android中开启ProgressDialog进度条之后，屏蔽返回按键。

ProgressDialog pd;  
/** 
     * 等待连接滚动条 
     */ 
 private void initProgDialog() {  
 // TODO Auto-generated method stub 
        flag=false;  
        pd=new ProgressDialog(this);  
        pd.setIndeterminate(false);  
        pd.setMessage("请等待");  
        pd.setCancelable(false);  
        pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);  
        pd.show();  
    }  

pd.setOnKeyListener(new DialogInterface.OnKeyListener() {  
 
 @Override 
 public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {  
 // TODO Auto-generated method stub 
 if(keyCode==event.KEYCODE_SEARCH){  
 return true;  
                }  
 else{  
 return false;  
                }  
            }  
        });