IOS开发基础知识--碎片30
1:ios 相册操作 ALAssetsLibrary 知识点
a ALAssetsLibrary 实例为我们提供了获取相册(照片app)中的图片和视频的功能。在ios8 photos framework代替了ALAssetsLibrary。
在使用ALAssetsLibrary时，我们需要申明它的实例。
ALAssetsLibrary* library = [[ALAssetsLibrary alloc] init];
b. 迭代获取相册ALAssetsGroup：
- (void)enumerateGroupsWithTypes:(ALAssetsGroupType)types usingBlock:(ALAssetsLibraryGroupsEnumerationResultsBlock)enumerationBlock failureBlock:(ALAssetsLibraryAccessFailureBlock)failureBlock
ALASSetsGroupType类型:
ALAssetsGroupLibrary：从iTunes 来的相册内容（如本身自带的向日葵照片）。
ALAssetsGroupAlbum：设备自身产生或从iTunes同步来的照片，但是不包括照片流跟分享流中的照片。(例如从各个软件中保存下来的图片)
ALAssetsGroupEvent 相机接口事件产生的相册
ALAssetsGroupFaces 脸部相册（具体不清楚）
ALAssetsGroupSavedPhotos 相机胶卷照片
ALAssetsGroupPhotoStream 照片流
ALAssetsGroupAll 除了ALAssetsGroupLibrary上面所的内容。
例如：ALAssetsLibraryGroupsEnumerationResultsBlock
ALAssetsLibraryGroupsEnumerationResultsBlock listGroupBlock = ^(ALAssetsGroup *group, BOOL *stop) { ALAssetsFilter *onlyPhotosFilter = [ALAssetsFilter allPhotos]; [group setAssetsFilter:onlyPhotosFilter]; if ([group numberOfAssets] > 0) { [self.imageGroup addObject:group]; } else { [self.tableView performSelectorOnMainThread:@selector(reloadData) withObject:nil waitUntilDone:NO]; } };
上面就是迭代AlAssetsGroup的block。每迭代一次就把相应的AlAssetsGroup保存在一个可变的数组之中。AlAssetsGroup中的一些属性表明了这个相册的特征。比如：
posterImage 相册的缩略图
numberOfAssets 相册中照片的数量
c:Asset 属性
– valueForProperty:
1.ALAssetPropertyType 资源的类型（照片，视频）
2.ALAssetPropertyLocation 资源地理位置（无位置信息返回null）
3.ALAssetPropertyDuation 播放时长（照片返回ALErorInvalidProperty)
4.ALAssetPropertyOrientation 方向（共有8个方向，参见：ALAssetOrientation)
5.ALAssetPropertyDate 拍摄时间（包含了年与日时分秒）
6.ALAssetPropertyRepresentations 描述（打印看了下，只有带后缀的名称）
7.ALAssetPropertyURLs（返回一个字典，键值分别是文件名和文件的url）
8.ALAssetPropertyAssetURL 文件的url )
editable property（指示资源是否可以编辑，只读属性)
originalAsset property（原始资源。若没有保存修改后资源，则原始资源为nil）
for (ALAsset *asset in assets) { NSURL *assetURL＝ [asset valueForProperty:ALAssetPropertyAssetURL]; }
Accessing Representations
– defaultRepresentation
– representationForUTI:
– thumbnail（小正方形的缩略图）
– aspectRatioThumbnail（按原始资源长宽比例的缩略图）
另外一个小实例：
UIImage* ni = [UIImage imageNamed:@"new.png"]; //修改指定路径的图片资源内容，替换掉原来的内容 [asset setImageData:UIImageJPEGRepresentation(ni, 1.0) metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) { NSLog(@"new:%@",assetURL); }]; //根据给定的图片内容，重新生成一张新图 [asset writeModifiedImageDataToSavedPhotosAlbum:UIImageJPEGRepresentation(ni, 1.0) metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) { NSLog(@"new:%@",assetURL); }]; //获取资源图片的详细资源信息 ALAssetRepresentation* representation = [asset defaultRepresentation]; //获取资源图片的长宽 CGSize dimension = [representation dimensions]; //获取资源图片的高清图 [representation fullResolutionImage]; //获取资源图片的全屏图 [representation fullScreenImage]; //获取资源图片的名字 NSString* filename = [representation filename]; NSLog(@"filename:%@",filename); //缩放倍数 [representation scale]; //图片资源容量大小 [representation size]; //图片资源原数据 [representation metadata]; //旋转方向 [representation orientation]; //资源图片url地址，该地址和ALAsset通过ALAssetPropertyAssetURL获取的url地址是一样的 NSURL* url = [representation url]; NSLog(@"url:%@",url); //资源图片uti，唯一标示符 NSLog(@"uti:%@",[representation UTI]);
2:Attribute运用(几段代码)
其中addAttribute可以增加不同的属性，有些属性值是要在NSMutableParagraphStyle里面进行设置例如下面第一段代码中NSParagraphStyleAttributeName，有些可以直接设置值如NSForegroundColorAttributeName
NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init]; [style setLineSpacing:5]; [muttext addAttribute:NSParagraphStyleAttributeName value:style range:NSMakeRange(0, muttext.length)]; [muttext addAttribute:NSForegroundColorAttributeName value:[UIColor whiteColor] range:NSMakeRange(0, muttext.length)]; _myLabel.attributedText = muttext;
NSMutableParagraphStyle *paragraph=[[NSMutableParagraphStyle alloc]init]; paragraph.alignment=NSTextAlignmentCenter;//居中 NSDictionary* attrs =@{NSFontAttributeName:[UIFont fontWithName:@"AmericanTypewriter" size:30],//文本的颜色 字体 大小 NSForegroundColorAttributeName:[UIColor redColor],//文字颜色 NSParagraphStyleAttributeName:paragraph,//段落格式 // NSBackgroundColorAttributeName:[UIColor blueColor],//背景色 NSStrokeWidthAttributeName:@3, //描边宽度 NSStrokeColorAttributeName:[UIColor greenColor],//设置 描边颜色，和NSStrokeWidthAttributeName配合使用,设置了这个NSForegroundColorAttributeName就失效了 // NSStrikethroughStyleAttributeName:@1,//删除线，数字代表线条宽度 NSUnderlineStyleAttributeName:@(NSUnderlineStyleSingle),//下划线，值为一个枚举类型，大家可以分别试试 };
-(NSMutableAttributedString*)setTitle { NSMutableAttributedString *title = [[NSMutableAttributedString alloc] initWithString:@"准备量房"]; [title addAttribute:NSForegroundColorAttributeName value:COLOR_NAV_TITLE range:NSMakeRange(0, title.length)]; [title addAttribute:NSFontAttributeName value:SYSTEMFONT(18) range:NSMakeRange(0, title.length)]; return title; }
1.如果只是静态显示textView的内容为设置的行间距，执行如下代码： // textview 改变字体的行间距 NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init]; paragraphStyle.lineSpacing = 10;// 字体的行间距 NSDictionary *attributes = @{ NSFontAttributeName:[UIFont systemFontOfSize:15], NSParagraphStyleAttributeName:paragraphStyle }; textView.attributedText = [[NSAttributedString alloc] initWithString:@"输入你的内容" attributes:attributes]; 2.如果是想在输入内容的时候就按照设置的行间距进行动态改变，那就需要将上面代码放到textView的delegate方法里 -(void)textViewDidChange:(UITextView *)textView { // textview 改变字体的行间距 NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init]; paragraphStyle.lineSpacing = 20;// 字体的行间距 NSDictionary *attributes = @{ NSFontAttributeName:[UIFont systemFontOfSize:15], NSParagraphStyleAttributeName:paragraphStyle }; textView.attributedText = [[NSAttributedString alloc] initWithString:textView.text attributes:attributes]; }
3：中文输入法的键盘上有联想、推荐的功能，所以可能导致文本内容长度上有些不符合预期，导致越界
*** Terminating app due to uncaught exception 'NSRangeException', reason: 'NSMutableRLEArray replaceObjectsInRange:withObject:length:: Out of bounds'
处理方式如下（textView.markedTextRange == nil）
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text { if (textView.text.length >= self.textLengthLimit && text.length > range.length) { return NO; } return YES; } - (void)textViewDidChange:(UITextView *)textView { self.placeholder.hidden = (self.textView.text.length > 0); if (textView.markedTextRange == nil && self.textLengthLimit > 0 && self.text.length > self.textLengthLimit) { textView.text = [textView.text substringToIndex:self.textLengthLimit]; } }
4：UITableView滚动值获取
- (void)scrollViewDidScroll:(UIScrollView *)scrollView { UIColor *color = [UIColor blueColor]; CGFloat offsetY = scrollView.contentOffset.y; if (offsetY > 0) { CGFloat alpha = 1 - ((64 - offsetY) / 64); self.navigationController.navigationBar.backgroundColor = [color colorWithAlphaComponent:alpha]; } else { self.navigationController.navigationBar.backgroundColor = [color colorWithAlphaComponent:0]; } }
5：YYCache缓存的运用
#import <YYCache/YYCache.h> #import "UserInfo.h" @interface ViewController () @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. NSString *path = NSHomeDirectory();//主目录 NSLog(@"NSHomeDirectory:%@",path); YYCache *cache = [[YYCache alloc]initWithName:@"cacheTest"]; id getCache = [cache objectForKey:@"cache"]; if (getCache) { NSLog(@"getObject:%@",getCache); } else { [cache setObject:@"test" forKey:@"cache"]; NSLog(@"setObject:%@",getCache); } id getDicCache = [cache objectForKey:@"userDic"]; if (getDicCache) { NSDictionary *dic = (NSDictionary *)[cache objectForKey:@"userDic"]; NSLog(@"getDicObject:%@", dic); NSLog(@"getDicObject:%@", [dic objectForKey:@"name"]); } else { NSDictionary *dic = @{@"name":@"alex",@"age":@18}; [cache setObject:dic forKey:@"userDic"]; NSLog(@"setDicObject:%@",dic); } NSString *basePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES) firstObject]; basePath = [basePath stringByAppendingPathComponent:@"FileCacheBenchmarkLarge"]; YYKVStorage *yykvFile = [[YYKVStorage alloc] initWithPath:[basePath stringByAppendingPathComponent:@"yykvFile"] type:YYKVStorageTypeFile]; YYKVStorage *yykvSQLite = [[YYKVStorage alloc] initWithPath:[basePath stringByAppendingPathComponent:@"yykvSQLite"] type:YYKVStorageTypeSQLite]; YYDiskCache *yy = [[YYDiskCache alloc] initWithPath:[basePath stringByAppendingPathComponent:@"yy"]]; yy.customArchiveBlock = ^(id object) {return object;}; yy.customUnarchiveBlock = ^(NSData *object) {return object;}; int count = 1000; NSMutableArray *keys = [NSMutableArray new]; NSMutableArray *values = [NSMutableArray new]; for (int i = 0; i < count; i++) { NSString *key = @(i).description; NSNumber *value = @(i); [keys addObject:key]; [values addObject:value]; } //写入文件 for (int i = 44; i < count; i++) { [yykvFile saveItemWithKey:keys[i] value:[@"wujy" dataUsingEncoding:NSUTF8StringEncoding] filename:keys[i] extendedData:nil]; } //读取 YYKVStorageItem *item = [yykvFile getItemForKey:keys[200]]; NSString *aString = [[NSString alloc] initWithData:item.value encoding:NSUTF8StringEncoding]; NSLog(@"%@",aString); //写入数据库 for (int i = 0; i < count; i++) { [yykvSQLite saveItemWithKey:keys[i] value:[@"cnblogs" dataUsingEncoding:NSUTF8StringEncoding]]; } YYKVStorageItem *sqlitem = [yykvFile getItemForKey:keys[200]]; NSString *asqlString = [[NSString alloc] initWithData:sqlitem.value encoding:NSUTF8StringEncoding]; NSLog(@"%@",asqlString); }
6:打印所有注册的字体
#pragma mark - 打印系统所有已注册的字体名称 void enumerateFonts() { for(NSString *familyName in [UIFont familyNames]) { NSLog(@"%@",familyName); NSArray *fontNames = [UIFont fontNamesForFamilyName:familyName]; for(NSString *fontName in fontNames) { NSLog(@"\t|- %@",fontName); } } }
7：取图片某一像素点的颜色 在UIImage的分类中
- (UIColor *)colorAtPixel:(CGPoint)point { if (!CGRectContainsPoint(CGRectMake(0.0f, 0.0f, self.size.width, self.size.height), point)) { return nil; } CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); int bytesPerPixel = 4; int bytesPerRow = bytesPerPixel * 1; NSUInteger bitsPerComponent = 8; unsigned char pixelData[4] = {0, 0, 0, 0}; CGContextRef context = CGBitmapContextCreate(pixelData, 1, 1, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big); CGColorSpaceRelease(colorSpace); CGContextSetBlendMode(context, kCGBlendModeCopy); CGContextTranslateCTM(context, -point.x, point.y - self.size.height); CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, self.size.width, self.size.height), self.CGImage); CGContextRelease(context); CGFloat red = (CGFloat)pixelData[0] / 255.0f; CGFloat green = (CGFloat)pixelData[1] / 255.0f; CGFloat blue = (CGFloat)pixelData[2] / 255.0f; CGFloat alpha = (CGFloat)pixelData[3] / 255.0f; return [UIColor colorWithRed:red green:green blue:blue alpha:alpha]; }
