使用自定义数组适配器

Question

我正在学习使用自定义适配器，我认为我正朝着正确的方向前进，直到我对 class 自定义适配器的构造函数的超级方法有疑问。你能找出背后的问题吗？在此之前，我使用了 Simple Adapter，但我希望更灵活地控制布局。这是我的 xml 文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="10dp"
    android:paddingLeft="10dp"
    android:paddingRight="10dp">

    <!-- Name Label -->


    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Hello This is testing"
        android:id="@+id/guid"
        android:visibility="gone"/>

    <TextView
        android:id="@+id/name"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="2dip"
        android:paddingTop="6dip"
        android:textColor="#43bd00"
        android:text="name:"
        android:textStyle="bold"
        android:visibility="gone"/>

    <!-- Email label -->
    <TextView
        android:id="@+id/email"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="2dip"
        android:textColor="#acacac"
        android:text="email"
        android:textStyle="bold"
        />

    <!-- Mobile number label -->
    <TextView
        android:id="@+id/mobile"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="left"
        android:text="Mobile: "
        android:textColor="#5d5d5d"
        android:maxLines="1"/>


</LinearLayout>

这是我的片段class

public class NewsFragment extends Fragment{

    private ProgressDialog pDialog;// Progress Dialog
    ListView newsList;
    ArrayList<HashMap<String, String>> postList; //Declare Array
    private static String url = "http://wangeltmg.com/GKN_ADMIN/GET_POSTS/get_news.php";
    GetNews.CustomAdapter CA;

    // JSON Node names
    private static final String TAG_ID = "id";
    private static final String POST_ALLPOSTS = "posts";
    private static final String POST_ID = "ID";
    private static final String POST_TITLE = "post_title";
    private static final String POST_CONTENT = "post_content";
    private static final String GUID = "guid";


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.news, container, false);
        newsList = (ListView) view.findViewById(R.id.newsListView);
        TextView topic = (TextView) view.findViewById(R.id.topic);
        postList = new ArrayList<HashMap<String, String>>();
        //Get arguments
        Bundle args = getArguments();
        String mytopic = args.getString("Topic");
        //Set topic
        topic.setText(mytopic.toUpperCase());
        //Execute getContacts
        new GetNews().execute();

        newsList.setOnItemClickListener(new newsListClick());


        return view;
    }

    public class newsListClick implements ListView.OnItemClickListener{

        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Log.d("News List","Clicked " + id);
            android.support.v4.app.FragmentManager fragmentManager = getFragmentManager();
            android.support.v4.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            SinglePost singleFrag = new SinglePost();
            fragmentTransaction.replace(R.id.content_frame, singleFrag);
            fragmentTransaction.commit();
        }
    }


    //Async Task
    private class GetNews extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // Showing progress dialog
            pDialog = new ProgressDialog(getActivity());
            pDialog.setMessage("Please wait...");
            pDialog.setCancelable(false);
            pDialog.show();

        }

        @Override
        protected Void doInBackground(Void... arg0) {

            // Creating service handler class instance
            ServiceHandler sh = new ServiceHandler();

            // Making a request to url and getting response
            String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
            Log.d("Strings","Checking Json");
            Log.d("Response: ", "> " + jsonStr);

            if (jsonStr != null) {
                try {
                    JSONObject jsonObj = new JSONObject(jsonStr);
                    // contacts JSONArray
                    JSONArray posts = null;
                    // Getting JSON Array node
                    posts = jsonObj.getJSONArray(POST_ALLPOSTS);

                    // looping through All Contacts
                    for (int i = 0; i < posts.length(); i++) {

                        JSONObject c = posts.getJSONObject(i);
                        Log.d("Post->",posts.getJSONObject(i).toString());

                        String id = c.getString(POST_ID);

                        Log.d("Post->ID",id);
                        String post_title = c.getString(POST_TITLE);
                        String post_content = c.getString(POST_CONTENT);
                        String guid = c.getString(GUID);
                        Log.d("GUID->",guid);
                        //String gender = c.getString(TAG_GENDER);

                        // tmp hashmap for single post
                        HashMap<String, String> post = new HashMap<String, String>();

                        // adding each child node to HashMap key => value
                        post.put(POST_ID, id);
                        post.put(POST_TITLE, post_title);
                        post.put(POST_CONTENT, post_content);
                        post.put(GUID, guid);

                        // adding contact to contact list
                        postList.add(post);
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            } else {
                Log.e("ServiceHandler", "Couldn't get any data from the url");
            }

            return null;
        }

        @Override
        public void onPostExecute(Void result) {
            super.onPostExecute(result);
            // Dismiss the progress dialog
            if (pDialog.isShowing())
                pDialog.dismiss();

             // Updating parsed JSON data into ListView
            /*
            ListAdapter adapter = new SimpleAdapter(getActivity(), postList, R.layout.list_item,
                    new String[] { POST_TITLE,POST_CONTENT, GUID },
                    new int[] {R.id.email, R.id.mobile, R.id.guid });
            */

            CA = new CustomAdapter( getActivity(), R.layout.list_item, postList);
            newsList.setAdapter(CA);
        }

        public class CustomAdapter extends ArrayAdapter<HashMap<String, String>>{


            public CustomAdapter(Context context, int resource, ArrayList<HashMap<String, String>> objects) {
                //something is wrong with super
                super(context, resource, objects);

            }
            public View getView(int position, View convertView, ViewGroup Parent){
                if(convertView == null){
                    LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                    convertView = inflater.inflate(R.layout.list_item,null);

                }

                HashMap<String, String> objects = new HashMap<String, String>();

                TextView thisview = (TextView) convertView.findViewById(R.id.email);
                thisview.setText(objects.get(position).get(POST_TITLE));

                return convertView;
            }
        }//

    }
}

Answer 1

更改此行

CA = new CustomAdapter(this, R.layout.list_item, postList);

到

CA = new CustomAdapter(getActivity(), R.layout.list_item, postList);

注意： 当您使用 Fragment 时，您应该使用 getActivity() 作为 Context。

另外请记住，您使用的是 HashMap<String,String>，因此您的 ArrayAdapter 将是 ArrayAdapter<HashMap<String, String>> 而不是 ArrayAdapter<String>。

Answer 2

您正在扩展 ArrayAdapter<String> 并将 ArrayList 作为构造函数参数传递。它们必须是同一类型。

此外，您需要传递 Context 而不是您的异步任务 GetNews。

您还可以查看 BaseAdapter，其中不需要将任何数组作为构造函数参数传递。

Answer 3

要扩展 Piyush 的答案，您还需要修改 CustomAdapter 构造函数

来自这里：

public CustomAdapter(GetNews context, ... ) { }

至此

public CustomAdapter(Context context, ... ) { }

这是因为 getActivity() 将 return 一个 Activity，它是 Context class 的实例 - 不是 [=16 的实例=]

Answer 4

    private ArrayList<HashMap<String, String>> mList;
    public void setmList(ArrayList<HashMap<String, String>> mList) {
        this.mList = mList;
    }

    public CustomAdapter(Context context, int resource) {
        //something is wrong with super
        super(context, resource);
    }

并用设置列表初始化它

CA = new CustomAdapter(getActivity, R.layout.list_item);
CA.setmList(yourlist);

不知道为什么带有三个参数的 super 在这种情况下不起作用，但它肯定会解决您的问题

使用自定义数组适配器

Using custom array adapter

android

android-arrayadapter