Question

我正在从字符串数组创建简单的listview。我看过很多教程都说同样只有3行足以使它工作。我正在做同样但仍然得到NPE，几乎对此问题感到沮丧。无法弄清楚什么是错的，请帮助我。

我的代码在这里：

Mainfiest ：

   <uses-sdk
    android:minSdkVersion="16"
    android:targetSdkVersion="18" />

MainActivity.java

public class MainActivity extends Activity {
    ListView lv;
    String[] days = new String[] { "Sunday", "Monday", "Tuesday",
        "Wednesday", "Thursday", "Friday"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView) findViewById(R.id.listView1);

        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction().add(R.id.container, new PlaceholderFragment()).commit();
        }

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

    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            return rootView;
        }
    }
}

Answer 1

嘿，你错了配置代码。在这里你将listview放在片段xml中并在mainactivity类中编写代码，这样你就必须删除你的片段xml并将你的片段xml代码替换为mainactivity xml并删除下面的代码

if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }

来自onCreate（）的

OR

在片段类的OnCreateView中初始化Listview

public static class PlaceholderFragment extends Fragment {
    ListView lv;
String[] days = new String[] { "Sunday", "Monday", "Tuesday",
    "Wednesday", "Thursday", "Friday"};

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
            lv = (ListView) view.findViewById(R.id.listView1);
            ArrayAdapter<String> adapter = new ArrayAdapter<String>(GetActivity(),
            android.R.layout.simple_list_item_1, days);

            lv.setAdapter(adapter);
        return rootView;
    }
}

多数民众赞成......

Answer 2

更改

setContentView(R.layout.activity_main);

到

setContentView(R.layout.fragment_main);

Answer 3

您在活动中显示新片段。

if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
}

但是listview是在主要活动布局中声明的。因此，要查看列表视图，只需对上面的代码进行评论，然后查看。

Answer 4

您需要将“String [] days”中的项添加到“适配器”中，您可以使用方法adapter.add或adapter.addAll将项添加到ArrayAdapter。有关详细信息，请参阅此处的简单listView示例

http://windrealm.org/tutorials/android/android-listview.php

我的代码有什么问题？ Android简单列表视图示例

4 个答案: