fix: 修复初次启动时背景色不一致问题

MainForm.cs

@@ -35,18 +35,56 @@ namespace TimerApp
         public MainForm()
         {
             InitializeComponent();
+            // 在窗口显示前设置背景色，避免白色闪烁
+            // 确保所有控件在显示前都有正确的背景色
+            this.SuspendLayout();
+
+            // 先加载设置，以便知道应该使用什么背景色
+            _settings = AppSettings.Load();
+            bool dark = _settings.IsDarkMode;
+            Color bg = dark ? _darkBg : _lightBg;
+
+            this.BackColor = bg;
+            pnlSettings.BackColor = bg;
+            lblTimeLeft.BackColor = bg;
+            lblStatus.BackColor = bg;
+            label1.BackColor = bg;
+            label2.BackColor = bg;
+
+            // 设置文本框和按钮的初始背景色
+            Color panelColor = dark ? _darkPanel : _lightPanel;
+            txtWork.BackColor = panelColor;
+            txtRest.BackColor = panelColor;
+            btnWorkMinus.BackColor = panelColor;
+            btnWorkPlus.BackColor = panelColor;
+            btnRestMinus.BackColor = panelColor;
+            btnRestPlus.BackColor = panelColor;
+            btnStartStop.BackColor = dark ? Color.FromArgb(63, 63, 70) : Color.White;
+            btnReset.BackColor = dark ? Color.FromArgb(63, 63, 70) : Color.White;
+
+            // 优化绘制，减少闪烁
+            this.SetStyle(ControlStyles.AllPaintingInWmPaint |
+                         ControlStyles.UserPaint |
+                         ControlStyles.DoubleBuffer |
+                         ControlStyles.ResizeRedraw, true);
+
+            this.ResumeLayout(false);
         }
 
         private void MainForm_Load(object sender, EventArgs e)
         {
-            // Load settings
-            _settings = AppSettings.Load();
+            // Settings already loaded in constructor, just update text
             txtWork.Text = _settings.WorkMinutes.ToString();
             txtRest.Text = _settings.RestMinutes.ToString();
 
-            // Apply Theme
+            // Apply Theme - 确保在窗口显示前应用主题
             ApplyTheme();
 
+            // 强制刷新背景色，确保所有控件都正确显示
+            this.Invalidate(true);
+            pnlSettings.Invalidate(true);
+            this.Update();
+
             // Init monitor
             _monitor = new ActivityMonitor();
             ApplySettings();
@@ -78,6 +116,16 @@ namespace TimerApp
             SetupTextBoxPanel(txtWork, pnlSettings);
             SetupTextBoxPanel(txtRest, pnlSettings);
 
+            // 确保容器背景色正确（在 SetupTextBoxPanel 之后再次应用主题）
+            UpdateTextBoxStyle(txtWork, _settings.IsDarkMode);
+            UpdateTextBoxStyle(txtRest, _settings.IsDarkMode);
+
+            // 再次确保 pnlSettings 的背景色正确
+            bool dark = _settings.IsDarkMode;
+            Color bg = dark ? _darkBg : _lightBg;
+            pnlSettings.BackColor = bg;
+            pnlSettings.Refresh();
+
             _monitor.Start();
 
             // Set tray icon
@@ -122,6 +170,7 @@ namespace TimerApp
             Panel container = new Panel();
             container.Size = txt.Size; // 60x30
             container.Location = txt.Location;
+            // 确保容器背景色与文本框背景色一致
             container.BackColor = txt.BackColor;
 
             // Adjust textbox to be centered inside
@@ -136,6 +185,9 @@ namespace TimerApp
 
             // Ensure correct tab order and tagging
             container.Tag = txt.Tag; // Copy tag if any
+
+            // 确保容器背景色与父容器一致（如果文本框背景色与父容器不同）
+            // 这里容器应该使用文本框的背景色，因为它是文本框的容器
         }
 
         private void ValidateRange(TextBox txt, int min, int max)
@@ -175,9 +227,25 @@ namespace TimerApp
             Color text = dark ? _darkText : _lightText;
             Color btnBg = dark ? Color.FromArgb(45, 45, 48) : Color.White;
 
+            // 确保窗口和所有面板的背景色一致
             this.BackColor = bg;
             pnlTitle.BackColor = panel;
-            pnlSettings.BackColor = bg; // Revert to bg color (user preference)
+            // 强制设置 pnlSettings 的背景色，确保与窗口背景色一致
+            pnlSettings.BackColor = bg;
+            pnlSettings.Invalidate(); // 强制重绘
+            lblTimeLeft.BackColor = bg;
+            lblStatus.BackColor = bg;
+            label1.BackColor = bg;
+            label2.BackColor = bg;
+
+            // 确保所有标签都使用正确的背景色
+            foreach (Control ctrl in pnlSettings.Controls)
+            {
+                if (ctrl is Label label && label.BackColor != bg)
+                {
+                    label.BackColor = bg;
+                }
+            }
 
             lblTitle.ForeColor = dark ? Color.LightGray : Color.FromArgb(64, 64, 64);
             lblTimeLeft.ForeColor = text;