Hybrid App: 了解JavaScript如何与Native实现混合开发
2024-10-06 12:52:15
一、简介
Hybrid Development混合开发是目前移动端开发异常火热的新兴技术，它能够实现跨平台开发，极大地节约了人力和资源成本。跨平台开发催生了很多新的开源框架，就目前而言，在混合开发中比较流行的有FaceBook开源React Native，有Goggle开源的Flutter。React Native实现的是通过下发JS脚本的方式达到JS与Native交互。Flutter实现的则是通过采用现代响应式框架来构建UI，Flutter与ReactiveCocoa框架配合使用最佳。当然开发者也可以在Native中内嵌WebView的方式(WebKit)实现混合开发。虽然方式不同，但目的相同，都是跨平台，殊途同归吧。对跨平台有了粗略的了解后，再来看看iOS系统中对JS与Native是如何交互的，其实，系统是给开发者提供了一个极其强大的框架来实现这个功能的，即JavaScriptCore框架。这个框架通过定义JSValue值对象和声明JSExport协议作为桥梁完成Native与JS的通信。JS虽然是单线程语言，但是iOS是支持多线程执行任务的，开发者可以在异步情况下执行任意一个环境的JavaScript代码。大概结构图如下：
二、分析
参考这上图，可以看出JavaScriptCore框架结构还是很清晰的，JavaScriptCore中有那么几个核心的类在开发者是很常用的，需要弄懂它们代表的意思。
三、API
知道了这几个核心类的概念已经对这个框架有了个基本的认识，具体的API如何使用，我们可以选择性点击去深入研究一下。只有对它们的属性和方法都了如指掌，开发起来才能得心应手，手到擒来。哎呀妈，不废话了。。。例如JSContext和JSValue开发中必用的类，额外的可能还会用JSManagerValue，如下：
JSContetxt类：
//初始化，可以选择对应的虚拟机
- (instancetype)init;
- (instancetype)initWithVirtualMachine:(JSVirtualMachine *)virtualMachine; //执行js代码，返回js值对象
- (JSValue *)evaluateScript:(NSString *)script;
- (JSValue *)evaluateScript:(NSString *)script withSourceURL:(NSURL *)sourceURL; //获取当前的js上下文
+ (JSContext *)currentContext; //获取当前的js执行函数，返回js值对象
+ (JSValue *)currentCallee; //获取当前的js函数中this指向的对象，返回js值对象
+ (JSValue *)currentThis; //获取当前的js函数中的所有参数
+ (NSArray *)currentArguments; //js的全局对象
@property (readonly, strong) JSValue *globalObject; //js执行的异常数据
@property (strong) JSValue *exception;
@property (copy) void(^exceptionHandler)(JSContext *context, JSValue *exception); //js运行的虚拟机
@property (readonly, strong) JSVirtualMachine *virtualMachine; //js上下文名称
@property (copy) NSString *name; //分类
@interface JSContext (SubscriptSupport)
//获取和设置属性为js全局对象
- (JSValue *)objectForKeyedSubscript:(id)key;
- (void)setObject:(id)object forKeyedSubscript:(NSObject <NSCopying> *)key;
@end //分类（C函数风格）
@interface JSContext (JSContextRefSupport)
//获取和设置全局上下文
+ (JSContext *)contextWithJSGlobalContextRef:(JSGlobalContextRef)jsGlobalContextRef;
@property (readonly) JSGlobalContextRef JSGlobalContextRef;
@end
JSValue类：
//js上下文
@property (readonly, strong) JSContext *context; //使用OC数据初始化js值对象，创建有值的JSValue
+ (JSValue *)valueWithObject:(id)value inContext:(JSContext *)context;
+ (JSValue *)valueWithBool:(BOOL)value inContext:(JSContext *)context;
+ (JSValue *)valueWithDouble:(double)value inContext:(JSContext *)context;
+ (JSValue *)valueWithInt32:(int32_t)value inContext:(JSContext *)context;
+ (JSValue *)valueWithUInt32:(uint32_t)value inContext:(JSContext *)context;
+ (JSValue *)valueWithPoint:(CGPoint)point inContext:(JSContext *)context;
+ (JSValue *)valueWithRange:(NSRange)range inContext:(JSContext *)context;
+ (JSValue *)valueWithRect:(CGRect)rect inContext:(JSContext *)context;
+ (JSValue *)valueWithSize:(CGSize)size inContext:(JSContext *)context; //使用OC数据初始化js值对象，创建空的JSValue
+ (JSValue *)valueWithNewObjectInContext:(JSContext *)context;
+ (JSValue *)valueWithNewArrayInContext:(JSContext *)context;
+ (JSValue *)valueWithNewRegularExpressionFromPattern:(NSString *)pattern flags:(NSString *)flags inContext:(JSContext *)context;
+ (JSValue *)valueWithNewErrorFromMessage:(NSString *)message inContext:(JSContext *)context;
+ (JSValue *)valueWithNewPromiseInContext:(JSContext *)context fromExecutor:(void (^)(JSValue *resolve, JSValue *reject))callback;
+ (JSValue *)valueWithNewPromiseResolvedWithResult:(id)result inContext:(JSContext *)context;
+ (JSValue *)valueWithNewPromiseRejectedWithReason:(id)reason inContext:(JSContext *)context;
+ (JSValue *)valueWithNewSymbolFromDescription:(NSString *)description inContext:(JSContext *)context;
+ (JSValue *)valueWithNullInContext:(JSContext *)context;
+ (JSValue *)valueWithUndefinedInContext:(JSContext *)context; //js数据转OC数据
- (id)toObject;
- (id)toObjectOfClass:(Class)expectedClass;
- (BOOL)toBool;
- (double)toDouble;
- (int32_t)toInt32;
- (uint32_t)toUInt32;
- (NSNumber *)toNumber;
- (NSString *)toString;
- (NSDate *)toDate;
- (NSArray *)toArray;
- (NSDictionary *)toDictionary;
- (CGPoint)toPoint;
- (NSRange)toRange;
- (CGRect)toRect;
- (CGSize)toSize; //js值对象判断
@property (readonly) BOOL isUndefined;
@property (readonly) BOOL isNull;
@property (readonly) BOOL isBoolean;
@property (readonly) BOOL isNumber;
@property (readonly) BOOL isString;
@property (readonly) BOOL isObject;
@property (readonly) BOOL isArray;
@property (readonly) BOOL isDate;
@property (readonly) BOOL isSymbol;
- (BOOL)isEqualToObject:(id)value;
- (BOOL)isEqualWithTypeCoercionToObject:(id)value;
- (BOOL)isInstanceOf:(id)value; //js调用函数
- (JSValue *)callWithArguments:(NSArray *)arguments;
- (JSValue *)constructWithArguments:(NSArray *)arguments;
- (JSValue *)invokeMethod:(NSString *)method withArguments:(NSArray *)arguments; //js属性设置
- (JSValue *)valueForProperty:(JSValueProperty)property;
- (void)setValue:(id)value forProperty:(JSValueProperty)property;
- (BOOL)deleteProperty:(JSValueProperty)property;
- (BOOL)hasProperty:(JSValueProperty)property;
- (void)defineProperty:(JSValueProperty)property descriptor:(id)descriptor;
- (JSValue *)valueAtIndex:(NSUInteger)index;
- (void)setValue:(id)value atIndex:(NSUInteger)index;
- (JSValue *)objectForKeyedSubscript:(id)key;
- (JSValue *)objectAtIndexedSubscript:(NSUInteger)index;
- (void)setObject:(id)object forKeyedSubscript:(id)key;
- (void)setObject:(id)object atIndexedSubscript:(NSUInteger)index;
+ (JSValue *)valueWithJSValueRef:(JSValueRef)value inContext:(JSContext *)context; //OC与JS类型对应关系
Objective-C type | JavaScript type
---------------------+---------------------
nil | undefined
NSNull | null
NSString | string
NSNumber | number, boolean
NSDictionary | Object object
NSArray | Array object
NSDate | Date object
NSBlock (1) | Function object (1)
id (2) | Wrapper object (2)
Class (3) | Constructor object (3)
---------------------+---------------------
JSManagerValue类：
//对JSValue进行一层包装，对内存进行有效的管理，防止提前或者过度释放
+ (JSManagedValue *)managedValueWithValue:(JSValue *)value;
+ (JSManagedValue *)managedValueWithValue:(JSValue *)value andOwner:
- (instancetype)initWithValue:(JSValue *)value;
@property (readonly, strong) JSValue *value;
四、案例
[1] 首先打开Safari浏览器的web检查器，会用来查看js运行的效果 ，控制台打印
[2] 导入JavaScriptCore框架
[3] 导入头文件开始测试，Native调用JS
[3-1] 调用无参数的JS函数
native.js
-(void)nativeCallJs {
//方式一
//从js文件获取js代码
NSString *path = [[NSBundle mainBundle] pathForResource:@"native" ofType:@"js"];
NSData *jsData = [NSData dataWithContentsOfFile:path];
NSString *script = [[NSString alloc] initWithData:jsData encoding:NSUTF8StringEncoding];
//执行js代码
[self.jsContext evaluateScript:script];
}
-(void)nativeCallJs {
//方式二
//js代码写在端上
NSString *script = @"\
(function(){ \
console.log(\"native call js ------- Wellcome Native\");\
})();";
//执行js代码
[self.jsContext evaluateScript:script];
}
- (void)viewDidLoad {
[super viewDidLoad];
//js上下文
self.jsContext = [[JSContext alloc] init];
//native调用js
[self nativeCallJs];
}
[3-2] 调用有参数的JS函数
native.js
-(void)nativeCallJsWithArguments:(NSString *)argument {
//方式一
//从js文件获取js代码
NSString *path = [[NSBundle mainBundle] pathForResource:@"native" ofType:@"js"];
NSData *jsData = [NSData dataWithContentsOfFile:path];
NSString *jsString = [[NSString alloc] initWithData:jsData encoding:NSUTF8StringEncoding];
//拼接js参数
NSString *script = [NSString stringWithFormat:jsString,argument];
//执行js代码
[self.jsContext evaluateScript:script];
}
-(void)nativeCallJsWithArguments:(NSString *)argument {
//方式二
//js代码写在端上
NSString *jsString = @"\
function receive(argument) { \
console.log(\"native call js ------- Wellcome \"+argument);\
};\
receive('%@')";
//拼接js参数
NSString *script = [NSString stringWithFormat:jsString,argument];
//执行js代码
[self.jsContext evaluateScript:script];
}
- (void)viewDidLoad {
[super viewDidLoad];
//js上下文
self.jsContext = [[JSContext alloc] init];
//native调用js
[self nativeCallJsWithArguments:@"我的老哥"];
}
[4] 导入头文件开始测试，JS调用Native
注意：调用包括无参数和有参数的OC方法，这里使用代码块Block为例
-(void)jsCallNative {
//定义无参数block
void (^Block1)(void) = ^(){
NSLog(@"js call native ------- hello JavaScript");
};
//定义有参数block
void (^Block2)(NSString *) = ^(NSString *argument){
NSLog(@"js call native ------- hello JavaScript----Wellcome %@",argument);
};
//设置block为JSContext全局对象的属性，然后可以在safari控制台执行函数oc_block()输出打印;
[self.jsContext setObject:Block1 forKeyedSubscript:@"oc_block1"];
[self.jsContext setObject:Block2 forKeyedSubscript:@"oc_block2"];
}
- (void)viewDidLoad {
[super viewDidLoad];
//js上下文
self.jsContext = [[JSContext alloc] init];
//js调用native
[self jsCallNative];
}
[5]导入头文件开始测试， OC和JS对象的映射
//OC与JS数据传递的数据就是JSValue值对象，存储在JS的全局对象中
//存和取的过程
[self.jsContext setObject:(id) forKeyedSubscript:(NSObject<NSCopying> *)];
[self.jsContext objectForKeyedSubscript:(id)]
[5-1] 系统提供的OC数据类型，不用特殊存储，可以直接存取
//系统提供的OC数据类型，不用特殊存储，可以直接存取
[self.jsContext setObject:@"mac" forKeyedSubscript:@"os"];
JSValue *osValue = [self.jsContext objectForKeyedSubscript:@"os"];
NSString *osName = [osValue toString];
NSLog(@"-----osName = %@-----",osName);
-- ::17.471840+ 混合开发[:] -----osName = mac-----
[5-2] 特殊的OC类型，如自定义对象，则必须遵守JSExport协议，JS才能拿到自定义对象的所有属性和方法
#import <UIKit/UIKit.h>
#import <JavaScriptCore/JavaScriptCore.h> //遵守JSExport协议，使得JS在上下文中可以获取到OC中定义的属性和方法
@protocol PersonProtocol <JSExport>
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, assign) int grade;
@property (nonatomic, assign) float score;
-(void)description;
@end @interface Person : NSObject<PersonProtocol>
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, assign) int grade;
@property (nonatomic, assign) float score;
-(void)description;
@end #import "Person.h"
@implementation Person
-(void)description {
NSLog(@"姓名：name = %@",self.name);
NSLog(@"年龄：age = %d",self.age);
NSLog(@"年级：grade = %d",self.grade);
NSLog(@"分数：score = %.1f",self.score);
}
@end
//特殊的OC类型，自定义对象，则必须遵守JSExport协议，JS才能拿到自定义对象的所有属性和方法
Person *person = [[Person alloc] init];
person.name = @"张三";
person.age = ;
person.grade = ;
person.score = ;
[self.jsContext setObject:person forKeyedSubscript:@"personEntity"];
JSValue *personValue = [self.jsContext objectForKeyedSubscript:@"personEntity"]; //personEntity为OC在JS的对象形式
Person *xyq_person = (Person *)[personValue toObject];
[xyq_person description];
-- ::17.472563+ 混合开发[:] 姓名：name = 张三
-- ::17.472709+ 混合开发[:] 年龄：age =
-- ::17.472810+ 混合开发[:] 年级：grade =
-- ::17.472889+ 混合开发[:] 分数：score = 98.0
五、实践
到现在为止，相信我们对JS和Native的交互原理有了自己的理解。在案例中使用了js文件下发和解析的方式实现了Native执行JS代码，这个正是Facebook开源的React Native的设计思路。React Native支持跨平台，通过一套js文件就可以在Andriod和iOS上完成Native的界面渲染。现在我们通过一个小测试来模拟Hybrid App的构建原理，通过按钮点击切换控制器视图的背景色。
(1) 创建JavaScript脚本，在脚本中创建Native需要的任意UI控件存到数组，作为函数的返回值
UIKit.js
//定义一个自调用函数，JavaScript脚本加载完成立即执行
(function(){
return renderUI();
})(); /* JavaScript脚本 定义一个Label类
* rect：尺寸 text：文本 color：颜色
*/
function Label(rect,text,fontSize,textColor,textAlignment,bgColor){
this.rect = rect;
this.text = text;
this.fontSize = fontSize;
this.textColor = textColor;
this.textAlignment = textAlignment; //NSTextAlignmentCenter = 1
this.bgColor = bgColor;
this.type = "Label";
} /* JavaScript脚本 定义一个Button类
* rect：尺寸 text：文本 color：颜色 callFunction：函数
*/
function Button(rect,title,fontSize,titleColor,bgColor,callFunction){
this.rect = rect;
this.title = title;
this.fontSize = fontSize;
this.titleColor = titleColor;
this.bgColor = bgColor;
this.callFunction = callFunction;
this.type = "Button";
} /* JavaScript脚本 Rect类
* x：坐标x y：坐标y w：宽度 h：高度
*/
function Rect(x,y,w,h){
this.x = x;
this.y = y;
this.w = w;
this.h = h;
} /* JavaScript脚本 Color类
* r：red g：green b：black a：alpa
*/
function Color(r,g,b,a){
this.r = r;
this.g = g;
this.b = b;
this.a = a;
} //渲染方法，实例化上面类的对象
function renderUI() { //创建js标签对象
var screenWidth = 375.0;
var labeWidth = 200;
var labelRect = new Rect((screenWidth-labeWidth)*0.5, 100, labeWidth, 44);
var labeFontSize = 20;
var labelTextColor = new Color(1,0,0,1);
var labelBgColor = new Color(1,1,0,1);
var label = new Label(labelRect, "I From JS", labeFontSize, labelTextColor, 1, labelBgColor); //创建js按钮对象
var buttonWidth = 200;
var buttonRect = new Rect((screenWidth-buttonWidth)*0.5, 200, buttonWidth, buttonWidth);
var buttonFontSize = 40;
var buttonTitleColor = new Color(1,0,1,1);
var buttonbgColor = new Color(1,1,1,1);
var button = new Button(buttonRect,"Button",buttonFontSize,buttonTitleColor,buttonbgColor,function(r,g,b){
var randColor = new Color(r,g,b,1);
configEntity.chageViewColor(randColor);
}); //返回js对象
return [label, button]; }
(2) 创建自定义对象，遵守JSExport协议，添加为JS的全局对象的属性，作为与Native交互的桥接器
//自定义Config类
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <JavaScriptCore/JavaScriptCore.h> NS_ASSUME_NONNULL_BEGIN @protocol ConfigProtocol <JSExport>
-(void)chageViewColor:(JSValue *)colorValue;
@end @interface Config : NSObject<ConfigProtocol>
@property (nonatomic, strong) UIViewController *currentVc;
-(void)chageViewColor:(JSValue *)colorValue; //改变当前控制器视图背景色
@end NS_ASSUME_NONNULL_END
//Created by 夏远全 on 2019/11/12.
#import "Config.h"
@implementation Config
-(void)chageViewColor:(JSValue *)colorValue {
CGFloat red = colorValue[@"r"].toDouble;
CGFloat green = colorValue[@"g"].toDouble;
CGFloat blue = colorValue[@"b"].toDouble;
CGFloat alpha = colorValue[@"a"].toDouble;
self.currentVc.view.backgroundColor = [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}
@end
(3) 在VC中解析JavaScript脚本，获取UI控件元素，进行界面的渲染
#import "ViewController.h"
#import <JavaScriptCore/JavaScriptCore.h>
#import "Person.h"
#import "Config.h" @interface ViewController ()
@property (nonatomic, strong) JSContext *jsContext;
@property (nonatomic, strong) NSMutableArray *actions; //所有的回调函数
@end @implementation ViewController - (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor redColor]; //js上下文
self.jsContext = [[JSContext alloc] init]; //从JS文件获取UI进行渲染
[self renderUIFromJs];
} -(void)renderUIFromJs { //创建Config对象
Config *config = [[Config alloc] init];
config.currentVc = self;
[self.jsContext setObject:config forKeyedSubscript:@"configEntity"]; //从js文件获取js代码
NSString *path = [[NSBundle mainBundle] pathForResource:@"UIKit" ofType:@"js"];
NSData *jsData = [NSData dataWithContentsOfFile:path];
NSString *script = [[NSString alloc] initWithData:jsData encoding:NSUTF8StringEncoding]; //执行js代码
JSValue *jsValue = [self.jsContext evaluateScript:script];
for (int i=; i<jsValue.toArray.count; i++) { //取出每一个控件对象值
JSValue *subValue = [jsValue objectAtIndexedSubscript:i]; //创建控件
NSString *type = [subValue objectForKeyedSubscript:@"type"].toString;
if ([type isEqualToString:@"Label"]) { //this.rect = rect;
//this.text = text;
//this.fontSize = fontSize;
//this.textColor = textColor;
//this.textAlignment = textAlignment; //NSTextAlignmentCenter = 1
//this.bgColor = bgColor;
//this.type = "Label"; CGFloat X = subValue[@"rect"][@"x"].toDouble;
CGFloat Y = subValue[@"rect"][@"y"].toDouble;
CGFloat W = subValue[@"rect"][@"w"].toDouble;
CGFloat H = subValue[@"rect"][@"h"].toDouble;
NSString *text = subValue[@"text"].toString;
NSInteger fontSize = subValue[@"fontSize"].toInt32;
UIColor *textColor = [UIColor colorWithRed:subValue[@"textColor"][@"r"].toDouble green:subValue[@"textColor"][@"g"].toDouble blue:subValue[@"textColor"][@"b"].toDouble alpha:subValue[@"textColor"][@"a"].toDouble];
UIColor *bgColor = [UIColor colorWithRed:subValue[@"bgColor"][@"r"].toDouble green:subValue[@"bgColor"][@"g"].toDouble blue:subValue[@"bgColor"][@"b"].toDouble alpha:subValue[@"bgColor"][@"a"].toDouble];
NSTextAlignment alignment = subValue[@"textAlignment"].toInt32; UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(X, Y, W, H)];
label.text = text;
label.font = [UIFont systemFontOfSize:fontSize];
label.textColor = textColor;
label.textAlignment = alignment;
label.backgroundColor = bgColor;
[self.view addSubview:label]; }
if ([type isEqualToString:@"Button"]) { //this.rect = rect;
//this.title = title;
//this.fontSize = fontSize;
//this.titleColor = titleColor;
//this.bgColor = bgColor;
//this.type = "Button";
//this.callFunction = callFunction; CGFloat X = subValue[@"rect"][@"x"].toDouble;
CGFloat Y = subValue[@"rect"][@"y"].toDouble;
CGFloat W = subValue[@"rect"][@"w"].toDouble;
CGFloat H = subValue[@"rect"][@"h"].toDouble;
NSInteger fontSize = subValue[@"fontSize"].toInt32;
NSString *title = subValue[@"title"].toString;
UIColor *titleColor = [UIColor colorWithRed:subValue[@"titleColor"][@"r"].toDouble green:subValue[@"titleColor"][@"g"].toDouble blue:subValue[@"titleColor"][@"b"].toDouble alpha:subValue[@"titleColor"][@"a"].toDouble];
UIColor *bgColor = [UIColor colorWithRed:subValue[@"bgColor"][@"r"].toDouble green:subValue[@"bgColor"][@"g"].toDouble blue:subValue[@"bgColor"][@"b"].toDouble alpha:subValue[@"bgColor"][@"a"].toDouble]; JSValue *actionValue = subValue[@"callFunction"];
[self.actions addObject:actionValue]; UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(X, Y, W, H)];
[button setTitleColor:titleColor forState:UIControlStateNormal];
[button addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];
[button setTitle:title forState:UIControlStateNormal];
button.titleLabel.font = [UIFont systemFontOfSize:fontSize];
button.backgroundColor = bgColor;
button.tag = self.actions.count-;
[self.view addSubview:button];
}
}
} -(void)buttonClick:(UIButton *)button { JSValue *actionValue = [self.actions objectAtIndex:button.tag];
[actionValue callWithArguments:@[@(arc4random_uniform()),@(arc4random_uniform()),@(arc4random_uniform())]]; } - (NSMutableArray *)actions {
if (!_actions) {
_actions = [NSMutableArray array];
}
return _actions;
}
(4) 演示gif
六、思考
这个js文件目前是写死的放在了Bundle目录下，试想一下，如果在本地每次更改js文件后再重新渲染界面，是不是都得端上重新发版，例如样式相同改一个颜色啥的，发个版就太繁琐了。最好的做法是将js文件部署到服务器上，每次只需要更新js内容后提交到服务器，端上进入当前页面时，从服务器拉取新的js文件渲染界面即可，效率高，成本低，可以实现快速更新迭代。好开心，吃个竹子吧，
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