java - 从数组填充 ListView

Question

我想使用循环填充我的 ListView ，我最近尝试通过多次调用 SQL 中的数据来以非常低效的方式填充它。当我意识到效率有多低时，我开始使用数组从服务器一次性提取数据。我无法更改代码以使其正常工作。

我需要做的是找到一种循环访问下面的 JSONArrays 数组的方法(这对我来说不是困难的部分)，但要做到这一点，我需要让我的 GetSocietyDataASyncTask 返回上面的数组并找到一种方法将其传递给 SocietySearch.java 中的 OnCreate/done 方法(我的代码中的许多 Society 对象可以被忽略，并以某种方式替换为 List Society)

现在我相信我已经包含了所有相关代码，但如果您需要查看其他内容，请随时询问我。

Java 从我的数据库接收的数据如下所示:

[{"society_id":1,"name":"TestName1","email":"Test@email1","description":"TestDes1"},
{"society_id":2,"name":"TestName2","email":"Test@email2","description":"TestDes2"}]

SocietySearch 类:

public class SocietySearch extends AppCompatActivity {

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


    Society society = new Society(-1, null, null, null);
    ServerRequests serverRequest1 = new ServerRequests(SocietySearch.this);
    serverRequest1.GetSocietyDataAsyncTask(society, new GetSocietyCallback() {
        @Override
        public void done(final Society returnedSociety) {
            ListView lv = (ListView) findViewById(R.id.ListView);
            List<ListViewItem> items = new ArrayList<>();
            items.add(new ListViewItem() {{
                ThumbnailResource = R.drawable.test;
                Title = returnedSociety.socName;
                Subtitle = returnedSociety.socDes;
            }});
            CustomListViewAdapter adapter = new CustomListViewAdapter(SocietySearch.this, items);
            lv.setAdapter(adapter);
        }
    });
}


class ListViewItem {
    public int ThumbnailResource;
    public String Title;
    public String Subtitle;
}

ServerRequests 类的相关部分:

public class getSocietyDataAsyncTask extends AsyncTask<Void, Void, Society> {
        Society society;
        GetSocietyCallback societyCallback;

        public getSocietyDataAsyncTask(Society society, GetSocietyCallback societyCallback) {
            this.society = society;
            this.societyCallback = societyCallback;
        }

        @Override
        protected Society doInBackground(Void... params) {
            BufferedReader reader = null;
            Society returnedSociety = null;
            List<Society> societies = new ArrayList<>();
            try {
                URL url = new URL(SERVER_ADDRESS + "/getsocietydata.php");

                HttpURLConnection con = (HttpURLConnection) url.openConnection();

                con.setConnectTimeout(CONNECTION_TIMEOUT);
                con.setReadTimeout(CONNECTION_TIMEOUT);

                con.setRequestMethod("POST");

                con.setDoOutput(true);

                StringBuilder sb = new StringBuilder();
                reader = new BufferedReader(new InputStreamReader(con.getInputStream()));

                String line;
                while ((line = reader.readLine()) != null) { //Read until there is something available
                    sb.append(line + "\n");     //Read and save line by line
                }
                line = sb.toString();           //Saving complete data received in string

                //Check values received in Logcat
                Log.i("custom_check", "The values received in the store part are as follows:");
                Log.i("custom_check", line);


                JSONArray ja = new JSONArray(line);
                if (ja != null && ja.length() == 0) {
                    returnedSociety = null;
                } else {
                    for (int i = 0; i <ja.length(); i++) {
                        JSONObject json = ja.optJSONObject(i);
                        //Storing each Json in a variable
                        int society_id = json.getInt("society_id");
                        String socName = json.getString("name");
                        String socEmail = json.getString("email");
                        String socDes = json.getString("description");
                        returnedSociety = new Society(society_id, socName, socEmail, socDes);
                        societies.add(returnedSociety);
                    }
                    return returnedSociety;
                }


            } catch (Exception e) {
                e.printStackTrace();
                Log.d("Sample", "Error has occurred!\n" + e.toString());

            }


            finally {

                if (reader != null) {
                    try {
                        reader.close();     //Closing the
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }

            }
            return returnedSociety;
        }

        @Override
        protected void onPostExecute(Society returnedSociety) {
            super.onPostExecute(returnedSociety);
            progressDialog.dismiss();
            societyCallback.done(returnedSociety);
        }
    }

CustomListViewAdapter.java:

public class CustomListViewAdapter extends BaseAdapter {

    LayoutInflater inflater;
    List<SocietySearch.ListViewItem> items;

    public CustomListViewAdapter(Activity context, List<SocietySearch.ListViewItem> items) {
        super();

        this.items = items;
        this.inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public int getCount() {
        //Auto-generated method stub
        return items.size(); // TODO Maybe this can be my sql count?
    }

    @Override
    public Object getItem(int position) {
        //Auto-generated method stub
        return null;
    }

    @Override
    public long getItemId(int position) {
        //Auto-generated method stub
        return 0;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        //Auto-generated method stub

        ListViewItem item = items.get(position);

        View vi = convertView;

        if (convertView == null)
            vi = inflater.inflate(R.layout.item_row, null);

        ImageView test = (ImageView) vi.findViewById(R.id.imgThumbnail);
        TextView txtTitle = (TextView) vi.findViewById(R.id.txtTitle);
        TextView txtSubTitle = (TextView) vi.findViewById(R.id.txtSubTitle);

        test.setImageResource(item.ThumbnailResource);
        txtTitle.setText(item.Title);
        txtSubTitle.setText(item.Subtitle);


        return vi;
    }
}

ListView 放置文件 (item_row.xml):

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativeLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="5dip">

    <ImageView
        android:id="@+id/imgThumbnail"
        android:layout_width="78dip"
        android:layout_height="78dip"
        android:layout_alignParentLeft="true"
        android:layout_centerInParent="true"
        android:layout_marginLeft="-3dip"
        android:scaleType="centerInside"></ImageView>

    <TextView
        android:id="@+id/txtTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="6dip"
        android:layout_marginTop="6dip"
        android:layout_toRightOf="@+id/imgThumbnail"
        android:text="TextView"
        android:textAppearance="?android:attr/textAppearanceLarge"></TextView>

    <TextView
        android:id="@+id/txtSubTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/txtTitle"
        android:layout_marginLeft="6dip"
        android:layout_marginTop="3dip"
        android:layout_toRightOf="@+id/imgThumbnail"
        android:text="TextView"></TextView>

</RelativeLayout>

Answer 1

查看ArrayAdapter，特别是#notifyDataSetChanged。 (notifyDataSetChanged example)。您可以像您一样在 #onCreate 中设置 ListView，并存储对底层 Adapter 的引用。最初，Adapter 将为空，但当数据传入时，只需将其添加到 Adapter 并按照示例中的指导调用 #notifyDataSetChanged 即可。