iOS 开发中实用小技巧(1)

作者: 小兵快跑 | 来源:发表于2017-01-05 13:09 被阅读163次

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

相关文章

网友评论

延伸阅读

深度阅读

栏目导航

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

相关文章

网友评论

延伸阅读

深度阅读

栏目导航

热点阅读

感谢判若两人丶