iOS--开发小技巧(持续更新)

// 模糊效果

        UIBlurEffect *effect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark];
        UIVisualEffectView *test = [[UIVisualEffectView alloc] initWithEffect:effect];
        test.frame = self.view.bounds;
        test.alpha = 0;
        [self.view addSubview:test];
_mytext = test;
    
    UISlider *slidel = [[UISlider alloc]initWithFrame:CGRectMake(30, 300, 200, 20)];
    slidel.backgroundColor = [UIColor purpleColor];
    slidel.value = 0;
    slidel.maximumValue = 1.0;
    slidel.minimumValue = 0.0;
    [self.view addSubview:slidel];
    slidel.enabled = YES;
    [slidel addTarget:self action:@selector(act:) forControlEvents:UIControlEventValueChanged];
    - (void)act:(UISlider *)slider
{
    _mytext.alpha = slider.value;
    
}

// 隐藏手机的状态栏
-(BOOL)prefersStatusBarHidden {
    return YES;
}

self.automaticallyAdjustsScrollViewInsets = YES; // 不让系统帮咱们把scrollView及其子类的视图向下调整64

 //状态栏显示网络请求提示器
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    
    //将window显示在最外面.
    [[[[UIApplication sharedApplication] delegate] window] addSubview:self.view];
    

//cell高度
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    
    NSString *string = self.lrcArr[indexPath.row];
    
    CGRect frame = [string boundingRectWithSize:CGSizeMake([UIScreen mainScreen].bounds.size.width, 10000) options:(NSStringDrawingUsesLineFragmentOrigin) attributes:[NSDictionary dictionaryWithObject:[UIFont systemFontOfSize:17] forKey:NSFontAttributeName] context:nil];
    
    return frame.size.height;
    
}

// 在ARC工程中导入MRC的类  我们选中工程->选中targets中的工程,然后选中Build Phases->在导入的类后边加入标记 -  fno-objc-arc
// 在MRC工程中导入ARC的类 路径与上面一致,在该类后面加上标记 -fobjc-arc

//通过AV框架中的AVMakeRectWithAspectRatioInsideRect这个函数,可以将一个图片按比例凡在视图的中间,不需要计算:
#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 300, 300)];
    imageView.center = self.view.center;
    imageView.backgroundColor = [UIColor redColor];
    imageView.contentMode = UIViewContentModeScaleToFill;
    UIImage *image = [UIImage imageNamed:@"1.jpg"];
    imageView.image = image;
    
    CGRect iamgeAspectRect = AVMakeRectWithAspectRatioInsideRect(image.size, imageView.bounds);
    NSLog(@"iamgeAspectRect = %@, imageView =%@",NSStringFromCGRect(iamgeAspectRect),NSStringFromCGRect(imageView.frame));
    [self.view addSubview:imageView];
    
}

上线之后自动关闭打印日志,节省资源
//NSLog
#if DEBUG

#define NSLog(FORMAT, ...) fprintf(stderr, "[%s:%d行] %s
",[[[NSString stringWithUTF8String:__FILE__] lastPathComponent] UTF8String], __LINE__, [[NSString stringWithFormat:FORMAT, ##__VA_ARGS__] UTF8String])

#else

#define NSLog(FORMAT, ...) nil

#endif

动态加载高度

转而用WKWebView，监听estimatedProgress（WKWebView的加载进度）属性。

[self.webView addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew context:nil];添加监听。

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context{

　 if (self.webView.estimatedProgress < 1.0){

　　return;

}

　//完全加载后获取webview的高度

NSString *js = @"document.body.scrollHeight";

        [self.webView evaluateJavaScript:js completionHandler:^(id _Nullable height, NSError * _Nullable error) {

           NSLog(@"progress:%f height:%@",self.webView.estimatedProgress ,value);

        }];

 }

TableView不显示没内容的Cell怎么办？
self.tableView.tableFooterView = [[UIView alloc] init];

改变自定义返回按钮的frame,代码如下:
 UIButton * backButton = [UIButton buttonWithType:UIButtonTypeCustom];
    [backButton setFrame:CGRectMake(-15, 0, 60, 30)];
    [backButton setTitle:@"返回" forState:UIControlStateNormal];
    [backButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
    [backButton setImage:[UIImage imageNamed:@"返回.png"] forState:UIControlStateNormal];
    [backButton setTitleColor:[UIColor lightGrayColor] forState:UIControlStateHighlighted];
    [backButton addTarget:self action:@selector(backClick) forControlEvents:UIControlEventTouchUpInside];
    
    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 60, 30)];
    [view addSubview:backButton];
    UIBarButtonItem *item = [[UIBarButtonItem alloc] initWithCustomView:view];
    self.navigationItem.leftBarButtonItem = item;

iOS 判断字符串是纯汉字还是含有汉字
新建一个字符串的类别:

#import <Foundation/Foundation.h>

@interface NSString (China)

- (BOOL)isChinese;//判断是否是纯汉字

- (BOOL)includeChinese;//判断是否含有汉字

@end


#import "NSString+China.h"

@implementation NSString (China)

-(BOOL)isChinese
{
    NSString *match = @"(^[u4e00-u9fa5]+$)";
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF matches %@", match];
    return [predicate evaluateWithObject:self];
}

-(BOOL)includeChinese
{
    for(int i=0; i< [self length];i++)
    {
        int a =[self characterAtIndex:i];
        if( a >0x4e00&& a <0x9fff){
            return YES;
        }
    }
    return NO;
}


@end

#import "ViewController.h"
#import "NSString+China.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    NSString *string1 = @"Liuzhiwu 纯汉字";
    
    if (string1.isChinese) {
        
        NSLog(@"纯汉字");
    }
    else if (string1.includeChinese)
    {
        NSLog(@"包含汉字");
    }
    else{
        NSLog(@"纯字母");
    }
    
    
}

隐藏tabbar的坑:
我们有的时候需要隐藏和显示tabbar,但有的时候会出现黑色的条.是因为push的时候有动画的效果,可以使用下面的这种方法,也就是隐藏tabbar的另一种方法

 [self.navigationController setNavigationBarHidden:YES animated:animated];

快速查找工程文件
工程大了，常常不记得哪个文件在哪个文件夹的子目录下，或者记得也得不厌其烦地层层打开，可以 cmd + shift + O组合键调出Open Quickly窗口，快速查找所需文件。

禁止锁屏:
[UIApplication sharedApplication].idleTimerDisabled = YES;
或
[[UIApplication sharedApplication] setIdleTimerDisabled:YES];

判断视图是不是指定视图的子视图
BOOL isView = [textView isDescendantOfView:self.view];

防止scrollView手势覆盖侧滑手势
[scrollView.panGestureRecognizerrequireGestureRecognizerToFail:self.navigationController.interactivePopGestureRecognizer];

改变导航栏的alpha
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    //第一种方法
//    CGFloat offsetToShow = 200.0;//滑动多少就完全显示
//    CGFloat alpha = 1 - (offsetToShow - scrollView.contentOffset.y) / offsetToShow;
//    [[self.navigationController.navigationBar subviews] objectAtIndex:0].alpha = alpha;
    //第二种方法
    CGFloat offsetToShow = 200.0;
    CGFloat alpha = (offsetToShow - scrollView.contentOffset.y) / offsetToShow - 1;
    
    [self.navigationController.navigationBar setShadowImage:[UIImage new]];
    [self.navigationController.navigationBar setBackgroundImage:[self imageWithColor:[[UIColor orangeColor]colorWithAlphaComponent:alpha]] forBarMetrics:UIBarMetricsDefault];
}
//生成一张纯色的图片
- (UIImage *)imageWithColor:(UIColor *)color
{
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return theImage;
}

获取硬盘总容量与可用容量:
NSFileManager *fileManager = [NSFileManager defaultManager];
NSDictionary *attributes = [fileManager attributesOfFileSystemForPath:NSHomeDirectory() error:nil];

NSLog(@"容量%.2fG",[attributes[NSFileSystemSize] doubleValue] / (powf(1024, 3)));
NSLog(@"可用%.2fG",[attributes[NSFileSystemFreeSize] doubleValue] / powf(1024, 3));

//图片与字符串相互转换

-(NSString *)UIImageToBase64Str:(UIImage *) image  
{  
    NSData *data = UIImageJPEGRepresentation(image, 1.0f);  
    NSString *encodedImageStr = [data base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];  
    return encodedImageStr;  
}

//字符串转图片  
-(UIImage *)Base64StrToUIImage:(NSString *)_encodedImageStr  
{  
    NSData *_decodedImageData   = [[NSData alloc] initWithBase64Encoding:_encodedImageStr];  
    UIImage *_decodedImage      = [UIImage imageWithData:_decodedImageData];  
    return _decodedImage;  
}

//根据Label文字,自适应高度
CGRect rect = [contentString boundingRectWithSize:CGSizeMake(tableView.bounds.size.width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName :[UIFont systemFontOfSize:15]} context:nil] ;

 @param CGSize 规定文本显示的最大范围
        @param options 按照何种设置来计算范围
        @param attributes 文本内容的一些属性,例如字体大小,字体类型等  (字体不一样,高度也不一样)
        @parma context 上下文 可以规定一些其他的设置 但是一般都是nil

//导航栏渐变效果
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    //第一种方法
//    CGFloat offsetToShow = 200.0;//滑动多少就完全显示
//    CGFloat alpha = 1 - (offsetToShow - scrollView.contentOffset.y) / offsetToShow;
//    [[self.navigationController.navigationBar subviews] objectAtIndex:0].alpha = alpha;
    //第二种方法
    CGFloat offsetToShow = 200.0;
    CGFloat alpha = (offsetToShow - scrollView.contentOffset.y) / offsetToShow - 1;
    
    [self.navigationController.navigationBar setShadowImage:[UIImage new]];
    [self.navigationController.navigationBar setBackgroundImage:[self imageWithColor:[[UIColor orangeColor]colorWithAlphaComponent:alpha]] forBarMetrics:UIBarMetricsDefault];
}
//生成一张纯色的图片
- (UIImage *)imageWithColor:(UIColor *)color
{
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return theImage;
}

//导航栏自动缩放效果
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CGFloat offsetY = scrollView.contentOffset.y + scrollView.contentInset.top;
    
    CGFloat scale = 1.0;
    // 放大
    if (offsetY < 0) {
        // 允许下拉放大的最大距离为300
        // 1.5是放大的最大倍数，当达到最大时，大小为：1.5 * 70 = 105
        // 这个值可以自由调整
        scale = MIN(1.5, 1 - offsetY / 300);
    } else if (offsetY > 0) { // 缩小
        // 允许向上超过导航条缩小的最大距离为300
        // 为了防止缩小过度，给一个最小值为0.45，其中0.45 = 31.5 / 70.0，表示
        // 头像最小是31.5像素
        scale = MAX(0.45, 1 - offsetY / 300);
    }
    
    self.headerImageView.transform = CGAffineTransformMakeScale(scale, scale);
    
    // 保证缩放后y坐标不变
    CGRect frame = self.headerImageView.frame;
    frame.origin.y = -self.headerImageView.layer.cornerRadius / 2;
    self.headerImageView.frame = frame;
}

 

在使用SDWebImage加载较多图片造成内存警告时，定期调用

 [[SDImageCache sharedImageCache] setValue:nil forKey:@"memCache"];

可解决。