android隨機項目from arraylist

Question

我想從arraylist中獲得隨機項目。我的代碼，我試圖不工作。

EDIT

ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>(); 
map.put(KEY_NAME, parser.getValue(e, KEY_NAME)); 
map.put(KEY_ADD, parser.getValue(e, KEY_ADD)); --edited code 
menuItems.add(map); 

int index = random.nextInt(menuItems.size()); 
HashMap<String, String> itm = menuItems.get(index); 
System.out.println(itm); 

：

 int index = random.nextInt(menuItems.size()); 
    HashMap<String, String> itm = new HashMap<String, String>(); 
    itm = menuItems.get(index); 
    String randomstring = itm.get(MyClass.KEY_NAME); 

    System.out.println(randomstring); 

接收的NullPointerException使用代替

Answer 1

HashMap<String, String> itm =new HashMap<String, String>(); 
itm = menuItems.get(index); 
System.out.println(itm); 

HashMap<String, String> itm = menuItems.get(index); 
System.out.println(itm); 

在當前代碼中，您在使用它之前未初始化hashmap itm