setSelection on Spinner based on rowId

I have a Spinner View that's populated through a SimpleCursorAdapter.

Based on the selection I need to save the rowid in the entry database (position won't work 开发者_如何学Cbecause things can be added and deleted from the Spinner Database).

This I can do by using spinner.getAdapter().getItemId(pos);. But When I edit an entry I need to make the Spinner position selected that is associated with this rowid (currently).

spinner.setSelection(position); won't work because I have the rowid, I need a way to find the current position of the item in the current spinner based on the rowid in the database.

If you want to set the selection of a Spinner thats backed by a CursorAdapter, you can loop through all the items in the Cursor and look for the one you want (assuming that the primary key in your table is named "_id"):

Spinner spinner = (Spinner) findViewById(R.id.spinner);
spinner.setAdapter(new SimpleCursorAdapter(...));

for (int i = 0; i < spinner.getCount(); i++) {
    Cursor value = (Cursor) spinner.getItemAtPosition(i);
    long id = value.getLong(value.getColumnIndex("_id"));
    if (id == rowid) {
        spinner.setSelection(i);
    }
}

If you want to get the rowid of a selected item, you can do something similar:

Cursor cursor = (Cursor) spinner.getSelectedItem();
long rowid = cursor.getLong(cursor.getColumnIndex("_id"));

There might be a quicker way to do it, but that's always worked for me.

Had an idea when writing this, made a hashtable with rowid->pos when populating the spinner and then used that. Might help someone if they're searching.

I agree with Erich Douglass's above answer but i found fastest loop syntax which will be useful while spinner.getCount() is greater than 50k to 100k.

/* 1 (fastest) */
for (int i = initializer; i >= 0; i--) { ... }

/* 2 */
int limit = calculateLoopLimit();
for (int i = 0; i < limit; i++) { ... }

/* 3 */
Type[] array = getMyArray();
for (Type obj : array) { ... }

/* 4 */
for (int i = 0; i < array.length; i++) { ... }

/* 5 */
for (int i = 0; i < this.var; i++) { ... }

/* 6 */
for (int i = 0; i < obj.size(); i++) { ... }

/* 7 (slowest) */
Iterable<Type> list = getMyList();
for (Type obj : list) { ... }

So i think we can use here second for better performance:

int spinnerCount = spinner.getCount();
for (int i = 0; i < spinnerCount; i++) {
    Cursor value = (Cursor) spinner.getItemAtPosition(i);
    long id = value.getLong(value.getColumnIndex("_id"));
    if (id == rowid) {
        spinner.setSelection(i);
    }
}

I think that instead of a for loop is better a while, because when you find your item, can break the loop.

int spinnerCount = spinner.getCount();
int i = 0;
while(i++ < spinnerCount) {
    Cursor value = (Cursor) spinner.getItemAtPosition(i);
    long id = value.getLong(value.getColumnIndex("_id"));
    if (id == rowid) {
        spinner.setSelection(i);
        break;
    }
}

First step, create view for your data set, with joins etc.:

CREATE VIEW my_view AS
  SELECT _id, field FROM my_table

Second step:

CREATE VIEW my_view2 AS
  SELECT count(*) AS row_id, q1.*
  FROM my_view AS q1
  LEFT JOIN my_view AS q2
  WHERE q1._id >= q2._id
  GROUP BY q1._id

Then simply:

SELECT * FROM my_view2

Results:

row_id | _id | field

1   4   XbMCmUBFwb
2   6   Te JMejSaK
3   8   dDGMMiuRuh
4   10  phALAbnq c
5   11  EQQwPKksIj
6   12  PAt tbDnf
7   13  f zUSuhvM
8   14  TIMBgAGhkT
9   15  OOcnjKLLER

To get position by id:

SELECT * FROM my_view2 WHERE _id=11

Results:

row_id | _id | field

5   11  EQQwPKksIj

Hope that help

https://stackoverflow.com/a/5040748/1206052

dziobas

has provided an awesome answer.. But I am not surprised why nobody has recommended it.. just want to make some correction in his answer..

CREATE VIEW my_view2 AS
  SELECT count(*) AS row_id, q1.*
  FROM my_view AS q1
  LEFT JOIN my_view AS q2
  ON (q1._id >= q2._id)
  GROUP BY q1._id

I just replaced "where" with "on" that is required by join..

now u have all the items with their Positions associated with there ID's..

Just assign the ROW_id to the setselection() of spinner

Why do it the hard way when you can do it the right way?

I refer to the manual:

http://d.android.com/reference/android/widget/AdapterView.OnItemSelectedListener.html#onItemSelected%28android.widget.AdapterView%3C?%3E,%20android.view.View,%20int,%20long%29

example code:

spinner.setOnItemSelectedListener(new OnItemSelectedListener() {
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id)
        {
            int index = spinner.getSelectedItemPosition();
            Toast.makeText(getBaseContext(), 
                "You have selected item : " + index + " which is row " + id, 
                Toast.LENGTH_SHORT).show();                
        }
        public void onNothingSelected(AdapterView<?> arg0) {}
    });

Thanks to evancharlton on #android-dev for this enlightment. :)