Develop Reference

Getting ArrayList size zero on accessing from another class

I am new to Android. I am accessing an ArrayList from another class but i am getting zero size of ArrayList in accessing class. In main class, it shows a positive value of size of array list. I dont know why i am getting zero size in accessing class. Check my code for mistakes.
Tab3Tracks Class
public class Tab3Tracks extends ListFragment {
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
}
private ArrayList<String> trackslist = new ArrayList<>();
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.tab3tracks, container, false);
final String trackid = MediaStore.Audio.Media._ID;
final String trackno = MediaStore.Audio.Media.TRACK;
final String trackname = MediaStore.Audio.Media.TITLE;
final String path = MediaStore.Audio.Media.DATA;
Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
ContentResolver cr = getContext().getContentResolver();
final String[] projection = {trackid,trackno,trackname,path
};
final Cursor cursor = cr.query(uri,projection,null,null,null);
if (cursor!=null){
if(cursor.moveToFirst()){
do{
int trackIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE);
trackslist.add(cursor.getString(trackIndex));
}while(cursor.moveToNext());
}System.out.println(trackslist.size());
} cursor.close();
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
getActivity(),R.layout.playlist_item,R.id.songTitle,trackslist
);
setListAdapter(adapter);
return v;
}
public ArrayList<String> getList(){
return trackslist;
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
int songIndex = position;
// Starting new intent
Intent in = new Intent(getActivity(), NowPlaying.class);
// Sending songIndex to PlayerActivity
in.putExtra("songIndex", songIndex);
startActivityForResult(in, 100);
}
}
NowPlaying Class
public class NowPlaying extends AppCompatActivity {
public ArrayList<String> songsList = new ArrayList<String>();
public Tab3Tracks tab3tracks;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.player);
// Getting all songs list
tab3tracks = new Tab3Tracks();
songsList= tab3tracks.getList();
System.out.println("songsListSize"+songsList.size());
System.out.println("List" +songsList);
}

Your ArrayList is initialized, but nothing is ever added.
trackslist.add(cursor.getString(trackIndex));
That is nested inside onCreateView, causing it to only be called once. You might want to consider adding onTOuchListener to the activity and add your code there inside the listener so it updates whenever the screen is touched.
Adding inside a thread might work too, but it really depends on your code.

onCreateView of Tab3Tracks will be called by android if fragment will inflate a view, so your array is empty because this code
trackslist.add(cursor.getString(trackIndex));
doesn't call anytime

Android Studio ListView - null pointer exception when trying to extract text from selected item

I'm trying to save text from the selected item of a ListView in OnItemClick.
I've tried so many different methods to no avail, I think I'm missing something really stupidly obvious here...
SnakesListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String choice = SnakesListView.getItemAtPosition(position).toString();
Intent intent = new Intent(SnakeList.this, SnakeProfile.class);
intent.putExtra("SelectedSnakeName", choice);
startActivity(intent);
}
});
The data is being displayed fine, I just can't seem to reference it.
The line causing the exception:
String choice = SnakesListView.getItemAtPosition(position).toString();
Full code for this activity
public class SnakeList extends Activity {
ListView SnakesListView;
Cursor cursor;
Button NewSnakeBtn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_snake_list);
SnakesListView = (ListView) findViewById(R.id.SnakesListView);
NewSnakeBtn = (Button) findViewById(R.id.NewSnake);
SQLiteDatabase db = openOrCreateDatabase("snakeDB", Context.MODE_PRIVATE, null); // ACCESSES DB
cursor = db.rawQuery("SELECT name FROM snakes", null); // SETS cursor TO RESULTS OF QUERY
List<String> SnakeNamesList = new ArrayList<String>();
ArrayAdapter SnakeNamesAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, SnakeNamesList);
SnakeNamesList.clear(); // REMOVES ANY NAMES CURRENTLY IN NAME ARRAY TO AVOID DUPLICATES
SnakesListView.setAdapter(SnakeNamesAdapter);
if (cursor.moveToFirst()) {
cursor.moveToFirst(); // MOVES CURSOR TO FIRST POSITION
do SnakeNamesList.add(cursor.getString(0)); // RETURNS STRING FROM FIRST COLUMN (NAME)
while (cursor.moveToNext());
}
NewSnakeBtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
startActivity(new Intent(SnakeList.this, NewSnake.class));
}
});
SnakesListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String choice = SnakesListView.getItemAtPosition(position).toString();
Intent intent = new Intent(SnakeList.this, SnakeProfile.class);
intent.putExtra("SelectedSnakeName", choice);
startActivity(intent);
}
});
}

No use of referencing the ListView; you can get the value from adapter itself.
Change
String choice = SnakesListView.getItemAtPosition(position).toString();
to
String choice = SnakeNamesAdapter.getItem(position).toString();

declare the string arraylist(SnakeNamesList) as global variable and
change
String choice = SnakesListView.getItemAtPosition(position).toString();
to
String choice = SnakeNamesList.get(position);

Android load data from SQLite Database into next activity

I have a listView which loads data from SQLite database and right now I would want to implement an onclicklistener to the list. When users click on the list, it should bring them to the next activity and load the corresponding data into TextView. My question is how would I pass the data of the list for example it is a list of "Topics" and user click on the topic "My Home". I want to pass the topic "My Home" to the next activity so that I know which corresponding data to be retrieved respectively.
How do I go about it? Do I "putExtras" to the new Intent? or there is another way. Below are part of my codes which display the listview:
ListView listContent = (ListView) findViewById(R.id.contentlist);
mySQLiteAdapter = new SQLiteAdapter(this);
mySQLiteAdapter.openToRead();
Cursor cursor = mySQLiteAdapter.queueAll();
startManagingCursor(cursor);
String[] from = new String[] { SQLiteAdapter.KEY_CONTENT };
int[] to = new int[] { R.id.text };
SimpleCursorAdapter cursorAdapter = new SimpleCursorAdapter(this, R.layout.listrow, cursor, from, to);
listContent.setAdapter(cursorAdapter);
mySQLiteAdapter.close();
//Onclick ListView setlistener
listContent.setTextFilterEnabled(true);
listContent.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Intent summaryIntent = new Intent(DocumentListActivity.this, ViewDocumentActivity.class);
// summaryIntent.putExtra("SummTopic", value);
}
});
EDITED:
This part is on the next activity.
Intent i = getIntent();
extraTopic = i.getStringExtra("SummTopic");
mydb = openOrCreateDatabase(DBNAME, Context.MODE_PRIVATE,null);
Cursor allrows = mydb.rawQuery("SELECT * FROM "+ TABLE + " WHERE topic = \" " + extraTopic + " \" " , null);
Integer cindex = allrows.getColumnIndex("topic");
Integer cindex1 = allrows.getColumnIndex("text1");
Integer cindex2 = allrows.getColumnIndex("text2");
I got an error while retrieving from database:
android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 0
Please help.
Thank you.

public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Intent summaryIntent = new Intent(DocumentListActivity.this, ViewDocumentActivity.class);
Cursor c = (Cursor)parent.getItemAtPosition(position);
summaryIntent.putExtra("SummTopic", c.getString(c.getColumnIndex(SQLiteAdapter.KEY_CONTENT)));
startActivity(summaryIntent);
}
or you can pass id (summaryIntent.putExtra("SummTopicId", id);) of this row and "ask db" in next Activity for Topic with this id
EDIT:
protected void onCreate(Bundle savedInstanceState){
Intent i = getIntent();
String extraTopic = i.getStringExtra("SummTopic");
//or long extraTopic = i.getLongExtra("SummTopic"); if you put id there (which is better)
mydb = openOrCreateDatabase(DBNAME, Context.MODE_PRIVATE,null);
String[] args = new String[] { extraTopic };
//or String[] args = new String[] { Long.toString(extraTopic) }; with id version
Cursor singleRow = mydb.rawQuery("SELECT * FROM "+ TABLE + " WHERE topic=?" , args);
//args is better then escaping special chars in query
//and it should be single row so we've changed var name :)
if(singleRow.moveToFirst()){ //we should do moveToFirst before we can use Cursor
Integer cindex = allrows.getColumnIndex("topic");
Integer cindex1 = allrows.getColumnIndex("text1");
Integer cindex2 = allrows.getColumnIndex("text2");
//setup views and stuff ....
}else{
Toast.makeText(this, "Oops we did not find topic, detail activity was closed", Toast.LENGTH_SHORT).show();
finish();
}
}

After you have used setContentView(...) you need to reference your String and get the text such as...
EditText et = (EditText) findViewById(R.id.my_edit_text);
String theText = et.getText().toString();
To pass it to another Activity you use an Intent. Example...
Intent i = new Intent(this, MyNewActivity.class);
i.putExtra("text_label", theText);
startActivity(i);
In the new Activity (in onCreate()), you get the Intent and retrieve the String...
public class MyNewActivity extends Activity {
String uriString;
#Override
protected void onCreate(...) {
...
Intent i = getIntent();
uriString = i.getStringExtra("text_label");
}
}
EDITED :
to get String From Listview you can apply below code and get ITEM String and Pass it to Next Activity:
listContent.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
String ITEM=listContent.getItemAtPosition(position);
//Intent summaryIntent = new Intent(DocumentListActivity.this, // ViewDocumentActivity.class);
// summaryIntent.putExtra("SummTopic", value);
}
});

You can use Intent for this.
Intent intent= new Intent(context,classname.class);
intent.putExtra("name",string);
You can get it in the target class name using intent.getextra().

I guess you are using an adapter to fill your list with some data. So you need to override getItem(int position) method in your adapter:
#Override
public Object getItem(int position) {
//Note that return type should be the same you you use to initilise items oof the adapter. E.g. String or some custom Topic class
Object someObject = mObjects[position];
return someObject;
}
Then you need to set an item click listener to you list
mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
Object someObject = adapterView.getItemAtPosition(i);
Intent i = new Intent(this, MyNewActivity.class);
i.putExtra("text_label", someObject.toString());
startActivity(i);
}
});

Custom Adapter List View

I need some help with my project. I've created a Custom Adapter, since I want my List View to display 5 textview, instead of one that I managed to do so far. This is my CustomAdapterPn activity:
public class CustomAdapterPn extends BaseAdapter {
private static ArrayList<Poniedzialek> searchPnArrayList;
private LayoutInflater mInflater;
public CustomAdapterPn(final Context context, final ArrayList<Poniedzialek> results) {
searchPnArrayList = results;
mInflater = LayoutInflater.from(context);
}
public int getCount() {
return searchPnArrayList.size();
}
public Object getItem(int position) {
return searchPnArrayList.get(position);
}
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = mInflater.inflate(R.layout.entry, null);
holder = new ViewHolder();
holder.txtSession = (TextView) convertView.findViewById(R.id.textSession);
holder.txtName = (TextView) convertView.findViewById(R.id.textName);
holder.txtStart = (TextView) convertView.findViewById(R.id.textStartTime);
holder.txtEnd = (TextView) convertView.findViewById(R.id.textEndTime);
holder.txtRoom = (TextView) convertView.findViewById(R.id.textRoom);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.txtSession.setText(searchPnArrayList.get(position).getTypeOfSession());
holder.txtName.setText(searchPnArrayList.get(position).getName());
holder.txtStart.setText(searchPnArrayList.get(position).getStartTime());
holder.txtEnd.setText(searchPnArrayList.get(position).getEndTime());
holder.txtRoom.setText(searchPnArrayList.get(position).getRoom());
return convertView;
}
static class ViewHolder {
TextView txtSession;
TextView txtName;
TextView txtStart;
TextView txtEnd;
TextView txtRoom;
}
}
And this is Activity where I wish to use this CustomAdapter. Note that I was using ArrayAdapter to display list items - I didn't modify the code yet, since I am clueless what should I do to manage this custom adapter correctly ( I was trying to, but nothing worked out well ). I am a newbie, so it's quite hard for me to get this, although I was reading tons of tutorials.
public class PoniedzialekActivity extends Activity implements OnClickListener, OnItemClickListener{ // z ListActivity na Activity
private Button butPnAdd;
private Button butPnDelete;
private ListView list_Pn;
private static final int DIALOG_ALERT = 10;
// We need some kind of Adapter to made the connection between ListView UI component and SQLite data set.
private ListAdapter pn_list_adapter;
// We need this while we read the query using Cursor and pass data
private ArrayList<Poniedzialek> pn_list;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_poniedzialek);
butPnAdd = (Button) findViewById(R.id.butPnAdd);
butPnAdd.setOnClickListener(this);
butPnDelete = (Button) findViewById(R.id.butPnDel);
butPnDelete.setOnClickListener(this);
// Initialize UI components
list_Pn = (ListView) findViewById(R.id.listPn);
list_Pn.setOnItemClickListener(this);
pn_list = new ArrayList<Poniedzialek>();
// For the third argument, we need a List that contains Strings.
//We decided to display undergraduates names on the ListView.
//Therefore we need to create List that contains undergraduates names
pn_list_adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, populateList());
list_Pn.setAdapter(pn_list_adapter);
}
#Override
public void onClick(View v) {
if(v.getId()==R.id.butPnAdd){
Intent i = new Intent(PoniedzialekActivity.this,dodawaniePoniedzialek.class);
startActivity(i);
}
if(v.getId()==R.id.butPnDel){
showDialog(DIALOG_ALERT);
}
}
/**
* DIALOG
*/
protected Dialog onCreateDialog(int id) {
switch (id) {
case DIALOG_ALERT:
// Create out AlterDialog
Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Czy na pewno chcesz usunac wszystkie wpisy ?");
builder.setCancelable(true);
builder.setPositiveButton("Tak", new OkOnClickListener());
builder.setNegativeButton("Nie", new CancelOnClickListener());
AlertDialog dialog = builder.create();
dialog.show();
}
return super.onCreateDialog(id);
}
private final class CancelOnClickListener implements
DialogInterface.OnClickListener {
public void onClick(DialogInterface dialog, int which) {
// Nic nie robi
}
}
private final class OkOnClickListener implements
DialogInterface.OnClickListener {
public void onClick(DialogInterface dialog, int which) {
DeletePn();
onResume();
}
}
public void DeletePn(){
DatabaseHelper openHelperClass = new DatabaseHelper(this);
SQLiteDatabase sqliteDatabase = openHelperClass.getWritableDatabase();
sqliteDatabase.delete(DatabaseHelper.PN_TABLE, null, null);
}
#Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
// TODO Auto-generated method stub
}
// To create a List that contains undergraduate names, we have to read the SQLite database
//We are going to do it in the separate method
public List<String> populateList(){
// We have to return a List which contains only String values. Lets create a List first
List<String> pn_string_list = new ArrayList<String>();
// First we need to make contact with the database we have created using the DbHelper class
DatabaseHelper openHelperClass = new DatabaseHelper(this);
// Then we need to get a readable database
SQLiteDatabase sqliteDatabase = openHelperClass.getReadableDatabase();
// We need a a guy to read the database query. Cursor interface will do it for us
//(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy)
Cursor cursor = sqliteDatabase.query(DatabaseHelper.PN_TABLE, null, null, null, null, null, null);
// Above given query, read all the columns and fields of the table
startManagingCursor(cursor);
// Cursor object read all the fields. So we make sure to check it will not miss any by looping through a while loop
while (cursor.moveToNext()) {
// In one loop, cursor read one undergraduate all details
// Assume, we also need to see all the details of each and every undergraduate
// What we have to do is in each loop, read all the values, pass them to the POJO class
//and create a ArrayList of undergraduates
String session = cursor.getString(cursor.getColumnIndex(DatabaseHelper.PN_KEY_TYPE_OF_SESSION));
String start = cursor.getString(cursor.getColumnIndex(DatabaseHelper.PN_KEY_START_TIME));
String end = cursor.getString(cursor.getColumnIndex(DatabaseHelper.PN_KEY_END_TIME));
String name = cursor.getString(cursor.getColumnIndex(DatabaseHelper.PN_KEY_NAME));
String room = cursor.getString(cursor.getColumnIndex(DatabaseHelper.PN_KEY_ROOM));
// Finish reading one raw, now we have to pass them to the POJO
Poniedzialek pn = new Poniedzialek();
pn.setTypeOfSession(session);
pn.setName(name);
pn.setStartTime(start);
pn.setEndTime(end);
pn.setRoom(room);
// Przekazujemy pn do arraylist
pn_list.add(pn);
// But we need a List of String to display in the ListView also.
// That is why we create "pn_string_list"
pn_string_list.add(name);
}
// Jezeli Baza Danych nie zostanie zamknieta dostaniemy error
sqliteDatabase.close();
return pn_string_list;
}
// If you don't write the following code, you wont be able to see what you have just insert to the database
#SuppressWarnings("unchecked")
#Override
protected void onResume() {
super.onResume();
pn_list_adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, populateList());
list_Pn.setAdapter(pn_list_adapter);
((ArrayAdapter<String>) pn_list_adapter).notifyDataSetChanged(); // dodano
list_Pn.refreshDrawableState(); // dodanoe
list_Pn.invalidate(); // dodanoe
}
} // end PoniedzialekActivity

Create an object for your custom adapter class CustomAdapterPn and set this custom adapter object to list view . Not the array adapter .

Look at this lines and make changes according to it,
CustomAdapterPn pn_list_adapter; //change 1
pn_list = new ArrayList<Poniedzialek>();
populateList() // Change 2
pn_list_adapter = new CustomAdapterPn(this,pn_list); // Change 3
list_Pn.setAdapter(pn_list_adapter);
Try this and let me know what happen..

How to append an id to a ListViewItem using SimpleCursorAdapter and SQLiteDatabase

I've been searching on this for a while now, but I can't find anything that could help me solve my problem.
I have a list of categories in a listview. I fetch these from a SQLiteDatabase and use a SimpleCursorAdapter to put them in the list.
This works fine...
Now, if I click a category, I want to launch a new activity displaying all items with that specific category. Passing parameters to the new activity isn't a problem - found a nice tutorial on how to do this here: Passing data or parameter to another activity
My problem is that I can't get the id out of the selected view... I want the id from the selected category so I can get the items with that categoryId.
This is where I try and get the id out of the view - I've used a lot of different methods (including some fiddling with listview, item and position, ... this is my most recent attempt) and don't know what to try next...
#Override
public void onItemClick(AdapterView<?> listview, View item, int position,
long itemId) {
Intent intent = new Intent();
Bundle bun = new Bundle();
bun.putInt("categoryId", (int) itemId);
intent.setClass(MainActivity.this, ItemsPerCategoryActivity.class);
intent.putExtras(bun);
startActivity(intent);
}
Has anybody encountered the same problem and if you have, do you have some advice for me on how to do this?
This is how the problem got solved:
Cursor c = (Cursor)listview.getAdapter().getItem(position);
int id = c.getInt(c.getColumnIndex(_ID)); //0 = index id
//Log.d("Category id", id + "");
Intent intent = new Intent();
Bundle bun = new Bundle();
bun.putInt("categoryId", id);
intent.setClass(MainActivity.this, ItemsPerCategoryActivity.class);
intent.putExtras(bun);
startActivity(intent);

Try following
#Override
public void onItemClick(AdapterView<?> listview, View item, int position,
long itemId) {
Cursor c = (Cursor)adatper.getItem(position); //adapter = cursor adapter object
int id = c.getInt(0)// 0 is index of id.
Intent intent = new Intent();
Bundle bun = new Bundle();
bun.putInt("categoryId", id);
intent.setClass(MainActivity.this, ItemsPerCategoryActivity.class);
intent.putExtras(bun);
startActivity(intent);
}

For this,you have can use custom adapter and there,you can set ids in a HashMap.Here is an example:
public class DemoAdapter extends SimpleCursorAdapter
{
Cursor dataCursor;
LayoutInflater mInflater;
Context context;
public static HashMap<Integer,String> myList=new HashMap<Integer,String>();
public DemoAdapter(Context context, int layout, Cursor dataCursor, String[] from,int[] to)
{
super(context, layout, dataCursor, from, to);
this.context=context;
this.dataCursor = dataCursor;
mInflater = LayoutInflater.from(context);
this.fromWhere=fromWhere;
}
#Override
public View getView(final int position, View convertView, ViewGroup parent)
{
final ViewHolder holder;
if(convertView==null)
{
convertView = mInflater.inflate(R.layout.my_list_item, null);
holder = new ViewHolder();
holder.cName=(TextView)convertView.findViewById(R.id.contactName);
convertView.setTag(holder);
}
else
holder=(ViewHolder)convertView.getTag();
dataCursor.moveToPosition(position);
String id=Integer.toString(dataCursor.getInt(dataCursor.getColumnIndexOrThrow("_id")));
myList.put(position, id);
holder.cName.setText(dataCursor.getString("contact_name"));
return convertView;
}
static class ViewHolder
{
TextView cName;
}
}
Now,use it like-
listView.setOnItemClickListener(new OnItemClickListener{
#Override
public void onItemClick(AdapterView<?> arg0, View view, int position,long id) {
int id=Integer.parseInteger(DemoAdapter.myList.get(position));
}
});