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iOS开发基础知识--碎片46
1:带中文的URL处理
// http://static.tripbe.com/videofiles/视频/我的自拍视频.mp4NSString *path = (__bridge_transfer NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(NULL,(__bridge CFStringRef)model.mp4_url, CFSTR(""),CFStringConvertNSStringEncodingToEncoding(NSUTF8StringEncoding));2:取WebView高度
- (void)webViewDidFinishLoad:(UIWebView *)webView { CGFloat height = [[webView stringByEvaluatingJavaScriptFromString:@"document.body.offsetHeight"] floatValue]; CGRect frame = webView.frame; webView.frame = CGRectMake(frame.origin.x, frame.origin.y, frame.size.width, height); } 另外一种方式利用KVO实例：-(void)viewDidLoad{ // KVO,作为一个观察者,只要属性"contentSize"发生变化,回调方法里面就会通知 [_webView.scrollView addObserver:self forKeyPath:@"contentSize" options:NSKeyValueObservingOptionNew context:NULL];}// 回调方法- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{ if(object == _webView.scrollView && [keyPath isEqualToString:@"contentSize"]) { // 得到最大的Y坐标 CGSize size = _webView.scrollView.contentSize; if (size.height > 568.0) { // 遮挡广告 _hideBottomImage = [[UIImageView alloc] initWithFrame:CGRectMake(0, size.height-67, ScreenWidth, 67)]; _hideBottomImage.image = [UIImage imageNamed:@"banner"]; [_webView.scrollView addSubview:_hideBottomImage]; } } else { // 调用父类的方法 [super observeValueForKeyPath:keyPath ofObject:object change:change context:context]; }}- (void)dealloc{//---->在ARC环境下也能调用dealloc方法,只是不需要写[super dealloc] // 移除KVO,否则会引起资源泄露 [_webView.scrollView removeObserver:self forKeyPath:@"contentSize"];}
3:UIView的部分圆角问题
UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(120, 10, 80, 80)];view2.backgroundColor = [UIColor redColor];[self.view addSubview:view2]; UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:view2.bounds byRoundingCorners:UIRectCornerBottomLeft | UIRectCornerBottomRight cornerRadii:CGSizeMake(10, 10)];CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];maskLayer.frame = view2.bounds;maskLayer.path = maskPath.CGPath;view2.layer.mask = maskLayer;//其中，byRoundingCorners:UIRectCornerBottomLeft |UIRectCornerBottomRight//指定了需要成为圆角的角。该参数是UIRectCorner类型的，可选的值有：* UIRectCornerTopLeft* UIRectCornerTopRight* UIRectCornerBottomLeft* UIRectCornerBottomRight* UIRectCornerAllCorners
4：强制App直接退出
- (void)exitApplication { AppDelegate *app = [UIApplication sharedApplication].delegate; UIWindow *window = app.window; [UIView animateWithDuration:1.0f animations:^{ window.alpha = 0; } completion:^(BOOL finished) { exit(0); }];}5：修改占位符颜色和大小
textField.placeholder = @"请输入用户名"; [textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"]; [textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];
6：取消系统的返回手势
self.navigationController.interactivePopGestureRecognizer.enabled = NO;
7：改WebView字体/颜色
UIWebView设置字体大小，颜色，字体： UIWebView无法通过自身的属性设置字体的一些属性，只能通过html代码进行设置 在webView加载完毕后：
- (void)webViewDidFinishLoad:(UIWebView *)webView { NSString *str = @"document.getElementsByTagName(‘body‘)[0].style.webkitTextSizeAdjust= ‘60%‘"; [webView stringByEvaluatingJavaScriptFromString:str]; }或者加入以下代码NSString *jsString = [[NSString alloc] initWithFormat:@"document.body.style.fontSize=%f;document.body.style.color=%@",fontSize,fontColor]; [webView stringByEvaluatingJavaScriptFromString:jsString];8：WebView图片自适应屏幕
- (void)webViewDidFinishLoad:(UIWebView *)webView { NSString *js = @"function imgAutoFit() { var imgs = document.getElementsByTagName(‘img‘); for (var i = 0; i < imgs.length; ++i) { var img = imgs[i]; img.style.maxWidth = %f; } }"; js = [NSString stringWithFormat:js, [UIScreen mainScreen].bounds.size.width - 20]; [webView stringByEvaluatingJavaScriptFromString:js]; [webView stringByEvaluatingJavaScriptFromString:@"imgAutoFit()"];}9：BOOL / bool / Boolean / NSCFBoolean的区别
10：nil / Nil / NULL / NSNull区别
a、nil：一般赋值给空对象；
b、NULL：一般赋值给nil之外的其他空值。如SEL等；
举个栗子（好重啊~）：
[NSApp beginSheet:sheet
modalForWindow:mainWindow
modalDelegate:nil //pointing to an object
didEndSelector:NULL //pointing to a non object/class
contextInfo:NULL]; //pointing to a non object/class
c、NSNULL：NSNull只有一个方法：+ (NSNull *) null;
[NSNull null]用来在NSArray和NSDictionary中加入非nil（表示列表结束）的空值.
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionary];mutableDictionary[@"someKey"] = [NSNull null]; // Sets value of NSNull singleton for `someKey`NSLog(@"Keys: %@", [mutableDictionary allKeys]); // @[@"someKey"]
d、当向nil发送消息时，返回NO，不会有异常，程序将继续执行下去；
而向NSNull的对象发送消息时会收到异常。
11:子类中实现 -isEqual: 和 hash
@interface Person@property NSString *name;@property NSDate *birthday;- (BOOL)isEqualToPerson:(Person *)person;@end@implementation Person- (BOOL)isEqualToPerson:(Person *)person { if (!person) { return NO; } BOOL haveEqualNames = (!self.name && !person.name) || [self.name isEqualToString:person.name]; BOOL haveEqualBirthdays = (!self.birthday && !person.birthday) || [self.birthday isEqualToDate:person.birthday]; return haveEqualNames && haveEqualBirthdays;}#pragma mark - NSObject- (BOOL)isEqual:(id)object { if (self == object) { return YES; } if (![object isKindOfClass:[Person class]]) { return NO; } return [self isEqualToPerson:(Person *)object];}- (NSUInteger)hash { return [self.name hash] ^ [self.birthday hash];}iOS开发基础知识--碎片46
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