开发细节(二)

1. 利用Auto Layout整体排列控件

下面的代码演示了一个控件如何在其父容器中垂直水平居中：

UIView *box = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 200, 150)];
box.backgroundColor = [UIColor grayColor];
[self.view addSubview:box];

UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setTitle:@"a button" forState:UIControlStateNormal];
[button sizeToFit];
button.translatesAutoresizingMaskIntoConstraints = NO;
[box addSubview:button];

NSMutableArray *array = [[NSMutableArray alloc] init];

[array addObjectsFromArray:[NSLayoutConstraint
                            constraintsWithVisualFormat:@"V:[box]-(<=1)-[button]"
                            options:NSLayoutFormatAlignAllCenterX
                            metrics:nil
                            views:NSDictionaryOfVariableBindings(box,button)]];

[array addObjectsFromArray:[NSLayoutConstraint
                            constraintsWithVisualFormat:@"H:[box]-(<=1)-[button]"
                            options:NSLayoutFormatAlignAllCenterY
                            metrics:nil
                            views:NSDictionaryOfVariableBindings(box,button)]];

[box addConstraints:array];

下面的代码演示了多个控件其父容器中水平左对齐，垂直居中：

UIView *box = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 200, 150)];
box.backgroundColor = [UIColor grayColor];
[self.view addSubview:box];
    
UILabel *label = [[UILabel alloc] init];
label.text = @"a label";
[label sizeToFit];
label.backgroundColor = [UIColor redColor];
label.translatesAutoresizingMaskIntoConstraints = NO;
[box addSubview:label];

UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setTitle:@"a button" forState:UIControlStateNormal];
[button sizeToFit];
button.translatesAutoresizingMaskIntoConstraints = NO;
[box addSubview:button];

NSMutableArray *array = [[NSMutableArray alloc] init];

[array addObjectsFromArray:[NSLayoutConstraint
                            constraintsWithVisualFormat:@"V:|-[button]-|"
                            options:NSLayoutFormatAlignAllLeft
                            metrics:nil
                            views:NSDictionaryOfVariableBindings(button)]];

[array addObjectsFromArray:[NSLayoutConstraint
                            constraintsWithVisualFormat:@"|-15-[myLabel]-5-[myButton]"
                            options:NSLayoutFormatAlignAllCenterY
                            metrics:nil
                            views:@{@"myLabel":label, @"myButton":button}]];

[box addConstraints:array];

2. ScrollView利用Auto Layout管理控件

3. IB_DESIGNABLE,IBInspectable配合XIB实现自定义控件

#import <UIKit/UIKit.h>

@interface MyTempView : UIView

@property (weak, nonatomic) IBOutlet UIView *contentView;
@property (weak, nonatomic) IBOutlet UILabel *myLabel;

@end

#import "MyTempView.h"

IB_DESIGNABLE
@interface MyTempView ()

@property (nonatomic) IBInspectable NSString *myText;
@end

@implementation MyTempView

- (void)setMyText:(NSString *)myText {
    self.myLabel.text = myText;
}

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        [self commonSetup];
    }
    return self;
}

- (instancetype)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if (self) {
        [self commonSetup];
    }
    return self;
}

- (UIView *)loadViewFromNib {
    NSBundle *bundle = [NSBundle bundleForClass:[self class]];
    
    //xib文件名与类文件名不同
//    UIView *view = [[bundle loadNibNamed:@"abc" owner:self options:nil] firstObject];
    
    //xib文件名与类文件名相同
    UIView *view = [[bundle loadNibNamed:NSStringFromClass([self class])  owner:self options:nil] firstObject];
    
    return view;
}

- (void)commonSetup {
    UIView *nibView = [self loadViewFromNib];
    nibView.frame = self.bounds;
    // the autoresizingMask will be converted to constraints, the frame will match the parent view frame
    nibView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    // Adding nibView on the top of our view
    [self addSubview:nibView];
}
@end

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="10116" systemVersion="15E65" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES">
    <dependencies>
        <deployment identifier="iOS"/>
        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="10085"/>
    </dependencies>
    <objects>
        <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner" customClass="MyTempView">
            <connections>
                <outlet property="contentView" destination="iN0-l3-epB" id="a2U-Rp-jYq"/>
                <outlet property="myLabel" destination="IIE-8B-dDU" id="mM8-Li-TQ0"/>
            </connections>
        </placeholder>
        <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
        <view contentMode="scaleToFill" id="iN0-l3-epB">
            <rect key="frame" x="0.0" y="0.0" width="600" height="600"/>
            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
            <subviews>
                <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" fixedFrame="YES" text="Label" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="IIE-8B-dDU">
                    <rect key="frame" x="27" y="32" width="162" height="21"/>
                    <fontDescription key="fontDescription" name="HelveticaNeue" family="Helvetica Neue" pointSize="17"/>
                    <color key="textColor" cocoaTouchSystemColor="darkTextColor"/>
                    <nil key="highlightedColor"/>
                </label>
            </subviews>
            <color key="backgroundColor" white="0.66666666666666663" alpha="1" colorSpace="calibratedWhite"/>
        </view>
    </objects>
</document>

4. 自定义控件利用delegate触发事件

#import "ViewController.h"
#import "MyView.h"

@interface ViewController () <MyDelegate>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    MyView *view1 = [[MyView alloc] initWithFrame:CGRectMake(30, 30, 250, 300)];
    view1.backgroundColor = [UIColor greenColor];
    view1.delegate = self;
    [self.view addSubview:view1];
}

- (void)eat:(NSString *)food {
    NSLog(@"wayne eat %@", food);
}

- (void)read:(NSString *)book {
    NSLog(@"wayne read a book called %@", book);
}
@end

#import <UIKit/UIKit.h>

@protocol MyDelegate <NSObject,UICollectionViewDelegate>
@optional
- (void)sing:(NSString *)song;
- (void)read:(NSString *)book;
@required
- (void)eat:(NSString *)food;
@end

@interface MyView : UIView

@property (nonatomic, weak) id <MyDelegate> delegate;

@end

#import "MyView.h"

@implementation MyView

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if(self) {
        [self initDataAndUI];
    }
    return self;
}

- (void)initDataAndUI {
    UIButton *firstButton = [UIButton buttonWithType:UIButtonTypeCustom];
    [firstButton setTitle:@"Eat Button" forState:UIControlStateNormal];
    [firstButton setBackgroundColor:[UIColor purpleColor]];
    [firstButton sizeToFit];
    [firstButton addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:firstButton];
}

- (void)buttonClicked:(id)sender {

    [(id<MyDelegate>)self.delegate eat:@"an apple"];
    
    
    [self.delegate read:@"Robinson Crusoe"];
}
@end

5. NSJSONSerialization的NSJSONReadingOptions参数

NSJSONReadingMutableContainers -- 返回可变容器，NSMutableDictionary或NSMutableArray

NSJSONReadingMutableLeaves -- 返回的JSON对象中字符串的值为NSMutableString

NSJSONReadingAllowFragments -- 允许JSON字符串最外层既不是NSArray也不是NSDictionary，但必须是有效的JSON Fragment

kNilOptions -- 不设置该参数，返回不可变的NSDictionary

NSString *str = @"{"name":"wayne"}";

//设置为kNilOptions后尝试修改字典内容，会导致报错
//NSMutableDictionary *dict = [NSJSONSerialization JSONObjectWithData:[str dataUsingEncoding:NSUTF8StringEncoding] options:kNilOptions error:nil];

NSMutableDictionary *dict = [NSJSONSerialization JSONObjectWithData:[str dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingMutableContainers error:nil];

[dict setObject:@"tom" forKey:@"name"];

NSLog(@"dict= %@,type= %@",dict,[dict class]);

NSString *num=@"32"; //ok
num = @"ABC"; //error
num = @""ABC""; //ok

NSError *error;
NSData *createdData = [num dataUsingEncoding:NSUTF8StringEncoding];
id response=[NSJSONSerialization JSONObjectWithData:createdData options:NSJSONReadingAllowFragments error:&error];
NSLog(@"Response= %@,type= %@",response,[response class]);

6. 一个嵌套JSON解析

NSString *jsonString = @"{"Products":[{"Appliances": {"TV": {"SONY":{"ProductName":"SONY G9", "Size":"48 inch"}, "LETV":{"ProductName":"S50 Air", "Size":"50 inch"} }}}, {"Digital": {"Camera": {"Canon":{"ProductName":"EOS 70D", "pixel":"2020"}}}}]}";

NSError *error;
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:[jsonString dataUsingEncoding:NSUTF8StringEncoding] options:kNilOptions error:&error];
NSLog(@"JSON:%@",json);

if (json) {
    NSArray *products = [json objectForKey:@"Products"];

    NSDictionary *appliancesDict = products[0]; //Appliances
    NSLog(@"appliancesDict: %@",appliancesDict);
    NSDictionary *digitalDict = products[1]; //Digital
    NSLog(@"digitalDict: %@",digitalDict);
    
    NSLog(@"Digital:%@",[digitalDict objectForKey:@"Digital"]);
    NSLog(@"Camera:%@",[[digitalDict objectForKey:@"Digital"] objectForKey:@"Camera"]);
    NSLog(@"Canon:%@",[[[digitalDict objectForKey:@"Digital"] objectForKey:@"Camera"] objectForKey:@"Canon"]);
    NSLog(@"ProductName:%@",[[[[digitalDict objectForKey:@"Digital"] objectForKey:@"Camera"] objectForKey:@"Canon"] objectForKey:@"ProductName"]);
    NSLog(@"pixel:%@",[[[[digitalDict objectForKey:@"Digital"] objectForKey:@"Camera"] objectForKey:@"Canon"] objectForKey:@"pixel"]);
}