Android: Is it possible to update MatrixCursor line (as solution to views resetting on rotate)

Question

I am having trouble with a ListView based on a MatrixCursor resetting values on keyboard minimize and orientation change.

The matrix cursor is filled with data from a SQL database. This is done because I want the original database columns to be rows in the listview:

public void fillList(boolean rewrite, int rewrite pos, int) {
    myCols = getColArray();    
    SQLiteDatabase myDB = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, SQLiteDatabase.OPEN_READONLY); 
    myCursor = myDB.query("Scoring", statCols, null, null, null, null, null);

    String[] menuCols = new String[] { "_id","Item","Value"};
    int []to = new int[]{R.id.listitem, R.id.listitem_value}; 

    mc = new MatrixCursor(menuCols);

    for (int i = 0; i < (mChoices.size()); i++) {
        statCursor.moveToPosition(draftId);
        String item = mChoices.get(i);          

        String valueString = "";
        int valueCol = statCursor.getColumnIndex(item);
        int value = statCursor.getInt(valueCol);                      
        valueString = (String.valueOf(value));

        mc.addRow(new Object[] {
            i,
            item,
            valueString                                         
        });
    }

This fillList() method is called in my onCreate. This cursor is then used to populate the ListView by extending SimpleCursorAdapter. My goal for the fragement is to allow the user to click on one of the list items, causing Dialog with an EditText line to appear:

@Override
public void onListItemClick(ListView l, final View v, int position, long id) {

    final TextView valueL = (TextView) v.findViewById(R.id.listitem_value);
    String valueString = (String) valueL.getText();
    int value = 100;
    try {
        value = Integer.parseInt(valueString);
    } catch(NumberFormatException nfe) {
    }

    //Create dialog layout
    View view = getActivity().getLayoutInflater().inflate(R.layout.numberpick_popup, null);
    final EditText mInputText = (EditText) view.findViewById(R.id.myText);

    //Create Dialog
    AlertDialog.Builder builder =  new AlertDialog.Builder(this.getActivity());
    builder.setTitle(title);

    builder.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            valueL.setText(mInputText.getText().toString());
            return;
        }
    });

    builder.setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            return;
        }
    });

    builder.setView (view);
    final AlertDialog dialog = builder.create ();
    dialog.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE);
    dialog.show();
}

The problem I am having is when the fragment layout regenerates on keyboard hidden or orientation change, causing fillData to be called and overwriting any of the values I had updated in the list. This happens if I choose OK on the dialog without first minimizing the keyboard, or on any orientation change.

My thinking is that there should be some way to overwrite the values in the MatrixCursor when new data is entered from the dialog. However I don't know if this is possible or if the cursor would even survive the state changes.

Any help would be greatly appreciated.

Answer 1

I worked around this by creating a HashMap of key value pairs in my list adaptor and adding the changed values there. So in bindView() I would check if the key existed there for the row being initialized and if so then use those values instead of from the cursor.

I simply did

HashMap<Long,String>

since I only needed one value that could change but you could easily create a custom class and make yours

HashMap<Long,CustomClass>

so you could change lots of values.

So when changing the values initially just remember to update that HashMap with the new values so on redraw of your List the correct values are shown. This works well because by nature a MatrixCursor alone is usually pretty small. This wouldn't be smart on a really large list because the HashMap would grow out of control and take up too much memory. Let me know if you have any questions.