iOS中 项目开发易错知识点总结

点击return取消textView 的响应者

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [_contactTextFiled resignFirstResponder];
    return YES;
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{

    if([text isEqualToString:@"
"]){

        [textView resignFirstResponder];
        [_contactTextFiled becomeFirstResponder];
        return YES;
    }
    return YES;
}

iOS一行代码将所有子视图从父视图上移除

这里主要利用了一个makeObjectsPerformSelector:函数。这个函数可以在很多场景下使用从而简化代码。

[xxxView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];

有效解决刷新单个cell或者section闪一下的问题：

[UIView setAnimationsEnabled:NO];
[_listTable beginUpdates];
[_listTable reloadSections:[NSIndexSet indexSetWithIndex:indexPath.section] withRowAnimation:UITableViewRowAnimationNone];
[_listTable endUpdates];
[UIView setAnimationsEnabled:YES];

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画出下列曲线：

UIView *myCustomView = [[UIView alloc]initWithFrame:CGRectMake(0, 204,kScreenWidth, 120)];
myCustomView.backgroundColor = [UIColor whiteColor];
[view addSubview:myCustomView];

UIBezierPath *bezierPath = [UIBezierPath bezierPath];
[bezierPath moveToPoint:CGPointMake(0,0)];
[bezierPath addCurveToPoint:CGPointMake(myCustomView.width, 0) controlPoint1:CGPointMake(0, 0) controlPoint2:CGPointMake(myCustomView.width/2, 40)];
[bezierPath addLineToPoint:CGPointMake(myCustomView.width, myCustomView.height)];
[bezierPath addLineToPoint:CGPointMake(0, myCustomView.height)];
[bezierPath closePath];

CAShapeLayer *shapLayer = [CAShapeLayer layer];
shapLayer.path = bezierPath.CGPath;
myCustomView.layer.mask = shapLayer;
myCustomView.layer.masksToBounds = YES;

当你使用 UISearchController 在 UITableView 中实现搜索条，在搜索框已经激活并推入新的 VC 的时候会发生搜索框重叠的情况：那就是 definesPresentationContext 这个布尔值！

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TabBar的隐藏与消失：

- (void)hidesTabBar:(BOOL)hidden{
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0];

    for (UIView *view in self.tabBarController.view.subviews){

        if ([view isKindOfClass:[UITabBar class]]) {
            if (hidden) {
                [view setFrame:CGRectMake(view.frame.origin.x, [UIScreen mainScreen].bounds.size.height, view.frame.size.width , view.frame.size.height)];
            }else{
                [view setFrame:CGRectMake(view.frame.origin.x, [UIScreen mainScreen].bounds.size.height - 49, view.frame.size.width, view.frame.size.height)];
            }
        }else{
            if([view isKindOfClass:NSClassFromString(@"UITransitionView")]){
                if (hidden){
                    [view setFrame:CGRectMake(view.frame.origin.x, view.frame.origin.y, view.frame.size.width, [UIScreen mainScreen].bounds.size.height)];
                }else{

                    [view setFrame:CGRectMake(view.frame.origin.x, view.frame.origin.y, view.frame.size.width, [UIScreen mainScreen].bounds.size.height - 49 )];
                }
            }
        }
    }
    [UIView commitAnimations];
}

获取cell上按钮所在分区和行数：

UIView *view = [sender superview]; // 获取父视图的view
GCCollectGroupCellTableViewCell *cell = (GCCollectGroupCellTableViewCell*)[view superview]; // 获取cell
NSIndexPath *indexPath = [_listTable indexPathForCell:cell]; // 获取cell对应的分区
NSLog(@"%@",detailArr[indexPath.section-1][indexPath.row][@"comname"]);

NSAttributedString 与NSString互转：

NSAttributedString * attrStr = [[NSAttributedString alloc] initWithData:[_CompanyFileds.comname dataUsingEncoding:NSUnicodeStringEncoding] options:@{ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType } documentAttributes:nil error:nil];
_CompanyFileds.comname = attrStr.string;

监控UITextField 变化：

// 注册监听
    [[NSNotificationCenter defaultCenter]postNotificationName:UITextFieldTextDidChangeNotification object:nil];
    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(changeForKeyWord:) name:UITextFieldTextDidChangeNotification object:nil];


// 监听_pageTextField.text变化
- (void)changeForKeyWord:(NSNotification *)sender
{
    [self checkNum:_pageTextField.text];
}
- (BOOL)checkNum:(NSString *)str
{
    NSString *regex = @"^[0-9]+(.[0-9]{2})?$";
    NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
    BOOL isMatch = [pred evaluateWithObject:str];
    if (!isMatch && _pageTextField.text.length>0) {
        UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:nil message:@"页码只能输入数字哦" delegate:self cancelButtonTitle:@"重新输入" otherButtonTitles:nil, nil nil];
        alertView.delegate = self;
        [alertView show];
        return NO;
    }
    return YES;
}

监听UITextField的点击事件

[[NSNotificationCenter defaultCenter]postNotificationName:UITextFieldTextDidBeginEditingNotification object:nil];
        [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(enterEdited:) name:UITextFieldTextDidBeginEditingNotification object:nil];

- (void)enterEdited:(NSNotification *)sender
{
    事件写这里！希望帮到你！
}

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解决添加到父视图手势影响子视图手势的解决办法：（手势冲突）

//方法一：
#pragma mark--UIGestureRecognizerDelegate
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    if([touch.view isKindOfClass:[UIButton class]]||[touch.view isKindOfClass:[UITableViewCell class]]||[touch.view isKindOfClass:[UITextField class]]||[touch.view isKindOfClass:[UITextView class]])
    {
        return NO;
    }
    return YES;
}

//方法二：
//UIView的exclusiveTouch属性
//通过设置[self setExclusiveTouch:YES];可以达到同一界面上多个控件接受事件时的排他性，从而避免一些问题。

UITextField 边框样式及内容调整：

//1. 设置的时候在ib里面记得选择无边框的，要不然随便你设置，都是无效的，也是坑死了。
  _textBoxName.layer.borderWidth=1.0f;
    _textBoxName.layer.borderColor=[UIColorcolorWithRed:0xbf/255.0fgreen:0xbf/255.0fblue:0xbf/255.0falpha:1].CGColor;

   //2.在uitextfield 中文字最左边距离左侧边框的距离
    _textBoxName.leftView=[[UIViewalloc] initWithFrame:CGRectMake(0,0, 16,51)];
    _textBoxName.leftViewMode=UITextFieldViewModeAlways;

图片旋转控制：

#pragma mark ----- 更新按钮动画
- (void)rotate360DegreeWithImageViews:(UIImageView *)myViews{
    CABasicAnimation *rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 2.0 ];
    rotationAnimation.duration = 1.0;
    rotationAnimation.cumulative = YES;rotate360DegreeWithImageViews
    rotationAnimation.repeatCount = 100000;
    [myViews.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];
}
[myViews.layer removeAllAnimations]; // 停止

改变cell的选中颜色：

cell.selectedBackgroundView = [[UIView alloc] initWithFrame:cell.frame];
cell.selectedBackgroundView.backgroundColor = COLOR_BACKGROUNDVIEW;
不需要任何颜色可以这么设置：
cell.selectionStyle = UITableViewCellSelectionStyleNone;

取整问题：

Objective-C拓展了C,自然很多用法是和C一致的。比如浮点数转化成整数，就有以下四种情况。
1.简单粗暴，直接转化


float f = 1.5; int a; a = (int)f; NSLog("a = %d",a);
输出结果是1。（int）是强制类型转化，丢弃浮点数的小数部分。

2.高斯函数，向下取整


float f = 1.6; int a; a = floor(f); NSLog("a = %d",a);
输出结果是1。floor()方法是向下取整，类似于数学中的高斯函数 [].取得不大于浮点数的最大整数，对于正数来说是舍弃浮点数部分，对于复数来说，舍弃浮点数部分后再减1.

3.ceil函数，向上取整。


float f = 1.5; int a; a = ceil(f); NSLog("a = %d",a);
输出结果是2。ceil()方法是向上取整，取得不小于浮点数的最小整数，对于正数来说是舍弃浮点数部分并加1，对于复数来说就是舍弃浮点数部分.

4.通过强制类型转换四舍五入。

float f = 1.5; int a; a = (int)(f+0.5); NSLog("a = %d",a);