我有sql DB，我试图在listView中显示查询的值。我为listView创建了一个自定义适配器。问题是 我无法在listView上看到任何数据。
主要代码
public class _songs_playlist extends AppCompatActivity {
ArrayList<songsarray> listofsoongs = new ArrayList<songsarray>();
private static int SPLASH_TIME_OUT=2000;
AlertDialog alertDialog;
private boolean loggedIn = false;
String type;
String result;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__songs_playlist);
new JSONParse().execute();
MyCustomAdapterSongs itemsAdapter = new MyCustomAdapterSongs(this, listofsoongs);
ListView listView = (ListView) findViewById(R.id.listView1);
listView.setAdapter(itemsAdapter);
itemsAdapter.notifyDataSetChanged();
}
private class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
alertDialog=new AlertDialog.Builder(_songs_playlist.this).create();
alertDialog.setTitle("Upadting Data");
pDialog = new ProgressDialog(_songs_playlist.this);
pDialog.setMessage("Getting Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
HTTPHandler sh = new HTTPHandler();
String login_URL = "http://2f179dfb.ngrok.io/getsong.php";
try {
//Fetching the boolean value form sharedpreferences
URL url = new URL(login_URL);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);
httpURLConnection.setDoInput(true);
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"));
result = "";
String line = "";
while ((line = bufferedReader.readLine()) != null) {
result += line;
}
bufferedReader.close();
inputStream.close();
httpURLConnection.disconnect();
Log.e("RESULT", result);
JSONObject jsonObject = new JSONObject(result);
JSONArray result1 = jsonObject.getJSONArray("result");
for (int i = 0; i < result1.length(); i++) {
JSONObject c = result1.getJSONObject(i);
String id = c.getString("songID");
String names = c.getString("songName");
String ss = c.getString("singerName");
listofsoongs.add(new songsarray(ss,id,names));
}
return jsonObject;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
if(true)
{
}
else
{
}
}
}
}
自定义数组适配器的代码
public class MyCustomAdapterSongs extends ArrayAdapter<songsarray> {
Context context;
ArrayList<songsarray> items;
public MyCustomAdapterSongs(Activity context, ArrayList<songsarray> songsarrays) {
super(context, 0, songsarrays);
this.context=context;
this.items=songsarrays;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View listItemView = convertView;
if (listItemView == null) {
listItemView = LayoutInflater.from(getContext()).inflate(
R.layout.itemlist, parent, false);
}
TextView nameTextView = (TextView) listItemView.findViewById(R.id.textView1);
nameTextView.setText(currentAndroidFlavor.getSingername());
Log.e("hhhh", nameTextView.getText().toString());
TextView numberTextView = (TextView) listItemView.findViewById(R.id.textView2);
numberTextView.setText(currentAndroidFlavor.getSongname());
Log.e("jjjj", numberTextView.getText().toString());
CheckBox ch=(CheckBox)listItemView.findViewById(R.id.checkBox1);
ch.setSelected(currentAndroidFlavor.isSelected());
return listItemView;
}
@Override
public int getCount() {
if(items == null)
return 0;
return items.size();
}
@Override
public songsarray getItem(int i) {
return items.get(i);
}
}
答案 0 :(得分：1)
在itemsAdapter.notifyDataSetChanged()内致电onPostExecute。
在AsyncTask完成之前，您的列表是空的。
您必须使适配器成为Activity类的成员变量
答案 1 :(得分：0)
在代码中，我可以看到您正在更新HttpOp.setDefaultHttpClient(HttpClientBuilder.create().build());
中的列表，但您没有通知适配器进行更改。
在onPostExecute方法中，您需要调用doInBackground并确保您没有在itemsAdapter.notifyDataSetChanged()内调用它，因为在后台线程中您无法进行与UI相关的工作。
答案 2 :(得分：0)
检查此代码段中的EDITS
`
public class _songs_playlist extends AppCompatActivity {
ArrayList<songsarray> listofsoongs = new ArrayList<songsarray>();
private static int SPLASH_TIME_OUT=2000;
AlertDialog alertDialog;
private boolean loggedIn = false;
String type;
String result;
//EDIT 1: Make these member variables
MyCustomAdapterSongs itemsAdapter;
ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__songs_playlist);
//EDIT 2: get references your views before AsyncTask
listView = (ListView) findViewById(R.id.listView1);
new JSONParse().execute();
}
private class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
alertDialog=new AlertDialog.Builder(_songs_playlist.this).create();
alertDialog.setTitle("Upadting Data");
pDialog = new ProgressDialog(_songs_playlist.this);
pDialog.setMessage("Getting Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
HTTPHandler sh = new HTTPHandler();
String login_URL = "http://2f179dfb.ngrok.io/getsong.php";
try {
//Fetching the boolean value form sharedpreferences
URL url = new URL(login_URL);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);
httpURLConnection.setDoInput(true);
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"));
result = "";
String line = "";
while ((line = bufferedReader.readLine()) != null) {
result += line;
}
bufferedReader.close();
inputStream.close();
httpURLConnection.disconnect();
Log.e("RESULT", result);
JSONObject jsonObject = new JSONObject(result);
JSONArray result1 = jsonObject.getJSONArray("result");
for (int i = 0; i < result1.length(); i++) {
JSONObject c = result1.getJSONObject(i);
String id = c.getString("songID");
String names = c.getString("songName");
String ss = c.getString("singerName");
listofsoongs.add(new songsarray(ss,id,names));
}
return jsonObject;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
//EDIT 3: set your adapter here as this method will be called on the UI Thread
itemsAdapter = new MyCustomAdapterSongs(this, listofsoongs);
listView.setAdapter(itemsAdapter);
}
}
}
}
`