这个时代，真正的技术博客太少了，都是到处抄袭，想找答案，找思路，搜索10个文章，9个是一样的，抄就不能加点自己理解吗。
前段时间app中接了网页支付的业务（会跳转到其他支付应用），没太怎么注意JSContext跳转后会失效的问题，后面改版才发现。
网上有几种方案，各有各的说法，但是应用到目前的项目中是不符合的，方案有二：
一，js判断是否拿到注入的类，如果拿不到js重新加载（？？？跟没说一样）
二，每次跳转出去就移除webView,跳转回来再创建webView(什么鬼，说的啥？？？移除webView就把webView移除栈区，新创建的页面怎么回到上一层？？）
UIWebView Delegate 有4个方法，但是当前场景都用不上，归根结底是注入的时机问题，使用jsContext进行js注入的时候,如果网页跳转到其他页面,注入的js有一定几率会丢失.
添加分类 UIWebView+TS_JavaScriptContext
在js注入的类中实现TS_JavaScriptContext的代理方法
实现代码
.h
#import <UIKit/UIKit.h>
#import <JavaScriptCore/JavaScriptCore.h>
@protocol TSWebViewDelegate <UIWebViewDelegate>
@optional
- (void)webView:(UIWebView *)webView didCreateJavaScriptContext:(JSContext*) ctx;
@end
@interface UIWebView (TS_JavaScriptContext)
@property (nonatomic, readonly) JSContext* ts_javaScriptContext;
@end
.m
#import "UIWebView+TS_JavaScriptContext.h"
#import <JavaScriptCore/JavaScriptCore.h>
#import <objc/runtime.h>
static const char kTSJavaScriptContext[] = "ts_javaScriptContext";
static NSHashTable* g_webViews = nil;
@interface UIWebView (TS_JavaScriptCore_private)
- (void) ts_didCreateJavaScriptContext:(JSContext *)ts_javaScriptContext;
@end
@protocol TSWebFrame <NSObject>
- (id) parentFrame;
@end
@implementation NSObject (TS_JavaScriptContext)
- (void) webView: (id) unused didCreateJavaScriptContext: (JSContext*) ctx forFrame: (id<TSWebFrame>) frame
{
NSParameterAssert( [frame respondsToSelector: @selector( parentFrame )] );
// only interested in root-level frames
if ( [frame respondsToSelector: @selector( parentFrame) ] && [frame parentFrame] != nil )
return;
void (^notifyDidCreateJavaScriptContext)() = ^{
for ( UIWebView* webView in g_webViews )
{
NSString* cookie = [NSString stringWithFormat: @"ts_jscWebView_%lud", (unsigned long)webView.hash ];
[webView stringByEvaluatingJavaScriptFromString: [NSString stringWithFormat: @"var %@ = '%@'", cookie, cookie ] ];
if ( [ctx[cookie].toString isEqualToString: cookie] )
{
[webView ts_didCreateJavaScriptContext: ctx];
return;
}
}
};
if ( [NSThread isMainThread] )
{
notifyDidCreateJavaScriptContext();
}
else
{
dispatch_async( dispatch_get_main_queue(), notifyDidCreateJavaScriptContext );
}
}
@end
@implementation UIWebView (TS_JavaScriptContext)
+ (id) allocWithZone:(struct _NSZone *)zone
{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
g_webViews = [NSHashTable weakObjectsHashTable];
});
NSAssert( [NSThread isMainThread], @"uh oh - why aren't we on the main thread?");
id webView = [super allocWithZone: zone];
[g_webViews addObject: webView];
return webView;
}
- (void) ts_didCreateJavaScriptContext:(JSContext *)ts_javaScriptContext
{
[self willChangeValueForKey: @"ts_javaScriptContext"];
objc_setAssociatedObject( self, kTSJavaScriptContext, ts_javaScriptContext, OBJC_ASSOCIATION_RETAIN);
[self didChangeValueForKey: @"ts_javaScriptContext"];
if ( [self.delegate respondsToSelector: @selector(webView:didCreateJavaScriptContext:)] )
{
id<TSWebViewDelegate> delegate = ( id<TSWebViewDelegate>)self.delegate;
[delegate webView: self didCreateJavaScriptContext: ts_javaScriptContext];
}
}
- (JSContext*) ts_javaScriptContext
{
JSContext* javaScriptContext = objc_getAssociatedObject( self, kTSJavaScriptContext );
return javaScriptContext;
}
@end
实现
//页面跳转回来JS注入
- (void)webView:(UIWebView *)webView didCreateJavaScriptContext:(JSContext*) ctx {
ctx[@"JsBridge"] = self;
}
