Loading Two Sql Columns Into A Listview But Only Need To Display The First Column Android
Solution 1:
Issue
using ArrayAdapter only allows a a single item to be passed, thus unless you resort to complicated/messy/inefficient methods ArrayAdapter is only really suitable for a single value.
Fix
You could use an ArrayList where your_object has members for all the required values. i.e phonenumber and phonename. Noting that unless you use a Custom Adapter that you should override the the toString method to extract the data that you want to be displayed, as that is what a standard ArrayAdapter uses.
Alternative (use a CursorAdapter)
An alternative would be to use a Cursor Adapter (e.g. SimpleCursorAdapter), you can then return the Cursor and use it directly. However, a CursorAdapter REQUIRES a column specifically name _id (BaseColumns._ID can be used).
One of the clear advantages of a Cursor adapter is the the 4th paremmter passed to the onItemClick/onItemLongClick is the id of the row (if used correctly) allowing a single value to then get/update/delete/pass the respective selected row.
- As such I'd recommend a Cursor Adapter for a ListView and hence the more comprehensive answer.
You may think I don;t have such a column. However, you can use the normally hidden rowid column and dynamically create a column named _id.
You could have a method, in the database helper (DataDBAdapter) such as :-
publicCursorgetAllRowsAsCursor()
{
String[] columns = newString[]{"rowid AS " + BaseColumns._ID,"*"}
return = mDB.query(TBL_MYTABLE,null,null,null,null,null,null)
}
The ManageList method could then be :-
privatevoidmanageListView(Context context) {
myCursor = dbhelper.getAllRowsAsCursor();
// Only setup the adapter and the ListView if the adapter hasn't been setupif(arrayAdapter == null)
{
// Instantiate the adapter
arrayAdapter = newSimpleCursorAdapter(context,android.R.layout.simple_list_item_1,myCursor,newString[]{DataAdapter.COl_MYTABLE_PHONENAME},newint[]{android.R.id.text1},0);
display_contacts1.setAdapter(arrayAdapter); //<<<<<<<<<< Tie the adpater to the ListView// Set the ListViews OnItemClick Listener
display_contacts1.setOnItemClickListener(newAdapterView.OnItemClickListener()
{
@OverridepublicvoidonItemClick(AdapterView<?> parent, View view, int position, long id)
{
String namedisplay = arrayAdapter.getItem(position); //<<<<<<<<<< this gets the phone nameString phonenumber = myCursor,getString(myCursor.getColumnIndex(DataAdapter.COL_MYTABLE_PHONENUMBER);
Toast.makeText(view.getContext(), namedisplay + " Selected for Communication", Toast.LENGTH_SHORT).show();
Toast.makeText(view.getContext(), phonenumber, Toast.LENGTH_SHORT).show();
}
});
} else {
arrayAdapter.swapCursor(myCursor);
}
Notes
- MyCursor would be declared as a class variable e.g.
Cursor MyCursor; - Instaed of
ArrayAdapter<String> arrayAdapter;you would haveSimpleCursorAdapter arrayAdapter;
- The above is in-principle code and has not been tested, so there may be errors and/or omissions.
Working Example
The following is the code based upon the code from the previous question asked (which this appears to follow on from). It has two ListViews the old and a new one that uses a SimpleCursorAdapter. Clicking an item display phone number and also id. Lon Clicking an Item deletes that item (refreshing both ListViews).
DataDBAdapter.java has two new methods (so add these) :-
//<<<<<<<<<< ADDEDpublicCursorgetAllRowsAsCursor() {
return mDB.query(TBL_MYTABLE,null,null,null,null,null,null);
}
public int delete(long id) {
String whereclause = COL_MYTABLE_ID + "=?";
String[] whereargs = newString[]{String.valueOf(id)};
return mDB.delete(TBL_MYTABLE,whereclause,whereargs);
}
SelectModemFragment.java is now :-
publicclassSelectModemFragmentextendsFragment {
privateSelectModemViewModel mViewModel;
ListView display_contacts1;
ArrayAdapter<String> arrayAdapter;
ArrayList<String> thelist;
DataDBAdapter dbhelper;
//<<<<<<<<<< ADDEDListView display_contacts2;
SimpleCursorAdapter sca;
CursorMyCursor;
publicstaticSelectModemFragmentnewInstance() {
returnnewSelectModemFragment();
}
@OverridepublicViewonCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.select_modem_fragment, container, false);
display_contacts1 = view.findViewById(R.id.lv001); //<<<<<<<<<< top listview ArrayAdapter<String>
display_contacts2 = view.findViewById(R.id.lv002);
dbhelper = newDataDBAdapter(view.getContext());
AddSomeData();
manageListView(view.getContext());
manageListView2();
return view;
}
@OverridepublicvoidonActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mViewModel = ViewModelProviders.of(this).get(SelectModemViewModel.class);
// TODO: Use the ViewModel
}
//Sets up the ListView if not already setupprivatevoidmanageListView(Context context) {
thelist = dbhelper.getAllRowsAsList(); //<<<<<<<<<< extract the list (just the phone names) from the database// Only setup the adapter and the ListView if the adapter hasn't been setupif (arrayAdapter == null) {
// Instantiate the adapter
arrayAdapter = newArrayAdapter<>(context,android.R.layout.simple_list_item_1,thelist); //<<<<<<<<<< list included
display_contacts1.setAdapter(arrayAdapter); //<<<<<<<<<< Tie the adpater to the ListView// Set the ListViews OnItemClick Listener
display_contacts1.setOnItemClickListener(newAdapterView.OnItemClickListener() {
@OverridepublicvoidonItemClick(AdapterView<?> parent, View view, int position, long id) {
String name = arrayAdapter.getItem(position); //<<<<<<<<<< this gets the phone nameToast.makeText(view.getContext(),"You clicked the phone named " + name,Toast.LENGTH_SHORT).show();
}
});
} else {
//<<<<<<<<<< MODIFIED to cope with changes (needs to rebuild the array within the adpater)
arrayAdapter.clear();
for (Strings: thelist) {
arrayAdapter.add(s);
}
arrayAdapter.notifyDataSetChanged();
}
}
//<<<<<<<<<< ADDED FOR CursorAdapterprivatevoidmanageListView2() {
MyCursor = dbhelper.getAllRowsAsCursor();
if (sca == null) {
sca = newSimpleCursorAdapter(
getContext(),
android.R.layout.simple_list_item_1,
MyCursor,
newString[]{DataDBAdapter.COl_MYTABLE_PHONENAME},
new int[]{android.R.id.text1},
0
);
display_contacts2.setAdapter(sca);
display_contacts2.setOnItemClickListener(newAdapterView.OnItemClickListener() {
@OverridepublicvoidonItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(view.getContext(),
"You Clicked the phone name " +
MyCursor.getString(MyCursor.getColumnIndex(DataDBAdapter.COl_MYTABLE_PHONENAME)) +
". The phonenumber is " +
MyCursor.getString(MyCursor.getColumnIndex(DataDBAdapter.COL_MYTABLE_PHONENUMBER)) +
". The ID (as passed) is " + String.valueOf(id) +
". The ID (from Cursor) is " + String.valueOf(MyCursor.getLong(MyCursor.getColumnIndex(DataDBAdapter.COL_MYTABLE_ID)))
,
Toast.LENGTH_SHORT).show();
}
});
//<<<<<<<<<< EXTRA delete row on long click
display_contacts2.setOnItemLongClickListener(newAdapterView.OnItemLongClickListener() {
@OverridepublicbooleanonItemLongClick(AdapterView<?> parent, View view, int position, long id) {
dbhelper.delete(id);
manageListView2();
manageListView(getContext());
returntrue;
}
});
} else {
sca.swapCursor(MyCursor);
}
}
// Add some testing data (only if none already exists)privatevoidAddSomeData() {
if (DatabaseUtils.queryNumEntries(dbhelper.getWritableDatabase(),DataDBAdapter.TBL_MYTABLE) < 1) {
dbhelper.insert("Phone 1", "0000000000");
dbhelper.insert("Phone 2", "1111111111");
}
}
@OverridepublicvoidonResume() {
super.onResume();
manageListView2();
manageListView(getContext());
}
@OverridepublicvoidonDetach() {
super.onDetach();
MyCursor.close();
}
}
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