Android后退事件处理

    public long lastClickTime = 0;    public void onBackPressed(){       if(lastClickTime <= 0){         Toast.makeText(this, "再按一次退出程序", 1).show();         lastClickTime = System.currentTimeMillis();//记录当前时间     }else{         long currentClickTime = System.currentTimeMillis();//记录当前时间         if(currentClickTime-lastClickTime <= 1000){ //时间差小于1000毫秒             finish(); //退出         }else{             Toast.makeText(this, "再按一次退出程序", 1).show();             lastClickTime = currentClickTime; //刷新时间         }      }   }