Develop Reference

App get crashed when trying to display Data through listview

I'm trying to get data using retrofit2 and display those data using a list passing through as a parameter of Custom adapter. When I store data in a List in onResponse() method, in onResponse() method list have some value. But in oncreate() method its give me null. Though, I declared List as global. When I run the app sometimes its display nothing and sometimes app get crash. I know it's sounds like crazy. But it's happen. so, I want to know, what's wrong with my Code? how can I display data in listview?
Forgive me if something wrong with my question pattern yet this my maiden question at this site.
MainActivity`
public class LaboratoryValues extends AppCompatActivity {
public List<Data> productList = null;
List<Data>arrayList = null;
int size;
String st;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_laboratory_values);
//productList = new ArrayList<Data>();
getInvestigation();
for(int i =0; i < size; i++){
st = arrayList.get(i).getName();
}
System.out.println("Name : "+st);//here print Name : null
ListView lview = (ListView) findViewById(R.id.listview);
ListviewAdapter adapter = new ListviewAdapter(this, arrayList);
lview.setAdapter(adapter);
}
private void getInvestigation() {
/* final ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
progressDialog.setCancelable(false); // set cancelable to false
progressDialog.setMessage("Please Wait"); // set body
progressDialog.show(); // show progress dialog*/
ApiInterface apiService =
Api.getClient(ApiInterface.BASE_URL).create(ApiInterface.class);
Call<Investigation> investigationCall = apiService.getInvestigation();
investigationCall.enqueue(new Callback<Investigation>() {
#Override
public void onResponse(Call<Investigation> call, Response<Investigation> response) {
arrayList = response.body().getData();
//productList.addAll(arrayList);
size = response.body().getData().size();
for (int i = 0; i < size; i++) {
System.out.println("Name : " + arrayList.get(i).getName());//here printing Name is ok
}
}
#Override
public void onFailure(Call<Investigation> call, Throwable t) {
Toast.makeText(getApplicationContext(),"data list is empty",Toast.LENGTH_LONG).show();
}
});
}
}
Custom Adapter (listviewAdapter)
public class ListviewAdapter extends BaseAdapter {
public List<Data> productList;
Activity activity;
//Context mContext;
public ListviewAdapter(Activity activity, List<Data> productList) {
super();
this.activity = activity;
this.productList = productList;
}
#Override
public int getCount() {
return productList.size();
}
#Override
public Object getItem(int position) {
return productList.get(position);
}
#Override
public long getItemId(int position) {
return position;
}
private class ViewHolder {
TextView name;
TextView normal_finding;
TextView increased;
TextView decreased;
TextView others;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
LayoutInflater inflater = activity.getLayoutInflater();
if (convertView == null) {
convertView = inflater.inflate(R.layout.listview_row, null);
holder = new ViewHolder();
holder.name = convertView.findViewById(R.id.name);
holder.normal_finding =convertView.findViewById(R.id.normal_finding);
holder.increased = convertView.findViewById(R.id.increased);
holder.decreased = convertView.findViewById(R.id.decreased);
holder.others =convertView.findViewById(R.id.others);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
Data item = productList.get(position) ;
holder.name.setText(item.getName());
System.out.println("holderName : "+item.getName() );
holder.normal_finding.setText(item.getNormal_finding());
System.out.println("holderName : "+item.getNormal_finding() );
holder.increased.setText(item.getIncreased());
holder.decreased.setText(item.getDecreased());
holder.others.setText(item.getOthers());
return convertView;
}
}

It's perfectly normal that it dosent work.
putting your method getInvistigation() before the loop does not mean that the response of your request was done
Calling a webservice creates another thread that waits for the server to send the response, sometimes the response takes time depends from the server and the latency of your internet connection.
you simply need to place the treatment (the loop and adapter) inside getInvistagion after getting the data.

update listview using spinner data in android

Am trying to update my listview on every selection of the spinner. but its not working. Instead of getting new data, listview is repeating the same values.
I am unable to find out what is my mistake.
here is my avtivity code:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
setContentView(R.layout.activity_performance_details);
PerfList = new ArrayList<PerformanceListItem>();
months = (Spinner) findViewById(R.id.load_month);
listview_performance = (ListView) findViewById(R.id.performance_details_list);
sadapter = new PerformanceAdapter(PerformanceDetails.this, PerfList);
months.setOnItemSelectedListener(this);
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
Spinner a=(Spinner)parent;
if(a.getId() == R.id.load_month) {
monthid =1+(int)months.getSelectedItemPosition();
Toast.makeText(getApplicationContext(),""+monthid,Toast.LENGTH_LONG).show();
new setAsyncTask_performance().execute();
}
}
after selecting spinner data it is sent to server and from server its relevant data is fetched and sent back to the list view. now when i first time select the spinner it show the data accordingly. But on second selection it will include the previous data without updating the listview
Adapter Code:
public class PerformanceAdapter extends BaseAdapter {
private Activity activity;
private LayoutInflater inflater;
private Context context;
private List<PerformanceListItem> performanceList;
public PerformanceAdapter(Activity activity, List<PerformanceListItem> PList) {
this.activity = activity;
this.performanceList = PList;
}
#Override
public int getCount() {
return performanceList.size();
}
#Override
public Object getItem(int position) {
return performanceList.get(position);
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (inflater == null) {
inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
if (convertView == null) {
convertView = inflater.inflate(R.layout.performance_itemlist, null);
}
Animation slideUp = AnimationUtils.loadAnimation(activity, R.anim.slide_up);
TextView staffName = (TextView) convertView.findViewById(R.id.perf_staffName);
TextView staffDesignation = (TextView) convertView.findViewById(R.id.perf_Design);
TextView staffPerformance = (TextView) convertView.findViewById(R.id.perf_performance);
PerformanceListItem plist = performanceList.get(position);
staffName.setText(plist.getpStaffName());
staffDesignation.setText(plist.getpDesignation());
staffPerformance.setText(plist.getpPerformance());
slideUp.setDuration(500);
convertView.startAnimation(slideUp);
slideUp = null;
return convertView;
}
}
and this is my performance list to get and set data
PerformanceListItems code:
public class PerformanceListItem {
private String pSid;
private String pStaffName;
private String pDesignation;
private String pPerformance;
private String pList;
public PerformanceListItem(){
}
public PerformanceListItem(String pList){
this.pList = pList;
}
public String getpSid(){
return pSid;
}
public void setpSid(String pSid){
this.pSid = pSid;
}
public String getpStaffName(){
return pStaffName;
}
public void setpStaffName(String pStaffName){
this.pStaffName = pStaffName;
}
public String getpDesignation(){
return pDesignation;
}
public void setpDesignation(String pDesignation){
this.pDesignation = pDesignation;
}
public String getpPerformance(){
return pPerformance;
}
public void setpPerformance(String pPerformance){
this.pPerformance = pPerformance;
}
}
After debugging the entire code i found that my JSONObject is not updating with new value
any help would be appreciable.

Update the data of your adapter when you execute this
new setAsyncTask_performance().execute();
If you want to show only the new data just remove all your listview items then update the data and set the adapter again.

dont set adapter in oncreate. Set your adapter in Asynctask Post execute. and set your array inside doinbackground along with getting data task.

Add load more button to listview in android

I am working on android projects. In my application I am getting the data from php webservice. I added my data to different arraylists and set them to listadapter. But my problem is it is taking very long time to display the data in list. Hence now I want to display first 10 items and want to keep a loadmore button at the bottom of the screen. Once the load more button is clicked the next 10 items need to display. Please can anybody help me in this regard. I would really appreciate for this help.
Thank you in advance.
Code:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main1);
Longop op = new Longop();
op.execute("");
}
public void loadSomeDummyData() {
try {
response = CustomHttpClient
.executeHttpPost(
"http://website.com/folder/testfile.php",
postParameters);
for (int i = 1; i < arr1.length - 1; i++) {
id.add(new String(arr[0]));
name.add(new String(arr[1]));
dateofbirth.add(new String(arr[2]));
status.add(new String(arr[3]));
}
} catch (Exception e) {
e.printStackTrace();
}
}
private class Longop extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... params) {
loadSomeDummyData();
return "Executed";
}
#Override
protected void onPostExecute(String result) {
mdialog.dismiss();
myListView.setAdapter(new MyArrayAdapter(Sample.this,
R.layout.list, id, name, dateofbirth,
status));
}
#Override
protected void onPreExecute() {
mdialog = ProgressDialog.show(Sample.this, "Please wait...",
"Retrieving data ...", true);
}
#Override
protected void onProgressUpdate(Void... values) {
}
}
private class MyArrayAdapter extends ArrayAdapter<String> {
// this list hold the data that we will see in listview
private List<String> myData = new ArrayList<String>();
private List<String> myData1 = new ArrayList<String>();
private List<String> myData2 = new ArrayList<String>();
private List<String> myData3 = new ArrayList<String>();
public MyArrayAdapter(Context context, int textViewResourceId,
List<String> objects, List<String> objects1,
List<String> objects2, List<String> objects3) {
super(context, textViewResourceId, objects);
// TODO Auto-generated constructor stub
context = getContext();
myData = objects;
myData1 = objects1;
myData2 = objects2;
myData3 = objects3;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
View v = convertView;
if (v == null) {
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = inflater.inflate(R.layout.list, null);
// Log.d(EKSI, "Getting the inflater from the system context");
}
String sid = myData.get(position);
String sname = myData1.get(position);
String dob = myData2.get(position);
String sstatus = myData3.get(position);
TextView entryTextView = (TextView) v.findViewById(R.id.id1);
entryTextView.setText(sid);
TextView entryTextView1 = (TextView) v
.findViewById(R.id.id2);
entryTextView1.setText(sname);
TextView entryTextView2 = (TextView) v
.findViewById(R.id.id3);
entryTextView2.setText(dob);
TextView entryTextView3 = (TextView) v
.findViewById(R.id.id4);
entryTextView3.setText(sstatus);
return v;
}
}

You could also use this lib
https://github.com/chrisbanes/Android-PullToRefresh.

I implement this function not base ListView that can do this;
Custom loading view,override onDraw menthod
Add loading view at the end of LinearLayout view. When loading view is show, it should call some methods to get data from server by HTTP.

you just need to inflate an xml in
lstView.addFooterView(R.layout.footer);
and handle onclick of the button residing in footer

Twitter4j pagination with pull-to-refresh-list (Chris Banes)

I try to implement homeline pagination via Twitter4j to pull-to-refresh list from Chris Banes. However, I have problems of that how to realize it. I have some notes how it should work but it isn't so, my pull refresh list doesn`t refresh. Have any ideas how to upload next 40 tweet to list on refresh?
Activity
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tweetlist);
initializeVars();
paging = new Paging(1, 40);
try {
ListView actualListView = pullToRefreshView.getRefreshableView();
tweets = twitter.getHomeTimeline(paging);
tweetAdapter = new TweetListAdapter(this, R.layout.customtweetlist, tweets);
actualListView.setAdapter(tweetAdapter);
} catch (TwitterException e) {
e.printStackTrace();
}
}
public void onRefresh() {
new GetDataTask().execute();
}
private class GetDataTask extends AsyncTask<Void, Void, List<Status>> {
protected List<twitter4j.Status> doInBackground(Void... params) {
paging.setPage(2);
try {
tweets = twitter.getHomeTimeline(paging);
} catch (TwitterException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return tweets;
}
protected void onPostExecute(List<twitter4j.Status> result) {
tweetAdapter.notifyDataSetChanged();
// Call onRefreshComplete when the list has been refreshed.
pullToRefreshView.onRefreshComplete();
super.onPostExecute(result);
}
}
My TweetAdapter
public class TweetListAdapter extends ArrayAdapter<Status> {
private final Context context;
private final List<Status> values;
public TweetListAdapter(Context context,int textViewResourceId, List<Status> tweets) {
super(context, textViewResourceId, tweets);
this.context = context;
this.values = tweets;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate(R.layout.customtweetlist, parent, false);
TextView textView = (TextView) rowView.findViewById(R.id.tvText);
ImageView imageView = (ImageView) rowView.findViewById(R.id.ivImage);
Status tweet = values.get(position);
textView.setText(tweet.getText());
// imageView.setImageBitmap(getBitmap(tweet.getProfileImageUrl()));
rowView.invalidate();
return rowView;
}
public static Bitmap getBitmap(String bitmapUrl) {
try {
URL url = new URL(bitmapUrl);
return BitmapFactory.decodeStream(url.openConnection() .getInputStream());
}
catch(Exception ex) {return null;}
}
}

So what's happening is that you're updating the tweets variable, which will update the Adapter's this.values value, HOWEVER that list is not what the adapter is using to render the list (if you want to know why, just dig into the ArrayAdapter code). The easiest way to fix the problem (and prevent further confusion) is to extend from BaseAdapter. It's a bit more work for you but you will have full control of what the adapter does (and will understand what's going on better).
To clean the code some more, you should also add a metod to your adapter that updates the value of this.values, you shouldn't depend on it referring to the same list as tweets.

OnItemClickListener getting data from model

I am fairly new to Android development and I am trying to build a ListView which get data from web service using gson. I have a model class, a list class, an adapter class and the activity class.
The list works fine and it got the data, and now I want to integrate the OnItemClickListener to it and pass the data to the 2nd activity. And I'd like to get the item id (DistrictId) and pass it to the next Activity(listView) instead of the row id. It would be great if someone could show me the light... as the documentation is not as clear to understand and because I am new.
Below is my code.
The model class
package com.sample.myapp;
public class DistrictModel {
private String id;
private String districtName;
public String getDistrictId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getDistrictName(){
return districtName;
}
public void setDistrictEN(String districtName){
this.districtName = districtName;
}
}
The List class
public class DistrictList {
private List<DistrictModel> districts;
public List<DistrictModel> getDistricts(){
return districts;
}
public void setDistrictList(List<DistrictModel> districts){
this.districts = districts;
}
}
The Adapter class
public class DistrictAdapter extends ArrayAdapter<DistrictModel>{
int resource;
String response;
Context context;
private LayoutInflater dInflater;
public DistrictAdapter(Context context, int resource, List<DistrictModel> objects) {
super(context, resource, objects);
this.resource = resource;
dInflater = LayoutInflater.from(context);
}
static class ViewHolder {
TextView title;
}
public View getView(int position, View convertView, ViewGroup parent)
{
ViewHolder holder;
//Get the current location object
DistrictModel lm = (DistrictModel) getItem(position);
//Inflate the view
if(convertView==null)
{
convertView = dInflater.inflate(R.layout.item_district, null);
holder = new ViewHolder();
holder.title = (TextView) convertView
.findViewById(R.id.district_name);
convertView.setTag(holder);
}
else
{
holder = (ViewHolder) convertView.getTag();
}
holder.title.setText(lm.getDistrictName());
return convertView;
}
}
The activity class
public class DistrictListActivity extends Activity{
LocationManager lm;
ArrayList<DistrictModel> districtArray = null;
DistrictAdapter districtAdapter;
DistrictList list;
ListView lv;
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.districtlist_layout);
lv = (ListView) findViewById(R.id.list_district);
districtArray = new ArrayList<DistrictModel>();
districtAdapter = new DistrictAdapter(DistrictListActivity.this, R.layout.item_district, districtArray);
lv.setTextFilterEnabled(true);
lv.setAdapter(districtAdapter);
try {
new DistrictSync().execute("http://aws.something.com/service");
} catch(Exception e) {}
lv.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View convertView, int position, long id) {
AlertDialog.Builder adb=new AlertDialog.Builder(DistrictListActivity.this);
adb.setTitle("LVSelectedItemExample");
adb.setMessage("Selected Item is = "+(lv.getItemIdAtPosition(position)));
adb.setPositiveButton("Ok", null);
adb.show();
}
}); **//i'd like to get the DistrictId from the json data.**
}
private class DistrictSync extends AsyncTask<String, Integer, DistrictList> {
protected DistrictList doInBackground(String... urls) {
DistrictList list = null;
int count = urls.length;
for (int i = 0; i < count; i++) {
try {
// ntar diganti service
RestClient client = new RestClient(urls[i]);
try {
client.Execute(RequestMethod.GET);
} catch (Exception e) {
e.printStackTrace();
}
String json = client.getResponse();
list = new Gson().fromJson(json, DistrictList.class);
//
} catch(Exception e) {}
}
return list;
}
protected void onProgressUpdate(Integer... progress) {
}
protected void onPostExecute(DistrictList dislist) {
for(DistrictModel lm : dislist.getDistricts())
{
districtArray.add(lm);
}
districtAdapter.notifyDataSetChanged();
}
}
}
For testing purpose, now I click the row it will show me the row id, so I know the onclick listener works, but I just want it to grab me the DistrictId so I can use it to pass to the next activity.
Thank you so much.

(out of my head) Try this:
((DistrictModel)lv.getAdapter().getItem(position)).getDistrictId();

Generally when you want to pass data from one Activity to another, you just place it into the Intent that you use to create the new Activity.
For example (and here are some additional examples):
Intent i = new Intent(context, MyNewActivity.class);
i.putExtra("MyCurrentHealth", mCurrentHealth);
context.startActivity(i);
To retrieve the data do this:
Bundle extras = getIntent().getExtras();
if (extra != null) {
... // Do stuff with extras
}