Android 按字母顺序对 ListView 进行排序

Question

所以我正在尝试为 ListView 排序一个简单的 ArrayAdapter。这是我尝试过的:

ListView lv;
String[] months = {
        "January",
        "February",
        "March",
        "April",
        "May",
        "June",
        "July",
        "August",
        "September",
        "October",
        "November",
        "December"
};

ArrayAdapter<String> adapter;
ArrayList<String> list;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    lv = (ListView) findViewById(R.id.listView1);
    lv.setFastScrollEnabled(true);
    adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, months);
    lv.setAdapter(adapter);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // TODO Auto-generated method stub

    switch (item.getItemId()) {
        case R.id.sortasc:
            list = new ArrayList<String>(Arrays.asList(months));
            Collections.sort(list);
            for (int i = 0; i < list.size(); i++) {
                System.out.println(list.get(i));
            }
            adapter.clear();
            adapter = new ArrayAdapter<String>(this,
                    android.R.layout.simple_list_item_1, list);
            adapter.notifyDataSetChanged();
            return true;
        case R.id.sortdesc:

            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

但是我得到 UnsupportedOperationException，这是怎么回事？我真的需要帮助。提前致谢!

Answer 1

在对项目进行排序后，您没有调用 setAdapter(adapter)。

像下面这样使用

adapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, list);
lv.setAdapter(adapter);
adapter.notifyDataSetChanged();

而不是

adapter.clear(); // Useless 
adapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, list);
adapter.notifyDataSetChanged();