更新帮助文档;更新cacheFile

app/src/main/assets/help/ruleHelp.md

@@ -31,8 +31,21 @@
 
 * 获取登录后的cookie
 ```
-java.getCookie("http://baidu.com", null) => userid=1234;pwd=adbcd
-java.getCookie("http://baidu.com", "userid") => 1234
+获取全部
+cookie.getCookie(url)
+获取某一键值
+cookie.getKey(url,key)
+```
+
+* 缓存网络文件
+```
+获取
+java.cacheFile(url)
+java.cacheFile(url,saveTime)
+执行内容
+eval(String(java.cacheFile(url)))
+删除缓存文件
+cache.delete(java.md5Encode16(url))
 ```
 
 * 请求头,支持http代理,socks4 socks5代理设置

app/src/main/java/io/legado/app/help/JsExtensions.kt

@@ -139,8 +139,9 @@ interface JsExtensions {
     fun cacheFile(url: String, saveTime: Int = 0): String? {
         val key = md5Encode16(url)
 	    val _cache = CacheManager.get(key)
-	    val value = ajax(url) ?: ""
-	if(_cache.isNullOrBlank()) {
+	    if(_cache.isNullOrBlank()) {
+	        log("首次下载${url}...")
+	        val value = ajax(url) ?: ""
             CacheManager.put(key, value as Any, saveTime)
          }
          return _cache