iOS开发基础知识--碎片30

[b]iOS开发基础知识--碎片30 [/b]

[b]1:ios 相册操作 ALAssetsLibrary 知识点[/b]

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]);

[b]2:Attribute运用(几段代码)[/b]

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];

}

[b]3：中文输入法的键盘上有联想、推荐的功能，[/b]

[b]所以可能导致文本内容长度上有些不符合预期，导致越界[/b]

*** 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];
}
}

[b] 4：UITableView滚动值获取[/b]

- (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];
}
}

[b]5：YYCache缓存的运用[/b]

#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);
}