In any Listview, the view are reused. As you scroll through the list, those that scroll up and off screen are recycled and used with newer information as it comes in below.
You need to keep track of your checkboxes with a sparse array. Mark the index in the array as cherked/unchecked as the user touches each. You then set the state of the checkbox based on the value in the array.
Here is some example code from an an older app, that does both a "select all" checkboxes as well as manages the entire list of those checked and unchecked. It was for a classroom attendance app I wrote, so it was much easier for a teacher to select "ALL" being in class and then unselect those that weren't present.
I have two checkboxes in this listview, and two sparse arrays, itemCheckedHere and itemCheckedLate (whether a student is in class, or was late).
public class MyDataAdapter extends SimpleCursorAdapter {
private Cursor c;
private Context context;
private Long classnum;
private gradeBookDbAdapter mDbHelper;
public static final int LATE=2;
public static final int ATTEND=1;
int idxCol;
int idx;
// itemChecked will store the position of the checked items.
public MyDataAdapter(Context context, int layout, Cursor c, String[] from,
int[] to, Long mRowId) {
super(context, layout, c, from, to);
this.c = c;
this.context = context;
mDbHelper = new gradeBookDbAdapter(context);
mDbHelper.open();
classnum = mRowId;
c.moveToFirst();
}
public class ViewHolder{
public TextView text;
public TextView text2;
public ImageView image;
public CheckBox here;
public CheckBox late;
}
public View getView(final int pos, View inView, ViewGroup parent) {
Bitmap bm;
ImageView studentPhoto;
View vi=inView;
final ViewHolder holder;
if (inView == null) {
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
vi = inflater.inflate(R.layout.show_attendance, null);
holder=new ViewHolder();
holder.text=(TextView)vi.findViewById(R.id.stuname);
holder.text2=(TextView)vi.findViewById(R.id.stuIndex);
holder.image=(ImageView)vi.findViewById(R.id.icon);
holder.here=(CheckBox)vi.findViewById(R.id.attend);
holder.late=(CheckBox)vi.findViewById(R.id.late);
vi.setTag(holder);
}
else
holder=(ViewHolder)vi.getTag();
c.moveToPosition(pos);
int index = c.getColumnIndex(gradeBookDbAdapter.KEY_NAME);
String name = c.getString(index);
holder.text.setText(name);
index = c.getColumnIndex(gradeBookDbAdapter.KEY_ROWID);
String Index = c.getString(index);
holder.text2.setText(Index);
bm = gradeBookDbAdapter.getStudentPhoto(name);
if (bm != null) {
holder.image.setImageBitmap(bm);
}
else {
// use icon image
holder.image.setImageResource(R.drawable.person_icon);
}
// pull out existing attend/late fields and set accordingly
int attend = c.getInt(c.getColumnIndex(gradeBookDbAdapter.KEY_ATTEND));
if(attend==1){
holder.here.setChecked(true);
itemCheckedHere.set(pos, true);
}
//else {
// holder.here.setChecked(false);
// itemCheckedHere.set(pos, false);
//}
int late = c.getInt(c.getColumnIndex(gradeBookDbAdapter.KEY_LATE));
if (late==1){
holder.late.setChecked(true);
itemCheckedLate.set(pos, true);
}
//else {
// holder.late.setChecked(false);
// itemCheckedLate.set(pos, false);
//}
if (selectAllTouched) {
if(selectAll){
holder.here.setChecked(true);
itemCheckedHere.set(pos, true);
int who= new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(who, classnum, ATTEND, 1, attendDate );
}
else{
holder.here.setChecked(false);
itemCheckedHere.set(pos, false);
int who = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(who, classnum, ATTEND, 0, attendDate );
}
}
holder.here.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
CheckBox cb = (CheckBox) v.findViewById(R.id.attend);
if (cb.isChecked()) {
itemCheckedHere.set(pos, true);
int Index = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(Index, classnum, ATTEND, 1, attendDate );
} else if (!cb.isChecked()) {
itemCheckedHere.set(pos, false);
int Index = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(Index, classnum, ATTEND, 0, attendDate );
}
}
});
holder.late.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
CheckBox cb = (CheckBox) v.findViewById(R.id.late);
if (cb.isChecked()) {
itemCheckedLate.set(pos, true);
int Index = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(Index, classnum, LATE, 1, attendDate );
} else if (!cb.isChecked()) {
itemCheckedLate.set(pos, false);
int Index = new Integer(holder.text2.getText().toString());
mDbHelper.updateAttend(Index, classnum, LATE, 0, attendDate );
}
}
});
holder.here.setChecked(itemCheckedHere.get(pos)); // this will Check or Uncheck the
holder.late.setChecked(itemCheckedLate.get(pos)); // this will Check or Uncheck the
// CheckBox in ListView
// according to their original
// position and CheckBox never
// loss his State when you
// Scroll the List Items.
return vi;
}
}
}