在clearRect（）和repaint（）之后无法在JPanel上绘制

I have a program which lets the user paint. But when the user clicks the clear button which calls clearRect() and repaint() the user can no longer keep painting on the same panel. Another issue I am having is that when the user clicks the save or open button (which open up a file explorer window), if the user presses cancel, the panel paints the file window onto the panel. How would I go about fixing these issues?I have a program which lets the user paint. But