iOS 开发中实用小技巧(1)

2017-01-05 本文已影响163人小兵快跑

首先谢谢各位大神的分享，小兵在这里整理收集iOS 开发中各种小技巧，有喜欢的可以关注下；

感谢判若两人丶

UITextField使用注意

先贴一个UITextField如何设置占位文字的颜色, 如果不先设置占位文字, 占位文字的颜色是不管用的:

//先设置占位文字
textField.placeholder = @"设置了占位文字内容以后, 才能设置占位文字的颜色";
//占位文字颜色
[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];

大家监听UITextField文字的改变会用到代理:

#pragma mark - <UITextFieldDelegate>
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
//这里监听文字改变
    return YES;
}

但是这个代理方法监听会有问题如下图:

2353624-366e3c826e58adaf.png

2353624-44c4588449a266b4.png

所以我们要监听UITextField的文字改变不建议使用代理, 我们用addTarget监听文字

[textField addTarget:self action:@selector(textEditingChanged) forControlEvents:UIControlEventEditingChanged];

TableView拉伸头部图片、导航栏渐变效果

 self.tableView.contentInset = UIEdgeInsetsMake(headH + tabBarH, 0, 0, 0);
    self.automaticallyAdjustsScrollViewInsets = NO;
    // 给导航条的背景图片传递一个空图片的UIImage对象
    [self.navigationController.navigationBar setBackgroundImage:[[UIImage alloc] init] forBarMetrics:UIBarMetricsDefault];
    // 隐藏底部阴影条，传递一个空图片的UIImage对象
    [self.navigationController.navigationBar setShadowImage:[[UIImage alloc] init]];
  //设置图片透明度
- (UIImage *)imageByApplyingAlpha:(CGFloat)alpha  image:(UIImage*)image {

    UIGraphicsBeginImageContextWithOptions(image.size, NO, 0.0f);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    CGRect area = CGRectMake(0, 0, image.size.width, image.size.height);
    CGContextScaleCTM(ctx, 1, -1);

    CGContextTranslateCTM(ctx, 0, -area.size.height);
    CGContextSetBlendMode(ctx, kCGBlendModeMultiply);
    CGContextSetAlpha(ctx, alpha);
    CGContextDrawImage(ctx, area, image.CGImage);

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;

}
- (UIImage *)imageWithColor:(UIColor *)color {

    // 描述矩形

    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    // 开启位图上下文

    UIGraphicsBeginImageContext(rect.size);

    // 获取位图上下文

    CGContextRef context = UIGraphicsGetCurrentContext();

    // 使用color演示填充上下文

    CGContextSetFillColorWithColor(context, [color CGColor]);

    // 渲染上下文

    CGContextFillRect(context, rect);

    // 从上下文中获取图片

    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();

    // 结束上下文

    UIGraphicsEndImageContext();

    return theImage;

}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{
    CGFloat offsetY = scrollView.contentOffset.y;
    CGFloat delta = offsetY - _lastOffsetY;
    // 往上拖动，高度减少。

    CGFloat height = headH - delta;
    if (height < headMinH) {

        height = headMinH;

    }
    _headHCons.constant = height;
    // 设置导航条的背景图片

    CGFloat alpha = delta / (headH - headMinH);

    // 当alpha大于1，导航条半透明，因此做处理，大于1，就直接=0.99

    if (alpha >= 1) {

        alpha = 0.99;

    }

    _nameLabel.alpha = alpha;

    // 设置导航条的背景图片

    UIImage *image = [UIImage imageWithColor:[UIColor colorWithWhite:1 alpha:alpha]];

    [self.navigationController.navigationBar setBackgroundImage:image forBarMetrics:UIBarMetricsDefault];
}

获取通讯录（联系人信息）

Unknown.png

Unknown-1.png

磁盘总空间大小

1、获取磁盘总空间大小

//磁盘总空间
+ (CGFloat)diskOfAllSizeMBytes{
    CGFloat size = 0.0;
    NSError *error;
    NSDictionary *dic = [[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:&error];
    if (error) {
#ifdef DEBUG
        NSLog(@"error: %@", error.localizedDescription);
#endif
    }else{
        NSNumber *number = [dic objectForKey:NSFileSystemSize];
        size = [number floatValue]/1024/1024;
    }
    return size;
}

2、获取磁盘可用空间大小

//磁盘可用空间
+ (CGFloat)diskOfFreeSizeMBytes{
    CGFloat size = 0.0;
    NSError *error;
    NSDictionary *dic = [[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:&error];
    if (error) {
#ifdef DEBUG
        NSLog(@"error: %@", error.localizedDescription);
#endif
    }else{
        NSNumber *number = [dic objectForKey:NSFileSystemFreeSize];
        size = [number floatValue]/1024/1024;
    }
    return size;
}

3、获取指定路径下某个文件的大小

//获取文件大小
+ (long long)fileSizeAtPath:(NSString *)filePath{
  NSFileManager *fileManager = [NSFileManager defaultManager];
  if (![fileManager fileExistsAtPath:filePath]) return 0;
  return [[fileManager attributesOfItemAtPath:filePath error:nil] fileSize];
}

4、获取文件夹下所有文件的大小

//获取文件夹下所有文件的大小
+ (long long)folderSizeAtPath:(NSString *)folderPath{
    NSFileManager *fileManager = [NSFileManager defaultManager];
    if (![fileManager fileExistsAtPath:folderPath]) return 0;
    NSEnumerator *filesEnumerator = [[fileManager subpathsAtPath:folderPath] objectEnumerator];
    NSString *fileName;
    long long folerSize = 0;
    while ((fileName = [filesEnumerator nextObject]) != nil) {
        NSString *filePath = [folderPath stringByAppendingPathComponent:fileName];
        folerSize += [self fileSizeAtPath:filePath];
    }
    return folerSize;
}

NSString处理

1、获取字符串(或汉字)首字母

//获取字符串(或汉字)首字母
+ (NSString *)firstCharacterWithString:(NSString *)string{
    NSMutableString *str = [NSMutableString stringWithString:string];
    CFStringTransform((CFMutableStringRef)str, NULL, kCFStringTransformMandarinLatin, NO);
    CFStringTransform((CFMutableStringRef)str, NULL, kCFStringTransformStripDiacritics, NO);
    NSString *pingyin = [str capitalizedString];
    return [pingyin substringToIndex:1];
}

2、将字符串数组按照元素首字母顺序进行排序分组


//将字符串数组按照元素首字母顺序进行排序分组
-(NSDictionary *)dictionaryOrderByCharacterWithOriginalArray:(NSArray *)array{
    if (array.count == 0) {
        return nil;
    }
    for (id obj in array) {
        if (![obj isKindOfClass:[NSString class]]) {
            return nil;
        }
    }
    UILocalizedIndexedCollation *indexedCollation = [UILocalizedIndexedCollation currentCollation];
    NSMutableArray *objects = [NSMutableArray arrayWithCapacity:indexedCollation.sectionTitles.count];
    //创建27个分组数组
    for (int i = 0; i < indexedCollation.sectionTitles.count; i++) {
        NSMutableArray *obj = [NSMutableArray array];
        [objects addObject:obj];
    }
    NSMutableArray *keys = [NSMutableArray arrayWithCapacity:objects.count];
    //按字母顺序进行分组
    NSInteger lastIndex = -1;
    for (int i = 0; i < array.count; i++) {
        NSInteger index = [indexedCollation sectionForObject:array[i] collationStringSelector:@selector(uppercaseString)];
        [[objects objectAtIndex:index] addObject:array[i]];
        lastIndex = index;
    }
    //去掉空数组
    for (int i = 0; i < objects.count; i++) {
        NSMutableArray *obj = objects[i];
        if (obj.count == 0) {
            [objects removeObject:obj];
        }
    }
    //获取索引字母
    for (NSMutableArray *obj in objects) {
        NSString *str = obj[0];
        NSString *key = [self firstCharacterWithString:str];
        [keys addObject:key];
    }
    NSMutableDictionary *dic = [NSMutableDictionary dictionary];
    [dic setObject:objects forKey:keys];
    return dic;
}

//获取字符串(或汉字)首字母
- (NSString *)firstCharacterWithString:(NSString *)string{
    NSMutableString *str = [NSMutableString stringWithString:string];
    CFStringTransform((CFMutableStringRef)str, NULL, kCFStringTransformMandarinLatin, NO);
    CFStringTransform((CFMutableStringRef)str, NULL, kCFStringTransformStripDiacritics, NO);
    NSString *pingyin = [str capitalizedString];
    return [pingyin substringToIndex:1];
}


NSArray *arr = @[@"guangzhou", @"shanghai", @"北京", @"henan", @"hainan"];
NSDictionary *dic = [Utilities dictionaryOrderByCharacterWithOriginalArray:arr];
NSLog(@"\n\ndic: %@", dic);

输出结果如下:

Unknown-2.png

UIImage 相关处理

1、对图片进行滤镜处理

#pragma mark - 对图片进行滤镜处理
// 怀旧 --> CIPhotoEffectInstant                         单色 --> CIPhotoEffectMono
// 黑白 --> CIPhotoEffectNoir                            褪色 --> CIPhotoEffectFade
// 色调 --> CIPhotoEffectTonal                           冲印 --> CIPhotoEffectProcess
// 岁月 --> CIPhotoEffectTransfer                        铬黄 --> CIPhotoEffectChrome
// CILinearToSRGBToneCurve, CISRGBToneCurveToLinear, CIGaussianBlur, CIBoxBlur, CIDiscBlur, CISepiaTone, CIDepthOfField
+ (UIImage *)filterWithOriginalImage:(UIImage *)image filterName:(NSString *)name{
    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *inputImage = [[CIImage alloc] initWithImage:image];
    CIFilter *filter = [CIFilter filterWithName:name];
    [filter setValue:inputImage forKey:kCIInputImageKey];
    CIImage *result = [filter valueForKey:kCIOutputImageKey];
    CGImageRef cgImage = [context createCGImage:result fromRect:[result extent]];
    UIImage *resultImage = [UIImage imageWithCGImage:cgImage];
    CGImageRelease(cgImage);
    return resultImage;
}

2、调整图片饱和度、亮度、对比度

/**
 *  调整图片饱和度, 亮度, 对比度
 *
 *  @param image      目标图片
 *  @param saturation 饱和度
 *  @param brightness 亮度: -1.0 ~ 1.0
 *  @param contrast   对比度
 *
 */- (UIImage *)colorControlsWithOriginalImage:(UIImage *)image
                                 saturation:(CGFloat)saturation
                                 brightness:(CGFloat)brightness
                                   contrast:(CGFloat)contrast{
    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *inputImage = [[CIImage alloc] initWithImage:image];
    CIFilter *filter = [CIFilter filterWithName:@"CIColorControls"];
    [filter setValue:inputImage forKey:kCIInputImageKey];

    [filter setValue:@(saturation) forKey:@"inputSaturation"];
    [filter setValue:@(brightness) forKey:@"inputBrightness"];
    [filter setValue:@(contrast) forKey:@"inputContrast"];

    CIImage *result = [filter valueForKey:kCIOutputImageKey];
    CGImageRef cgImage = [context createCGImage:result fromRect:[result extent]];
    UIImage *resultImage = [UIImage imageWithCGImage:cgImage];
    CGImageRelease(cgImage);
    return resultImage;
}

3、全屏截图

//全屏截图
+ (UIImage *)shotScreen{
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    UIGraphicsBeginImageContext(window.bounds.size);
    [window.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

4、截取一张 view 生成图片

//截取view生成一张图片
+ (UIImage *)shotWithView:(UIView *)view{
    UIGraphicsBeginImageContext(view.bounds.size);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

5、截取view中某个区域生成一张图片

//截取view中某个区域生成一张图片
+ (UIImage *)shotWithView:(UIView *)view scope:(CGRect)scope{
    CGImageRef imageRef = CGImageCreateWithImageInRect([self shotWithView:view].CGImage, scope);
    UIGraphicsBeginImageContext(scope.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rect = CGRectMake(0, 0, scope.size.width, scope.size.height);
    CGContextTranslateCTM(context, 0, rect.size.height);//下移
    CGContextScaleCTM(context, 1.0f, -1.0f);//上翻
    CGContextDrawImage(context, rect, imageRef);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGImageRelease(imageRef);
    CGContextRelease(context);
    return image;
}

6、判断是否为gif/png图片的正确姿势

//假设这是一个网络获取的URL
   NSString *path = @"http://pic3.nipic.com/20090709/2893198_075124038_2.gif";
   // 判断是否为gif
   NSString *extensionName = path.pathExtension;
    if ([extensionName.lowercaseString isEqualToString:@"gif"]) {
        //是gif图片
    } else {
        //不是gif图片
    }

什么难道你不是这么判断的么 ? 哦~ 我懂了, 难道你使用字符串截取来判断的吗 ? 哈哈开个玩笑!
以上判断看似是可以的,但是这不严谨的, 在不知道图片扩展名的情况下, 如何知道图片的真实类型 ? 其实就是取出图片数据的第一个字节, 就可以判断出图片的真实类型那该怎么做呢如下:

//通过图片Data数据第一个字节 来获取图片扩展名
- (NSString *)contentTypeForImageData:(NSData *)data {
    uint8_t c;
    [data getBytes:&c length:1];
    switch (c) {
        case 0xFF:
            return @"jpeg";
        case 0x89:
            return @"png";     
        case 0x47:
            return @"gif";        
        case 0x49:   
        case 0x4D:
            return @"tiff";        
        case 0x52:  
            if ([data length] < 12) {
                return nil;
            }
            NSString *testString = [[NSString alloc] initWithData:[data subdataWithRange:NSMakeRange(0, 12)] encoding:NSASCIIStringEncoding];
            if ([testString hasPrefix:@"RIFF"] && [testString hasSuffix:@"WEBP"]) {
                return @"webp";
            }
            return nil;
    }
    return nil;
}

7、设置图片圆角?

 //cornerRadius 设置为self.iconImage图片宽度的一半(圆形图片)
    self.iconImage.layer.cornerRadius = 20;
    self.iconImage.layer.masksToBounds = YES;

在此之后建议大家尽量不要这么设置, 因为使用图层过量会有卡顿现象, 特别是弄圆角或者阴影会很卡, 如果设置图片圆角我们一般用绘图来做:

/** 设置圆形图片(放到分类中使用) */
- (UIImage *)cutCircleImage {
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0);
    // 获取上下文
    CGContextRef ctr = UIGraphicsGetCurrentContext();
    // 设置圆形
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGContextAddEllipseInRect(ctr, rect);
    // 裁剪
    CGContextClip(ctr);
    // 将图片画上去
    [self drawInRect:rect];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

UILabel修改行距,首行缩进

1.UILabel修改文字行距,首行缩进
lineSpacing: 行间距
firstLineHeadIndent：首行缩进
font: 字体
textColor: 字体颜色
－ (NSDictionary *)settingAttributesWithLineSpacing:(CGFloat)lineSpacing FirstLineHeadIndent:(CGFloat)firstLineHeadIndent Font:(UIFont *)font TextColor:(UIColor *)textColor{
    //分段样式
    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    //行间距
    paragraphStyle.lineSpacing = lineSpacing;
    //首行缩进
    paragraphStyle.firstLineHeadIndent = firstLineHeadIndent;
    //富文本样式
    NSDictionary *attributeDic = @{
                                   NSFontAttributeName : font,
                                   NSParagraphStyleAttributeName : paragraphStyle,
                                   NSForegroundColorAttributeName : textColor
                                   };
    return attributeDic;
}

iOS 开发中实用小技巧(1)

感谢判若两人丶

UITextField使用注意

TableView拉伸头部图片、导航栏渐变效果

获取通讯录（联系人信息）

磁盘总空间大小

NSString处理

UIImage 相关处理

UILabel修改行距,首行缩进

猜你喜欢

热点阅读

iOS 开发中实用小技巧(1)

感谢 判若两人丶

UITextField使用注意

TableView拉伸头部图片、导航栏渐变效果

获取通讯录（联系人信息）

磁盘总空间大小

NSString处理

UIImage 相关处理

UILabel修改行距,首行缩进

猜你喜欢

热点阅读

感谢判若两人丶