fix: 修复下载列表对话框中，点击某个 item 取消下载按钮后下载列表无法再次显示的问题

MainWindow::notify 中焦点判断异常，未去除 QStyleSheetStyle 导致错误认为需要隐藏下载管理对话框

Log: 判断 focusIn 事件前排除 QStyleSheetStyle 对象

src/backend/downloadworker.cpp

@@ -1,9 +1,7 @@
 #include "downloadworker.h"
 
-#include <QEventLoop>
 #include <QProcess>
 #include <QRegularExpression>
-#include <QDir>
 #include <QtConcurrent>
 #include <QStandardPaths>
 

src/backend/downloadworker.h

@@ -2,9 +2,7 @@
 #define DOWNLOADWORKER_H
 
 #include <QObject>
-#include <QList>
-#include <QFile>
-#include <QNetworkReply>
+#include <QVector>
 
 class DownloadController : public QObject
 {
@@ -19,23 +17,19 @@ public:
     qint64 getFileSize(const QString& url);
     QString replaceDomain(const QString& url, const QString domain);
 
+signals:
+    void errorOccur(const QString& msg);
+    void downloadProcess(QString, qint64, qint64);
+    void downloadFinished();
+
 private:
     int threadNum;
     qint64 pidNumber = -1;
     QString filename;
     qint64 fileSize;
     QVector<QPair<qint64, qint64>> ranges;
-    QFile *file;
     bool finished = false;
     QVector<QString> domains;
-
-
-
-signals:
-    void errorOccur(const QString& msg);
-    void downloadProcess(QString, qint64, qint64);
-    void downloadFinished();
-
 };
 
 #endif // FILEDOWNLOADWORKER_H