In this post, I will describe first how to use Volley to populate dynamically a ListView, and then compare it against AsycnTask.
In this post, we will invoke a remote service to get contact information in JSON format, and we populate the items inside a ListView.This simple example is very useful to understand Volley library and how we can integrate it. We want to obtain something like the image shown below:
In this post, we will invoke a remote service to get contact information in JSON format, and we populate the items inside a ListView.This simple example is very useful to understand Volley library and how we can integrate it. We want to obtain something like the image shown below:
We have already covered this topic in a previous post, and this is the chance to underline the different approaches (Volley and AsyncTask).
Inside Volley, there is a class called JsonArrayRequest, that can be used to retrieve JSON Array as response. As always, we have two different listener; we have to implement:
one to get the response
another one to handle errors
The source code is shown below:
JsonArrayRequest jReq = new JsonArrayRequest(url,
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
List<Contact> result = new ArrayList<Contact>();
for (int i = 0; i < response.length(); i++) {
try {
result.add(convertContact(response
.getJSONObject(i)));
} catch (JSONException e) {
}
}
adpt.setItemList(result);
adpt.notifyDataSetChanged();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// Handle error
}
});
In onResponse method, we have a JSONArray object that holds the response. In this method, we traverse the json array and convert json data to Contact object, using convert method:
private final Contact convertContact(JSONObject obj) throws JSONException {
String name = obj.getString("name");
String surname = obj.getString("surname");
String email = obj.getString("email");
String phoneNum = obj.getString("phoneNum");
return new Contact(name, surname, email, phoneNum);
}
At the end, we set the new contact list in our adapter and call:
Volley JSONArrayRequest
Inside Volley, there is a class called JsonArrayRequest, that can be used to retrieve JSON Array as response. As always, we have two different listener; we have to implement:
one to get the response
another one to handle errors
The source code is shown below:
JsonArrayRequest jReq = new JsonArrayRequest(url,
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
List<Contact> result = new ArrayList<Contact>();
for (int i = 0; i < response.length(); i++) {
try {
result.add(convertContact(response
.getJSONObject(i)));
} catch (JSONException e) {
}
}
adpt.setItemList(result);
adpt.notifyDataSetChanged();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// Handle error
}
});
In onResponse method, we have a JSONArray object that holds the response. In this method, we traverse the json array and convert json data to Contact object, using convert method:
private final Contact convertContact(JSONObject obj) throws JSONException {
String name = obj.getString("name");
String surname = obj.getString("surname");
String email = obj.getString("email");
String phoneNum = obj.getString("phoneNum");
return new Contact(name, surname, email, phoneNum);
}
At the end, we set the new contact list in our adapter and call:
adpt.notifyDataSetChanged();
- See more at: http://www.survivingwithandroid.com/2013/11/android-volley-dynamic-listview.html#sthash.zkGmBQmR.dpuf
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Volley Vs AsyncTask
- See more at: http://www.survivingwithandroid.com/2013/11/android-volley-dynamic-listview.html#sthash.zkGmBQmR.dpuf
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