ArrayList的<散列映射<字符串，字符串>＆GT;获取值</hashmap <string，string>

Question

帮助从ArrayList

获取值

data = new ArrayList<Map<String, String>>();
for (int i = 0; i < marks.length; i++) {
    HashMap<String, String> m = new HashMap<String, String>();
    m.put("title", marks[i].getUserName());
    m.put("mark", marks[i].getMark().toString());
    m.put("type", marks[i].getType().toString());
    m.put("description", marks[i].getDescription());
    data.add(m);
}

尝试从适配器中取出一个ArrayList并将值写入数组：

data = simpleAdapter.getData();
MarksRead[] marksReads = new MarksRead[data.size()];
for (int i = 0; i < data.size(); i++) {
    marksReads[i].setDescription(data(i).get("description"));
    marksReads[i].setMark(Integer.valueOf(data.get(i).get("mark")));
    marksReads[i].setType(Integer.valueOf(data.get(i).get("type")));
}

在线marksReads[i].setDescription(data(i).get("description"));输出为Exception NullPointerException.

帮助，如何正确行事。

Answer 1

您必须先创建对象才能使用它

for (int i = 0; i < data.size(); i++) {
    marksReads[i] = new MarksReads();
    marksReads[i].setDescription(data(i).get("description"));
    marksReads[i].setMark(Integer.valueOf(data.get(i).get("mark")));
    marksReads[i].setType(Integer.valueOf(data.get(i).get("type")));
 }