toggleContinuousMode method
void
toggleContinuousMode()
切换持续绘图模式
Implementation
void toggleContinuousMode() {
_isContinuousMode = !_isContinuousMode;
debugPrint('持续绘图模式已${_isContinuousMode ? "启用" : "禁用"}');
_notifyModeChanged();
}