Android，从MySQL读取数据后，列表视图在屏幕显示关闭后填充

Question

我正在尝试从MySQL数据库中获取数据并将其显示在列表视图中。已成功检索数据，但在屏幕显示关闭之前不会填充列表视图。在填充列表视图之前，也不会显示进度对话框。有什么建议吗？

public class BestLinksActivity extends AppCompatActivity {
public ListView myListView;
public MyListViewAdapter mAdapter;
public List<HotelInfo> dataSource;
private String cityName;
ProgressDialog mProgressDialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_best_links);
    dataSource = new ArrayList<>();
    mProgressDialog = new ProgressDialog(BestLinksActivity.this);
    mProgressDialog.setMessage("Loading data...");
    Bundle extras = getIntent().getExtras();
    if (extras != null) {
        cityName = extras.getString("City");
    }
    DataBaseReader dbReader = new DataBaseReader();
    if (!(cityName.equals(null))) {
        dbReader.execute(cityName);
    } else {
        Toast.makeText(getApplicationContext(), "City name not specified", Toast.LENGTH_SHORT).show();
    }
    //Create adapter
    mAdapter = new MyListViewAdapter(getApplicationContext(), dataSource);
    //Configure the listview
    myListView = (ListView) findViewById(R.id.main_list_view);
    myListView.setAdapter(mAdapter);
    myListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {
            // ListView Clicked item value
            HotelInfo currentItem = dataSource.get(position);
            //Open url of the currentItem in web browser
            startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(currentItem.getLinkUrl())));
        }
    });
}
public String getTitle(String url) {
    String[] subStrings = url.split("/");
    String urlTitle = "";
    for (int i = 0; i < subStrings.length; i++) {
        if (subStrings[i].equals("t"))
            urlTitle = (subStrings[i + 1]);
    }
    urlTitle = urlTitle.replace("-", " ");
    urlTitle=((urlTitle.charAt(0)+"").toUpperCase()).concat(urlTitle.substring(1));
    return urlTitle;
}
public class DataBaseReader extends AsyncTask<String, Void, String> {
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        mProgressDialog.show();
    }

    @Override
    protected String doInBackground(String... params) {
        OkHttpClient okHttpClient = new OkHttpClient.Builder()
                .connectTimeout(15, TimeUnit.SECONDS)
                .writeTimeout(15, TimeUnit.SECONDS)
                .readTimeout(15, TimeUnit.SECONDS)
                .build();
        Log.d("CheckParam", params[0]);
        RequestBody postBody = new FormBody.Builder()
                .add("cityName", params[0])
                .build();
        Request myRequest = new Request.Builder()
                .url("http://172.18.0.32/extractData.php")
                .post(postBody)
                .build();
        String serverResponse = null;
        try {
            Response response = okHttpClient.newCall(myRequest).execute();
            serverResponse = response.body().string();
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            JSONObject myJsonObj = new JSONObject(serverResponse);
            JSONArray myJsonArray = myJsonObj.getJSONArray("server_response");
            for (int index = 0; index < myJsonArray.length(); index++) {
                JSONObject linkObject = myJsonArray.getJSONObject(index); //Otherwise, you will get last element
                HotelInfo myHotelInfo = new HotelInfo();
                myHotelInfo.setLinkUrl(linkObject.getString("Link"));
                myHotelInfo.setLinkTitle(getTitle(myHotelInfo.getLinkUrl()));
                dataSource.add(myHotelInfo);
            }

        }
        catch (JSONException e) {
            e.printStackTrace();
        }
        Log.d("MyKeyser", serverResponse);
        return serverResponse;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        Log.d("MyKey", s);
        if (mProgressDialog!=null && mProgressDialog.isShowing()) {
            mProgressDialog.dismiss();
        }
    }
}
}

Answer 1

将以下行添加到您的onPostExecute：

mAdapter.notifyDataSetChanged();

您需要通知适配器数据已更改。请参阅文档。

关于 ProgressBar ，您需要将其放在activity_best_links布局中的某个布局下。最好的方法是不以编程方式创建它，而是将其添加到您的 xml 布局文件中，请参阅此处的示例，然后通过 mProgress.setVisibility();