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] > )
        {
            [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:];
            [muttext addAttribute:NSParagraphStyleAttributeName value:style range:NSMakeRange(, muttext.length)];
            [muttext addAttribute:NSForegroundColorAttributeName value:[UIColor whiteColor] range:NSMakeRange(, muttext.length)];
            _myLabel.attributedText = muttext;

NSMutableParagraphStyle *paragraph=[[NSMutableParagraphStyle alloc]init];
 paragraph.alignment=NSTextAlignmentCenter;//居中  

NSDictionary* attrs =@{NSFontAttributeName:[UIFont fontWithName:@"AmericanTypewriter" size:],//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:@, //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(, title.length)];
    [title addAttribute:NSFontAttributeName value:SYSTEMFONT() range:NSMakeRange(, title.length)];
    return title;
}

.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 = ;// 字体的行间距 

    NSDictionary *attributes = @{
                                 NSFontAttributeName:[UIFont systemFontOfSize:],
                                 NSParagraphStyleAttributeName:paragraphStyle
                                 };
    textView.attributedText = [[NSAttributedString alloc] initWithString:@"输入你的内容" attributes:attributes];

.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 = ;// 字体的行间距

    NSDictionary *attributes = @{

                                 NSFontAttributeName:[UIFont systemFontOfSize:],

                                 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 > );

    if (textView.markedTextRange == nil && self.textLengthLimit >  && 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 > ) {
        CGFloat alpha =  - (( - offsetY) / );
        self.navigationController.navigationBar.backgroundColor = [color colorWithAlphaComponent:alpha];
    } else {
         self.navigationController.navigationBar.backgroundColor = [color colorWithAlphaComponent:];
    }
}

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":@};
        [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 = ;
    NSMutableArray *keys = [NSMutableArray new];
    NSMutableArray *values = [NSMutableArray new];
    for (int i = ; i < count; i++) {
        NSString *key = @(i).description;
        NSNumber *value = @(i);
        [keys addObject:key];
        [values addObject:value];
    }

    //写入文件
    for (int i = ; i < count; i++) {
        [yykvFile saveItemWithKey:keys[i] value:[@"wujy" dataUsingEncoding:NSUTF8StringEncoding]
                         filename:keys[i] extendedData:nil];
    }

    //读取
    YYKVStorageItem *item = [yykvFile getItemForKey:keys[]];
    NSString *aString = [[NSString alloc] initWithData:item.value encoding:NSUTF8StringEncoding];
    NSLog(@"%@",aString);

    //写入数据库
    for (int i = ; i < count; i++) {
        [yykvSQLite saveItemWithKey:keys[i] value:[@"cnblogs" dataUsingEncoding:NSUTF8StringEncoding]];
    }

    YYKVStorageItem *sqlitem = [yykvFile getItemForKey:keys[]];
    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 = ;
    int bytesPerRow = bytesPerPixel * ;
    NSUInteger bitsPerComponent = ;
    unsigned char pixelData[] = {, , , };

    CGContextRef context = CGBitmapContextCreate(pixelData,
                                                 ,
                                                 ,
                                                 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[] / 255.0f;
    CGFloat green = (CGFloat)pixelData[] / 255.0f;
    CGFloat blue  = (CGFloat)pixelData[] / 255.0f;
    CGFloat alpha = (CGFloat)pixelData[] / 255.0f;

    return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}