Develop Reference

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);

How to get info from ListFragment

I have a ListFragment that is populated using a CursorLoader. Once the ListFragment is populated, I have an OnItemClickListener method in which I want to identify which item from the List Fragment the user chose. How do I do this? I've tried:
String item = getListAdapter().getItem(position);
String item = getListAdapter().getItem(position).toString();
and
String item = (String) ((Fragment) getListAdapter().getItem(position)).getString(0);
where position is an integer passed to the onClickItemListener method like so:
public void onListItemClick(ListView l, View v, int position, long id)
All of these throw Cast Exceptions of one type or another. I'm stumped. This seems like a simple thing to do. For your reference, here's how the List Fragment is populated:
private SimpleCursorAdapter mAdapter;
private static final String[] PROJECTION = new String[] { "_id", "stitchname" };
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Intent myData = getActivity().getIntent();
Bundle info = myData.getExtras();
String[] dataColumns = { "stitchname" };
int[] viewIDs = { R.id.stitchlist1 };
mAdapter = new SimpleCursorAdapter(getActivity(), R.layout.stitchlist, null, dataColumns, viewIDs, 0);
setListAdapter(mAdapter);
getLoaderManager().initLoader(0, info, (LoaderCallbacks<Cursor>) this);
}
#Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
String selection = "stitchlevel=?";
String[] selectionArgs = new String[] {args.getString("Level")};
return (Loader<Cursor>) new CursorLoader(getActivity(), STITCHES_URI, PROJECTION, selection, selectionArgs, null);
}
Any suggestions would be most welcome, thanks!

You are overriding the wrong method. You said you are using an ListFragment, so you may have been declaring your CursorAdapter/ArrayAdapter somewhere in your Fragment. In that case, do the following:
class yourFragemt extends ListFragment{
//Member Variable
private SimpleCursorAdapter mAdapter;
....
#Override
public void onItemClick(AdapterView<?> arg0, View arg1, int pos, long arg3) {
Cursor c = (Cursor) mAdapter.getItem(pos);
String value = c.getString(c
.getColumnIndex(ColumnIndex));
}
}

The answer is as follows:
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Cursor c = ((SimpleCursorAdapter)l.getAdapter()).getCursor();
c.moveToPosition(position);
String item = c.getString(1);
}
I got the answer from the second link provided to me by Georgy Gobozov in a comment, above.

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);
}
});

How to get the index of a clicked item into another activity?

I have a activity (Contato) that shows a ListView of the contacts i have in my database(banco > contatos > nome, telefone (database>table>rows)). When a Contact Info is clicked a Dialog comes up and shows me the info and 3 button (OK/Alterar/Delete) when i hit Alterar it sends me to another activity(Alterarcontato) which i have 2 Edit Texts and 1 Button.
So when i get send to the Alterarcontato activity i still want to have the index o the Contact i clicked so I can change it's values ( with db.update).
Contato.java code ListView that shows the dialog and has it's index.
ListView user = (ListView) findViewById(R.id.lvShowContatos);
//String = simple value ||| String[] = multiple values/columns
String[] campos = new String[] {"nome", "telefone"};
list = new ArrayList<String>();
c = db.query( "contatos", campos, null, null, null, null, null);
c.moveToFirst();
if(c.getCount() > 0) {
while(true) {
list.add(c.getString(c.getColumnIndex("nome")).toString());
if(!c.moveToNext()) break;
}
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, list);
user.setAdapter(adapter);
user.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
reg = position;
c.moveToPosition(reg);
String nome = c.getString(c.getColumnIndex("nome"));
String telefone = c.getString(c.getColumnIndex("telefone"));
ShowMessage(nome, telefone);
}
});
Alterarcontato.java code that has the editTexts and button to then alter the values.
EditText nomeA = (EditText) findViewById(R.id.etNomeAlter);
EditText telefoneA = (EditText) findViewById(R.id.etTelefoneAlter);
final String nomeB = nomeA.getText().toString();
final String telefoneB = telefoneA.getText().toString();
String where = "id=?";
String[] whereArgs = {"nome", "telefone"};
ContentValues dataToInsert = new ContentValues();
dataToInsert.put("nome", nomeB);
dataToInsert.put("telefone", telefoneB);
db.update("contatos", dataToInsert, where, whereArgs);
But as shown in Contato.java code i don't have any ID for the contacts, so the String where = "id=?"; is kinda of invalid, so how do i get the index already from Contact.java to get shown in the Alterarcontato.java so when i put some writing in it and hit the button, the values change in the database?
Thank you.

setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
reg = position;
c.moveToPosition(reg);
String nome = c.getString(c.getColumnIndex("nome"));
String telefone = c.getString(c.getColumnIndex("telefone"));
ShowMessage(nome, telefone);
/// The above method will show the dialog with contact info right..? SO from the dialog you are launching the activity to edit the info. While starting the activity you have to pass the index. Like below :
Intent intent = new Intent(getApplicationContext(), Alterarcontato.class);
// the index is the variable which contains the index of the selected contact in your dialog.
intent.putExtra("key", index);
startActivity(intent);
<-- Alterarcontato.java -->
public class Alterarcontato extends Activity {
private Integer mIndex;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mIndex = getIntent().getExtras().getInt("key");
}
}

You can try the given link, i hope this may help you
Contacts Contract API

Have a look at this description on the Android Developers' site. It provides good step-by-step instructions. Essentially, you have to create an Intent and use the putExtra() method to pass the data.
Edit: Also, have a look at this answer to a similar question about getting the row ID in the ListActivity using onListItemClick().

How can i convert this code so i can get the row from list view

I want to be able to fetch a row from a list view and populate textViews in a different activity. I want to be able to do this onclick of an item with the list view..
public class CBFilter extends Activity {
ListView RecipeNames;
Cursor cursor;
SimpleCursorAdapter adapter;
CBDataBaseHelper data;
SQLiteDatabase data2;
TextView RecipeText;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
RecipeNames = (ListView) findViewById(R.id.List1);
RecipeNames.setTextFilterEnabled(true);
RecipeText = (TextView) findViewById(R.id.recipeText);
adapter = new SimpleCursorAdapter (this, 0, cursor, null, null);
data = new CBDataBaseHelper(this);
data.open();
cursor = data.query();
startManagingCursor(cursor);
String[] from = {CBDataBaseHelper.KEY_NAME};
int[] to = { R.id.recipeText};
adapter = new SimpleCursorAdapter(this, R.layout.row, cursor, from, to);
RecipeNames.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
public void CreateNew(View view){
Intent myIntent = new Intent(this, CBCreate.class);
startActivity(myIntent);
}
}
How can i convert this code in order to achieve the required functionality.. thanks Stefan

try like this
public void onListItemClick(ListView parent, View v, int position, long id) {
String string = from[position]); // this depends on your Adapter ...
Intent i = new Intent(CheckData.this,ShowData.class);
i.putExtra("SELECTED", string);
startActivity(i);
i got it from this link , it will be use full for you :
Use of SQLite