURL) {
} completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, BOOL finished) {
if (image) {
AXLog(@"w = %f, h = %f",image.size.width,image.size.height);
}
}];
七、获取网络图片平均色
①阿里云OSS
#define kColor_Image_Get @"x-oss-process=image/average-hue"
+ (void)getImageColorPath:(NSString *)imagePath colorBlock:(ImgColorBlock)colorBlock{
NSString *path = [NSString stringWithFormat:@"%@%@?%@",kHeadUrl,imagePath,kColor_Image_Get];
[NetWorkManager getOrPostWithType:Get withUrlString:path withParams:nil loadingImageArr:nil progress:^(float progress) {
} toShowView:nil success:^(NSDictionary *object) {
NSString *color = [object objectForKey:@"RGB"];
// AXLog(@"%@",[color substringFromIndex:2]);
if (colorBlock) {
colorBlock([color substringFromIndex:2]);
}
} fail:^(NSError *error) {
AXLog(@"error : %@", error);
} showHUD:NO];
}
②参考：http://www.cocoachina.com/bbs/read.php?tid=181490
-(UIColor*)mostColor{
#if __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_6_1
int bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast;
#else
int bitmapInfo = kCGImageAlphaPremultipliedLast;
#endif
//第一步 先把图片缩小 加快计算速度. 但越小结果误差可能越大
CGSize thumbSize=CGSizeMake(50, 50);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL,
thumbSize.width,
thumbSize.height,
8,//bits per component
thumbSize.width*4,
colorSpace,
bitmapInfo);
CGRect drawRect = CGRectMake(0, 0, thumbSize.width, thumbSize.height);
CGContextDrawImage(context, drawRect, self.CGImage);
CGColorSpaceRelease(colorSpace);
//第二步 取每个点的像素值
unsigned char* data = CGBitmapContextGetData (context);
if (data == NULL) return nil;
NSCountedSet *cls=[NSCountedSet setWithCapacity:thumbSize.width*thumbSize.height];
for (int x=0; x八、获取本地视频截图
+ (UIImage *)getVideoImage:(NSString *)videoPath {
AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:videoPath] options:nil];
AVAssetImageGenerator *gen = [[AVAssetImageGenerator alloc] initWithAsset:asset];
gen.appliesPreferredTrackTransform = YES;
CMTime time = CMTimeMakeWithSeconds(0.0, 600);
NSError *error = nil;
CMTime actualTime;
CGImageRef image = [gen copyCGImageAtTime:time actualTime:&actualTime error:&error];
UIImage *thumb = [[UIImage alloc] initWithCGImage:image];
CGImageRelease(image);
return thumb;
}