ListFragment 中 ArrayList 中的 JSON 解析抛出 getApplicationContext() 错误

Question

我正在开发一个应用程序，它在ListFragment 中显示一些基本的解析 JSON。 我关注了http://www.androidhive.info/2012/01/android-json-parsing-tutorial，它在ListActivity 中运行良好。然后我开始制作自己的应用程序。我在 Android Studio 1.5 中创建了新项目，添加了 Navigation Drawer Activity，因为我有更多的事情要做/显示，并开始将代码重写为片段。除了 getApplicationContext() 和 Cannot resolve method getApplciationContext() 错误的一个疯狂问题仍未解决之外，这基本上很容易。

这是我的片段的一部分：

public class Den1Fragment extends ListFragment {

private ProgressDialog pDialog;

// JSON Node names
private static final String TAG_CONTACTS = "contacts";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_EMAIL = "email";
private static final String TAG_ADDRESS = "address";
private static final String TAG_GENDER = "gender";
private static final String TAG_PHONE = "phone";
private static final String TAG_PHONE_MOBILE = "mobile";
private static final String TAG_PHONE_HOME = "home";
private static final String TAG_PHONE_OFFICE = "office";

// contacts JSONArray
JSONArray contacts = null;

// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    return inflater.inflate(R.layout.fragment_den1, container, false);

    contactList = new ArrayList<>();

    ListView lv = getListView();

    // Listview on item click listener
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {
            // getting values from selected ListItem
            String name = ((TextView) view.findViewById(R.id.name))
                    .getText().toString();
            String cost = ((TextView) view.findViewById(R.id.email))
                    .getText().toString();
            String description = ((TextView) view.findViewById(R.id.mobile))
                    .getText().toString();

            // Starting single contact activity
            Intent in = new Intent(getApplicationContext(), // TODO error!
                    SingleContactActivity.class);
            in.putExtra(TAG_NAME, name);
            in.putExtra(TAG_EMAIL, cost);
            in.putExtra(TAG_PHONE_MOBILE, description);
            startActivity(in);

        }
    });
    // Calling async task to get json
    new GetContacts().execute();
}

如果我添加 Intent in = new Intent(**getActivity().**getApplicationContext(), SingleContactActivity.class); 错误将移动到 contactList = new ArrayList<>(); 并且 Android Studio 不知道如何解决它，甚至谷歌搜索也没有带来太多想要的结果。 我尝试以不同的重写顺序再次执行此操作，发现如果我离开 setContentView(R.layout.activity_main); 而不是将其更改为 return inflater.inflate(R.layout.fragment_den1, container, false);，setContentView 会变为红色，但 contactList 行保持“正常”。

编辑

content_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
android:id="@+id/content_frame"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:showIn="@layout/app_bar_main"
tools:context=".MainActivity">

<ListView
    android:id="@android:id/list"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>
</LinearLayout>

错误报告：

java.lang.RuntimeException: Unable to start activity ComponentInfo{cz.ludato.festapp/cz.ludato.festapp.MainActivity}: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list'
Caused by: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list'
at cz.ludato.festapp.Den1Fragment.onViewCreated(Den1Fragment.java:54)

Answer 1

试试这个代码：

public class Den1Fragment extends ListFragment {

private ProgressDialog pDialog;

// JSON Node names
private static final String TAG_CONTACTS = "contacts";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_EMAIL = "email";
private static final String TAG_ADDRESS = "address";
private static final String TAG_GENDER = "gender";
private static final String TAG_PHONE = "phone";
private static final String TAG_PHONE_MOBILE = "mobile";
private static final String TAG_PHONE_HOME = "home";
private static final String TAG_PHONE_OFFICE = "office";

// contacts JSONArray
private JSONArray contacts = null;

// Hashmap for ListView
private ArrayList<HashMap<String, String>> contactList = new ArrayList<>();;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_den1, container, false);
ListView lv = getListView();

// Listview on item click listener
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

    @Override
    public void onItemClick(AdapterView<?> parent, View view,
                            int position, long id) {
        // getting values from selected ListItem
        String name = ((TextView) view.findViewById(R.id.name))
                .getText().toString();
        String cost = ((TextView) view.findViewById(R.id.email))
                .getText().toString();
        String description = ((TextView) view.findViewById(R.id.mobile))
                .getText().toString();

        Intent in = new Intent(getActivity(), SingleContactActivity.class);
        in.putExtra(TAG_NAME, name);
        in.putExtra(TAG_EMAIL, cost);
        in.putExtra(TAG_PHONE_MOBILE, description);
        getActivity().startActivity(in); 

    }
});

// Calling async task to get json
new GetContacts().execute();

return view;
}