优化

app/src/main/java/io/legado/app/ui/association/FileAssociationViewModel.kt

@@ -35,9 +35,10 @@ class FileAssociationViewModel(application: Application) : BaseAssociationViewMo
                 } else {
                     val file = DocumentFile.fromSingleUri(context, uri)
                     content = file?.readText(context) ?: throw NoStackTraceException("文件不存在")
-                    fileName = file!!.name ?: ""
+                    fileName = file.name ?: ""
                 }
-                if (content.isJson()) {
+                when {
+                    content.isJson() -> {
                         //暂时根据文件内容判断属于什么
                         when {
                             content.contains("bookSourceUrl") ->
@@ -54,11 +55,14 @@ class FileAssociationViewModel(application: Application) : BaseAssociationViewMo
                                 importHttpTTS(content, finally)
                             else -> errorLiveData.postValue("格式不对")
                         }
-                } else if (fileName.matches(bookFileRegex)) {
+                    }
+                    fileName.matches(bookFileRegex) -> {
                         importBookLiveData.postValue(uri)
-                } else {
+                    }
+                    else -> {
                         throw NoStackTraceException("$fileName 暂未支持的本地书籍格式(TXT/UMD/EPUB)")
                     }
+                }
             } else {
                 onLineImportLive.postValue(uri)
             }