安卓混合开发设置返回键为返回上一网页

1. @Override  
2.     public boolean onKeyDown(int keyCode, KeyEvent event) {  
3.         // TODO Auto-generated method stub  
4.         if(keyCode == KeyEvent.KEYCODE_BACK && webView.canGoBack()){  
5.             webView.goBack();  
6.             return true;  
7.         }else{  
8.             if((System.currentTimeMillis()-exitTime) > 2000){      
9.                 Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();                                    
10.                 exitTime = System.currentTimeMillis();   
11.             } else {    
12.                 finish();    
13.             }    
14.         }  
15.         return true;  
16.     }