为什么Canvas.getGraphics()获取不到呢
用的是jdk1.7,我是java新手,
		panel=new Panel();			
		Canvas canvas=new Canvas();
		canvas.setSize(500, 500);
		canvas.setBackground(Color.black);		
		canvas.setVisible(true);
		canvas.setEnabled(true);
		panel.add(canvas);
		panel.setLayout(null);
		Graphics gp = canvas.getGraphics();
		gp.drawArc(30, 30, 30, 30, 30, 30);
------解决方案--------------------
文明一点